EBIO Test #3 Homework Questions & Practice Quiz & Clickers
If alleles of the two genes assort independently, what is the predicted ratio of parental:recombinant types from cross (iii)? 3:1 2:2 1:3 0:4 4:0
2:2
If an organism normally has 34 chromosomes, how many molecules of DNA should there be in the G1 phase of the cell cycle? A) 136 B) 34 C) 68 D) 17
B) 34 There is one DNA molecule per chromosome.
Human skin cells typically have 46 chromosomes. A human skin cell in G2 phase has ___________ chromosomes, ____________ chromatids, and ______________ DNA molecules. A) 92, 92, 46 B) 46, 92, 92 C) 23, 46, 46 D) 46, 46, 46 E) 23, 23, 23
B) 46, 92, 92
"2n rule": the number of possible chromosome sorting combinations = 2n remember: n is the haploid number If an organism has a diploid number of 6 chromosomes, how many different combinations of maternal and paternal chromosomes are possible in its gametes? A) 6 B) 8 C) 12 D) 16 E) 3
B) 8
Countin' chrom's... Suppose that at the end of G2 phase, a skin cell (in some species of mammal) has 16 chromatids total. How many chromosomes will each cell produced from this cell have after mitosis and cytokinesis are complete? A) 4 B) 8 C) 16 D) 32 E) not enough information given to answer question
B) 8
Chemotherapy drugs stop the cell cycle. Why are stomach upset, hair loss, and immune system depression all common side effects of chemotherapy? A) Cells in these tissues are more sensitive to toxins than others B) Compared to other tissues, cells in these tissues are marked by higher rates of cell division. C) Cells in these tissues are generally not replaced after being damaged D) All of the above
B) Compared to other tissues, cells in these tissues are marked by higher rates of cell division.
In an adult human, mitosis would ONLY occur in tumors. A) True B) False
B) False
Suppose you accidentally cut your finger. Healing a wound like this does NOT require mitosis. A) True B) False
B) False
True or false? In diploid organisms, a dominant phenotype will only be expressed if the individual is homozygous dominant for that trait. A) True B) False
B) False A dominant phenotype is indeed expressed if the individual is homozygous dominant for that trait, but the dominant phenotype is also expressed if the individual is heterozygous for the trait. In fact, heterozygous expression is the definition of dominant.
True or false? The M phase is characterized by the replication and division of a cell's chromosomes. A) True B) False
B) False Cells replicate their chromosomes during the S phase and divide partition their chromosomes during the M phase.
When, precisely, in the life cycle of a sexually reproducing organism does the transition from haploid to diploid occur? A) Meiosis I B) Fertilization C) Meiosis II D) When crossing over happens E) Mitosis
B) Fertilization
Most of the cells in your body right now are in which phase of the cell cycle? A) G2 B) G0 C) G1 D) S phase E) Mitotic phase
B) G0
For the following question, please refer to the list of four processes given here using the Roman numerals preceding each one. I. Chromosomes line up in middle of cell II. Homologous chromosomes separate III. Sister chromatids separate IV. DNA is replicated Mendel's "Law of Segregation" finds a mechanistic basis most clearly in which process? A) None of these B) II C) IV D) III E) I
B) II
Recall Mendel's pea plants: the allele for purple flowers, P, is dominant to the allele for white flowers, p. A very large number of offspring from a cross of two plants are observed. If ALL of those offspring have purple flowers, what are the possible genotypes of the parents in the cross? A) PP × PP only B) PP × PP, PP × Pp, or PP × pp C) PP × PP, PP × Pp, PP × pp, or Pp × Pp D) pp × pp only E) Not enough information is given
B) PP × PP, PP × Pp, or PP × pp
Researchers began a study of a cultured cell line. Their preliminary observations showed them that the cell line did not exhibit either density-dependent inhibition or anchorage dependence. What could they conclude right away? A) The cells originated in the nervous system. B) The cells show characteristics of tumors. C) The cells were originally derived from an elderly organism. D) The cells have altered series of cell cycle phases.
B) The cells show characteristics of tumors.
This chromosome has two chromatids, joined at the centromere. What process led to the formation of the two chromatids? A) The two chromatids were formed by synapsis and the formation of a synaptonemal complex. B) The two chromatids were formed by duplication of a chromosome. C) The two chromatids were formed by fertilization, bringing together maternal and paternal chromatids.
B) The two chromatids were formed by duplication of a chromosome. Read about formation of chromatids.
Why do neurons and some other specialized cells divide infrequently? A) They no longer produce cyclins. B) They have been shunted into G0. C) They no longer carry receptors for signal molecules. D) They no longer have active nuclei.
B) They have been shunted into G0.
What is true of all cancers? A) They are inherited. B) They have escaped normal cell cycle controls. C) They are caused by chemical carcinogens.
B) They have escaped normal cell cycle controls. Read about the consequences of escaping the cell cycle.
Which of the following statements about INTERPHASE is FALSE? A) DNA is replicated during interphase B) Very few of our cells are in interphase at any one time C) Cells can remain in interphase until their demise D) Growth of the cell happens during interphase E) Cells can halt their progress in the cell cycle by going from G1 to G0
B) Very few of our cells are in interphase at any one time
What is an allele? A) a type of chromosome B) an alternative version of a gene C) the dominant form of a gene D) a variety of pea plant used by Mendel E) the recessive form of a gene
B) an alternative version of a gene A diploid organism carries two alleles for each autosomal gene. The two alleles are found at comparable locations (loci) on homologous chromosomes. The alleles may be identical or slightly different, but they affect the same genetic character.
If allele combinations are always preserved ("strict dependent assortment"), which combinations of traits should NEVER be observed? A) black body with vestigial wings B) black body with normal wings AND gray body with vestigial wings C) black body with normal wings AND black body with vestigial wings D) gray body with normal wings E) gray body with normal wings AND gray body with vestigial wings
B) black body with normal wings AND gray body with vestigial wings
In general terms, normally a cell in your body crosses a checkpoint in the cell cycle when ... A) it receives a "go-ahead" signal directly from your brain. B) concentrations of proteins in the cytoplasm reach the appropriate level. C) it receives a "go-ahead" signal from your external environment. D) concentrations of DNA in the nucleus reach the appropriate level. E) a mutation in the DNA occurs.
B) concentrations of proteins in the cytoplasm reach the appropriate level.
If a diploid organism possesses one dominant allele and one recessive allele for a particular gene, then ________ of its gametes will possess the dominant allele and ________ of its gametes will possess the recessive allele. A) all, none B) half, half C) none, all D) 75%, 25% E) Not enough information is given
B) half, half
Mendel did not know about genes or chromosomes per se. However, in modern terms, Mendel's "law of segregation" can be phrased as stating that the TWO alleles an individual possesses for a given gene SEPARATE during gamete formation. If the two alleles an individual possesses for a given gene "segregate" (i.e., separate) during gamete formation, what is happening at the chromosomal level during the process of this separation? A) diploid cells are arising from haploid ones B) haploid cells are arising from diploid ones C) could be either A or B D) not enough information to choose between A and B
B) haploid cells are arising from diploid ones
In general, the frequency with which crossing over occurs between two linked genes depends on __________. A) whether the genes are dominant or recessive B) how far apart they are on the chromosome C) the characters the genes code for D) the phase of meiosis in which the crossing over occurs E) whether the genes are on the X or some other chromosome
B) how far apart they are on the chromosome The farther apart two genes are on a chromosome, the greater the probability that a crossover will occur between them, and therefore the greater the recombination frequency.
Use the completed Punnett square in Part B to answer the questions below about the F2 generation. Answer each question in the table by dragging the correct label to the appropriate location. Labels can be used once, more than once, or not at all.
Question 1 simply asks about the probability of forming a yellow seed in the F2, which is 3/4. Question 2 introduces the concept of conditional probability. Although there are two genotypes in the F2 that will breed true (YY and yy), only one of them is yellow. Thus, the question adds a new condition: Among yellow seeds only, 1/3 are true-breeding. Questions 3 and 4 require a full evaluation of all eight possible groupings of three randomly selected F2 seeds. Each grouping has its own probability, shown in the table below. For question 3, there are seven possible groupings that have at least one yellow seed (shown in blue in the table); the sum of their individual probabilities yields the final answer (63/64). Note that you could have also calculated this answer by subtracting the probability of the one category that doesn't fit the criterion (Green, Green, Green) from the total probability (1 - 1/64 = 63/64). For question 4, there are three possible groupings that have one green and two yellow seeds (shown in bold in the table); the sum of their individual probabilities yields the final answer (27/64).
When does chromosome (DNA) duplication occur?
S Phase
Homologous chromosomes
-have the same genes in the same locations -carry the same genes
Biologically speaking, what part(s) of a parent is/are physically duplicated and passed on to offspring? A) Genes B) Cells C) Brains D) Physical appearance E) All of the above
A) Genes
Punnett squares are convenient ways to represent the types and frequencies of gametes and progeny in experimental crosses. This Punnett square shows the results of a Yy x Yy cross to form F2 progeny. Use your understanding of Mendel's law of segregation and the rules of probability to complete the Punnett square for this cross. First identify the gametes. Use pink labels to identify the male and female gamete types and white labels to identify the gamete frequencies. Then identify the F2 progeny. Use pink labels to identify the progeny genotypes and white labels to identify the progeny frequencies.
A Punnett square is a convenient method for representing Mendel's law of segregation in a visual form. Using a Punnett square allows one to easily see gamete types and frequencies, as well as the genotypes and frequencies of progeny formed by random gamete fusion. The genotype frequencies inside a Punnett square are calculated using the multiplication rule: The probability of two independent events occurring simultaneously is the product of their individual probabilities. In this example, the genotype frequencies inside the square (¼) are the product of the gamete frequencies that led to their formation (½ x ½ = ¼).
A cell at the very beginning of meiosis has a total of 4 chromatids. What is "n" for the cell? A) 1 B) 2 C) 4 D) 8 E) Can not be determined from information provided
A) 1
Normal human gametes carry _____ chromosomes. A) 23 B) 46 pairs of C) 5 D) 46 E) 23 pairs of
A) 23 This is the number of chromosomes in a single set of human chromosomes.
If an organism has a diploid number of 6 chromosomes, how many different combinations of maternal and paternal chromosomes are possible in its gametes? A) 8 B) 12 C) 3 D) 16 E) 6
A) 8 2^(# haploid cells)
For the next question, please use the following information: Recall that in humans, males typically have one X and one Y chromosome, and females typically have two X chromosomes. "Colorblindness" in humans is usually caused by a recessive allele of a gene located on the X chromosome. Considering this gene, let's call the dominant allele for normal color vision " B ", and let's call the recessive allele for colorblindness " b ". Given that Sam's son is colorblind, if the son's mother has normal color vision, her genotype is most likely to be A) Bb B) bb C) BB or Bb D) BB E) Bb or bb
A) Bb
When one allele is dominant to another, what is the most common biological mechanism for this dominance? A) Dominant alleles often encode functional products, whereas recessive alleles often do not encode functional products B) Dominant alleles subdue or repress recessive alleles C) Cellular machinery recognizes which allele is dominant and only reads the instructions from that one D) A dominant allele on one chromosome causes the other, homologous chromosome (containing the recessive allele) to be completely inactivated
A) Dominant alleles often encode functional products, whereas recessive alleles often do not encode functional products
Which statement provides the best description of the interphase portion of the cell cycle? A) During interphase, a cell is metabolically active. B) Interphase is a brief period between mitosis and chromosome duplication. C) Interphase is a resting stage prior to cell division.
A) During interphase, a cell is metabolically active. Interphase accounts for about 90% of the cell cycle and includes many key events critical to the cell cycle. It is not a resting stage; the cell is metabolically active during this phase.
Which of the following is true of a species that has a chromosome number of 2n = 16? A) Each cell has eight homologous pairs. B) A gamete from this species has four chromosomes. C) The species has 16 sets of chromosomes per cell. D) During the S phase of the cell cycle there will be 32 separate chromosomes.
A) Each cell has eight homologous pairs.
Most of the cells in your body are diploid. How did they become this way? A) Each of us is a product of sexual reproduction, having one set of genes from our mother and one set of genes from our father. B) The number of chromosomes inside cells is doubled each time mitosis happens, so cells wind up with multiple copies of the genome. C) The number of chromosomes inside cells is cut in half each time mitosis happens, so cells have to have two sets at all times to be ready for the next mitosis. D) At any given time, most cells in your body are stopped between S phase and G2 phase, so they have two copies of everything.
A) Each of us is a product of sexual reproduction, having one set of genes from our mother and one set of genes from our father.
For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable? A) It targets only rapidly dividing cells. B) It is safe enough to limit all apoptosis. C) It does not affect metabolically active cells. D) It only attacks cells that are density dependent.
A) It targets only rapidly dividing cells.
When, precisely, in the life cycle of a sexually reproducing organism does the transition from diploid to haploid occur? A) Meiosis I B) Fertilization C) Meiosis II D) When crossing over happens E) Mitosis
A) Meiosis I
What is the best evidence telling you whether this cell is diploid or haploid? A) The cell is diploid because it contains two sets of chromosomes. B) The cell is diploid because each chromosome consists of two chromatids. C) The cell is haploid because the chromosomes are not found in pairs.
A) The cell is diploid because it contains two sets of chromosomes. Only diploid cells contain two sets of chromosomes, one maternal and one paternal. Read about diploid cells.
For the first several divisions of early frog embryos, cells proceed directly from the M phase to the S phase and back to M without gaps. Which of the following is likely to be true about dividing cells in early frog embryos? A) The cells get smaller with each generation. B) The number of chromosomes decreases with each generation. C) Frog embryos do not have DNA. D) The cells do not divide by mitosis.
A) The cells get smaller with each generation Without gap phases, the cells have no opportunity to grow.
Which of the following is a function of the S phase in the cell cycle? A) The synthesis of sister chromatids B) The separation of sister chromatids C) The synchronization of organelle division D) The sorting of chromosomes
A) The synthesis of sister chromatids DNA replication occurs during S phase and results in two sister chromatids for each original chromosome.
Cell division is an essential process during the development of a cat. A) True B) False
A) True
Mitosis is essential for healthy functioning of adult organisms. A) True B) False
A) True
Mitosis is essential for the growth of a baby. A) True B) False
A) True
True or false? The same phenotype can be produced by more than one genotype. A) True B) False
A) True Since there exist dominant and recessive versions of many genes, a phenotype that is based upon the dominant version will be expressed in both homozygous (AA) and heterozygous (Aa) genotypes.
When purple flowers are crossed with each other, as in the F1 generation, what does the hypothesis of blending inheritance predict their offspring (the "F2 generation") should look like? A) all purple B) all white C) purplish white
A) all purple
Suppose that a certain gene functions to enforce a checkpoint on the cell cycle. A mutation causing the loss of this gene's function would cause a person to ... A) be more likely to have cancer at some point in his/her life. B) develop an extra limb. C) have cancer immediately. D) lose the capability to produce gametes. E) be extra protected from ever getting cancer.
A) be more likely to have cancer at some point in his/her life.
Mendel did not know about genes or chromosomes per se. However, in modern terms, Mendel's "law of segregation" can be phrased as stating that the TWO alleles an individual possesses for a given gene SEPARATE during gamete formation. If a cell in G1 phase possesses exactly TWO alleles for a given gene, the cell must be A) diploid B) haploid C) could be either A or B D) not enough information to choose between A and B
A) diploid
In human bodies, mitosis does NOT directly: A) produce haploid cells. B) help you grow. C) help organs develop. D) help repair damage. E) produce diploid cells.
A) produce haploid cells.
What is crossing over? A) the exchange of homologous portions of nonsister chromatids B) making an RNA copy of a DNA strand C) the movement of genetic material from one chromosome to a nonhomologous chromosome D) also referred to as the "independent assortment of chromosomes" E) a direct consequence of the separation of sister chromatids
A) the exchange of homologous portions of nonsister chromatids The result of the exchange of homologous portions of nonsister chromatids is new combinations of genetic material (genetic recombination).
You continue your genetic analysis by crossing the forked and pale mutant lines with each other. The leaves of the F1 are light green (intermediate between pale and wild-type leaves) and forked. The F2 has six phenotypic classes, as shown below.You designate the forked mutant allele as F (wild type = f+) and the pale mutant allele as p (wild type = P). 1. Consider the alleles for leaf color first. Drag the white labels to the white targets to identify the genotype of each F2 class. Remember that p (the pale mutant allele) and P (the wild-type allele) are incompletely dominant to each other. 2. Consider the alleles for leaf shape next. Drag the blue labels to the blue targets to identify the genotype of each F2 class. Remember that F (the forked mutant allele) is dominant to f+ (the wild-type allele).
Alleles P and p are incompletely dominant to each other. Therefore, each genotype has a distinct phenotype. That is why you are able to assign definite genotypes for leaf color to each F2 plant. Allele F is dominant to f+. Therefore, you cannot be certain whether forked leaves are homozygous dominant or heterozygous. That is why you must assign the genotype F_ to the F2 plants in the top row. For the unforked leaves in the bottom row, you know they must be homozygous for the wild-type allele.
You decide to conduct a genetic analysis of these mutant lines by crossing each with a pure wild-type line. The numbers in the F2 indicate the number of progeny in each phenotypic class. From these results, determine the relationship between the mutant allele and its corresponding wild-type allele in each line. Label each mutant line with the best statement from the list below. Labels may be used once, more than once, or not at all.
An allele is never intrinsically "dominant" or "recessive." Instead, these terms describe a relationship between two alleles. This relationship is evaluated by examining a heterozygote: The allele that determines the phenotype of the heterozygote is dominant to the other (recessive) allele. Some heterozygotes have a phenotype that is intermediate between the phenotypes of the two homozygotes. This situation is the result of incomplete dominance: Neither allele is completely dominant to the other.
For the following question, please use the following information: In humans, a recessive allele of a gene on the X chromosome causes humans to be "colorblind." A colorblind man and a woman whose genotype is homozygous for normal color vision have children together. What percentage of their offspring are expected be colorblind? A) Too little information given to choose an answer B) 0% C) 25% D) 50% E) 75%
B) 0%
Two mice are heterozygous for albinism (Aa) . The dominant allele (A) codes for normal pigmentation, and the recessive allele (a) codes for no pigmentation. What percentage of their offspring would have an albino phenotype? A) 75 B) 25 C) 50 D) 100
B) 25 The offspring would be in a 3:1 ratio of normally pigmented mice to albino mice.
Practice making and interpreting a Punnet square. Suppose there are two alleles of a gene, called A and a, and A is dominant to a. In a cross, Aa x Aa, among the offspring there are _____ possible genotypes and _____ possible phenotypes. A) 4, 3 B) 3, 2 C) 2, 1 D) 1, 2 E) 2, 4
B) 3, 2
Which of the following is TRUE about meiosis and sexual life cycles? A) the haploid stage in a sexual life cycle is always just a unicellular gamete B) meiosis halves the number of chromosomes; fertilization restores the diploid number C) meiosis is unique to sexually reproducing animals D) all diploid organisms reproduce strictly sexually
B) meiosis halves the number of chromosomes; fertilization restores the diploid number
What are most of your cells doing right now? A) growing larger B) specialized functions that make your organs work C) replicating their DNA D) preparing for division E) nothing; they are just waiting around
B) specialized functions that make your organs work
Mitosis and meiosis are different in A) whether or not sister chromatids are separated B) the number of cells produced C) the replication of genetic material before any division has occurred D) the occurrence of cytokinesis E) the involvement of a spindle to help guide the movements of chromosomes
B) the number of cells produced
Mitosis yields _________ daughter cells that are genetically ____________ and that have ____ ____ number of chromosomes compared to the parent cell. A) four, identical, the same B) two, identical, the same C) two, identical, half the D) four, different, the same E) four, different, half the
B) two, identical, the same
In science, what does it mean when observations contradict the predictions of a hypothesis? A) we should double-down on our efforts to find data supporting the hypothesis B) we should consider alternative hypotheses (if we weren't already) C) we should manipulate our data to make it look like we found support for the hypothesis D) we should ignore the observations, because our hypothesis must be correct E) we should ignore science, because we don't like what it is telling us
B) we should consider alternative hypotheses (if we weren't already)
Which of the following is/are NOT a part of maintaining checkpoints on the cell cycle? A) concentrations of molecules in the cytoplasm B) your brain directly telling each cell when it is allowed to pass a checkpoint C) genes that encode molecules involved in cell cycle regulation D) cells sensing that they are anchored to the correct tissue E) cells sensing how crowded they are
B) your brain directly telling each cell when it is allowed to pass a checkpoint
Considering a cell in G1 phase, each of its chromosomes is composed of ____ DNA molecule(s) and ______ chromatid(s). A) 2, 4 B) 2, 2 C) 1, 1 D) 4, 4 E) 1, 2
C) 1, 1
In the previous question, the expected ratio of the different possible phenotypes in the offspring of that cross is A) 4:1 B) 1:2:1 C) 3:1 D) 2:1:1 E) 1:0
C) 3:1
Here are Mendel's four hypotheses. 1. Alternative versions of heritable "factors" (i.e., alleles) account for variations in inherited characters 2. An organism inherits two alleles, one from each parent 3. If the two alleles at a locus differ, then one (the dominant allele) determines the organism's appearance. 4. The "law of segregation" Though Mendel didn't know about "ploidy" per se, two of these hypotheses together constitute the idea of alternations between haploid and diploid in sexual life cycles. Specifically, #______ is similar to saying meiosis makes haploid gametes, and #_______ is similar to saying fertilization makes a diploid zygote. A) 1, 2 B) 4, 3 C) 4, 2 D) 3, 1 E) 1, 4
C) 4, 2
Who has the highest percentage of cells in S phase? A) A body builder B) An adult cancer patient C) A fetus D) A sumo wrestler E) Your professor
C) A fetus
What is the difference between heterozygous and homozygous individuals? A) Homozygotes have one chromosome while heterozygotes have two similar chromosomes. B) The homozygote will express the dominant trait and the heterozygote will express the recessive trait. C) All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ. D) Heterozygotes carry two copies of a gene while homozygotes only carry one.
C) All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ. Since homozygotes carry two identical copies of a gene, all of the gametes will carry the same version. Heterozygotes have two different versions, so there will be two different types of gametes.
Vinca alkaloids from the Madagascar periwinkle bind to spindle building blocks, preventing their assembly. Which process in the cell cycle is most directly blocked by Vinca alkaloids? A) Chromosome condensation B) Degradation of nuclear membrane C) Attachment of spindle to chromosomes D) Separation of sister chromatids E) Cytokinesis
C) Attachment of spindle to chromosomes
For the following question, please refer to the list of four processes given here using the Roman numerals preceding each one. I. Chromosomes line up in middle of cell II. Homologous chromosomes separate III. Sister chromatids separate IV. DNA is replicated Which of the following gives a correct ordering of events leading up to and during meiosis? (note: for simplicity, some steps we learned about are obviously left out) A) IV, I, III, I, II B) I, III, I, III, IV C) IV, I, II, I, III D) I, II, IV, I, III E) IV, IV, III, II, I
C) IV, I, II, I, III
Which of Mendel's four hypotheses can, on its own, directly explain why there are NO white flowers in the F1 generation and why the purple F1's look just as purple as the purple plants in the parental ("P") generation? A) Alternative versions of heritable "factors" (i.e., alleles) account for variations in inherited characters B) For each character an organism inherits two alleles, one from each parent C) If the two alleles at a locus differ, then one (the dominant allele) determines the organism's appearance, and the other (the recessive allele) has no noticeable effect on appearance. D) The "law of segregation"
C) If the two alleles at a locus differ, then one (the dominant allele) determines the organism's appearance, and the other (the recessive allele) has no noticeable effect on appearance.
If an organism with the genotype AaBb produces gametes, what proportion of the gametes would be Bb? A) 1/2 B) 1/4 C) None D) 3/4
C) None Alleles of the same gene must separate during gamete formation; thus, the two B alleles would be distributed to different gametes.
Which of the following best describes the relationship between genes and chromosomes? A) Genes and chromosomes are separated from each other during meiosis B) Genes have DNA, but chromosomes do not C) One chromosome contains many genes D) One gene contains many chromosomes E) Chromosomes come in different versions, but genes do not
C) One chromosome contains many genes
Podophyllotoxin from American and Himalayan mayapples prevents DNA replication In which part of the cell cycle would a cell be stalled by podophyllotoxin? A) Mitosis B) Cytokinesis C) S phase D) G2 E) G1
C) S phase
Below is a picture of a child's skin cell, showing 6 of the cell's chromosomes, all of which have been replicated. 3 chromosomes were inherited from from the child's mom, and 3 from the child's dad. Which of the following best describes a pair of homologous chromosomes? A) Any pair consisting of two chromosomes inherited from one parent B) A pair consisting of two chromosomes inherited one each from different parents C) Two chromosomes, one inherited from each parent, that have the same genes as each other D) Any two chromosomes having different genes. E) There are no homologous chromosomes in this cell.
C) Two chromosomes, one inherited from each parent, that have the same genes as each other
Under the hypothesis of strict dependent assortment, which of the following types of gametes would an F1 individual produce? A) YR only B) YR, Yr, and yR only C) YR and yr only D) yr only E) Yr, yR, and yr only
C) YR and yr only
P generation of experiment: *True breeding* yellow round crossed with *true breeding* green wrinkled Y=yellow y=green R=round r=wrinkled What are the genotypes of (1) yellow round and (2) green wrinkled in the P generation? (use information/letters from previous slides) A) Yellow round = yr Green wrinkled = YR B) Yellow round = Yr Green wrinkled = yR C) Yellow round = YYRR Green wrinkled = yyrr D) Yellow round = YYrr Green wrinkled = yyRR E) None of the above
C) Yellow round = YYRR Green wrinkled = yyrr
Why does each parent in the P generation make only one kind of gamete? A) because only one gamete is produced during the two rounds of meiosis B) because we are only going to look at one offspring C) because each parent is homozygous for both genes D) because mutations happened E) because only dominant alleles are passed on to gametes
C) because each parent is homozygous for both genes
One difference between cancer cells and normal cells is that cancer cells ________. A) are unable to synthesize DNA B) are arrested at the S phase of the cell cycle C) continue to divide even when they are tightly packed together D) cannot function properly because they are affected by density-dependent inhibition E) are always in the M phase of the cell cycle
C) continue to divide even when they are tightly packed together
When constructing a Punnett square, the symbols on the outside of the boxes represent _______, while those inside the boxes represent _______. A) gametes, parents B) progeny, gametes C) gametes, progeny D) parents, gametes
C) gametes, progeny The Punnett square is representing all of the possible combinations of the gametes from each parent, with the progeny represented in the interior of each box.
Mendel did not know about genes or chromosomes per se. However, in modern terms, Mendel's "law of segregation" can be phrased as stating that the TWO alleles an individual possesses for a given gene SEPARATE during gamete formation. Mendel's "law of segregation" finds its mechanistic basis most clearly in the behavior of chromosomes during A) S phase of Interphase B) mitosis C) meiosis I D) meiosis II E) all of the above
C) meiosis I
The original (ultimate) source of all genetic variation is A) recombination B) crossing over C) mutation D) independent assortment E) random fertilization
C) mutation
In science, what is the difference between an "observation" and a "prediction"? A) no difference; they are the same thing B) predictions are true statements; observations are subjective interpretations C) predictions are what you expect if a given hypothesis is correct; observations are what you actually find or measure. D) predictions are used to judge whether or not an observation is valid
C) predictions are what you expect if a given hypothesis is correct; observations are what you actually find or measure.
Which of the following descriptions correctly defines a genome? A) representation of a complete set of a cell's polypeptides B) a karyotype C) the complete set of an organism's genes D) the complete set of an organism's polypeptides
C) the complete set of an organism's genes
The most likely reason that the characters of "seed color" and "seed shape" showed independent assortment in Mendel's experiments is that A) the genes for these two characters were very close together on the same chromosome B) these two characters were the product of the same gene C) the genes for these two characters were on different chromosomes D) the genes for both characters were sex-linked
C) the genes for these two characters were on different chromosomes
Suppose you counted 1000 offspring from cross (iii), and 800 of the offspring had either a gray body with normal wings OR a black body with vestigial wings. From this you should conclude that ... A) alleles of the two genes assort independently B) the genes are both on the X chromosome C) the two genes are on the same chromosome, 20 map units apart D) something went wrong in your experiment E) the two genes are on the same chromosome, 80 map units apart
C) the two genes are on the same chromosome, 20 map units apart
A tall, purple-flowered pea plant (TtPp) is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the "1" in the 9:3:3:1 ratio)? A) TtPp B) TTpp C) ttpp D) TTPP
C) ttpp The smallest phenotypic group consists of the homozygous recessive plants, which in this case are short and white flowered.
For the following question, please use the following information. Consider two imaginary genes, a "hair gene" and a "beard gene", in an imaginary population of aliens. Since we're imagining things, let's also imagine that the aliens have diploid genomes and life cycles just like human beings. Each gene has two possible alleles. For the hair gene, H is the dominant allele for straight hair, and h is the recessive allele for curly hair. For the beard gene, B is the dominant allele for a small beard, and b is the recessive allele for a giant bushy beard. In these aliens, males and females can both have beards, and neither gene is on a sex chromosome. You are a geneticist trying to understand heredity in these aliens. You start by observing offspring from the following cross: P generation: HHBB × hhbb The offspring produced from the parental (P) cross are the F1 generation. Suppose than an individual with genotype HhBB mates with an individual whose genotype is hhBB. What do you predict about the number of different phenotypes of offspring that they would have, and in what ratio? A) four phenotypes in a 9:3:3:1 ratio B) four phenotypes in a 1:1:1:1 ratio C) two phenotypes in a 1:1 ratio D) only one phenotype having straight hair with a small beard E) two phenotypes in a 3:1 ratio
C) two phenotypes in a 1:1 ratio If you build the Punnet square for this problem, note that the HhBB parent makes two kinds of gametes: HB and hB. The other parent makes only one kind of gamete, hB. Thus, the offspring are 50% HhBB, and 50% hhBB, that is, 50% curly hair with a small beard, and 50% straight hair with a small beard.
A purple flower is crossed with a white flower. What does the hypothesis of blending inheritance predict that their offspring should look like? A. all purple B. all white C. purplish-white
C. purplish-white
A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes. A) 64 B) 8 C) 30 D) 16 E) 32
D) 16 16 is half of 32.
Put the following processes in the right order from start to finish from interphase through mitosis: 1. Sister chromatids separate 2. DNA is replicated 3. Chromosomes condense 4. Chromosomes line up in the middle of the cell 5. Nuclear envelope dissolves A) 5 --> 2 --> 3 --> 1 --> 4 B) 4 --> 3 --> 2 --> 5 --> 1 C) 2 --> 5 --> 1 --> 4 --> 3 D) 2 --> 3 --> 5 --> 4 --> 1 E) 3 --> 4 --> 2 --> 5 --> 1
D) 2 --> 3 --> 5 --> 4 --> 1 DNA is replicated Chromosomes condense Nuclear envelope dissolves Chromosomes line up in the middle of the cell Sister chromatids separate
Suppose you were building a picture or a physical model of a cell in order to demonstrate the principle of independent assortment. What is the SMALLEST number of chromosomes you could put inside your model cell in order to do this? Why? A) 1 B) 2 C) 3 D) 4 E) 6
D) 4
Which of the following could be ways that keep the cell from passing the G2 checkpoint? A) Degrading (breaking down) cyclin proteins during G2 B) Producing proteins that inhibit the formation of "mitosis promoting factor" C) Producing proteins that help cyclin and CDK come together D) A and B E) A, B, and C
D) A and B
Which of these cells is (are) haploid? A) A and D B) B C) D D) C and D E) B and C
D) C and D Once meiosis I is completed, cells are haploid.
For the following question, please use the following information. Consider two imaginary genes, a "hair gene" and a "beard gene", in an imaginary population of aliens. Since we're imagining things, let's also imagine that the aliens have diploid genomes and life cycles just like human beings. Each gene has two possible alleles. For the hair gene, H is the dominant allele for straight hair, and h is the recessive allele for curly hair. For the beard gene, B is the dominant allele for a small beard, and b is the recessive allele for a giant bushy beard. In these aliens, males and females can both have beards, and neither gene is on a sex chromosome. You are a geneticist trying to understand heredity in these aliens. You start by observing offspring from the following cross: P generation: HHBB × hhbb The offspring produced from the parental (P) cross are the F1 generation. Suppose that F1 individuals mate with each other and produce the F2 generation. In the F2 generation, what combination(s) of traits would be predicted by the hypothesis of independent assortment, but should NOT occur according to the hypothesis of strict dependent assortment? A) Curly hair with a giant bushy beard, straight hair with a small beard B) Straight hair with a small beard only C) Curly hair with a small beard only D) Curly hair with a small beard, straight hair with a giant bushy beard E) Curly hair with a giant bushy beard only
D) Curly hair with a small beard, straight hair with a giant bushy beard
Which of the following lists the processes involved in Meiosis in the correct order? A) Separation of homologous chromosomes → Cell division → DNA replication → Separation of sister chromatids → Cell division B) DNA replication → Separation of sister chromatids → Cell division → Separation of homologous chromosomes → Cell division C) DNA replication → Separation of homologous chromosomes → Separation of sister chromatids → Cell division → Cell division D) DNA replication → Separation of homologous chromosomes → Cell division → Separation of sister chromatids → Cell division E) DNA replication → Separation of sister chromatids → Cell division → Separation of homologous chromosomes → Cell division
D) DNA replication → Separation of homologous chromosomes → Cell division → Separation of sister chromatids → Cell division
If an adult human being loses an arm in an accident, it does not re-grow. Why not? A) Cell division does not occur in adults B) Damaged tissues are not repaired in adults C) Old cells in your organs are never replaced by newer cells D) Developmental processes for growing limbs are not reactivated when a limb is lost later in life E) When the person's arm is lost, so are the person's genes for growing an arm.
D) Developmental processes for growing limbs are not reactivated when a limb is lost later in life
At the very beginning of meiosis, a cell in your ovary/testis has 46 chromosomes. At the end of meiosis I (but before meiosis II), this cell will have given rise to two cells that are each ________ and each have ________ chromosomes and ________ chromatids. A) Diploid, 46, 46 B) Haploid, 46, 92 C) Diploid, 23, 46 D) Haploid, 23, 46 E) Haploid, 92, 92
D) Haploid, 23, 46
A chromosome you inherited from your mother might be different from any of the chromosomes she inherited from either of her parents. Why is this possible? A) Mutation only B) Crossing over only C) Independent assortment only D) Mutation and/or crossing over E) Mutation, crossing over, and/or independent assortment
D) Mutation and/or crossing over Mutation creates new alleles, and crossing over creates new combinations of alleles. Independent assortment, however, does not change the alleles on a given chromosome.
The copying of chromosomes occurs during which of the following phases of the cell cycle? A) G2 phase B) G1 phase C) M phase D) S phase
D) S phase Chromosomes must undergo replication before mitosis can occur; this copying occurs during the S phase.
Chromosomes are duplicated in ________ and the duplicates are separated during ________. A) S phase; G2 phase B) G2 phase; interphase C) Mitosis; cytokinesis D) S phase; mitosis E) Cytokinesis; mitosis
D) S phase; mitosis
For the following question, please use the following information: In humans, a recessive allele of a gene on the X chromosome causes humans to be "colorblind." In the following question, " c " is the recessive allele that causes colorblindness, " c+ " is the dominant allele for normal color vision, and " Y " is the human Y chromosome. Your professor (Sam) and his wife (Becca) both have normal color vision, but their son is colorblind. What do you know about Sam's and Becca's genotypes? A) Sam = c+ c+, Becca = c+ c+ B) Sam = c+ c, Becca = c+ c C) Sam = c Y, Becca = c c D) Sam = c+ Y, Becca = c+ c E) Too little information given to choose an answer
D) Sam = c+ Y, Becca = c+ c
Under the hypothesis of independent assortment, which of the following types of gametes would an F1 individual produce and in what ratio? A) 100% YR only B) YR, Yr, and yR only, in a 1:1:1 ratio (33% each) C) YR, Yr, and yR only, in a 2:1:1 ratio D) YR, Yr, yR, and yr, in a 1:1:1:1 ratio (25% each) E) YR, Yr, yR, and yr, in a 9:3:3:1 ratio
D) YR, Yr, yR, and yr, in a 1:1:1:1 ratio (25% each)
Mendel's "law" of independent assortment = alleles for each character segregate independently during gamete formation Given what YOU know about the relationship between genes and chromosomes (which Mendel did NOT), this "law" would likely be violated for two genes that A) affect the same character B) each have more than two alleles in the population C) each have only a single allele in the population D) are on the same chromosome E) experience mutations
D) are on the same chromosome
In science, what is required to test a hypothesis? A) gathering data that support the hypothesis B) making a strong argument (without data) for why the hypothesis should be true (or false) C) asking people to vote on whether or not they think the hypothesis is true D) gathering data and checking whether the data are consistent with or contradict predictions of the hypothesis E) getting a politician and news media to endorse the hypothesis
D) gathering data and checking whether the data are consistent with or contradict predictions of the hypothesis
Human gametes are produced by _____. A) mitosis B) fertilization C) the cell cycle D) meiosis E) asexual reproduction
D) meiosis Meiosis produces haploid gametes from a diploid parental cell.
One replicated chromosome (consisting of two sister chromatids) contains a total of ... A) two single-stranded DNA molecules. B) one double-stranded DNA molecule. C) four double-stranded DNA molecules. D) two double-stranded DNA molecules.
D) two double-stranded DNA molecules.
What name is given to the most common phenotype in a natural population? A) autosome B) locus C) mutant phenotype D) wild type E) genotype
D) wild type The most common phenotype is the wild type.
For the following question, please use the following information. Read carefully! There is a gene in humans that influences how many fingers a person has on each hand. In the following question, " F " is a dominant allele that produces 6 fingers per hand, and " f " is a recessive allele that produces 5 fingers per hand. The gene is NOT sex linked (i.e., it is NOT on the X or Y chromosome). Consider a heterozygous woman (Ff ) and a man with 5 fingers on each hand. If this man and woman have children together, what percentage of their offspring would you expect to have five fingers on each hand? A) 75% B) 25% C) 0% D) 100% E) 50%
E) 50%
Which of the following contribute(s) to the variation in offspring produced by sexual reproduction? A) Crossing over B) Mutation C) Independent assortment D) Random fertilization E) All of these
E) All of these
Which of the following is consistent with the hypothesis of blending inheritance? A) Crossing a purple-flowered pea plant with a white-flowered pea plant produces only purple-flowered offspring B) Great variability in traits is found within any biological population. C) Crossing two pea plants with yellow seeds produces some offspring with green seeds D) A phenotype from the "P" generation of a heredity experiment disappears in the "F1" generation then reappears in the "F2" generation E) Crossing a red flower with a white flower yields a pink flower
E) Crossing a red flower with a white flower yields a pink flower
The mushrooms we put on pizza are multicellular, haploid organisms. Which of the following ordering of events in a mushroom's life cycle explains why its multicellular life stage is haploid? A) Fertilization, followed by Growth by mitosis, followed by Meiosis B) Fertilization followed by Growth by meiosis C) Two rounds of fertilization followed by Growth by mitosis D) None of these answers are correct E) Fertilization, followed by Meiosis, followed by Growth by mitosis
E) Fertilization, followed by Meiosis, followed by Growth by mitosis
How are sister chromatids and homologous chromosomes different from each other? A) They are not different. Homologous chromosomes and sister chromatids are both identical copies of each other. B) Sister chromatids are only formed during mitosis. Homologous chromosomes are formed during meiosis. C) Homologous chromosomes are identical copies of each other. One sister chromatid comes from the father, and one comes from the mother. D) Homologous chromosomes are closely associated with each other in both mitosis and meiosis. Sister chromatids are only associated with each other during mitosis. E) Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication.
E) Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication. One homologous chromosome comes from the father, and the other comes from the mother. Sister chromatids are identical copies of each other.
During which of the following does the separation of sister chromatids occur? A) Mitosis only B) Meiosis I only C) Meiosis II only D) Mitosis and Meiosis I E) Mitosis and Meiosis II
E) Mitosis and Meiosis II
Suppose a scientist "tricked" a cell to skip straight from G1 phase (of interphase) to the Mitotic phase. Which of the following processes would be IMPOSSIBLE for this cell during mitosis? A) Breakdown of nuclear envelope B) Condensation of chromosomes C) Assembly of mitotic spindle D) Attachment of spindle to chromosomes E) Separation of sister chromatids
E) Separation of sister chromatids
Which of the following is TRUE for BOTH mitosis and meiosis? A) The parent and daughter cells have the same ploidy. B) The daughter cells are genetically identical to each other. C) Homologous chromosomes are separated during a division. D) Crossing over occurs. E) Sister chromatids are eventually separated.
E) Sister chromatids are eventually separated.
The cell cycle must be regulated in a multicellular organism in order to ... A) maintain the proper cell number in tissues. B) activate cell division when repair of a tissue is needed. C) halt cell division when repair of a tissue is complete. D) prevent cancer. E) all of these answers are correct.
E) all of these answers are correct.
For the following question, please use the following information: In humans, a recessive allele of a gene on the X chromosome causes humans to be "colorblind." A man with normal vision and a colorblind woman have children together. We can expect that _________ of their sons and _________ of their daughters will be colorblind. A) half, none B) none, half C) all, half D) half, all E) all, none
E) all, none
The physical process that makes gene linkage incomplete is A) segregation B) mitosis C) the lining up of chromosomes in the middle of the cell D) cyclin reaching a threshold concentration E) crossing over
E) crossing over
Which of the following can NOT contribute to genetic variation in offspring arising from sexual reproduction? A) crossing over during meiosis in the parents B) independent assortment during meiosis in the parents C) random fertilization D) errors during DNA replication before meiosis E) mutations in DNA caused by UV rays hitting an a parent's dividing skin cells
E) mutations in DNA caused by UV rays hitting an a parent's dividing skin cells
Suppose you were studying the heredity of two characters that were influenced by two genes that happened to be located on the same chromosome. This might likely result in you making observations that contradict: A) the universal life cycle of sexually reproducing organisms. B) all of these C) the hypothesis of particulate inheritance. D) the "law of segregation." E) the "law of independent assortment."
E) the "law of independent assortment."
Your dog has puppies. A pair of homologous chromosomes inside a puppy's cell A) must be genetically identical B) must have the same alleles in the same locations C) were both inherited from the same parent D) will fight with each other to determine which one will be dominant E) will have the same genes at the same locations
E) will have the same genes at the same locations
For the following question, please use the following information: Recall that in humans, males typically have one X and one Y chromosome, and females typically have two X chromosomes. "Colorblindness" in humans is usually caused by a recessive allele of a gene located on the X chromosome. Considering this gene, let's call the dominant allele for normal color vision " B ", and let's call the recessive allele for colorblindness " b ". Sam's son is "colorblind." From whom did the son most likely inherit the colorblind allele? A) His father (Sam) only B) His mother only C) He inherited a copy of this allele from both parents D) Any of these answers is equally likely E) None of these answers are possible
His mother only
During which of the following does the separation of homologous chromosomes occur? A) Mitosis only B) Meiosis I only C) Meiosis II only D) Mitosis and Meiosis I E) Mitosis and Meiosis II
Meiosis I only
One character in peas that Mendel studied was yellow versus green seeds. A cross between a homozygous yellow line (YY) and a homozygous green line (yy) will result in F1 plants that are heterozygous (Yy) for this trait and produce yellow seeds. The figure shows a cross between the homozygous dominant plant with yellow seeds and the homozygous recessive plant with green seeds. At F1, all plants are heterozygous and have yellow seeds. The heterozygous plant with genotype Y uppercase y lowercase can give two types of gametes. These gametes are labeled by question marks. When an F1 plant undergoes meiosis, what gamete types will it produce, and in what proportions? Use your understanding of Mendel's law (or principle) of segregation to label each gamete possibility as "correct" or "incorrect
Mendel's law of segregation states that allele pairs segregate equally into gametes during meiosis. This means that a gamete will have only one allele of any given gene, and that the probability of a gamete having one allele or the other is equal (and therefore ½, or 50%, for either allele).
Separation of sister chromatids occurs when?
Mitotic phase
This diagram shows a diploid nucleus (2n=8) in which chromosome replication has occurred in preparation for mitosis (top) and meiosis (bottom). The nucleus at top right is now in prophase of mitosis; the nucleus at bottom right is now in prophase I of meiosis. Drag the labels to their appropriate targets to correctly identify the various chromosome structures. Labels can be used more than once.
To understand the process of meiosis, it is essential that you can differentiate between sister chromatids, nonsister chromatids, homologous chromosomes, and non-homologous chromosomes.
Which of the above crosses would give us information about whether or not the two genes are linked? (iii) only (i) only (ii) only both (i) and (ii) both (ii) and (iii)
both (ii) and (iii)