BI 204 Exam 1, Weeks 1-4
Review the pedigree shown and choose the most accurate statement about the inheritance of an X-linked recessive mutation.
For recessive X-linked traits, most of the affected individuals are males. For X-linked traits, males only need one copy to express the trait in their phenotype. Females would need two copies of the recessive allele to express the trait in their phenotype
A human cell with a total of 23 chromosomes is:
Haploid
How did Mendel make crosses with his plants?
He grew plants from seeds and fertilized the ovules of one plant with the pollen from another.
In his cross, what did Mendel do?
He studied traits controlled by a single gene.
What is the primary difference between natural selection and artificial selection?
Humans drive artificial selection.
The figure shown illustrates the results of a series of observations and experiments on tail length in male African widowbirds. The black bars represent manipulated tail lengths by researchers (they actually added length to the tail feathers of the experimental birds). From the black bars on the figure, we see clearly that the male birds that have been artificially manipulated to have super-long tails are very good at attracting mates, approximated by the number of active nests for each male. What most likely explains why the male tails we see in nature (open bars on the figure) are so much shorter?
If males in nature had the most successful tail length from the experimental study, they would not be able to fly well enough to escape predation.
Humans can have many different eye colors ranging from blue to brown. Which of the statements could explain this array of different eye colors?
In human populations there are many alleles of the genes affecting eye color, not just two.
Consider two pea plant genes. The dominant allele of the first pea plant gene is represented by the capital letter A, and the recessive allele of the same pea plant gene is represented by the lowercase letter a. The dominant allele of the second pea plant gene is represented by the capital letter B, and the recessive allele of the same pea plant gene is represented by the lowercase letter b.If an individual that is homozygous dominant for both genes (Individual I) is crossed with an individual that is heterozygous for both genes (Individual II), calculate the probability that the offspring will have the genotype AABB. Assume the inheritance of this gene obeys Mendel's principles of segregation and independent assortment.
0.25 In order for the offspring of the test cross between Individuals I and II to have the genotype AABB, both individuals must contribute the dominant alleles for both genes. Individual I is homozygous dominant for both genes and has the genotype AABB. Therefore, the probability of passing on the dominant allele for each gene is 1. Individual II is heterozygous for both genes and has the genotype AaBb. The probability of passing on the dominant allele for each gene is 0.50. Since these alleles obey Mendel's principles of segregation and independent assortment, to calculate the probability of the offspring being homozygous dominant for both genes, we use the multiplication rule: 1 x 1 x 0.50 x 0.50 = 0.25. Alternatively, one could use a Punnett square to determine the probability.
If the frequency of allele A is 0.7 in a population that is in Hardy-Weinberg equilibrium, what would the frequency of the heterozygous Aa genotype be?
0.42 Frequencies of alleles in a population must equal 1.0. If the frequency of allele A (p) is 0.7, then the frequency of allele a (q) is 1.0 - 0.7 = 0.3. Using the HW equilibrium, the frequency of heterozygotes equals 2pq. To calculate: 2(0.7)(0.3) = 0.42.
When the F1 plants are allowed to self fertilize, they produced both yellow and green peas in the next generation. How is this explained?
In the F1 heterozygotes, the alleles segregate from each other when gametes form and then combine to make homozygotes and heterozygotes offspring.
The dominant allele of a pea plant gene is represented by the capital letter A and the recessive allele of the same gene is represented by the lowercase letter a.If a heterozygous Individual I is crossed with a homozygous recessive Individual II, calculate the probability that the offspring will have the genotype aa. Assume the inheritance of this gene obeys Mendel's principle of segregation.
0.50 In order for the offspring of the test cross between Individuals I and II to have the genotype aa, both individuals must contribute a recessive allele. Individual I is heterozygous and has the genotype Aa. Therefore, the probability that Individual I will contribute a recessive allele for this gene is 0.50. Individual II is homozygous recessive and has the genotype aa. Therefore, the probability that Individual II will contribute a recessive allele for this gene is 1. Since these alleles obey Mendel's principles of segregation, to calculate the probability that the offspring will have the genotype aa, we use the multiplication rule: 0.50 x 1 = 0.50. Alternatively, one could use a Punnett square to determine the probability.
A researcher is studying the color of grasshopper exoskeletons. Assume that this phenotype is caused by the action of two alleles. Green grasshoppers have the genotype AA and brown grasshoppers have the genotype aa. If the frequency of the A allele in this population is 0.2, what is the frequency of the a allele?
0.8 The frequency of all alleles in a population must equal 1.0. If the frequency of one allele is 0.2, then the frequency of the other allele is 1.0 - 0.2 = 0.8.
Color blindness is a recessive X-linked trait in humans. In a family where the mother is color-blind and the father is normal, the probability of their having a color-blind son is:
1
The dominant allele of a pea plant gene is represented by the capital letter A and the recessive allele of the same gene is represented with the lowercase letter a.
1 In order for the offspring of the test cross between Individuals I and II to express the dominant phenotype, they need to inherit at least one dominant allele. Because Individual I is homozygous dominant (genotype AA), the probability that Individual I will contribute a dominant allele for this gene is 1. This means that all the offspring of the testcross between Individuals I and II will have at least one dominant allele. Therefore, the probability that the offspring will express the dominant phenotype is 1. Alternatively, one could use a Punnett square to determine the probability.
Consider the image. If the ostrich egg shown in the photo is not fertilized, it is composed of approximately how many cells?
1 cell
Flower color in snapdragons is due to a gene with incomplete dominance: CRCR plants have red flowers, CRCW have pink flowers, and CWCW plants have white flowers. What types and ratios of flower color are expected among the progeny of a pink × white cross?
1 pink:1 white
You are given two populations of true-breeding tomato plants with two traits that assort independently. Using the multiplication rule, how many of the F2 progeny would you expect to have a recessive phenotype for both traits?
1/16
Color blindness is a recessive X-linked trait in humans. In a family where the mother is heterozygous for color blindness and the father is color-blind, the probability of their having a color-blind daughter is:
1/2
A male fly that is homozygous for recessive alleles at two linked autosomal genes is mated with a wild-type female fly that is homozygous dominant for both alleles. All F1 offspring are then randomly mated. If the genes are so close as to have no recombination, what proportion of offspring will be homozygous for both mutations in the F2 generation?
1/4 Note that since the two genes do not recombine, there are only four potential genotypes in the offspring mimicking monohybrid cross. All F1 offspring are heterozygous. When two heterozygous individuals are mated, 1/4 of their offspring will be homozygous recessive.
Suppose that in humans the ability to roll the tongue (R) is dominant to being unable to roll it (r), and having freckles (F) is dominant to having no freckles (f). If a woman heterozygous for both traits married a man with no freckles who couldn't roll his tongue, what is the probability that they would have a freckled, tongue-rolling child?
1/4 The chance the child has both traits is the chance the child inherits the dominant allele of each from their mother. Inheriting the dominant allele of R (1/2) AND the dominant allele of F (1/2) = 1/2 × 1/2 = 1/4.
For most genes on the human X chromosome, what percent of XY males with a mutant allele on the X chromosome will express the mutant phenotype?
100%
The fruit fly cross shown here analyzes the transmission of two genes on the X chromosome. The male parent has mutant alleles for both the white gene (w-) which results in white eyes and the crossveinless gene (cv-) which results in the absence of crossveins of the fly wings. The female parent has nonmutant forms of these genes (w+ and cv+). A cross between siblings of the F1 generation—a red-eyed, crossveined female and a red-eyed, crossveined male—generates F2 progeny. Examine the genotype of the F2 male progeny. Notice that the progeny fall into two groups. The numbers of male F2 progeny with each of the four observed phenotypes are: Red-eyed, crossveined = 357 White-eyed, crossveinless = 341 Red-eyed, crossveinless = 52 White-eyed crossveined = 45 What is the map distance between the genes w and cv?
12.2 To determine the map distance, divide the number of recombinant progeny by the total number of offspring.
You are given two true-breeding groups of gerbils. The gerbils in the first group have black fur and curly tails; the gerbils in the second group have yellow fur and straight tails. When you produce an F1 generation, you see only gerbils with black fur and curly tails. When you produce an F2 generation, you see that 75% of the gerbils have black fur and 25% have yellow fur. You also see that 25% of the gerbils have straight tails and 75% have curly tails. If the single alleles responsible for coat color and tail appearance sort independently, how many of the black gerbils in this generation are expected to have straight tails?
25%
In a cross between two individuals who are heterozygous for two traits determined by dominant and recessive alleles (Aa Bb), what is the expected ratio of offspring for the trait determined by the first gene (Aa)?
3:1
If nondisjunction occurs in the first meiotic division, how many of the four possible gametes produced from meiosis will have the wrong number of chromosomes?
4
If there are 100 diploid individuals in a population and 20 are homozygous for B, 60 are heterozygous, and 20 are homozygous for b, what is the allele frequency of B?
50 percent For a population of 100 individuals there would be 200 total alleles in the population because they are diploid. 20 homozygotes for B would have 2(20) = 40 alleles. Each heterozygote has one copy of the B allele which means 60 B alleles. 40 + 60 = 100 total B alleles in the population. 100/200 = ½ or 50% for the frequency of the B allele in the population
A woman has her personal genome analyzed for the BRCA1 mutation after learning that her father is heterozygous and carries one mutant allele. What is her chance of inheriting the mutant allele from her father?
50%
Two alleles of a given gene exist in a population: CTGT and TGTC. (Note: The codes given are only for the transcribed strand of the DNA in the two alleles.) Three possible single crossover events are possible between these two alleles. As a result of the three different crossover events, how many total new alleles (new sequences of DNA) could be produced?
6
A true-breeding black rabbit is crossed with a true-breeding white rabbit. If the black color trait is dominant, which of the outcomes represents the expected phenotype of an F2 generation consisting of eight individuals?
6 black rabbits, 2 white rabbits, 0 gray rabbits
In a cross between two individuals who are heterozygous for two traits determined by dominant and recessive alleles (Aa Bb), what is the expected ratio of phenotypes for the traits determined by both genes?
9:3:3:1
Why is DNA sequencing the gold standard for measuring genetic variation?
It determines the exact genetic sequence and, thus, the absolute variation in a population.
In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, R- means the individual has either the genotype RR or Rr. In Duroc pigs, genotypes R- S- have red coats, R- ss and rr S- have sandy-colored coats, and rr ss pigs are white. R and S show independent assortment. What is the ratio of red : sandy : white among progeny of the cross Rr Ss x Rr Ss?
9:6:1 Use a Punnett square: all the genotypes homozygous recessive for one gene and heterozygous for the other gene would be sandy-colored. The others would be red except for the double homozygote recessive which would be white. This results in a 9:6:1 ratio.
Which of the answer choices may be a characteristic of an advantageous mutation?
It facilitates successful reproduction.
Why would a compound that interferes with bacterial cell wall synthesis be useful for treating a bacterial infection?
It would limit growth of the bacterial population through cell division. When bacterial cells grow and divide by binary fission, they must construct new cell walls. Blocking the synthesis of cell walls would slow or block bacterial growth
The secondary sex ratio of newborns in the United States is 105 males : 100 females. Which of the answer choices is the accepted hypothesis to explain why this observed ratio doesn't this match the 1:1 predicted primary sex ratio?
Males and females have different survival rates between conception and birth.
Which of the below is the simplest self-replicating entity that can exist as an independent unit of life?
A cell
Which of the below is true regarding scientific inquiry?
A scientific theory can be traced back to one or more hypotheses that were eventually supported by a large number of experiments
What is a gene?
A segment of DNA which codes for a particular protein product
Under experimental conditions, we can delete the gene for the motor protein involved in contraction of the contractile ring during animal cell cytokinesis. Which of the results might you predict?
Additional rounds of the cell cycle continue producing a multinucleate cell.
Homologous chromosomes separate from each other in:
Meiosis I
In fruit flies, what kind of eye color would be expressed in male progeny from a white-eyed female and a red-eyed male?
All males would have white eyes. In order for a female to have white eyes, she would be homozygous for the white-eye allele. The only gametes she can make will have the white-eye allele. Every son will get this allele from their mother and will have the white-eye phenotype.
In which phase of mitosis do sister chromatids separate?
Anaphase
In which phase of mitosis do spindle microtubules shorten?
Anaphase
When do sister chromatids separate in meiosis?
Anaphase II
Prokaryotic cells found in extreme, harsh environments often belong to the domain:
Archaea
According to the tree of life.....
Archaea are more closely related to Eukarya than to Bacteria
Mendel's experiments with garden peas differed from those of other plant hybridizers of his time in that:
Mendel studied true-breeding strains instead of poorly defined material. Mendel focused on a small number of easily contrasted traits instead of a large number of more complex traits. Mendel quantified his results and looked for statistical patterns instead of simply noting the presence or absence of a trait among a group of offspring.
Ronald Fisher developed a critical idea for the modern synthesis of Darwin and Mendel. What is the basis of this synthesis?
Multiple genes can explain the continuous nature of most observed traits.
The process of cytokinesis involves components of the cytoskeleton. It is most similar to what other cytoskeletal function
Muscle contraction
During DNA replication occasional errors can occur resulting in a change in a nucleotide base, for example instead of adding a T, a C is added. If this is not corrected by mismatch repair or other mechanisms, this change represents a:
Mutation
For an individual who is heterozygous for two genes, Aa and Bb, what does independent assortment predict?
Offspring inheriting the dominant (A) allele of the first gene are equally likely to inherit either the dominant (B) or the recessive (b) allele of the second gene.
Which of the statements is true regarding Y-linked traits?
Only males will demonstrate a Y-linked trait.
In contrast to positive and negative selection, _____ selection acts to maintain two or more alleles in a population.
Balancing
What is the source of single nucleotide polymorphisms (SNPs) in the human population?
Point Mutations
On Island X the plant population contains only two species. One plant species produces only very large seeds, and the other produces only small seeds. There is only one species of bird on the island, and the birds use these seeds as their only food source. Currently there is a wide range of beak sizes within the population of birds as shown in the diagram below. Small-beaked birds are better able to consume the smaller seeds, while large-beaked birds are better at consuming the larger seeds. Birds with intermediate beak size can make use of both seed sizes. A disease is introduced to the island which kills only the plants that produce the large seeds. Consider changes in the bird population following the death of all plants that produce large seeds. Which portion(s) of the finch population will be selected against and least likely to have their genes represented in the next generations?
Portion C only
In scientific inquiry, hypotheses lead most directly to:
Predictions
Crossing over occurs during which step in meiosis?
Prophase I
During which phase of meiosis do homologous chromosomes synapse with crossing-over between homologous chromosomes?
Prophase I
Replication of DNA in a eukaryote occurs during which phase of the cell cycle?
S phase
A student was studying cell growth using cells grown in laboratory cultures. The cultures were synchronized so that all of the cells passed through the same stage of the cell cycle at the same time. The cells were examined during five different periods of time, intervals (A-E). The amount of DNA present per cell was determined for each interval. The graph shows the result of this study.
S phase. During S phase, cells replicate their chromosomes and double the amount of DNA per cell
Which of the statements is true regarding the SRY gene?
SRY is involved in human sex determination.
Why does genetic drift have more of an impact on the evolution of small populations than large ones?
Sampling from generation to generation is more variable in small populations than large.
Female starlings (birds) that lay clutches of four or five eggs have more surviving young than those with either larger or smaller clutches. This is an example of:
Stabilizing selection
Morgan's discovery of a white-eyed male was important because the mutant gene proved to be in:
The X chromsome
Which one of the statements regarding the human Y chromosome is true?
The Y chromosome contains approximately 50 protein-coding genes
Which of the choices is a characteristic of meiotic cell division?
Cell division results in the production of gametes.
In order for a population of Fer-de-lance pit vipers to evolve coloration and cryptic patterns that help them better blend into their environment, what must be true about their coloration?
Certain coloration/patterns must result in higher survival and/or reproduction The coloration/pattern of the snakes must be variable in the population The coloration/pattern of the snakes must be a heritable trait
What is the fundamental concept that causes gel electrophoresis of proteins to work?
Different proteins have different charges and sizes.
Huntington's disease is a devastating neurological disorder. If a child of an affected parent receives one copy of the Huntington allele, he or she will develop Huntington's disease. Thus, Huntington's disease is considered a _____ trait.
Dominant
You are examining a human pedigree for a trait. You notice that the trait appears in every generation, is equally likely to occur in males and females, and about half of the offspring are affected when one parent is affected. The trait is most likely:
Dominant
With independent assortment, the ratio of phenotypes in the F2 generation of a cross between true-breeding strains (AA bb x aa BB) can be described as 9:3:3:1 when A and B are dominant over a and b. To what phenotype does the "9" in the ratio refer?
Dominant for both traits
Mitotic Division: When is the DNA of the cells' chromosomes copied?
During S phase
Sexual reproduction results in an increase in genetic diversity because:
During metaphase I, the bivalents line up in a random orientation so that gametes inherit a random set of maternally and paternally derived chromosomes. During prophase I, genes that are paternally and maternally derived recombine so that the gametes have chromosomes that are different from the parents' chromosomes. The random orientation of bivalents assures that gametes receive a random mix of maternal and paternal homologs. This happens in the formation of eggs and sperm, so the zygote formed from their fusion creates a random mix from both parents. Recombination in prophase I mixes regions of maternal and paternal homologs to provide more genetic diversity. During fertilization, the gametes that fuse are random so that a large number of chromosomal combinations are possible in the new organism.
In the F2 generation of a homozygous round (AA) × homozygous wrinkled (aa) cross in peas, three seeds are chosen at random. What is the probability that all three seeds are round?
(3/4)^3
If you analyze the sequences of the two copies of any of the chromosomes shown in the karyotype, there would be slight sequence differences. What could account for the small differences between a few of the homologous chromosomes?
Each homologous chromosome in a pair is from a different parent.
A controlled way of asking and answering unbiased questions about the world is called a(n):
Experiment
Consider two pea plant genes. The dominant allele of the first pea plant gene is represented by the capital letter A and the recessive allele of the same pea plant gene is represented by the lowercase letter a. The dominant allele of the second pea plant gene is represented by the capital letter B and the recessive allele of the same pea plant gene is represented with the lowercase letter b.If an individual that is homozygous dominant for both genes (Individual I) is crossed with an individual that is heterozygous for both genes (Individual II), calculate the probability that the offspring that will exhibit the recessive phenotype for both genes. Assume the inheritance of this gene obeys Mendel's principles of segregation and independent assortment.
0 (zero) In order for the offspring to exhibit the recessive phenotype, they must have the genotype aabb. The probability that Individual I will contribute a dominant allele for both genes is 1. This means that the genotype of the offspring will always have a dominant allele for both genes and will never express the recessive phenotype. Therefore, the probability is 0. Alternatively, one could use a Punnett square to determine the probability.
In a population of Mendel's garden peas, the frequency of dominant yellow-flowered plants is 50%. The population is in Hardy-Weinberg equilibrium. What is the frequency of the recessive allele in the population?
The frequency cannot be determined from the data provided.
In Drosophila, the red-eye allele for eye color exhibits complete dominance over the recessive white-eye allele. In some of Thomas Hunt Morgan's initial experiments, he crossed red-eyed female flies with white-eyed males. When Morgan crossed the F1 red-eyed heterozygous females with red-eyed males, he found that half of the male progeny were white-eyed. What is the most likely explanation of this result?
The gene responsible for eye color is on the X chromosome.
In this partial image of anaphase I of meiosis, most of a chromosome is shaded dark, whereas a portion of what is in the circle is shaded light. Which of the statements best explains the meaning of this shading?
The light part came from the homolog by crossing over.
What is the result of a mutation that occurs in somatic cells?
The mutation may be expressed in the individual, but will not be passed along to its offspring.
When Mendel crossed yellow peas with green peas, the next generation was all yellow. How is this explained?
The parental plants pass one of their two alleles on to the offspring which is heterozygous, and the A allele is dominant to the a allele.
Which of the answer choices is true of a cross involving a sex-linked gene but not of a cross involving an autosomal gene?
The phenotype outcomes of females and males can be different.
What would happen if a pair of sister chromatids only connected to the mitotic spindle at one of their kinetochores?
The sister chromatids would not separate. Each chromatid is pulled to the opposite pole by a spindle fiber. If the spindle fiber was not attached to one of the chromatids, it would not separate from the other chromatid, and both would end up in the same daughter cell. The chromosome would not line up properly at metaphase. One of the daughter cells would have an extra copy of that chromosome.
In the pedigree shown, a set of parents (at the top) have three children—two daughters and a son. That son (on the right hand side of the pedigree) has a family in which none of the children are affected. However, one of his grandchildren is affected. How could the trait disappear in one generation and reappear in the next?
The trait was absent in the son's children because they each carried at least one dominant allele.
Imagine that you have crossed two types of peonies, one with purple flowers and long stems, and the other with white flowers and short stems. When you cross these flowers, you get the following numbers of progeny: 83 with purple flowers and short stems; 29 with purple flowers and long stems; 26 with white flowers and short stems; and 9 with white flowers and long stems. Based on these data, what can you say about genes that define flower color and stem length?
These genes sort independently.
When a 9:3:3:1 ratio of phenotypes is produced by a cross between two individuals, which phenotypes are present in the rarest class that is represented by only 1 of the 16 possible genotypes of offspring?
These offspring have the recessive phenotype of both traits.
Which of the statements accurately describes the inheritance of mitochondrial and chloroplast genomes?
These organelles are partitioned with the cytoplasm during gamete formation.
Which one of the statements explains a characteristic of both all living organisms and all nonliving material?
They both conform to the basic laws of chemistry and physics.
Pairing of homologous chromosomes in prophase of meiosis I appears to be critical for proper alignment, crossing over, and subsequent separation. This pairing is facilitated by the sharing of sequence homology between homologous chromosomes. If X and Y chromosomes are so different, how can they achieve the necessary pairing?
They share short homologies at their respective tips.
How many experiments have been conducted worldwide to test Darwin's initial hypothesis regarding natural selection?
Thousands
True or false: Errors in chromosome segregation can occur in either the first or second meiotic division.
True
Which scenario accurately reflects Mendel's principle of segregation in humans?
Two alleles, A and a, have an equal chance of being passed down to the offspring.
The addition rule requires which option?
Two outcomes (such as having the genotype BB or Bb) are mutually exclusive in an organism.
When Mendel crossed true-breeding dominant yellow-seed plants with true-breeding recessive green-seed plants, the offspring were phenotypically:
Yellow-seed plants
The wild-type allele for the BRCA1 gene is represented by capital letter A, and the mutant allele for the BRCA1 gene is represented by lowercase letter a. Ruth and Isaac are both heterozygous for the mutant BRCA1 allele. The genotypes of Ruth and Isaac's offspring are ⅓ AA and ⅔ Aa. Although the mutant BRCA1 allele obeys Mendelian inheritance patterns, these genotypes do not match the predicted ratios. What is the most likely reason?
Zygotes with two mutant BRCA1 alleles are not viable. Because zygotes with two mutant BRCA1 alleles are not viable, one of the three possible genotypes is not represented in the offspring, and this distorts the Mendelian ratios.
At the genetic level, evolution is:
a change in the frequency of an allele or genotype over time.
In crosses involving linked genes, recombinant offspring result from:
a crossover
The fur color in a colony of mice has been brown for many generations. One gene appears to code for the fur color pigment. In a recent litter of mouse pups, one mouse was born with white fur. Which of the answer choices could have caused this change in fur color?
a mutation in the DNA sequence of the gene for brown fur
The Y-linked trait of hairy ears has been passed down for many generations in a certain family. A hairy-eared male in this family would be expected to have:
a paternal grandfather with hairy ears.
A testcross of an organism of unknown genotype is done when the organism is crossed to another organism that is:
a recessive homozygote.
For a trait such as flower color in snapdragons that is determined by two alleles with incomplete dominance, the offspring of true-breeding parents show an intermediate phenotype. This is also what would be expected of blending inheritance. The difference is that:
a trait with Mendelian inheritance shows segregation in the F2 generation and produces both original phenotypes.
If an XY male carries a mutation on his X chromosome, _______________ will receive the mutant X.
all of his daughters
Recall that alleles of a single gene will segregate from one another during anaphase I. When do alleles for two different genes—located in two different chromosomes—segregate?
anaphase I
Genes located along the X chromosome:
are called X-linked genes
A population in biology refers to a group of individuals in the same geographic area that:
are the same species
Genes in different chromosomes _____ during meiosis. Genes that are very close together in the same chromosome are _____.
assort independently; linked
The process of cell division in a prokaryotic cell is called:
binary fission
How does meiosis generate genetic diversity?
both crossing over at prophase I and random alignment of homologs at metaphase I Genetic diversity is from the sequence differences that differ on the homologs derived from each parent. The way those slightly different chromosomes are mixed and then divided up to form gametes is the process that generates genetic diversity in each gamete. It is enhanced by the fact that homologs undergo recombination in Meiosis I, so the homologs are also mixed up.
What cellular process(es) is/are responsible for the increase in protein content associated with the gap phases of the cell cycle?
both transcription and translation Increased protein content comes most directly from translation, but translation requires RNA produced from transcription, so both are required.
A heterozygous female harboring one mutant allele for hemophilia is called a(n) _____ for that trait.
carrier
When carrying out a controlled experiment, it is important to:
change only one variable at a time.
What type of selection occurs when an environmental condition, for example food source characteristics, causes selection toward one extreme of a trait's range of variation?
directional
Which type of selection increases overall genetic variation in a population?
disruptive selection As the extremes of a distribution are selected for, the ends of the distribution will move away from the mean. This increases the total range of values representing variation in the population
Mitotic Division: When does a cell undergoing cell division actually divide into two new "daughter cells"?
during cytokinesis
In meiosis, recombination occurs:
during only prophase I and involves exchange between chromatids of homologous chromosomes.
When calculating the allele frequency of allele A in a population, you multiply the frequency of individuals who are homozygous for A by 2 because:
each individual who is homozygous for A has two copies of the allele. For diploid populations homozygous individuals with that allele will have two copies. This would not be enough to calculate allele frequency for the population. The alleles present in heterozygotes would also have to be added in to the calculation.
Genes that modify the phenotypic expression of other genes show:
epistasis.
A wild-type fruit fly:
exhibits the most common phenotype in the population.
What is nondisjunction?
failure of chromosomal separation
The _____________ two loci are on a chromosome, the more likely they will be separated by crossover events during gamete formation, and thus the frequency of recombination between loci on a chromosome can be used to measure the _______________ between those loci.
farther apart; genetic distance
Migration reduces genetic differences between populations by allowing gene _______ between the two.
flow
You are given two populations of true-breeding tomato plants with two simple dominant/recessive traits that sort independently. Using the multiplication rule, how many different phenotypic combinations would you expect to see in the F2 generation? In what phenotypic ratio?
four; 9:3:3:1
All the alleles present in all individuals in a species are referred to as the _____ of that species.
gene pool
A normal female who carries a recessive X-linked allele for hemophilia will pass it on to:
half of both her sons and daughters.
Prophase of meiosis I has some important differences from prophase of mitosis. These differences include: ___________ pair, and _________ occurs.
homologous chromosomes; crossing over
A recessive trait is expressed when the genotype is:
homozygous only.
A testcross involves crossing with a(n) _____ individual and is used to determine the _____ of the tested parent.
homozygous recessive; genotype
The concept of a molecular clock allows a population geneticist to estimate:
how long two populations of the same species have been separated.
Females of a species of parasitic wasps locate their prey, a leaf-eating caterpillar, by hunting for it visually. One year, one female appeared in the wasp population with the ability to locate the prey by smell. The most likely place of occurrence of the mutation causing this change was:
in the DNA in the egg cell that developed into the individual with the new phenotype.
In normal meiosis, when do homologous chromosomes separate from each other?
in the first meiotic division
Genes that are linked do not show:
independent assortment
Which of the choices is/are considered traits?
leaf shape in trees fur color in cats beak size in owls height in humans
The ratio of recombinants to total number of progeny can be simplified to a percentage, and 1 percent recombination is equal to 1 _____, which represents the distance between two linked genes.
map unit
Most of life's diversity is:
microbial.
In humans, one reason why mitochondrial inheritance is strikingly different from nuclear inheritance is that:
mitochondrial DNA is maternally inherited.
Variation is the raw material that natural selection can act upon in a population. Besides recombination, which of the answer choices can also produce new alleles in a population?
mutation Mutation changes the DNA sequence and produces a new allele in the population. The mutation increases the amount of variation in the population. Meiosis can produce variation through recombination by producing new arrangements of alleles.
The contractile ring that leads to cytokinesis in animal cells has been shown to be made primarily of actin filaments (microfilaments). Which motor protein would you predict is involved in contraction of the ring?
myosin
Which of the answer choices is not a contributor to genetic drift?
natural selection
During meiosis crossing over takes place between:
non-sister chromatids.
In which type of nondisjunction could the two copies of a chromosome in a gamete be heterozygous?
nondisjunction in the first meiotic division
A reproductive cell, or gamete, has:
one allele of each gene.
An allele is:
one of several forms of a gene.
In humans and other animals, maternal inheritance is characteristic of mitochondrial diseases that often affect _____ phosphorylation.
oxidative
Two examples of X-linked inheritance in humans are:
red-green color blindness and hemophilia.
Reproduction by mitotic cell division:
results in two daughter cells that are genetically identical.
What process can account for the phenomenon wherein a normal XY male produces a sperm carrying two Y chromosomes?
second-division nondisjunction If nondisjunction occurred in the first division, the X and Y chromosomes would not separate and sperm would form with X and Y chromosomes. Only nondisjunction in the second division, in which the Y sister chromatids failed to separate, could a sperm be formed that had two Y chromosomes.
Which of the answer choices is an example of stabilizing selection?
selection for average birth weight in humans
______ selection is a form of selection that works on reproductive ability, even if the traits selected for limit the organism's chance of survival.
sexual
In a fish species the eggs tend to be fertilized more often by the mid-sized males and less often by the largest and smallest males. This is an example of:
stabilizing selection
Genes that are close together in the same chromosome:
tend to be transmitted together
In some experiments, several identical groups are set up, keeping conditions similar among them. In the _____ group, a change is deliberately introduced. In the _____ group, this change is not introduced. In this way, the researcher can determine if the change has an effect.
test; control
Recessive alleles in the X chromosome are expressed in males because:
the Y chromosome does not contain the wild-type allele.
A phenotype is:
the expression of a trait in an individual. Physical observation.
What does the term 2pq represent in the Hardy-Weinberg equation?
the frequency of heterozygotes
Which of Mendel's findings is not applicable when predicting the results of crosses involving genes that are closely linked?
the law of independent assortment
The centrosome is:
the microtubule organizing center for the mitotic spindle.
The principle of independent assortment holds that:
the pattern of inheritance of one trait does not influence the pattern of inheritance of another trait.
In Mendel's crosses:
the plants he started with had two alleles of each gene.
Nucleic acids are important information storage molecules present in virtually every cell. Which of the processes is carried out by a cell when it accesses that information in the DNA of the genes?
transcription and translation
T or F: In humans, fruit flies, and many other organisms, most of the genes on the X chromosome are not found on the Y chromosome.
true
The fruit fly cross shown here analyzes the transmission of two genes on the X chromosome. The male parent has mutant alleles for both the white gene (w-) which results in white eyes and the crossveinless gene (cv-) which results in the absence of crossveins of the fly wings. The female parent has nonmutant forms of these genes (w+ and cv+). In the parental generation, the genotype of the female parent is _____, and the genotype of the male parent is _____.
w+cv+/w+cv+; w-cv-/Y
Genetic drift is more likely to cause evolution in a small population than in a large one because:
with fewer individuals, which individuals mate can have larger effects in small populations.
