Bio Exam 3 Review
Ignoring crossover, how many kinds of gametes can be produced by an organism with a diploid number of 8?
16 The number of possible combinations when chromosomes sort independently during meiosis is 2n, where n is the haploid number of the organism. A cell with a diploid number of 8 would have a haploid, or n number, of 4. The possible number of combinations of chromosomes would therefore be 16.
How many chromatids does a human somatic cell contain after interphase and just prior to mitosis?
92
Ras, a small G protein located at the plasma membrane, is often mutated in different types of cancer. Ras normally signals to a cell that it should divide. Cancer cells divide uncontrollably. Which of the following changes to Ras would you expect to see in a cancer cell that has mutated Ras present?
A mutation that means Ras cannot hydrolyze GTP to GDP
__________ occurs when a single gene affects the phenotype of many characters in an individual.
A pleiotropic effect
Human blood groups are governed by three alleles, IA, IB, and i. IA and IB are codominant and i is recessive to both. A man who has type B blood and a woman who has type A blood could have children of which of the following phenotypes?
A, B, AB, or O
Which of the following structures is/are part of the mitotic spindle? Kinetochore microtubules The aster All of the listed responses are part of the mitotic spindle. Centrosome Nonkinetochore microtubules
All of the listed responses are part of the mitotic spindle.
Which of the following statements correctly describes the difference(s) between mitosis and binary fission?
Binary fission involves the replication and division of a single chromosome, whereas mitosis involves the division of multiple, replicated chromosomes. Prokaryotes (bacteria and archaea) can undergo a type of reproduction in which the cell grows to roughly double its size and then divides to form two cells. The term binary fission, meaning "division in half," refers to this process and to the asexual reproduction in prokaryotes. In E. coli, the process of cell division is initiated when the DNA of the bacterial chromosome begins to replicate at a specific place on the chromosome called the origin of replication, producing two origins. As the chromosome continues to replicate, one origin moves rapidly toward the opposite end of the cell. Using the techniques of modern DNA technology to tag the origins of replication with molecules that glow green in fluorescence microscopy, researchers have directly observed the movement of bacterial chromosomes. This movement is reminiscent of the poleward movements of the centromere regions of eukaryotic chromosomes during anaphase of mitosis, but bacteria don't have visible mitotic spindles or even microtubules.
What is the difference between a benign tumor and a malignant tumor?
Cells of benign tumors do not metastasize; those of malignant tumors do.
Which of the following statements describes what happens to cells undergoing apoptosis?
Cells shrink and form lobes, which are eventually shed as membrane fragments. cells do not lyse (this would harm the neighboring cells)
What appears to be the mechanism for genomic imprinting?
DNA methylation that silences particular genes and DNA methylation that activates particular genes
Regarding the role of cohesin protein in maintaining cohesion between sister chromatids, which of the following statements is false? During meiosis I, cohesion holds sister chromatids together along their lengths as chiasmata form between homologs and during meiosis II, cohesion holds sister chromatids together along their lengths as the second meiotic spindle forms During meiosis I, cohesion holds sister chromatids together along their lengths as chiasmata form between homologs. During meiosis II, cohesion holds sister chromatids together along their lengths as the second meiotic spindle forms. Cleavage of cohesins between sister chromatid arms at anaphase I allows homologs to separate. During meiosis I, cohesion holds sister chromatids together along their lengths as chiasmata form between homologs and cleavage of cohesins between sister chromatid arms at anaphase I allows homologs to separate.
During meiosis II, cohesion holds sister chromatids together along their lengths as the second meiotic spindle forms.
A G protein is active when __________.
GTP is bound to it
Which of the following occurs in meiosis, but not mitosis? The nuclear envelope disappears. Sister chromatids undergo disjunction. The cells formed have the same combination of genes as found in the initial cell. A spindle apparatus forms. Homologous chromosomes separate.
Homologous chromosomes separate.
Which of the following statements describes the function of inositol trisphosphate (IP3) as a second messenger?
Inositol trisphosphate binds to an IP3-gated calcium channel, causing the release of calcium ions from the endoplasmic reticulum.
How does adenylyl cyclase help transmit signals within a cell?
It converts ATP to cAMP, which then broadcasts the signal to the rest of the cell.
What effect does ligand binding have on receptor tyrosine kinase proteins?
Ligand binding causes them to phosphorylate and form dimers.
Testosterone and estrogen are lipid-soluble signal molecules that cross the plasma membrane by simple diffusion. If these molecules can enter all cells, why do only specific cells respond to their presence?
Nontarget cells lack the intracellular receptors that, when activated by the signal molecule, can interact with genes in the cell's nucleus.
What happens during the process of paracrine signaling?
Numerous cells simultaneously receive and respond to the molecules of growth factor produced by a single cell in their vicinity.
In a typical pea experiment, two true-breeding plants with distinct traits of a single character are called the __________, and the offspring are called the __________, which will always be __________.
P (or parental) generation; F1 (or first filial) generation; hybrid This mating, or crossing, of two true-breeding varieties is called hybridization.
Which of the following events does not occur during interphase of the cell cycle? Separation of the sister chromatids Duplication of the chromosomes Protein production Growth of the cell Production of the endoplasmic reticulum Production of new mitochondria
Separation of the sister chromatids
Which of the following statements best describes the process of hormonal signaling?
Specialized cells release hormone molecules, which travel via the circulatory system to other parts of the body, where they reach target cells that can recognize and respond to the hormones.
A cell biologist examined the DNA content of a cell from a fruit fly larva during the G1 phase and determined that it had 150 units of DNA. After measuring the DNA content of the same type of cell after the G2 phase, it was discovered that the cell had 300 units of DNA. How is this possible?
The DNA was replicated during the S phase of interphase, which occurs between the two G phases.
Which choice below is a basic difference between Mendel's particulate hypothesis and the hypothesis of blending inheritance?
The blending inheritance hypothesis, but not the particulate hypothesis, maintained that after a mating, the genetic material provided by each of the two parents is mixed in the offspring, losing its individual identity.
The function of the mitotic cell cycle is to produce daughter cells that __________.
The function of the mitotic cell cycle is to produce daughter cells that __________.
What did Sutherland discover about glycogen metabolism in liver cells?
The hormone epinephrine binds to a specific receptor on the plasma membrane of the liver cell.
What kind of protection does the Genetic Information Nondiscrimination Act of 2008 provide the public with regard to the use of genetic information?
The law prohibits the use of genetic test information to deny insurance coverage or employment to individuals.
How does the process of mitosis differ between most eukaryotes and other eukaryotes such as diatoms and dinoflagellates?
The nuclear envelope fragments in most eukaryotes but remains intact in diatoms and dinoflagellates.
Which of the following statements about homologous chromosomes is correct?
They have genes for the same traits at the same loci.
Which of the following events occurs during telophase of mitosis?
Two distinct daughter nuclei form in the cell.
Huntington's disease is an example of a genetic disorder caused by __________.
a lethal dominant allele that afflicts an individual later in life
During telophase***
a new nuclear envelope begins to synthesize, the mitotic spindle breaks down, the chromatin uncoils, and cytokinesis begins.
The process of phosphorylation is very important as a cellular mechanism for regulating protein activity. Phosphorylation does this by ___________.
activating or inactivating proteins
The F1 generation differed from the F2 in Mendel's experiments in that __________.
all of the F1 showed the dominant phenotype, but only three-fourths of the F2 did
An alternative version of a gene is called a(n) __________.
allele
The life cycle called __________ in plants has two multicellular stages: the __________ and the __________.
alternation of generations; haploid gametophyte; diploid sporophyte
In Klinefelter syndrome, individuals are phenotypically male, but have reduced sperm production and may have some breast development in adolescence. The cells of Klinefelter individuals have two X chromosomes and one Y (they are XXY instead of XY). This occurs because of what meiotic error?
aneuploidy Ideally, the meiotic spindle distributes chromosomes to daughter cells without error. But there is an occasional mishap, called a nondisjunction, in which the members of a pair of homologous chromosomes do not move apart properly during meiosis I or sister chromatids fail to separate during meiosis II. In these cases, one gamete receives two of the same type of chromosome and another gamete receives no copy. The other chromosomes are usually distributed normally. If either of the aberrant gametes unites with a normal one at fertilization, the zygote will also have an abnormal number of a particular chromosome, a condition known as aneuploidy. Nondisjunction of sex chromosomes produces a variety of aneuploid conditions. Having an extra X chromosome affects males much more than females. In males, the extra X chromosome causes Klinefelter syndrome: abnormally small testes and sterility; some breast enlargement and other female body characteristics; and intelligence may be subnormal.
G-protein-linked receptors __________, whereas receptor tyrosine kinases __________.
are not enzymes; have enzymatic function
Sister chromatids differ from nonsister chromatids in that sister chromatids __________.
are products of the S phase of the cell cycle and are two copies of one chromosome
A clone is the product of __________.
asexual reproduction and mitosis
The region of a chromosome holding the two double strands of replicated DNA together is called __________.
centromere
Mendel studied __________, heritable features that vary among individuals; each variant is called a __________.
characters (flower color); trait (purple or white)
The complex of DNA and protein that makes up a eukaryotic chromosome is properly called __________.
chromatin
During prophase***
chromatin condenses into distinct chromosomes, the nucleolus disappears, and the mitotic spindle apparatus begins to form. In addition, centrosomes move away from each other during prophase, apparently propelled along the surface of the nucleus by the lengthening bundles of microtubules between them. This structure is responsible for maneuvering the chromosomes around the cell during mitosis.
In addition to the ABO system, humans have other blood groups, including the MN system. Individuals who have alleles for both M and N show __________ for the M and N red blood cell surface antigens.
codominance
A red bull is crossed with a white cow and all of the offspring are roan, an intermediate color that is caused by the presence of both red and white hairs. This is an example of genes that are __________.
codominant
In animal cell mitosis, the cleavage furrow forms during which stage of the cell cycle?
cytokinesis
Regardless of whether an organism is an animal, a plant, a fungus, or an algal cell, all zygotes are __________ and are formed during the __________ of two __________ gametes.
diploid; fertilization; haploid
During interphase, the genetic material of a typical eukaryotic cell is __________.
dispersed in the nucleus as long strands of chromatin
Observations of cancer cells in culture support the hypothesis that cancer cells __________.
do not exhibit density-dependent inhibition
Genomic imprinting in mammals appears to primarily affect genes involved in __________.
embryonic development In recent years, geneticists have identified two to three dozen traits in mammals that depend on which parent passed along the alleles for those traits. Such variation in phenotype depending on whether an allele is inherited from the male or female parent is called genomic imprinting. Genomic imprinting occurs during gamete formation and results in the silencing of a particular allele of certain genes. Because these genes are imprinted differently in sperm and eggs, a zygote expresses only one allele of an imprinted gene, which it inherited from either the female or the male parent. Genomic imprinting is thought to affect only a small fraction of the genes in mammalian genomes, but most of the known imprinted genes are critical for embryonic development. The Igf2 gene in mice is an example of a growth factor required for normal prenatal development. Experiments have also shown that organisms with improperly imprinted genes often die before birth.
In which part of cell are calcium ions usually found?
endoplasmic reticulum Calcium ions are actively transported out of the cell and actively imported from the cytosol into the endoplasmic reticulum (and, under some conditions, into mitochondria and chloroplasts) by various protein pumps. As a result, the calcium concentration in the ER is usually much higher than that in the cytosol.
Darwin realized the importance of heritable variation to evolution __________.
even though he never read any of Gregor Mendel's work Darwin (1809-1882) and Mendel (1822-1884)
What is the result when a diploid cell undergoes meiosis?
four haploid cells
A life cycle in which the only multicellular form is haploid is most typical of __________.
fungi
A pair of genetic structures carrying genes that control the same inherited characters are called __________.
homologous chromosomes
Chromatids are __________.
identical copies of each other if they are part of the same chromosome
In incomplete dominance, the offspring will have an appearance that's
intermediate between those of the two parental types
Characteristic of the bdelloid rotifer is that it __________.
is an example of an animal that has not reproduced sexually in 40 million years
A difference between the mechanisms of cAMP and Ca2+ in signal transduction is that cAMP __________ and Ca2+ __________.
is synthesized by an enzyme in response to a signal; is released from intracellular stores An enzyme embedded in the cell membrane, adenylyl cyclase, converts ATP to cAMP in the cytoplasm in response to an extracellular signal. cAMP then activates protein kinase A.
How is nitric oxide different from other signal molecules?
it is a gas It enters the cell through a ligand-gate ion channel. None of the listed responses is correct. It can phosphorylate cAMP. It binds to a membrane receptor. It activates a G protein. Intracellular receptor proteins are found in either the cytoplasm or the nucleus of target cells. To reach such a receptor, a signaling molecule passes through the target cell's plasma membrane. A number of important signaling molecules can do this because they are either hydrophobic enough or small enough to cross the hydrophobic interior of the membrane. These hydrophobic chemical messengers include the steroid hormones and thyroid hormones of animals. Another chemical signaling molecule with an intracellular receptor is nitric oxide (NO), a gas; its very small molecules readily pass between the membrane phospholipids. Nitric oxide binds to an intracellular receptor. Nitric oxide does not phosphorylate cAMP. Nitric oxide passes through the phospholipid bilayer, not a ligand-gated ion channel. Nitric oxide does not activate a G protein.
The major contribution of sex to evolution is that __________.
it provides a method to increase genetic variation
A small molecule that specifically binds to a larger molecule is called a(n) __________.
ligand (signal molecule)
When a platelet contacts a damaged blood vessel, it is stimulated to release thromboxane A2. Thromboxane A2 in turn stimulates vascular spasm and attracts additional platelets to the injured site. In this example thromboxane A2 is acting as a __________.
local regulator
Individuals with an extra X chromosome __________.
may have subnormal intelligence or be at risk for learning disabilities
Fertilization involving a gamete that has no copy of a particular chromosome will lead to a missing chromosome in the zygote (so that the cell has 2n ‒ 1 chromosomes); the aneuploid zygote is said to be ________ for that chromosome
monosomic
Which life cycle stage is found in plants but not animals?
multicellular haploid called the sporophyte Meiosis in the sporophyte produces haploid cells called spores. Unlike a gamete, a haploid spore doesn't fuse with another cell but divides mitotically, generating a multicellular haploid stage called the gametophyte. Gametes and zygotes are found in all life cycles. Multicellular and unicellular diploid cells are found in animals as well as plants.
The effect of the environment on a phenotype is referred to as __________.
multifactorial
Human ABO groups are best described as an example of __________.
multiple alleles
In meiosis, __________ of __________ cross over and form __________.
nonsister chromatids; homologous pairs; chiasmata
Why does testosterone not affect all cells in the body?
only certain cells have cytoplasmic receptors for testosterone Intracellular receptor proteins are found in either the cytoplasm or the nucleus of target cells.
In humans, height and skin color have continuous variation in the population because of __________.
polygenic inheritance Skin pigmentation in humans is also controlled by many separately inherited genes. Here, we'll simplify the story in order to explain the concept of polygenic inheritance. Let's consider three genes, with a dark-skin allele for each gene (A, B, or C) contributing one "unit" of darkness (also a simplification) to the phenotype and being incompletely dominant to the other allele (a, b, or c). In our model, an AABBCC person would be very dark, whereas an aabbcc individual would be very light. An AaBbCc person would have skin of an intermediate shade. Because the alleles have a cumulative effect, the genotypes AaBbCc and AABbcc would result in the same genetic contribution (three units) to skin darkness. There are seven skin color phenotypes that could result from a mating between AaBbCc heterozygotes. In a large number of such matings, the majority of offspring would be expected to have intermediate phenotypes (skin color in the middle range).
The zipper-like complex that forms in meiosis occurs during __________ and is called the __________.
prophase I and is called the synaptonemal complex Early in prophase I, the two members of a homologous pair associate loosely along their lengths. Each gene on one homolog is aligned precisely with the corresponding gene on the other homolog. The DNA of two nonsister chromatids—one maternal and one paternal—is broken by specific proteins at precisely corresponding points. Next, the formation of a zipper-like structure called the synaptonemal complex holds one homolog tightly to the other. During this association, called synapsis, the DNA breaks are closed up so that each broken end is joined to the corresponding segment of the nonsister chromatid. Thus, a paternal chromatid is joined to a piece of maternal chromatid beyond the crossover point, and vice versa. These points of crossing over become visible as chiasmata (singular, chiasma) after the synaptonemal complex disassembles and the homologs move slightly apart from each other. The homologs remain attached because sister chromatids are still held together by sister chromatid cohesion even though some of the DNA may no longer be attached to its original chromosome.
In a phosphorylation cascade, __________ phosphorylate proteins, and __________ dephosphorylate them.
protein kinases, protein phosphatases
Second messengers tend to be water-soluble and small. This accounts for their ability to __________.
rapidly move throughout the cell by diffusion
The stage of cell signaling in which a chemical signal is "detected" when the signaling molecule binds to a receptor protein located at the cell's surface is called __________.
reception
The ability to observe meiosis in gamete production supported Mendel's first law of __________, which applies when __________ separate, and supported Mendel's second law of __________, which applies when __________ sort __________.
segregation; homologous pairs; independent assortment; alleles; independently
Genetic diversity requires __________.
sexual reproduction, independent assortment, crossing over between nonsister chromatids of homologous chromosomes, and random fertilization
Certain yeast cells secrete a molecule called the -factor. The purpose of this molecule is to
stimulate a yeast cell to grow toward the cell Researchers have learned that yeast cells identify their mates by chemical signaling. There are two sexes, or mating types. One of these is called an a cell. Cells of mating type a secrete a signaling molecule called a factor that can bind to specific receptor proteins on nearby cells. The binding of -factor to a cells causes the two cells to grow toward each other and also bring about other cellular changes. The received signal is converted to a specific cellular response in a series of steps called a signal transduction pathway. The result is the fusion, or mating, of two cells of opposite type. The -factor molecule does not kill nearby yeast or bacterial cells and only leads to the attraction of cells of opposite mating types.
Which of the following phases of mitosis is essentially the opposite of prometaphase in terms of the nuclear envelope?
telophase
How many genes are present in the human genome?
tens of thousands
One event occurring during prophase is __________.
the beginning of the formation of a spindle apparatus
During anaphase***
the centrioles are at opposite ends of the cell. The paired centromeres of each chromosome are separated by spindle microtubules, liberating the sister chromatids, which begin moving toward opposite poles of the cell.
IP3 (inositol trisphosphate) is produced from __________. Ca2+ protein kinase A activation phospholipase C the cleavage of a certain kind of phospholipid in the plasma membrane DAG
the cleavage of a certain kind of phospholipid in the plasma membrane
During metaphase***
the mitotic spindle aligns the chromosomes at the metaphase plate, a region along the equator of the cell
Wild type refers to __________.
the most common phenotype thought to be found in the natural population
During prometaphase***
the nuclear envelope fragments and the kinetochores attach to microtubules In addition to the nuclear envelope fragmenting: The microtubules extending from each centrosome can now invade the nuclear area. The chromosomes have become even more condensed. Each of the two chromatids of each chromosome now has a kinetochore, a specialized protein structure at the centromere. Some of the microtubules attach to the kinetochores, becoming "kinetochore microtubules," which jerk the chromosomes back and forth. Nonkinetochore microtubules interact with those from the opposite pole of the spindle.
During binary fission in a bacterium __________.
the origins of replication move apart
In people with sickle-cell disease, red blood cells break down, clump, and clog the blood vessels. The blood vessels and the broken cells accumulate in the spleen. Among other things this leads to physical weakness, heart failure, joint pain, and brain damage. Such a suite of symptoms can be explained by __________.
the pleiotropic effects of the sickle-cell allele occurs when one gene influences two or more seemingly unrelated phenotypic traits.
What is a locus?
the precise location of a gene on a chromosome
In liver cells, epinephrine stimulates the breakdown of glycogen. As the signal-transduction pathway progresses, __________.
the signal is amplified
Evidence that cell signaling evolved early in the history of life comes from __________.
the similarity of the mechanisms in organisms that have a very distant common ancestor
Mendel's law of segregation states that __________.
the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes
Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because __________.
they amplify the original signal manyfold
The stage of cell signaling in which the signal is converted to a form that can bring about a response in the cell is called __________.
transduction
When an individual has an additional chromosome, that chromosome set is called __________, and the condition is known as __________.
trisomic; aneuploidy
The process called __________ reduces the chromosome number by __________.
two consecutive cell divisions
You perform a testcross using F1 dihybrid flies. If, in the resulting offspring, the percentages of parental and recombinant offspring are about the same, this would indicate that the two genes are __________.
unlinked
In incomplete dominance, the offspring __________.
will have an appearance that's intermediate between those of the two parental types i.e. red and white equals pink
f the two traits that Mendel looked at in his dihybrid cross of smooth yellow peas with wrinkled green peas had been controlled by genes that were located near each other on the same chromosome, then the F2 generation __________.
would have deviated from the 9:3:3:1 phenotypic ratio that is predicted by the law of independent assortment
In Labrador retrievers, a dog that has the genotype BBee, where BB produces black-pigmented fur and ee produces yellow-pigmented fur, would have __________ fur and would exhibit __________.
yellow; epistasis
