Chapter 10, 11, 12, 13
Which recombination frequency corresponds to perfect linkage and violates the law of independent assortment? a. 0 b. 0.25 c. 0.50 d. 0.75
0
Which recombination frequency corresponds to independent assortment and the absence of linkage? a. 0 b. 0.25 c. 0.50 d. 0.75
0.50
If there are 20 chromatids in a cell, how many centromeres are there?
10
Imagine you are performing a cross involving seed color in garden pea plants. What F1 offspring would you expect if you cross true-breeding parents with green seeds and yellow seeds? Yellow seed color is dominant over green. a. 100 percent yellow-green seeds b. 100 percent yellow seeds c. 50 percent yellow, 50 percent green seeds d. 25 percent green, 75 percent yellow seeds
100 percent yellow seeds
If a cell contains 12 chromosomes at the end of meiosis I, how many chromosomes will the daughter cells contain at the end of meiosis II? a. 3 b. 6 c. 12 d. 24
12
Which of the following codes describes position 12 on the long arm of chromosome 13? a. 13p12 b. 13q12 c. 12p13 d. 12q13
13q12
If a muscle cell of a typical organism has 32 chromosomes, how many chromosomes will be in a gamete of that same organism?
16
If a sperm cell contains 8 chromosomes, it comes from an animal that has ______ chromosomes.
16
The amount of DNA in a cell is measured right after mitosis and found to be 8 picograms. How many picograms of DNA would be found in a nucleus in the G2 phase?
16
Assuming no gene linkage, in a dihybrid cross of AABB x aabb with AaBb F1 heterozygotes, what is the ratio of the F1 gametes (AB, aB, Ab, ab) that will give rise to the F2 offspring? a. 1:1:1:1 b. 1:3:3:1 c. 1:2:2:1 d. 4:3:2:1
1:1:1:1
In a mating between two individuals that are heterozygous for a recessive lethal allele that is expressed in utero, what genotypic ratio (homozygous dominant:heterozygous:homozygous recessive) would you expect to observe in the offspring? a. 1:2:1 b. 3:1:1 c. 1:2:0 d. 0:2:1
1:2:0
A cat has a total of 40 chromosomes in its body cells. How many in its sex cells?
20
A cell biologist produces a karyotype of mouse somatic cells arrested in mitosis. She sees 40 chromosomes, which is completely normal for mice. Based on this information, what is the haploid number of chromosomes for mice?
20
Consider a cross to investigate the pea pod texture trait, involving constricted or inflated pods. Mendel found that the traits behave according to a dominant/recessive pattern in which inflated pods were dominant. If you performed this cross and obtained 650 inflated-pod plants in the F2 generation, approximately how many constricted-pod plants would you expect to have? a. 600 b. 165 c. 217 d. 468
217
A 2n cell of a bat has 44 chromosomes, how many chromosomes will you find in one of his gametes
22
In humans, sperm cell have ___________ chromosomes and are ___________________, while skin cells have _____________ chromosomes are are diploid.
23. haploid. 46 diploid
If the diploid number of chromosomes for an organism is 52, what will the haploid number of chromosomes be? a. 26 b. 48 c. 112 d. 24
26
How many different offspring genotypes are expected in a trihybrid cross between parents heterozygous for all three traits when the traits behave in a dominant and recessive pattern? How many phenotypes? a. 64 genotypes; 16 phenotypes b. 16 genotypes; 64 phenotypes c. 8 genotypes; 27 phenotypes d. 27 genotypes; 8 phenotypes
27 genotypes; 8 phenotypes
If the probability of event A is 3/4 and the probability of event B is 1/4, then the probability of both A and B occurring at the same time is a. 3/4. b. 1/4. c. 1 or absolute certainty. d. 1/2. e. 3/16.
3/16.
Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?
32
If a woman is a carrier for the color-blind recessive allele and her husband is normal, what are their chances that a son will be color-blind? a. None since the father is normal. b. 50% since the mother is the only carrier. c. 100% because the mother has the gene. d. 25% because the mother is a hybrid. e. None since he will also be just a carrier.
50% since the mother is the only carrier.
Explain the difference between a proto-oncogene and a tumor suppressor gene.
A proto-oncogene is a segment of DNA that codes for one of the positive cell cycle regulators. If that gene becomes mutated so that it produces a hyperactivated protein product, it is considered an oncogene. A tumor suppressor gene is a segment of DNA that codes for one of the negative cell cycle regulators. If that gene becomes mutated so that the protein product becomes less active, the cell cycle will run unchecked. A single oncogene can initiate abnormal cell divisions; however, tumor suppressors lose their effectiveness only when both copies of the gene are damaged.
The F2 offspring of a classic Mendelian monohybrid cross between homozygous dominant and homozygous recessive parents would produce the genotype(s) a. AA and Aa. b. Aa and aa. c. AA, Aa, and aa. d. AA only. e. Aa only.
AA, Aa, and aa.
If the parents are AO and BO genotypes for the ABO blood group, their children could include which of the following genotypes? a. AO and BO only b. AO, BO, and AB only c. AA, BB, and AB only d. AO, BO, and OO only e. AO, BO, AB, and OO only
AO, BO, AB, and OO only
If an individual with a dominant phenotype is crossed with an individual with a recessive phenotype, 4 of their 9 offspring show the recessive phenotype. What is the genotype of the first parent? a. AA b. Aa c. aa d. The answer cannot be determined from this information.
Aa
The offspring of a monohybrid testcross would have what possible genotype(s)? a. AA and Aa. b. Aa and aa. c. AA, Aa, and aa. d. AA only. e. aa only.
Aa and aa.
Some plants fail to produce chlorophyll, and this trait appears to be recessive. Many plants also self-pollinate. If we locate a pea plant that is heterozygous for this trait, self-pollinate it and harvest seeds, what are the likely phenotypes of these seeds when they germinate? a. All will be green with chlorophyll since that is the dominant trait. b. All will be white and lack chlorophyll since this is self-pollinated. c. About one-half will be green and one-half white since that is the distribution of the genes in the parents. d. About one-fourth will be white and three-fourths green since it is similar to a monohybrid cross between heterozygotes. e. About one-fourth will be green and three-fourths white since it is similar to a monohybrid cross between heterozygotes.
About one-fourth will be white and three-fourths green since it is similar to a monohybrid cross between heterozygotes.
If gametes had the same number of chromosomes as body cells, and an organism had 12 chromosomes in its body cells, how many chromosomes would it have after three generations? How does this illustrate the necessity of meiosis for gamete formation?
After three generations: 96 chromosomes Meiosis is necessary because it splits the chromosomes in half.
Why do cells go through cell division? a. Growth b. Reproduction c. Repair d. All of the above
All of the above
Which characteristic of pea plants were important in their selection as Mendel's research organism? a. Peas are easy to cultivate. b. Pea plants have a short generation time. c. Pea plants are self-pollinating but can be cross-fertilized easily. d. Many true-breeding varieties were available. e. All of the above were important characteristics in Mendel's selection.
All of the above were important characteristics in Mendel's selection.
In the use of a Punnett square for genetic results of crossing individuals a. all different kinds of sperm are lined up either horizontally or vertically. b. all different kinds of eggs are lined up either horizontally or vertically. c. the results show the offspring's expected genotypes. d. All of the choices are correct e. A and B only.
All of the choices are correct.
As many as 60 % of people in malaria-infected regions of Africa have the sickle-cell allele, but only about 10% of the U.S. population of African ancestry carries the allele. Malaria remains a major disease in central Africa but has not been a serious problem in the U.S. for many generations. What is/are the reason(s) for the difference in the percentages and what is a reasonable statement about future percentages? a. The presence of malaria in Africa maintains the advantage of the heterozygous sickle-cell trait, and the prevalence of malaria will likely continue to preserve the 60% rate. b. The U. S. percentage may have always been somewhat lower due to immigration from nonmalaria regions, but changes in sites and rates of immigration could occur. c. Lack of widespread malaria in the United States would have made both homozygous and heterozygous carriers of sickle-cell undergo several generations of negative selection, and we should expect this to continue unless innovative therapies give all individuals an equal chance of surviving and reproducing. d. All of the choices are reasonable.
All of the choices are reasonable.
Computer simulations are sometimes used to demonstrate the outcome of monohybrid fruit fly crosses, where a student can run generation after generation of fruit flies with 100 offspring produced each generation, half male and half female, and a 3-to-1 phenotype ratio (or 75 to 25) in the F1 generation. Compared with real genetics results, a. rarely would exactly 100 fly offspring be produced or survive. b. an exact balance between males and females would be rare. c. a precise 3-to-1 ratio would be uncommon. d. All of the choices are true.
All of the choices are true.
Which of the following is/are true about sexual reproduction? a. At the cellular level is the opposite of reproduction since it involves two cells fusing to become one. b. It requires the development of organs such as the uterus, which are of no immediate survival advantage to the individual but are advantageous to the species. c. It regularly produces a wider array of adaptations to the external environment in a shorter period of time. d. It regularly produces a wider array of adaptations to the internal environment (disease agents, parasites) in a shorter period of time. e. All of the choices are true.
All of the choices are true.
In a comparison of the stages of meiosis to the stages of mitosis, which stages are unique to meiosis and which stages have the same events in both meiosis and mitosis?
All of the stages of meiosis I, except possibly telophase I, are unique because homologous chromosomes are separated, not sister chromatids. In some species, the chromosomes do not decondense and the nuclear envelopes do not form in telophase I. All of the stages of meiosis II have the same events as the stages of mitosis, with the possible exception of prophase II. In some species, the chromosomes are still condensed and there is no nuclear envelope. Other than this, all processes are the same.
In pea plants, the gene for round seed (R) is dominant, and wrinkled seeds (r) are recessive. The endosperm of the pea is also either starchy, a dominant gene (S), or waxy (s). What can be said of a fully heterozygous, dihybrid cross? a. It is impossible to secure offspring that are homozygous for both dominant genes. b. It is impossible to secure offspring that are homozygous for both recessive genes. c. It is impossible to secure offspring that are homozygous for one dominant gene such as round seed and homozygous recessive for the other recessive waxy gene. d. All of these choices are impossible combinations in a dihybrid cross. e. All of these choices are possible combinations in a dihybrid cross.
All of these choices are possible combinations in a dihybrid cross.
Which of the following is NOT a difference between anaphase I and anaphase II? a.. At the end of anaphase I, each chromosome is composed of two chromatids and at the end of anaphase II, sister chromatids have separated, becoming daughter chromosomes b. Anaphase I occurs in a haploid cell while anaphase II occurs in a diploid cell. c. Sister chromatids separate during anaphase II while homologous chromosomes separate during anaphase I. d. The cell undergoing anaphase II is genetically different from what it contained while undergoing anaphase I.
Anaphase I occurs in a haploid cell while anaphase II occurs in a diploid cell.
During which phase of mitosis and meiosis will the state of the chromosome be the same? a. Anaphase II and Anaphase b. Prophase II and Prophase c. Metaphase I and Metaphase d. Telophase I and Telophase
Anaphase II and Anaphase
Describe how the duplicated bacterial chromosomes are distributed into new daughter cells without the direction of the mitotic spindle.
As the chromosome is being duplicated, each origin moves away from the starting point of replication. The chromosomes are attached to the cell membrane via proteins; the growth of the membrane as the cell elongates aids in their movement.
When crossing a true-breeding red snapdragon flower with a true-breeding white flower of the same species, we secure all pink offspring. This would seem to support the pre-Mendel view that inheritance is a blending of parental traits. However, Mendel and conventional wisdom agree that "blending" of parental traits is not correct and that particles of inheritance are actually involved because a. in the case of incomplete dominance, only radioactive isotope tracers can follow the actual hereditary particles b. under blending theory, over many generations only the average (or pink flowers) would remain; there would be no way to get back to pure red and white c. it is possible to cross the pink F-1 generation and secure a predictable proportion of pure red and white flowers again, which is not accounted for under the blending theory d. there is no way to directly prove incomplete dominance is not a case of blending, but we can be sure of genes because of the other cases of dominance, etc., where genes are the only logical explanation. e. B and C are true
B and C are true
The particulate theory of inheritance a. preceded Mendel's research by a century. b. was proposed by Mendel. c. is based on particles or hereditary units we now call genes. d. All of the choices are correct. e. B and C only
B and C only
The ability to roll the edges of the tongue upward in a U-shape has been considered to be an inherited ability. The standard assumption is that tongue-rolling is a dominant allele at a single gene locus. Which of the following would cast doubt on this assumption? a. A teacher reports that after testing her class on the ability to roll their tongue, with very little effort the non-tongue-rollers can learn to also roll their tongues. b. A student who can roll his tongue has a mother and father, both of whom cannot. c. A student who cannot roll his tongue has a mother and father, both of whom can. d. Both A and B are situations that would cast doubt on this assumption.
Both A and B are situations that would cast doubt on this assumption.
What steps are necessary for Cdk to become fully active?
Cdk must bind to a cyclin, and it must be phosphorylated in the correct position to become fully active.
Which of the following is not true in regard to crossover? a. Spindle microtubules guide the transfer of DNA across the synaptonemal complex. b. Non-sister chromatids exchange genetic material. c. Chiasmata are formed. d. Recombination nodules mark the crossover point.
Chiasmata are formed.
theory proposing that chromosomes are the vehicles of genes and that their behavior during meiosis is the physical basis of the inheritance patterns that Mendel observed
Chromosomal Theory of Inheritance
Use the probability method to calculate the genotypes and genotypic proportions of a cross between AABBCc and Aabbcc parents.
Considering each gene separately, the cross at A will produce offspring of which half are AA and half are Aa; B will produce all Bb; C will produce half Cc and half cc. Proportions then are (1/2) × (1) × (1/2), or 1/4 AABbCc; continuing for the other possibilities yields 1/4 AABbcc, 1/4 AaBbCc, and 1/4 AaBbcc. The proportions therefore are 1:1:1:1.
In the genus Lacerta are species of lizards that are female and do not mate. They undergo "endomitosis" where one extra chromosome replication results in a tetraploid cell before meiosis begins. Normal female 2n offspring result without fertilization. What change(s) from regular meiosis (in preparation for fertilization) would be required to produce this system? a. The haploid cell products of meiosis II fuse. b. Meiosis stops after meiosis I and does not proceed to meiosis II. c. Cytokinesis does not follow "endomitosis" that results in a tetraploid cell. d. During anaphase II, the sister centromeres fail to separate and daughter cells will not form. e. During anaphase II, the daughter chromosomes are non-disjunctive and are all pulled to one daughter cell.
Cytokinesis does not follow "endomitosis" that results in a tetraploid cell.
Briefly describe the events that occur in each phase of interphase.
During G1, the cell increases in size, the genomic DNA is assessed for damage, and the cell stockpiles energy reserves and the components to synthesize DNA. During the S phase, the chromosomes, the centrosomes, and the centrioles (animal cells) duplicate. During the G2 phase, the cell recovers from the S phase, continues to grow, duplicates some organelles, and dismantles other organelles.
Which of the following statements is correct about the chromosomal position during mitosis and meiosis? a. During metaphase of mitosis the duplicated chromosomes are at the metaphase plate while during metaphase I of meiosis the bivalents are present at the metaphase plate b. During metaphase I of meiosis the duplicated chromosomes are at the metaphase plate while during metaphase of mitosis the bivalents are present at the metaphase plate c. During metaphase of mitosis the homologues separate while during metaphase I of meiosis the sister chromatids separate d. During metaphase I of meiosis the homologues separate while during metaphase of mitosis the sister chromatids separate
During metaphase of mitosis the duplicated chromosomes are at the metaphase plate while during metaphase I of meiosis the bivalents are present at the metaphase plate
Describe the process that results in the formation of a tetrad.
During the meiotic interphase, each chromosome is duplicated. The sister chromatids that are formed during synthesis are held together at the centromere region by cohesin proteins. All chromosomes are attached to the nuclear envelope by their tips. As the cell enters prophase I, the nuclear envelope begins to fragment, and the proteins holding homologous chromosomes locate each other. The four sister chromatids align lengthwise, and a protein lattice called the synaptonemal complex is formed between them to bind them together. The synaptonemal complex facilitates crossover between non-sister chromatids, which is observed as chiasmata along the length of the chromosome. As prophase I progresses, the synaptonemal complex breaks down and the sister chromatids become free, except where they are attached by chiasmata. At this stage, the four chromatids are visible in each homologous pairing and are called a tetrad.
Which statement is NOT true about homologues in meiosis I? a. Homologous chromosomes pair to form a tetrad. b. Homologous chromosomes separate and go to different daughter cells. c. Each homologue's centromere splits to form two chromosomes. d. Homologues exchange genetic material between non-sister chromatids. e. Homologues interact with the spindle as if they were one chromosome.
Each homologue's centromere splits to form two chromosomes.
Explain epistatis in terms of its Greek-language roots "standing upon."
Epistasis describes an antagonistic interaction between genes wherein one gene masks or interferes with the expression of another. The gene that is interfering is referred to as epistatic, as if it is "standing upon" the other (hypostatic) gene to block its expression.
first filial generation in a cross; the offspring of the parental generation
F1
. In a classic Mendelian monohybrid cross between a homozygous dominant parent and a homozygous recessive parent, which generation is always completely heterozygous? a. F1 generation b. F2 generation c. F3 generation d. P generation
F1 generation
second filial generation produced when F1 individuals are self-crossed or fertilized with each other
F2
True or False: A change in the chromosome number resulting from nondisjunction is called euploidy.
False
True or False: A lattice holds the members of a bivalent together in such a way that the RNA of the non-sister chromatids is aligned.
False
True or False: Cystic fibrosis and Niemann-Pick Disease are common autosomal dominant disorders.
False
True or False: If an individual is heterozygous for a particular trait, the gametes that individual produces will contain 3/4 dominant and 1/4 recessive alleles.
False
True or False: Only one of the four daughter cells becomes a functional gamete in spermatogenesis
False
True or False: Oogenesis always involves an equal division of cell contents in the formation of an egg and polar bodies
False
True or False: Primary nondisjunction occurs during meiosis II when the sister chromatids fail to separate and both daughter chromosomes go in the same gamete.
False
True or False: The correct number of chromosomes in a species is known as aneuploidy
False
tubulin-like protein component of the prokaryotic cytoskeleton that is important in prokaryotic cytokinesis (name origin: Filamenting temperature-sensitive mutant Z)
FtsZ
distinct from the G1 phase of interphase; a cell in G0 is not preparing to divide
G0 phase
At which of the cell cycle checkpoints do external forces have the greatest influence? a. G1 checkpoint b. G2 checkpoint c. M checkpoint d. G0 checkpoint
G1 checkpoint
(also, first gap) first phase of interphase centered on cell growth during mitosis
G1 phase
Put the following stages of the cell cycle in order: G2, S, G1, M.
G1, S, G2, M
Which of the following shows the correct sequence of the cell cycle? a. Mitosis-> G1->S->G2->cytokinesis b. S->G1-> G2-> mitosis-> cytokinesis c. cytokinesis->mitosis->G1->S->G2 d. G1->S->G2->mitosis->cytokinesis
G1->S->G2->mitosis->cytokinesis
(also, second gap) third phase of interphase during which the cell undergoes final preparations for mitosis
G2 phase
What aspect of Mendel's background gave him the necessary tools to discover the laws of inheritance? a. He was a monk. b. He was a teacher. c. He lived in Austria. d. He had studied mathematics and probability. e. He corresponded with Charles Darwin.
He had studied mathematics and probability.
Which is associated with the inability to produce factor VIII in the blood? a. Williams syndrome b. trisomy 21 c. color-blindness d. Hemophilia A e. Duchenne muscular dystrophy
Hemophilia A
Compare and contrast a human somatic cell to a human gamete.
Human somatic cells have 46 chromosomes: 22 pairs and 2 sex chromosomes that may or may not form a pair. This is the 2n or diploid condition. Human gametes have 23 chromosomes, one each of 23 unique chromosomes, one of which is a sex chromosome. This is the n or haploid condition.
p53 can trigger apoptosis if certain cell cycle events fail. How does this regulatory outcome benefit a multicellular organism?
If a cell has damaged DNA, the likelihood of producing faulty proteins is higher. The daughter cells of such a damaged parent cell would also produce faulty proteins that might eventually become cancerous. If p53 recognizes this damage and triggers the cell to self-destruct, the damaged DNA is degraded and recycled. No further harm comes to the organism. Another healthy cell is triggered to divide instead.
What cell cycle events will be affected in a cell that produces mutated (non-functional) cohesin protein?
If cohesin is not functional, chromosomes are not packaged after DNA replication in the S phase of interphase. It is likely that the proteins of the centromeric region, such as the kinetochore, would not form. Even if the mitotic spindle fibers could attach to the chromatids without packing, the chromosomes would not be sorted or separated during mitosis.
Outline the steps that lead to a cell becoming cancerous.
If one of the genes that produces regulator proteins becomes mutated, it produces a malformed, possibly non-functional, cell cycle regulator, increasing the chance that more mutations will be left unrepaired in the cell. Each subsequent generation of cells sustains more damage. The cell cycle can speed up as a result of the loss of functional checkpoint proteins. The cells can lose the ability to self-destruct and eventually become "immortalized."
Which is NOT true about daughter cells of mitosis or meiosis? a. In meiosis, daughter cells are haploid. b. In meiosis, there are four daughter cells. c. In mitosis, there are two daughter cells. d. In mitosis, the daughter cells are genetically identical. e. In meiosis, the daughter cells are genetically identical.
In meiosis, the daughter cells are genetically identical.
What is the function of the fused kinetochore found on sister chromatids in prometaphase I?
In metaphase I, the homologous chromosomes line up at the metaphase plate. In anaphase I, the homologous chromosomes are pulled apart and move to opposite poles. Sister chromatids are not separated until meiosis II. The fused kinetochore formed during meiosis I ensures that each spindle microtubule that binds to the tetrad will attach to both sister chromatids.
What phase does a cell stay in the longest?
Interphase
Interkinesis is different from interphase in which way? a. Interkinesis occurs after a cell finishes a nuclear division. b. Interkinesis is the stage that precedes a prophase stage. c. Interphase involves DNA replication and interkinesis does not. d. Interkinesis can be variable in length.
Interphase involves DNA replication and interkinesis does not.
What is the role of the spindle during mitosis?
It helps separate the chromosomes
What is the importance of crossing-over? a. It provides extra genetic material for the daughter cells. b. It increases the likelihood that daughter cells contain different genetic material. c. It produces the proteins that are associated with DNA in chromosomes. d. It increases chromosome condensation. e. It separates the homologous chromosomes
It increases the likelihood that daughter cells contain different genetic material.
The genotype XXY corresponds to
Klinefelter syndrome
List some reasons why a cell that has just completed cytokinesis might enter the G0 phase instead of the G1 phase.
Many cells temporarily enter G0 until they reach maturity. Some cells are only triggered to enter G1 when the organism needs to increase that particular cell type. Some cells only reproduce following an injury to the tissue. Some cells never divide once they reach maturity.
In which phase of mitosis do the sister chromatids line up on the equator of the cell?
Metaphase
Which of the following statements about nondisjunction is true? a. Nondisjunction only results in gametes with n+1 or n-1 chromosomes. b. Nondisjunction occurring during meiosis II results in 50 percent normal gametes. c. Nondisjunction during meiosis I results in 50 percent normal gametes. d. Nondisjunction always results in four different kinds of gametes.
Nondisjunction occurring during meiosis II results in 50 percent normal gametes.
Which is NOT true according to Mendel's law of segregation? a. Each individual contains two factors for each trait. b. One factor must be dominant and one factor recessive in each individual. c. Factors separate from each other during gamete formation. d. Each gamete contains one copy of each factor. e. Fertilization restores the presence of two factors.
One factor must be dominant and one factor recessive in each individual.
parental generation in a cross
P0
Explain the roles of the positive cell cycle regulators compared to the negative regulators.
Positive cell regulators such as cyclin and Cdk perform tasks that advance the cell cycle to the next stage. Negative regulators such as Rb, p53, and p21 block the progression of the cell cycle until certain events have occurred.
In which phase of mitosis does the nucleus disappear, centrioles move to the poles, and chromosomes condense into sister chromatids?
Prophase
visual representation of a cross between two individuals in which the gametes of each individual are denoted along the top and side of a grid, respectively, and the possible zygotic genotypes are recombined at each box in the grid
Punnett square
Explain how the random alignment of homologous chromosomes during metaphase I contributes to the variation in gametes produced by meiosis.
Random alignment leads to new combinations of traits. The chromosomes that were originally inherited by the gamete-producing individual came equally from the egg and the sperm. In metaphase I, the duplicated copies of these maternal and paternal homologous chromosomes line up across the center of the cell. The orientation of each tetrad is random. There is an equal chance that the maternally derived chromosomes will be facing either pole. The same is true of the paternally derived chromosomes. The alignment should occur differently in almost every meiosis. As the homologous chromosomes are pulled apart in anaphase I, any combination of maternal and paternal chromosomes will move toward each pole. The gametes formed from these two groups of chromosomes will have a mixture of traits from the individual's parents. Each gamete is unique.
Rb is a negative regulator that blocks the cell cycle at the G1 checkpoint until the cell achieves a requisite size. What molecular mechanism does Rb employ to halt the cell cycle?
Rb is active when it is dephosphorylated. In this state, Rb binds to E2F, which is a transcription factor required for the transcription and eventual translation of molecules required for the G1/S transition. E2F cannot transcribe certain genes when it is bound to Rb. As the cell increases in size, Rb becomes phosphorylated, inactivated, and releases E2F. E2F can then promote the transcription of the genes it controls, and the transition proteins will be produced.
Which of the following statements is true? a. Recombination of the body color and red/cinnabar eye alleles will occur more frequently than recombination of the alleles for wing length and aristae length. b. Recombination of the body color and aristae length alleles will occur more frequently than recombination of red/brown eye alleles and the aristae length alleles. c. Recombination of the gray/black body color and long/short aristae alleles will not occur. d. Recombination of the red/brown eye and long/short aristae alleles will occur more frequently than recombination of the alleles for wing length and body color.
Recombination of the red/brown eye and long/short aristae alleles will occur more frequently than recombination of the alleles for wing length and body color.
List the regulatory mechanisms that might be lost in a cell producing faulty p53.
Regulatory mechanisms that might be lost include monitoring of the quality of the genomic DNA, recruiting of repair enzymes, and the triggering of apoptosis.
DNA is replicated during ______ of the cell cycle.
S
Chromosomes are duplicated during what stage of the cell cycle?
S phase
What phase of mitotic interphase is missing from meiotic interkinesis? a. G0 phase b. G1 phase c. S phase d. G2 phase
S phase
second, or synthesis, stage of interphase during which DNA replication occurs
S phase
What is a likely evolutionary advantage of sexual reproduction over asexual reproduction? a. Sexual reproduction involves fewer steps. b. There is a lower chance of using up the resources in a given environment. c. Sexual reproduction results in variation in the offspring. d. Sexual reproduction is more cost-effective.
Sexual reproduction results in variation in the offspring.
It could be said that males are able to provide gametes with more genetic diversity than females for reproduction. One main reason would be: a. Males provide more genes in sperm than females provide in eggs. b. Crossing over occurs more often in the formation of sperm than in eggs. c. Spermatogenesis in males results in four functional sperm while oogenesis in females results in only one egg and three structures that contain genetic information that is lost when they disintegrate. d. Sperm that contain a recombination of genes are usually more successful in fertilizing an
Spermatogenesis in males results in four functional sperm while oogenesis in females results in only one egg and three structures that contain genetic information that is lost when they disintegrate.
Explain how the Chromosomal Theory of Inheritance helped to advance our understanding of genetics.
The Chromosomal Theory of Inheritance proposed that genes reside on chromosomes. The understanding that chromosomes are linear arrays of genes explained linkage, and crossing over explained recombination.
Eukaryotic chromosomes are thousands of times longer than a typical cell. Explain how chromosomes can fit inside a eukaryotic nucleus.
The DNA double helix is wrapped around histone proteins to form structures called nucleosomes. Nucleosomes and the linker DNA in between them are coiled into a 30-nm fiber. During cell division, chromatin is further condensed by packing proteins.
Describe the general conditions that must be met at each of the three main cell cycle checkpoints.
The G1 checkpoint monitors adequate cell growth, the state of the genomic DNA, adequate stores of energy, and materials for S phase. At the G2 checkpoint, DNA is checked to ensure that all chromosomes were duplicated and that there are no mistakes in newly synthesized DNA. Additionally, cell size and energy reserves are evaluated. The M checkpoint confirms the correct attachment of the mitotic spindle fibers to the kinetochores.
Name the common components of eukaryotic cell division and binary fission.
The common components of eukaryotic cell division and binary fission are DNA duplication, segregation of duplicated chromosomes, and division of the cytoplasmic contents.
There is a species of desert lizard where only females are known to exist-there are no males known. It is nevertheless necessary for two females to court and for one to assume the posture of a male to stimulate the female to produce eggs. No fertilization can occur, and the eggs develop into female lizards. What is the probable evolutionary mechanism for this occurring? a. The species is probably going extinct. b. The desert is relatively uniform and there is little advantage to maintaining variation, but the animal has not been able to completely evolve away from its heritage of sexual reproduction. c. This switch in mating behavior is the direct physical reflection of crossing-over. d. This is probably an asexual organism attempting to mimic sexual reproduction.
The desert is relatively uniform and there is little advantage to maintaining variation, but the animal has not been able to completely evolve away from its heritage of sexual reproduction.
Which of the following statements is true about the life cycle of animals? a. The gametes are the haploid phase of the animals life cycle. b. The gametes are the diploid phase of the life cycle. c. The products of the haploid phase of the life cycle are larger than those of the diploid phase. d. Meiosis is not a necessary component of the animal life cycle.
The gametes are the haploid phase of the animals life cycle.
Describe one of the reasons why the garden pea was an excellent choice of model system for studying inheritance.
The garden pea is sessile and has flowers that close tightly during self-pollination. These features help to prevent accidental or unintentional fertilizations that could have diminished the accuracy of Mendel's data.
What is the relationship between a genome, chromosomes, and genes?
The genome consists of the sum total of an organism's chromosomes. Each chromosome contains hundreds and sometimes thousands of genes, segments of DNA that code for a polypeptide or RNA, and a large amount of DNA with no known function.
Which of the following is the correct order of events in mitosis? a. Sister chromatids line up at the metaphase plate. The kinetochore becomes attached to the mitotic spindle. The nucleus reforms and the cell divides. Cohesin proteins break down and the sister chromatids separate. b. The kinetochore becomes attached to the mitotic spindle. Cohesin proteins break down and the sister chromatids separate. Sister chromatids line up at the metaphase plate. The nucleus reforms and the cell divides. c. The kinetochore becomes attached to the cohesin proteins. Sister chromatids line up at the metaphase plate. The kinetochore breaks down and the sister chromatids separate. The nucleus reforms and the cell divides. d. The kinetochore becomes attached to the mitotic spindle. Sister chromatids line up at the metaphase plate. Cohesin proteins break down and the sister chromatids separate. The nucleus reforms and the cell divides.
The kinetochore becomes attached to the mitotic spindle. Sister chromatids line up at the metaphase plate. Cohesin proteins break down and the sister chromatids separate. The nucleus reforms and the cell divides.
Chemotherapy drugs such as vincristine and colchicine disrupt mitosis by binding to tubulin (the subunit of microtubules) and interfering with microtubule assembly and disassembly. Exactly what mitotic structure is targeted by these drugs and what effect would that have on cell division?
The mitotic spindle is formed of microtubules. Microtubules are polymers of the protein tubulin; therefore, it is the mitotic spindle that is disrupted by these drugs. Without a functional mitotic spindle, the chromosomes will not be sorted or separated during mitosis. The cell will arrest in mitosis and die.
Lethal genes (genes that result in the failure to develop a vital organ or metabolic pathway) are nearly always recessive. Animal breeders who discover a unique trait and selectively breed to increase the occurrence of that trait often encounter a noticeable increase in lethal genes. Why? a. The lethal recessive gene may be incompletely dominant. b. Spreading the gene among offspring of both sexes will increase the likelihood it will be sex-linked and expressed. c. The selective-mating of closely related individuals, or inbreeding, increases chances that two recessive genes will "meet" in offspring. d. "Pleiotropy" - the gene that is being selected for this trait may have the second effect of being lethal. e. "Epistasis" - selection for the desired trait may result in "uncovering" the lethal gene.
The selective-mating of closely related individuals, or inbreeding, increases chances that two recessive genes will "meet" in offspring.
Describe the similarities and differences between the cytokinesis mechanisms found in animal cells versus those in plant cells.
There are very few similarities between animal cell and plant cell cytokinesis. In animal cells, a ring of actin fibers is formed around the periphery of the cell at the former metaphase plate (cleavage furrow). The actin ring contracts inward, pulling the plasma membrane toward the center of the cell until the cell is pinched in two. In plant cells, a new cell wall must be formed between the daughter cells. Due to the rigid cell walls of the parent cell, contraction of the middle of the cell is not possible. Instead, a phragmoplast first forms. Subsequently, a cell plate is formed in the center of the cell at the former metaphase plate. The cell plate is formed from Golgi vesicles that contain enzymes, proteins, and glucose. The vesicles fuse and the enzymes build a new cell wall from the proteins and glucose. The cell plate grows toward and eventually fuses with the cell wall of the parent cell.
Why do polar bodies form? a. They nurse the egg as it leaves the follicle. b. This is extra chromosomal material representing the X chromosome in each female cell. c. They orient the sperm toward the egg. d. They allow a reduction in chromosomes while preserving all the food for one egg. e. They orient the egg for penetration by the sperm.
They allow a reduction in chromosomes while preserving most of the cytoplasm for one egg.
True or False: Aneuploidy is a change in the number of chromosomes resulting from nondisjunction during meiosis.
True
True or False: Each gamete carries one factor, now called an allele, for each inherited trait.
True
True or False: Extra copies of sex chromosomes are more easily tolerated in humans than extra copies of autosomes.
True
True or False: In a case of incomplete dominance, the phenotypic ratio of the F2 generation is the same as the genotypic ratio.
True
True or False: It is estimated that an average of two or three cross-overs occur per human chromosome.
True
True or False: Jacobs Syndrome, XYY, results from nondisjunction during spermatogenesis.
True
True or False: Monosomy occurs when an individual has only one of a particular type of chromosome.
True
True or False: Polygenic traits such as height or weight are often influenced by the environment of the organism.
True
True or False: Sex chromosome aneuploids are better tolerated and have a better chance of producing survivors.
True
In 1940, two researchers named Weiner and Landsteiner discovered that about 85 percent of the human population sampled possessed a blood cell protein that had been previously detected in Rhesus monkeys. This blood type was labeled Rh positive, and Rh+ was found to be dominant over the absence of the blood factor (Rh). Under normal Mendelian inheritance, which of the following statements is FALSE? a. Two Rh+ parents could have an Rhchild. b. Two Rhparents could have an Rh+ child. c. An Rhchild would require that both parents be carriers of at least one Rhgene. d. It is possible with just one pair of parents to have children where some siblings are Rhand some are Rh+ . e. All of the choices are false.
Two Rh- parents could have an Rh+ child.
Unattached earlobes (EE or Ee) are described in the textbook as dominant over attached earlobes (ee). A couple both have unattached earlobes. Both notice that one of their parents on both sides has attached earlobes (ee). Therefore, they correctly assume that they are carriers for attached earlobes (Ee). The couple proceeds to have four children. a. They can be certain that three will be heterozygous and one homozygous recessive. b. If the first three are heterozygous, the fourth must be homozygous recessive. c. The children must repeat the grandparents' genotype (Ee). d. All children must have unattached earlobes since both parents possess the dominant gene for it. e. Two heterozygous, one homozygous recessive and one homozygous dominant is a likely outcome, but all heterozygous, or two, three or all four homozygous are also possible.
Two heterozygous, one homozygous recessive and one homozygous dominant is a likely outcome, but all heterozygous, or two, three or all four homozygous are also possible.
How would you perform a reciprocal cross for the characteristic of stem height in the garden pea?
Two sets of P0 parents would be used. In the first cross, pollen would be transferred from a true-breeding tall plant to the stigma of a true-breeding dwarf plant. In the second cross, pollen would be transferred from a true-breeding dwarf plant to the stigma of a true-breeding tall plant. For each cross, F1 and F2 offspring would be analyzed to determine if offspring traits were affected according to which parent donated each trait.
Abnormalities in the number of X chromosomes tends to have milder phenotypic effects than the same abnormalities in autosomes because of ________.
X inactivation
condensation of X chromosomes into Barr bodies during embryonic development in females to compensate for the double genetic dose
X inactivation
gene present on the X, but not the Y chromosome
X-linked
Generally, it is not possible to determine whether nondisjunction failed to occur in oogenesis or spermatogenesis. However, it is possible to assert that _________ resulted in nondisjunction in __________. a. XXY; oogenesis b. XYY; spermatogenesis c. XXX; oogenesis d. XXY; spermatogenesis e. XO; oogenesis
XYY; spermatogenesis
If a mutation occurs so that a fungus is no longer able to produce a minus mating type, will it still be able to reproduce?
Yes, it will be able to reproduce asexually.
The polar body is a. another name for an egg cell. b. a precursor cell that becomes an egg cell. c. a nonfunctional cell rudiment formed at the same time as an egg cell. d. the cell produced when fertilization occurs.
a nonfunctional cell rudiment formed at the same time as an egg cell.
To what does the term chiasma refer? a. the process of fertilization b. the life cycle of a fungus c. the process of crossing-over d. a structure that holds together homologues during crossing-over e. the period between meiosis I and meiosis II
a structure that holds together homologues during crossing-over
List and briefly describe the three processes that lead to variation in offspring with the same parents.
a. Crossover occurs in prophase I between non-sister homologous chromosomes. Segments of DNA are exchanged between maternally derived and paternally derived chromosomes, and new gene combinations are formed. b. Random alignment during metaphase I leads to gametes that have a mixture of maternal and paternal chromosomes. c. Fertilization is random, in that any two gametes can fuse.
Compare the three main types of life cycles in multicellular organisms and give an example of an organism that employs each.
a. In the haploid-dominant life cycle, the multicellular stage is haploid. The diploid stage is a spore that undergoes meiosis to produce cells that will divide mitotically to produce new multicellular organisms. Fungi have a haploid-dominant life cycle. b. In the diploid-dominant life cycle, the most visible or largest multicellular stage is diploid. The haploid stage is usually reduced to a single cell type, such as a gamete or spore. Animals, such as humans, have a diploid-dominant life cycle. c. In the alternation of generations life cycle, there are both haploid and diploid multicellular stages, although the haploid stage may be completely retained by the diploid stage. Plants have a life cycle with alternation of generations.
What is the main prerequisite for clearance at the G2 checkpoint? a. cell has reached a sufficient size b. an adequate stockpile of nucleotides c. accurate and complete DNA replication d. proper attachment of mitotic spindle fibers to kinetochores
accurate and complete DNA replication
gene variations that arise by mutation and exist at the same relative locations on homologous chromosomes
allele
Which type of life cycle has both a haploid and diploid multicellular stage? a. asexual b. diploid-dominant c. haploid-dominant d. alternation of generations
alternation of generations
life-cycle type in which the diploid and haploid stages alternate
alternation of generations
What are alleles? a. genes for different traits, such as hair color or eye color b. alternative forms of a gene for a single trait, such as blue eyes or brown eyes c. the locations of genes on a chromosome d. recessive forms of a kind of characteristic carried by genes e. dominant forms of a kind of characteristic carried by genes
alternative forms of a gene for a single trait, such as blue eyes or brown eyes
What is the blending theory of inheritance? a. Mendel's theory of how the traits of parents are passed to offspring through the gametes b. Darwin's theory of how traits are passed from all parts of the parent's body into the gamete to be transmitted to the offspring c. the modern theory of how genetic information is passed from parents to offspring d. an old theory that said that offspring show traits intermediate between those of the parents
an old theory that said that offspring show traits intermediate between those of the parents
If the M checkpoint is not cleared, what stage of mitosis will be blocked? a. prophase b. prometaphase c. metaphase d. anaphase
anaphase
Separation of the sister chromatids is a characteristic of which stage of mitosis? a. prometaphase b. metaphase c. anaphase d. telophase
anaphase
The phase of mitosis in which the sister chromatids separate from each other
anaphase
stage of mitosis during which sister chromatids are separated from each other
anaphase
During which stage of meiosis does homologue separation occur? a. prophase I b. anaphase I c. telophase I d. prophase II e. anaphase II
anaphase I
At which stage of meiosis are sister chromatids separated from each other? a. prophase I b. prophase II c. anaphase I d. anaphase II
anaphase II
At which stage of meiosis is each chromosome composed of a single chromatid? a. prophase I b. metaphase II c. anaphase II d. prophase II e. metaphase I
anaphase II
individual with an error in chromosome number; includes deletions and duplications of chromosome segments
aneuploid
Mendel performed hybridizations by transferring pollen from the _______ of the male plant to the female ova.
anther
any of the non-sex chromosomes
autosome
In bacterial cell, the cell divides into two nearly two nearly equal halves. This process is referred to as:
binary fission
prokaryotic cell division process
binary fission
7. Another name for a tetrad is a/an a. homologue. b. bivalent. c. öocyte. d. gamete. e. polar body.
bivalent.
Identify which event will occur during Prophase I of meiosis but does not occur during prophase of mitosis. a. bivalents will form b. nuclear envelope will dissolve c. centrioles will form in animal cells d. chromatin will condense into chromosomes
bivalents will form
hypothetical inheritance pattern in which parental traits are blended together in the offspring to produce an intermediate physical appearance
blending theory of inheritance
Which of the following crosses would always result in offspring that only display the dominant phenotype? a. TT x tt b. Tt x Tt c. TT x TT d. Tt x tt e. both A and C
both A and C
Women with X-linked disorders always pass the genes for the disorder to ______, while men with X-linked disorders always pass the genes for the disorder to _______. a. only their daughters; only their daughters b. both their daughters and sons; only their sons c. both their daughters and sons; only their daughters d. both their daughters and sons; their daughters and sons
both their daughters and sons; only their daughters
Many of the negative regulator proteins of the cell cycle were discovered in what type of cells? a. gametes b. cells in G0 c. cancer cells d. stem cells
cancer cells
Homologous chromosomes are similar in all of these characteristics EXCEPT: a. similar in size. b. carry the same alleles for all traits. c. carry genes for the same traits. d. similar in shape and location of the centromere.
carry the same alleles for all traits.
ordered sequence of events that a cell passes through between one cell division and the next
cell cycle
ordered series of events involving cell growth and cell division that produces two new daughter cells
cell cycle
mechanism that monitors the preparedness of a eukaryotic cell to advance through the various cell cycle stages
cell cycle checkpoint
FtsZ proteins direct the formation of a _______ that will eventually form the new cell walls of the daughter cells.
cell plate
The fusing of Golgi vesicles at the metaphase plate of dividing plant cells forms what structure? a. cell plate b. actin ring c. cleavage furrow d. mitotic spindle
cell plate
structure formed during plant cell cytokinesis by Golgi vesicles, forming a temporary structure (phragmoplast) and fusing at the metaphase plate; ultimately leads to the formation of cell walls that separate the two daughter cells
cell plate
(also, map unit) relative distance that corresponds to a recombination frequency of 0.01
centimorgan (cM)
rod-like structure constructed of microtubules at the center of each animal cell centrosome
centriole
By definition, a pericentric inversion includes the ________.
centromere
The ___________ holds the replicated sister chromatids together.
centromere
region at which sister chromatids are bound together; a constricted area in condensed chromosomes
centromere
The mitotic spindles arise from which cell structure? a. centromere b. centrosome c. kinetochore d. cleavage furrow
centrosome
All of the following are true concerning Down Syndrome EXCEPT a. it is caused by autosomal trisomy 21 b. in 23% of cases, the sperm contributes the extra chromosome c. it is the most common trisomy in humans d. chances of a woman having a child with Down Syndrome decreases with her age
chances of a woman having a child with Down Syndrome decreases with her age
(singular, chiasma) the structure that forms at the crossover points after genetic material is exchanged
chiasmata
At metaphase I, homologous chromosomes are connected only at what structures? a. chiasmata b. recombination nodules c. microtubules d. kinetochores
chiasmata
The first suggestion that chromosomes may physically exchange segments came from the microscopic identification of ________.
chiasmata
single DNA molecule of two strands of duplicated DNA and associated proteins held together at the centromere
chromatid
detachment, 180° rotation, and reinsertion of a chromosome arm
chromosome inversion
constriction formed by an actin ring during cytokinesis in animal cells that leads to cytoplasmic division
cleavage furrow
in a heterozygote, complete and simultaneous expression of both alleles for the same characteristic
codominance
proteins that form a complex that seals sister chromatids together at their centromeres until anaphase II of meiosis
cohesion
proteins that help sister chromatids coil during prophase
condensin
inheritance pattern in which a character shows a range of trait values with small gradations rather than large gaps between them
continuous variation
Which of the following events occurs during prophase I but does not occur during prophase of mitosis? a. crossing over b. nuclear envelope dissolves c. chromatin condenses into chromosomes d. centrioles appear in animal cells
crossing over
Which of the following steps would NOT lead to variation of genetic material? a. crossing over of homologous chromosomes b. crossing over of sister chromatids c. the random alignment of the chromosomes during metaphase I d. the combination of sperm and egg genes.
crossing over of sister chromatids
exchange of genetic material between non-sister chromatids resulting in chromosomes that incorporate genes from both parents of the organism
crossover
one of a group of proteins that act in conjunction with cyclin-dependent kinases to help regulate the cell cycle by phosphorylating key proteins; the concentrations of cyclins fluctuate throughout the cell cycle
cyclin
one of a group of protein kinases that helps to regulate the cell cycle when bound to cyclin; it functions to phosphorylate other proteins that are either activated or inactivated by phosphorylation
cyclin-dependent kinase
Which protein is a positive regulator that phosphorylates other proteins when activated? a. p53 b. retinoblastoma protein (Rb) c. cyclin d. cyclin-dependent kinase (Cdk)
cyclin-dependent kinase (Cdk)
The most common lethal genetic disease among Caucasians is a. neurofibromatosis. b. Tay-Sachs disease. c. phenylketonuria. d. albinism. e. cystic fibrosis.
cystic fibrosis.
division of the cytoplasm following mitosis that forms two daughter cells.
cytokinesis
You get one homologous chromosome from your ________ and one from your _______.
dad, mom
result of a cross between two true-breeding parents that express different traits for two characteristics
dihybrid
In what kind of classic Mendelian cross would you expect to find a ratio of 9:3:3:1 among the F2 offspring? a. monohybrid cross b. dihybrid cross c. testcross d. None of the choices is correct.
dihybrid cross
cell, nucleus, or organism containing two sets of chromosomes (2n)
diploid
life-cycle type in which the multicellular diploid stage is prevalent
diploid-dominant
inheritance pattern in which traits are distinct and are transmitted independently of one another
discontinuous variation
trait which confers the same physical appearance whether an individual has two copies of the trait or one copy of the dominant trait and one copy of the recessive trait
dominant
inheritance pattern in which an allele is lethal both in the homozygote and the heterozygote; this allele can only be transmitted if the lethality phenotype occurs after reproductive age
dominant lethal
The water buttercup produces thin leaves underwater, but those same tissues will produce broad leaves above the water. Individuals in the 1800's (when hunger and childhood diseases were common) averaged slightly over five feet tall, but their offspring in the 1900's were substantially taller on the average. This reflects the influence of a. polygenic inheritance. b. epistasis. c. gene linkage. d. genotype having no relationship to phenotype. e. environmental factors on gene expression
environmental factors on gene expression
antagonistic interaction between genes such that one gene masks or interferes with the expression of another
epistasis
individual with the appropriate number of chromosomes for their species
euploid
union of two haploid cells from two individual organisms
fertilization
Meiosis produces ________ daughter cells.
four haploid
haploid reproductive cell or sex cell (sperm, pollen grain, or egg)
gamete
a multicellular haploid life-cycle stage that produces gametes
gametophyte
physical and functional unit of heredity, a sequence of DNA that codes for a protein.
gene
___________ are changes to the order of nucleotides in a segment of DNA that codes for a protein.
gene mutations
An organism's traits are determined by the specific combination of inherited _____.
genes.
total genetic information of a cell or organism
genome
underlying genetic makeup, consisting of both physically visible and non-expressed alleles, of an organism
genotype
specialized cell line that produces gametes, such as eggs or sperm
germ cells
G1 is associated with what event?
growth of cell content
The overall function of meiosis includes all of the following EXCEPT a. gamete production. b. reduction of chromosome number (from 2N to N). c. providing genetic variation in sexually reproducing organisms. d. growth of the overall individual.
growth of the overall individual.
cell, nucleus, or organism containing one set of chromosomes (n)
haploid
Fungi typically display which type of life cycle? a. diploid-dominant b. haploid-dominant c. alternation of generations d. asexual
haploid-dominant
life-cycle type in which the multicellular haploid stage is prevalent
haploid-dominant
presence of only one allele for a characteristic, as in X-linkage; hemizygosity makes descriptions of dominance and recessiveness irrelevant
hemizygous
having two different alleles for a given gene on the homologous chromosome
heterozygous
The first level of DNA organization in a eukaryotic cell is maintained by which molecule? a. cohesin b. condensin c. chromatin d. histone
histone
one of several similar, highly conserved, low molecular weight, basic proteins found in the chromatin of all eukaryotic cells; associates with DNA to form nucleosomes
histone
The chromosomes that pair up during meiosis, are called __________ chromosomes.
homologous
A pair of identical chromosomes shown in a karyotype, one inherited from mom, and one inherited from dad are called
homologous chromosomes
The two copies of each type of chromosome found in normal somatic cells in an organism, throughout the cell cycle, are called:
homologous chromosomes
chromosomes of the same morphology with genes in the same location; diploid organisms have pairs of homologous chromosomes (homologs), with each homolog derived from a different parent
homologous chromosomes
process by which homologous chromosomes undergo reciprocal physical exchanges at their arms, also known as crossing over
homologous recombination
A recessive trait will be observed in individuals that are ________ for that trait.
homozygous
having two identical alleles for a given gene on the homologous chromosome
homozygous
A testcross involves an individual exhibiting the dominant phenotype but an unknown genotype being crossed with an individual that has a(n) ___________ genotype. a. homozygous dominant b. heterozygous dominant c. homozygous recessive d. any of the choices
homozygous recessive
process of mating two individuals that differ with the goal of achieving a certain characteristic in their offspring
hybridization
In mitosis, the two resulting nuclei are
identical to the starting cell and identical to each other.
In human females, when is meiosis II completed? a. at ovulation b. immediately after the sperm penetration of the secondary oocyte c. immediately after the sperm penetrates the primary oocyte d. None of the choices are correct.
immediately after the sperm penetration of the secondary oocyte
X-linked recessive traits in humans (or in Drosophila) are observed ________. a. in more males than females b. in more females than males c. in males and females equally d. in different distributions depending on the trait
in more males than females
If black and white true-breeding mice are mated and the result is all gray offspring, what inheritance pattern would this be indicative of? a. dominance b. codominance c. multiple alleles d. incomplete dominance
incomplete dominance
in a heterozygote, expression of two contrasting alleles such that the individual displays an intermediate phenotype
incomplete dominance
During _______________ the homologous chromosome pairs separate in a random fashion leading to genetic diversity among the offspring.
independent assortment
(also, interphase II) brief period of rest between meiosis I and meiosis II
interkinesis
The cell spends most of it's life in ________________.
interphase
period of the cell cycle leading up to mitosis; includes G1, S, and G2 phases (the interim period between two consecutive cell divisions
interphase
photographic image of a karyotype
karyogram
Which eukaryotic cell cycle event is missing in binary fission? a. cell growth b. DNA duplication c. karyokinesis d. cytokinesis
karyokinesis
mitotic nuclear division
karyokinesis
number and appearance of an individuals chromosomes; includes the size, banding patterns, and centromere position
karyotype
protein structure associated with the centromere of each sister chromatid that attracts and binds spindle microtubules during prometaphase
kinetochore
In agriculture, polyploid crops (like coffee, strawberries, or bananas) tend to produce ________.
larger yields
in a heterozygote, one trait will conceal the presence of another trait for the same characteristic
law of dominance
genes do not influence each other with regard to sorting of alleles into gametes; every possible combination of alleles is equally likely to occur
law of independent assortment
paired unit factors (i.e., genes) segregate equally into gametes such that offspring have an equal likelihood of inheriting any combination of factors
law of segregation
the sequence of events in the development of an organism and the production of cells that produce offspring
life cycle
phenomenon in which alleles that are located in close proximity to each other on the same chromosome are more likely to be inherited together
linkage
The location on a chromosome where a particular gene is located is known as the:
locus
position of a gene on a chromosome
locus
Assume a pericentric inversion occurred in one of two homologs prior to meiosis. The other homolog remains normal. During meiosis, what structure—if any—would these homologs assume in order to pair accurately along their lengths? a. V formation b. cruciform c. loop d. pairing would not be possible
loop
Responsible for creating sex cells are gametes called sperm and egg.
meiosis
a nuclear division process that results in four haploid cells
meiosis
first round of meiotic cell division; referred to as reduction division because the ploidy level is reduced from diploid to haploid
meiosis I
The part of meiosis that is similar to mitosis is ________.
meiosis II
second round of meiotic cell division following meiosis I; sister chromatids are separated into individual chromosomes, and the result is four unique haploid cells
meiosis II
stage of mitosis during which chromosomes are aligned at the metaphase plate
metaphase
During which stage of meiosis are the bivalents arranged along the equator? a. prophase I b. metaphase II c. anaphase II d. prophase II e. metaphase I
metaphase I
equatorial plane midway between the two poles of a cell where the chromosomes align during metaphase
metaphase plate
(also, karyokinesis) period of the cell cycle during which the duplicated chromosomes are separated into identical nuclei; includes prophase, prometaphase, metaphase, anaphase, and telophase
mitosis
The division of the nucleus is known as:
mitosis
period of the cell cycle during which duplicated chromosomes are distributed into two nuclei and cytoplasmic contents are divided; includes karyokinesis (mitosis) and cytokinesis
mitotic phase
apparatus composed of microtubules that orchestrates the movement of chromosomes during mitosis
mitotic spindle
species or biological system used to study a specific biological phenomenon to be applied to other different species
model system
result of a cross between two true-breeding parents that express different traits for only one characteristic
monohybrid
otherwise diploid genotype in which one chromosome is missing
monosomy
The ABO blood groups in humans are expressed as the IA, IB, and i alleles. The IA allele encodes the A blood group antigen, IB encodes B, and i encodes O. Both A and B are dominant to O. If a heterozygous blood type A parent (IAi) and a heterozygous blood type B parent (IBi) mate, one quarter of their offspring will have AB blood type (IAIB) in which both antigens are expressed equally. Therefore, ABO blood groups are an example of: a. multiple alleles and incomplete dominance b. codominance and incomplete dominance c. incomplete dominance only d. multiple alleles and codominance
multiple alleles and codominance
Since each child of two heterozygous parents has a 1/2 chance of receiving a recessive trait from each parent, a. if the first child is phenotypically recessive, then the next child must be phenotypically dominant. b. if the first child is phenotypically recessive, then the next child has a 3/4 chance of being phenotypically recessive. c. if the first child is phenotypically recessive, then the next child has a 1/2 chance of being phenotypically recessive. d. no matter what the first child's phenotype, the next child will have a 1/4 chance of being phenotypically recessive
no matter what the first child's phenotype, the next child will have a 1/4 chance of being phenotypically recessive.
failure of synapsed homologs to completely separate and migrate to separate poles during the first cell division of meiosis
nondisjunction
progeny resulting from homologous recombination that exhibits a different allele combination compared with its parents
nonparental (recombinant) type
subunit of chromatin composed of a short length of DNA wrapped around a core of histone proteins
nucleosome
In what organelle is the genetic material found inside?
nucleus
Before the time of Gregor Mendel and genetics, sexual reproduction was thought to produce a blending or equal mixing of the parents' traits. Today we know that a. offspring will be identical to one another and demonstrate traits exactly halfway between the parents' traits. b. offspring can vary from receiving over 99% of one parent's genes to receiving over 99% of the other parent's genes. c. offspring inherit essentially 50% of their genes from each parent, but two sibling offspring may share with each other from zero to 23 chromosomes in common from each parent, and further variation may occur due to crossing-over. d. offspring inherit copies of the same 23 pair of chromosomes from each of their parents but the rate of crossing-over makes them very dissimilar. e. there is one chance in 23 of getting identical sets of chromosomes from one parent, times two because there are two parents; therefore, two siblings out of every 46 are really identical except for crossing-over.
offspring inherit essentially 50% of their genes from each parent, but two sibling offspring may share with each other from zero to 23 chromosomes in common from each parent, and further variation may occur due to crossing-over.
A mutated gene that codes for an altered version of Cdk that is active in the absence of cyclin is a(n) _____.
oncogene
mutated version of a normal gene involved in the positive regulation of the cell cycle
oncogene
(also, ORI) region of the prokaryotic chromosome where replication begins (origin of replication)
origin
Which molecule is a Cdk inhibitor that is controlled by p53? a. cyclin b. anti-kinase c. Rb d. p21
p21
cell cycle regulatory protein that inhibits the cell cycle; its levels are controlled by p53
p21
Which negative regulatory molecule can trigger cell suicide (apoptosis) if vital cell cycle events do not occur? a. p53 b. p21 c. retinoblastoma protein (Rb) d. cyclin-dependent kinase (Cdk)
p53
cell cycle regulatory protein that regulates cell growth and monitors DNA damage; it halts the progression of the cell cycle in cases of DNA damage and may induce apoptosis
p53
Meiosis occurs during all of the following EXCEPT a. gametogenesis. b. oogenesis. c. pangenesis. d. spermatogenesis.
pangenesis.
inversion that occurs outside of the centromere
paracentric
progeny that exhibits the same allelic combination as its parents
parental types
inversion that involves the centromere
pericentric
The observable traits expressed by an organism are described as its ________.
phenotype
observable traits expressed by an organism
phenotype
Haiti is settled by peoples of both African and European ancestry. A young couple, both with mixed ancestry, marry and have several children. The children vary widely in the amount of skin melanin production, with one child being lighter than both parent, and one being darker. The simple explanation for this is a. epistasis. b. multiple alleles are available for the one chromosomal locus that governs skin color. c. the environment affected the phenotype that developed. d. polygenic inheritance. e. gene linkage.
polygenic inheritance.
individual with an incorrect number of chromosome sets
polyploid
The forked line and probability methods make use of what probability rule? a. test cross b. product rule c. monohybrid rule d. sum rule
product rule
probability of two independent events occurring simultaneously can be calculated by multiplying the individual probabilities of each event occurring alone
product rule
Attachment of the mitotic spindle fibers to the kinetochores is a characteristic of which stage of mitosis? a. prophase b. prometaphase c. metaphase d. anaphase
prometaphase
stage of mitosis during which the nuclear membrane breaks down and mitotic spindle fibers attach to kinetochores
prometaphase
The chromosomes become visible under a light microscope during which stage of mitosis? a. prophase b. prometaphase c. metaphase d. anaphase
prophase
stage of mitosis during which chromosomes condense and the mitotic spindle begins to form
prophase
The process of crossing over occurs in what meiotic phase?
prophase I
During which stage of meiosis does crossing-over occur? a. prophase I of meiosis I b. anaphase I of meiosis II c. telophase I of meiosis I d. prophase II of meiosis II e. anaphase II of meiosis I
prophase I of meiosis I
A gene that codes for a positive cell cycle regulator is called a(n) _____.
proto-oncogene
normal gene that when mutated becomes an oncogene
proto-oncogene
refers to a cell that is performing normal cell functions and has not initiated preparations for cell division
quiescent
trait that appears "latent" or non-expressed when the individual also carries a dominant trait for that same characteristic; when present as two identical copies, the recessive trait is expressed
recessive
inheritance pattern in which an allele is only lethal in the homozygous form; the heterozygote may be normal or have some altered, non-lethal phenotype
recessive lethal
paired cross in which the respective traits of the male and female in one cross become the respective traits of the female and male in the other cross
reciprocal cross
average number of crossovers between two alleles; observed as the number of nonparental types in a population of progeny
recombination frequency
protein assemblies formed on the synaptonemal complex that mark the points of crossover events and mediate the multistep process of genetic recombination between non-sister chromatids
recombination nodules
nuclear division that produces daughter nuclei each having one-half as many chromosome sets as the parental nucleus; meiosis I is a reduction division
reduction division
regulatory molecule that exhibits negative effects on the cell cycle by interacting with a transcription factor (E2F)
retinoblastoma protein (Rb)
Which is one of the seven characteristics that Mendel observed in pea plants? a. flower size b. seed texture c. leaf shape d. stem color
seed texture
Which of the following events does not occur during some stages of interphase? a. DNA duplication b. organelle duplication c. increase in cell size d. separation of sister chromatids
separation of sister chromatids
structure formed in a bacterial cell as a precursor to the separation of the cell into two daughter cells
septum
he purpose of meiosis is to form ________ cells.
sex
any gene on a sex chromosome
sex-linked
Which of the following is NOT a trait that is the result of, or is affected by, the interaction of more than one gene? a. human skin color b. cleft palate c. height d. sickle cell anemia
sickle cell anemia
Identical copies of chromatin held together by cohesin at the centromere are called _____.
sister chromatids.
all the cells of a multicellular organism except the gametes or reproductive cells
somatic cell
Species X reproduces asexually by fission and species Y reproduces sexually. Consider that all other relevant characteristics are similar between these species. When the environment gradually changes, then a. species X and Y will have an equal chance of surviving. b. species Y should have a better chance of surviving than species X. c. species X should have a better chance of surviving than species Y. d. neither species should have an advantage in surviving since organisms often become extinct when the environment changes.
species Y should have a better chance of surviving than species X.
haploid cell that can produce a haploid multicellular organism or can fuse with another spore to form a diploid cell
spore
A diploid, multicellular life-cycle stage that gives rise to haploid cells by meiosis is called a ________.
sporophyte
a multicellular diploid life-cycle stage that produces haploid spores by meiosis
sporophyte
probability of the occurrence of at least one of two mutually exclusive events is the sum of their individual probabilities
sum rule
formation of a close association between homologous chromosomes during prophase I
synapsis
What structure is most important in forming the tetrads? a. centromere b. synaptonemal complex c. chiasma d. kinetochore
synaptonemal complex
protein lattice that forms between homologous chromosomes during prophase I, supporting crossover
synaptonemal complex
Unpacking of chromosomes and the formation of a new nuclear envelope is a characteristic of which stage of mitosis? a. prometaphase b. metaphase c. anaphase d. telophase
telophase
stage of mitosis during which chromosomes arrive at opposite poles, decondense, and are surrounded by a new nuclear envelope
telophase
cross between a dominant expressing individual with an unknown genotype and a homozygous recessive individual; the offspring phenotypes indicate whether the unknown parent is heterozygous or homozygous for the dominant trait
test cross
Where in the human male does spermatogenesis occur? a. ovaries b. prostate gland c. epididymus d. testes
testes
two duplicated homologous chromosomes (four chromatids) bound together by chiasmata during prophase I
tetrad
Which statement is true about the life cycle of plants but not of animals? a. the gametophyte can be larger than the diploid generation b. they use sexual reproduction to produce new offspring c. they use meiosis in order to produce the gametes d. they will have a haploid and diploid phase of the life cycle
the gametophyte can be larger than the diploid generation
If a pea plant shows a recessive phenotype, a. the genotype may be TT or Tt. b. the genotype may be Tt or tt. c. the genotype can only be TT. d. the genotype can only be tt. e. the genotype may be TT, Tt, or tt.
the genotype can only be tt.
variation in the physical appearance of a heritable characteristic
trait
process by which one segment of a chromosome dissociates and reattaches to a different, nonhomologous chromosome
translocation
otherwise diploid genotype in which one entire chromosome is duplicated
trisomy
segment of DNA that codes for regulator proteins that prevent the cell from undergoing uncontrolled division
tumor suppressor gene
A diploid cell has_______ the number of chromosomes as a haploid cell.
twice
Which does NOT occur in meiosis? a. two daughter cells at completion b. four daughter cells at completion c. two nuclear divisions d. formation of bivalents
two daughter cells at completion
If individuals exhibiting a dominant phenotype are crossed and produce only offspring with the dominant phenotype, what would be the logical genotype of the parents? a. both are homozygous recessive b. one is heterozygous and one is homozygous dominant c. both are homozygous dominant d. both are heterozygous e. both B and C
two of the options may be correct
If a human who is a tongue roller (T) and has unattached ear lobes (E) marries a person who cannot roll their tongue and has attached earlobes, could they produce an offspring that was also a non-tongue roller with attached earlobes? What would be the genotype of the first parent? the second parent? a. yes; TtEe; ttee b. yes; TtEE; ttEe c. no; TTEE; ttee d. unable to determine from the information given
yes; TtEe; tree
The cell formed through fertilization of an egg by a sperm is called a/an
zygote.