exam 4

genetic drift

-responsible for the founder effect -responsible for the bottleneck effect -causes allele frequencies to fluctuate randomly

If there are two alleles of a gene, B and b, and the frequency of the B allele (p) is 0.90, the frequency of the b allele (q) is 0.30. 0.01. 0.81. 0.10. 0.09.

0.10.

If the genotypic frequencies for an allele in a population at Hardy-Weinberg equilibrium are 0.635 homozygous dominants, 0.430 heterozygotes, and 0.125 homozygous recessives, what is the frequency of the recessive allele? 0.01 0.65 0.35 0.875 0.125

0.35

For a gene A, a geneticist studying a population of butterflies found the following genotypes: 108 AA butterflies 144 Aa butterflies 48 aa butterflies What is the observed genotypic frequency of Aa individuals? 1.44 0.72 0.40 0.144 0.48

0.48

Solid black, black with tan belly, and agouti coat color in mice are all caused by alleles of the agouti gene. All three colors can be true-breeding. When using mice from true-breeding strains: (1) Black — Agouti F1s are all agouti, (2) Black — Black with Tan belly F1s are all black and tan, and (3) Black with Tan belly — Agouti F1s are all agouti. If you were to cross the F1s from (1) with the F1s from (2), what proportion of the resulting offspring would you expect to be black with a tan belly? 1/4 2/4 3/4 all none

1/4

A population genetic study of a certain insect revealed four alleles for the GPI (glucose-phosphate isomerase) locus. How many different genotypic classes should be found? 16 10 20 8 4

10 = n(n+1)/2 (kinds of heterozygotes = n(n-1)/2)

For alleles of genes in Hardy-Weinberg equilibrium, the frequency of heterozygotes is represented as p. 2pq. q. q2. p2.

2pq

With respect to the chromosomes involved in the translocation, 14 and 21, what is the total number of different gametes possible for a heterozygous carrier parent to produce? 4 3 2 6

6 During meiosis, the Robertsonian chromosome may sort to one pole of the cell alone, with the normal copy of chromosome 14, or the normal copy of chromosome 21. The other chromosomes migrate to the opposite pole.

How many different phenotypes are possible in a one gene/three allele system that displays codominance to each other?

6 number of genotypes = 3(3+1)/2 With three alleles, a1, a2, a3, each unique combination of two alleles results in a distinct phenotype. Possible combinations are: a1/a1 a1/a2 a1/a3 a2/a2 a2/a3 a3/a3

In pseudodominance, the dominant allele of a gene is ______, and the recessive allele is _________. A) deleted; expressed B) expressed; masked C) expressed; deleted D) deleted; masked

A) deleted; expressed

Thirty people are selected for a long-term mission to colonize a planet many light years away from Earth. The mission is successful and the population rapidly grows to several hundred individuals. However, certain genetic diseases are unusually common in this group, and their gene pool is quite different from that of the Earth population they have left behind. Which of the following phenomena has left its mark on this population? A) founder effect B) high rates of mutation C) bottleneck effect D) natural selection

A) founder effect

A man with the A blood type marries a woman with blood type B. Which blood type or types could their children have? A B O A, B, AB, or O

A, B, AB, or O Assuming that both the man and woman are heterozygous, their children could have any of the four possible phenotypes; A, B, AB, or O.

Which of the following statements regarding familial Down syndrome is false? A. If one parent is a translocation heterozygote for chromosomes 14/21, a child born to this parent is as likely to have Down syndrome as he is to be normal. B. Heterozygous carriers of the Robertsonian translocation that causes familial Down syndrome can have children who are phenotypically normal and are not carriers of the translocation. C. It accounts for approximately 5% of all Down syndrome cases. D. Heterozygous carriers of the Robertsonian translocation that cause familial Down syndrome can have children who are also carriers of the translocation.

A. If one parent is a translocation heterozygote for chromosomes 14/21, a child born to this parent is as likely to have Down syndrome as he is to be normal.

Which of the following statements best describes the relationship between the Hardy-Weinberg principle and the effects of natural selection? A. If selection can be quantified, relative fitness values can be calculated and used to appropriately modify the Hardy-Weinberg equation. B. Natural selection can influence the genotype frequencies predicted by Hardy-Weinberg, but allele frequencies are not affected. C. If it can be determined that selection favors a particular genotype, the Hardy-Weinberg equation should not be applied. D. The Hardy-Weinberg equation assumes that all genotypes occur with equal frequency, but if there is selection against one or more genotypes, equal frequency of all genotypes is not possible.

A. If selection can be quantified, relative fitness values can be calculated and used to appropriately modify the Hardy-Weinberg equation. Although Hardy-Weinberg predictions assume no selection, selection values, if known, can be used to modify predictions of the model.

If there are two alleles of a gene controlling coat color in a population of mice and the frequency of the dominant allele is 0.3, which of the following must be true? A. The frequency of the recessive allele is 0.7. B. There must be a mistake in the calculation because the frequency of the dominant allele cannot be smaller than the frequency of the recessive allele. C. The frequency of homozygous dominant mice in the population is 0.09. D. There is strong selection against the recessive allele.

A. The frequency of the recessive allele is 0.7.

Which of the following statements best describes the relationship between fitness and selection coefficient (s)? A. The stronger the selection against a given genotype, the lower the fitness associated with that genotype. B. The higher the fitness value associated with a given genotype, the stronger the selection against that genotype. C. Fitness is a qualitative measure whereas selection is a quantitative measure. D. The lower the fitness value associated with a given genotype, the weaker the selection against that genotype.

A. The stronger the selection against a given genotype, the lower the fitness associated with that genotype. Fitness = 1 - selection

The distinctive fur pattern of Siamese cats results when genes that are responsible for the coat color are influenced by A. temperature. B. age. C. X-inactivation. D. gender. E. other genes.

A. temperature.

In the Hardy-Weinberg model, the ideal population is non-migrating. very large. randomly mating. free of mutations. All of these

All of these

Nondisjunction of chromosomes may result in the addition of one homologous chromosome pair. the loss of a single chromosome. the addition of a single chromosome. the loss of one homologous chromosome pair. All of these

All of these

Which of the following traits is determined by programmed transposition? Pattern baldness in humans Eye color in Drosophila Mating types in yeast All of these None of these

All of these

Which of the following arrangements would yield the greatest reduction in gamete viability? An inversion heterozygote for a small inversion An inversion homozygote for a small inversion An inversion heterozygote for a large inversion An inversion homozygote for a large inversion

An inversion heterozygote for a large inversion A large heterozygous inversion will result in greater numbers of genes that are duplicated or deleted when crossing over occurs.

A and B antigens in human blood are produced by the conversion of ________ by the addition of a sugar group. A) anti-A and anti-B antibodies B) the H antigen C) hemoglobin D) α-N-acetylgalactosamine E) anti-O antibodies

B) the H antigen

Which of the following is the most likely example of codominance? A. A pure-breeding tall plant is crossed to a pure-breeding short plant. All their progeny are of medium height. B. A pure-breeding plant with red flowers is crossed to a pure-breeding plant with white flowers. All their progeny have flowers with some red patches and some white patches. C. A plant with red flowers is crossed to a plant with white flowers. Half their progeny have red flowers, the other half have white flowers. D. A pure-breeding plant with red flowers is crossed to a pure-breeding plant with white flowers. All their progeny have pink flowers.

B. A pure-breeding plant with red flowers is crossed to a pure-breeding plant with white flowers. All their progeny have flowers with some red patches and some white patches. Heterozygotes express both alleles

What is the genetic consequence of a homozygous translocation? A. Gene duplications and deletions B. An alteration in the linkage relationships of genes C. Abnormal pairing during meiosis D. Formation of abnormal chromatids following crossing-over E. Inviable gamete formation (semisterility)

B. An alteration in the linkage relationships of genes

Familial hypercholesterolemia is a genetic disease that affects approximately one in 500 people worldwide. There is more than one genetic cause of the disease. Class I is often described as an autosomal dominant disease. Affected individuals have cholesterol levels >250 as children and often >300 as adults. However, homozygotes have cholesterol levels of >600 as children and can die of heart attacks in their 20s. These individuals entirely lack a functional LDL receptor. Which of the following would be the best description of the inheritance of this form of hypercholesterolemia? A) Dominant epistatic B) Codominant C) Incompletely dominant D) Complementary E) Recessive epistatic

C) Incompletely dominant

Dicentric or acentric chromosomes may arise in meiosis after crossing over as a result of which kind of chromosomal mutation? A) deletion B) translocation C) inversion (paracentric) D) duplication

C) inversion (paracentric)

Neurofibromatosis is a dominantly inherited disease that can show mild, moderate, or severe symptoms. Every individual that inherits the dominant allele shows at least mild symptoms. This means that the disease allele shows A) variable penetrance and complete expressivity. B) variable penetrance and variable expressivity. C) variable expressivity and complete penetrance. D) complete penetrance and complete expressivity.

C) variable expressivity and complete penetrance.

Comb shape in chickens is controlled by A. one gene with incomplete dominance, resulting in three different phenotypes. B. the epistatic interaction of two genes, resulting in two different phenotypes. C. the interaction of two genes with complete dominance, resulting in four different phenotypes. D. the interaction of three alleles and codominance, resulting in four different phenotypes. E. None of these

C. the interaction of two genes with complete dominance, resulting in four different phenotypes.

Chromosomal mutations in prokaryotes or eukaryotes may occur A. as the result of exposure to chemicals. Therefore, all the choices listed are correct. B. as the result of exposure to radiation. C. spontaneously D. All of the choices listed are correct.

D. All of the choices listed are correct. Chromosomal mutations can occur spontaneously, or they can be induced by chemical or radiation treatment.

A person with type B blood could safely receive a transfusion of blood from someone with blood type A. O. B. AB. C. B. D. Both A and C E. Any of these

D. Both A and C

A Robertsonian translocation is considered non-reciprocal because _______. A. trisomies of chromosome 21 are viable, whereas monosomies of the same chromosome are not B. for every viable gamete formed, there are two inviable gametes formed C. an uneven number of gametes is produced in each meiosis D. the smaller of the two reciprocal products of translocated chromosomes is lost

D. the smaller of the two reciprocal products of translocated chromosomes is lost After several cell divisions, only the larger of the two translocated chromosomes remains. Its reciprocal is lost.

Dextral (D) and sinistral (d) shell coiling in the water snail Limnaea peregra is genetically determined by a maternal effect gene. From a population of mixed sinistral and dextral snails, a sinistral female and a dextral male are chosen. All the offspring are dextral. When the female offspring are mated, 50% produce only sinistral snails and the other 50% produce only dextral snails. What were the genotypes of the sinistral female and dextral male that were initially chosen? DD female and dd male dd female and DD male dd female and Dd male Dd female and dd male Dd female and Dd male

Dd female and dd male

Which of the following types of chromosomal mutation cannot revert to the wild-type state? Inversion Duplication Translocation Deletion Any of these may revert to wild-type

Deletion

Many scientists believe that the evolution of multigene families, such as the genes for hemoglobin, is a result of which type of genetic rearrangement? Nonreciprocal translocation Reciprocal translocation Inversion Duplication Deletion

Duplication

Which of the following will result in modifications to the expected Mendelian ratios? A. Incomplete dominance B. Gene interaction C. Incomplete penetrance D. Epistasis E. All of these

E. All of these

Two true-breeding mutant strains of Drosophila have black body color instead of the wild-type gray yellow. When the two strains are crossed, all the F1 flies have wild-type body color. How can these data be interpreted? A. A new mutation occurred in all the offspring. B. Complementation occurred. C. The mutations involved are on two different genes. D. Recombination occurred. E. Both B and C

E. Both B and C

In familial Down syndrome resulting from Robertsonian translocation, A. the affected individual has three copies of the long arm of chromosome 14, one of which is attached to chromosome 21. B. the affected individual has two copies of the long arm of chromosome 21, one of which is attached to part of chromosome 14. C. the affected individual has three copies of the complete chromosome 21. D. the affected individual is missing a copy of chromosome 21. E. the affected individual has three copies of the long arm of chromosome 21, one of which is attached to part of chromosome 14.

E. the affected individual has three copies of the long arm of chromosome 21, one of which is attached to part of chromosome 14. (two acrocentric chromosomes)

The degree to which a penetrant genotype is phenotypically expressed.

Expressivity

FMR1 is silenced in which disease

Fragile X syndrome- an x-linked recessive disease

Which of the following is not a form of genetic drift? Founder effect Population bottleneck Nonrandom mating Heterozygote advantage All of these are forms of genetic drift.

Heterozygote advantage Forms of genetic drift are: -the founder effect -population bottleneck -nonrandom mating

The chemical colchicine prevents the formation of microtubules. It is commonly used in certain experimental procedures to cause changes in cellular chromosomes. Which of the following changes is it likely to be used to create? Induction of chromosomal deletions in experimental cell lines Induction of chromosomal duplications in experimental cell lines Induction of mutant polyploid individuals Induction of mutant aneuploid individuals Prevention of nondisjunction in cell cultures

Induction of mutant polyploid individuals

Which of the following types of analysis allows scientists to visualize an individual's chromosomal makeup? Genetic crosses Pedigree analysis Deletion mapping Inheritance analysis Karyotype analysis

Karyotype analysis

Workers from a nearby greenhouse accidentally introduce white flower seeds into this population's habitat (mechanism and effect on allele frequencies)

Mechanism: gene flow (also called migration — is any movement of individuals) Effect on allele frequencies: frequency of white allele increases

A storm kills many plants at random (mechanism and effect)

Mechanism: genetic drift Effect on allele frequencies: allele frequencies change but not predictably

Plants with purple flowers attract more insects, which pollinate the plants (mechanism and effect on allele frequencies)

Mechanism: natural selection Effect on allele frequencies: frequency of purple allele increases

During an extreme heat wave, plants with white flowers survive better. (Mechanism and Effect on allele frequencies?)

Mechanism: natural selection Effect on allele frequencies: frequency of white allele increases

A monosomic cell would produce gametes with how many chromosomes? N+1 N N-1 N and N-1 N and N+1

N and N-1

A child with type AB blood could not be the offspring of a man with type ___ blood. A B AB O

O The child must inherit either an IA or an IB allele from the father; therefore, he could not have blood type O.

Which of the following methods is least useful for assessing levels of genetic variation in populations? Protein electrophoresis Phenotypic observation RFLP analysis DNA sequencing VNTRs

Phenotypic observation

Which of the following is not used to help identify individual chromosomes in a karyotype? Centromere position Banding pattern on staining Point mutations Chromosome size Heterochromatin regions

Point mutations

_________ results in multiple complete chromosome sets. Tandem duplication Nondisjunction Aneuploidy Polyploidy

Polyploidy duplication of the entire genome = polyploidy

Manx cats have no tails. When two Manx cats are bred together there is always a one third chance that a kitten will have a tail. When a Manx cat is bred to a cat with a normal tail there is a one-half chance that a kitten will have a tail. Which of the following is the best explanation for this? The Manx phenotype is caused by gene interactions. The Manx phenotype is a result of heteroplasmy. The Manx phenotype is dominant epistatic. The Manx phenotype is dominant, but the allele is a recessive lethal. The Manx genotype exhibits variable expression.

The Manx phenotype is dominant, but the allele is a recessive lethal.

True or false: For a gene with complete dominance, the recessive allele has no effect on the phenotype of a heterozygote.

True

True or false: Studies performed on identical twins separated at birth have shown that many phenotypes, such as IQ or alcoholism, are influenced by the person's genotype as well as by their environment.

True

True or false: The color dilution gene in horses is an example of incomplete dominance.

True

Allele frequencies can change across the geographic range of a species according to climate, geological features, or direction in the range. For instance, a certain allele frequency might go up along with the elevation or down as you go south in the species' range. This systematic change in frequency is referred to as heterosis. genetic drift. directional selection. q2. a cline.

a cline (geographic gradient in the frequency of a gene)

Cultivated wheat is descended from three distinct species, each with a diploid set of 14 chromosomes. Thus, it is an autotetraploid with 28 chromosomes. an allotriploid with 42 chromosomes. an allohexaploid with 42 chromosomes. an allohexaploid with 84 chromosomes. an allotriploid with 21 chromosomes.

an allohexaploid with 42 chromosomes.

gene flow

can introduce new alleles into a population's gene pool -- a result of the movement of fertile individuals or their gametes

Chronic Myeloid Leukemia defintion

cancer of white blood cells; typically in middle aged adults

A dicentric chromosome has two mutations. centromeres. centrosomes. arms. telomeres.

centromeres

All of the following could result from meiosis in a pericentric inversion heterozygote in which a single crossover occurred within the inversion loop except a _______. completely normal chromosome chromosome with some deleted regions chromosome with some duplicated regions chromosome with two centromeres

chromosome with two centromeres When the centromere is contained within the inversion, it is neither duplicated nor deleted.

Two persons who have recessive genetic deafness marry and have 6 children. All the children can hear. The reason they can hear is most likely due to epistasis. sex linkage. partial penetrance. pleiotropy. complementation.

complementation.

natural selection

consistently causes a population to become better adapted to its environment a result of differential success in reproduction cannot cause a harmful allele to become more common

A(n) ___ within a chromosome changes the amount of DNA in that chromosome. translocation inversion deletion point mutation

deletion There are four common types of chromosomal mutations involving changes in chromosome structure: deletions and duplications, both of which involve a change in the amount of DNA on a chromosome; inversions, which involve a change in the orientation of a chromosomal segment; and translocations, which involve a change in the location of a chromosomal segment.

Prader-Willi Syndrome chromosomal variation

deletion on chrosome 15 (paternally inherited)

Charcot-Marie-Tooth disease definition

disorder of the peripheral nervous system; progressive loss of muscle tissue and tissue sensation

Charcot-Marie-Tooth disease chromosomal variation

duplication on chromosome 17

A gene that masks the expression of a second gene is haplosufficient. incompletely dominant. epistatic. homeostatic.

epistatic epistasis is a form of gene interaction in which one gene masks the phenotypic expression of another.

A human cell containing two sets of 23 chromosomes is euploid. haploid. polyploid. aneuploid. None of these

euploid (balanced set of chromosomes) (Aneuploid- unbalanced) (Polyploid- multiple sets over 2)

True or false: A gene is known to have three alleles: p, q, and r. The frequency of p is estimated at 0.70. Thus, the frequencies or q and r must be 0.15 each.

false

True or false: According to the Hardy-Weinberg principle, at equilibrium the allele frequencies are dependent on the genotypic frequencies.

false

True or false: An allele that exhibits incomplete dominance is usually haplosufficient.

false

True or false: For eukaryotic organisms, polyploidy is always a lethal condition.

false

True or false: In a genotype with complete penetrance, less than 100% of individuals with a particular genotype exhibit the expected phenotype.

false

True or false: Mutants that make up a complementation group complement each other.

false

True or false: Sex-limited traits are caused by genes that are on sex chromosomes.

false

True or false: The Hardy-Weinberg relationship cannot be used to compute allele frequencies when one or more alleles are recessive.

false

True or false: Inversion loops do NOT form during meiosis in paracentric inversion heterozygotes.

false Loop formation allows pairing within inverted regions of homologous chromosomes regardless of whether the centromere is included in the inversion.

An X-linked homozygous color-blind woman gives birth to a son who is not color blind. He could have normal vision because he has Turner syndrome. is XYY. has triploidy. has Down syndrome. has Klinefelter syndrome.

has Klinefelter syndrome.

why a maternal spindle transfer is used

has been shown to cure mitochondrial disease

If a small region of a chromosome containing a non-essential gene is completely deleted, and an organism has two identical chromosomes with this deletion, then the organism is dead. has no alleles of that gene. will exhibit pseudodominance. has more heterochromatin. has recessive alleles of those genes.

has recessive alleles of those genes.

In the multiple allelic system for eye color in Drosophila, the phenotypic expression of the alleles depends on the sex of the fly. the temperature at which the flies are grown. how much pigment is produced by the alleles present. the interaction of alleles from two different genes. Both A and B

how much pigment is produced by the alleles present.

An example of this phenomenon is when some individuals with identical genotypes do not exhibit any of the expected phenotype.

incomplete penetrance

A mutation event occurs in which two different (nonhomologous) chromosomes end up with a small piece of the other. This mutation is a(n) paracentric inversion. intrachromosomal translocation. intrachromosomal duplication. interchromosomal translocation.

interchromosomal translocation. A translocation event in which there is a transfer of a chromosome segment from one chromosome into a nonhomologous chromosome is called an interchromosomal (between chromosomes) translocation.

Genetic drift may lead to Hardy-Weinberg equilibrium. loss of genetic variation in a population. increased heterozygosity at many loci. a decrease in the mutation rate of a particular gene. All of these

loss of genetic variation in a population.

maternal spindle transfer process

making a three parent embryo: -start with mother's egg with unhealthy mitochondria and a donor's egg with healthy mitochondria -donor nucleus is removed -the mother's nucleus is placed in the donor egg and fertilized

Dextral (D) and sinistral (d) shell coiling in the water snail Limnaea peregra is genetically determined. From a population of mixed sinistral and dextral snails, a sinistral female and a dextral male are chosen. All the offspring are dextral. When the female offspring are mated, 50% produce only sinistral snails and the other 50% produce only dextral snails. This form of inheritance is called partial penetrance. maternal effect. sex-linked inheritance. maternal inheritance. sex-limited inheritance.

maternal effect.

A(n) ________ inversion includes the centromere. concentric epicentric chromocentric paracentric pericentric

pericentric

A ___ inversion is a rearrangement of DNA that involves the centromere. translocated pericentric submetacentric paracentric

pericentric There are two types of inversions. A pericentric inversion includes the centromere, and a paracentric inversion does not include the centromere.

Prader-Willi Syndrome definition

physical, mental, and behavioral problems; hyperphagia

Most monoploid individuals do not survive because recessive lethal mutations cannot be masked by dominant alleles. they do not have the appropriate gene dosages. they have only one sex chromosome. they have missing genes. their cells cannot divide properly.

recessive lethal mutations cannot be masked by dominant alleles.

Chronic Myeloid Leukemia chromosomal variation

reciprocal translocation on chromosomes 9 and 22- Philadelphia chromosome

Seedless bananas are produced from sterile tetraploid allopolyploid plants. sterile triploid autopolyploid plants. fertile diploid plants that are unfertilized. monoploid plants grown from unfertilized seeds. Both C and D

sterile tetraploid allopolyploid plants.

True or false: Both changes in chromosome number and chromosome structure are believed to have resulted in novel genomes, leading to new species.

true

True or false: Duplications and deletions can be detected during meiosis by the presence of extrachromosomal loops that do not pair properly with their homolog.

true

True or false: In a dihybrid cross with independent assortment of the two genes, any deviation from the Mendelian 9:3:3:1 ratio indicates that the phenotype is the product of the interaction of two or more genes

true

True or false: Recessive lethals are often mutations in essential genes.

true

People affected by diseases caused by mtDNA defects show partial penetrance. have epistatic respiration. are sterile. inherited them through maternal effect. typically have cells that are heteroplasmons.

typically have cells that are heteroplasmons.

This explains why people with the same dominant gene for neurofibromatosis can display varying degrees of severity.

variable expressivity

Individuals with neurofibromatosis may have a range of phenotypes, from pigment spots on the skin to tumorlike growths. This is an example of gene magnification. age of onset. incomplete penetrance. variable expressivity. X-inactivation.

variable expressivity.