Genetic Launchpad Questions:

One centiMorgan equals how many map units? 100 10 1 50 1000

1

How many alleles does each diploid individual possesses at a specific locus? 0 1 2 3 4

2

The following testcross produces the progeny shown: Aa Bb x aa bb → 10 Aa Bb, 40 Aa bb, 40 aa Bb, 10 aa bb. What is the percent recombination between the A and B loci? 10% 20% 40% 50% 80%

20% Correct! 20% of the progeny have recombinant genotypes.

On average, dizygotic twins have about what percentage of their genes in common? 10% 25% 50% 75% 100%

50%

A woman who is homozygous for the sex-linked recessive condition of red-green colorblindness marries a man with normal vision. Among their possible children, which of the following would you expect not to see? All of the above would normally be expected to occur. A colorblind boy A boy with normal vision A girl with normal vision A girl who is heterozygous for the colorblind allele

A boy with normal vision Correct! All of the boys should be colorblind.

In human pedigrees, what does the circle symbol represent? A female A male A phenotypically normal individual An affected individual A mating between two related individuals

A female

A woman who is heterozygous for the sex-linked condition of red-green colorblindness marries a man with normal vision. Which of the following would you not expect to observe among their possible children? A son with normal vision and a daughter who is colorblind Two sons, one with colorblindness and the other with normal vision A son and a daughter, both with normal vision A son who is colorblind and a daughter with normal vision Two daughters who both have normal vision

A son with normal vision and a daughter who is colorblind

Two green corn plants are crossed and produce the following offspring: 2/3 green, 1/3 white. What is the genotype of the green progeny? aa AA and Aa AaBb AB Aa

Aa

Which of the following is an example of duplicate recessive epistasis? Seed shape and seed color in peas Coat color in Labrador retrievers Color in squash Albinism in snails None of the above

Albinism in snails

Sex-influenced characteristics are determined by what type of genes? X-linked Autosomal Y-linked Homologous a and c above

Autosomal

In mammals, each inactivated X chromosome forms a darkly staining body known as a _____ body. Barr Bridges Morgan Z body Lyon

Barr

Two children, a brother and his sister, are born with an autosomal recessive condition. They are believed to be the first two individuals in their extended family to have this disorder. What is the most likely genotypes for their parents? The father is likely heterozygous for the disorder, and the mother is likely homozygous for the disorder. The mother is likely heterozygous for the disorder, and the father is likely homozygous for the disorder. The mother is likely homozygous for the normal genotype, and the father is likely heterozygous for the disorder. The father is likely homozygous for the normal genotype, and the mother is likely heterozygous for the disorder. Both parents are likely heterozygous for the disorder.

Both parents are likely heterozygous for the disorder.

Which type of dominance occurs when the heterozygote includes the phenotypes of both homozygotes? Partial dominance Incomplete dominance Complete dominance Overdominance Codominance

Codominance

Which of the following is an example of dominant epistasis? Seed shape and seed color in peas Coat color in Labrador retrievers Color in squash Albinism in snails None of the above

Color in squash

An individual with Turner syndrome has how many Barr bodies? 0 1 2 3 4

Correct: 0

Genes A and B are linked. When no crossing over occurs in an individual with genotype Aa Bb, what proportion of the gametes will be recombinant? 1 ½ ¼ 0 The answer will vary depending uon how far apart the two gene are.

Correct: 0

Which genetic phenomenon would make it difficult to determine the mode of inheritance from analysis of a pedigree? With X-linked dominant inheritance, affected males can't have affected sons if their mates are normal. With autosomal recessive inheritance, affected children often have phenotypically normal parents. Males with a mitochondrial disorder do not pass it on to their children. Incomplete penetrance occurs with some genotypes. Only half the children will be likely be affected with an autosomal dominant trait if one of the parents is affected.

Correct: Incomplete penetrance occurs with some genotypes.

Karyotypes are commonly used to detect _____________ abnormalities. autosomal dominant X-linked recessive chromosome X-linked dominant autosomal recessive

Correct: chromosome

Linked genes occasionally switch from one homologous chromosome to the other through which process? Interference Separation of homologous chromosomes in anaphase II Linkage disequilibrium Crossing over Independent assortment

Crossing over

___ genes suppress the effect of other genes at a different locus. Dominant Lethal Epistatic Maternal Hypostatic

Epistatic

Which feature of human biology and culture is the biggest constraint to the study of human genetics in the United States? Family size Knowledge of human anatomy, physiology, and biochemistry Family records Small number of genes in the human genome Number of genetically influenced traits available for study

Family size

Fruit flies with XXY sex chromosomes and all other chromosomes normal in number have which sexual phenotype? Intersex Female Male Metamale Metafemale

Female Correct! The X:A ratio of these flies is 1.0, which specifies a female phenotype.

The ______________ of 2008 prohibits health insurers from using genetic information to make decisions about health insurance coverage and rates, and employers from using genetic information in employment decisions. Human Genome Law Genetic Information Nondiscrimination Act Genetic Screening Act Federal Budget Act Newborn Screening and Testing for Genetic Disorders Law

Genetic Information Nondiscrimination Act

In which type of inheritance is the phenotype of the offspring determined directly by the genotype of the mother? Sex-linked Sex-limited Genetic maternal effect X-linked Cytoplasmic

Genetic maternal effect

Assume that a mutation occurs in the XIST gene of a XY male that makes the gene inactive. What would you expect would be the phenotypic consequences of this mutation for the male? He would probably not survive because all his X-linked genes would be turned off. He would probably have no phenotypic consequences. He would have several female phenotypic characteristics since his Y chromosome would be inactivated. He would not have expression of some of his autosomal genes. He would have enhanced expression of his Y-linked genes.

He would probably have no phenotypic consequences. Correct! The XIST gene is involved in X inactivation and with XY males the X remains active.

Which genotype produces blood type A? IAIA IAi IAIB ii a and b above

IA is dominant to i, so both IAIA and IAi produce blood type A.

Which of the following statements is FALSE? Recombination rates vary among different species. There is variation in recombination rates among human chromosomes. In humans, recombination rates are about the same for males and females. Recombination does not take place at similar rates in all parts of a chromosome in humans. Recombination rates are different for humans compared to mice and rats.

In humans, recombination rates are about the same for males and females.

Which type of dominance occurs when the heterozygote has a phenotype that is intermediate to the phenotypes of the two homozygotes? Partial dominance Overdominance Codominanc Incomplete dominance Complete dominance

Incomplete dominance

What can be concluded about a trait that shows a concordance of 100% in monozygotic twins and 50% in dizygotic twins? is genetic. It is caused exclusively or almost exclusively by genetic factors. About 25% of the basis of the trait is genetic, while 75% of the basis is environmental. About 25% of the basis of the trait is environmental, while 75% of the basis It is caused exclusively or almost exclusively by environmental factors. About 50% of the basis of the trait is genetic, while 50% of the basis is environmental.

It is caused exclusively or almost exclusively by genetic factors.

Traits encoded by genes located on the X chromosome are termed X-_____ traits.

Linked

______ functions relate recombination frequencies to positions of genetic loci on a chromosome. Repulsion Hybridization Linkage disequilibrium Mapping Coupling

Mapping

Who was the scientist who first discovered darkly staining bodies in nuclei of cells from female cats which were later shown to be the inactive X chromosomes? Mary Lyon Murray Barr Thomas Hunt Morgan Calvin Bridges John Turner

Murray Barr

A two-strand double crossover between two linked genes produces what types of gametes? Assume that both crossovers occur on the same two chromatids. 50% recombinant and 50% nonrecombinant Recombinant only 75% nonrecombinant and 25% recombinant 25% nonrecombinant and 75% recombinant Nonrecombinant only

Nonrecombinant only

_____ occurs when one gene affects multiple characteristics. Dominance Phenocopy Complementation Penetrance Pleiotropy

Pleiotropy

Intrachromosomal recombination (recombination between genes on the same chromosome) occurs where in mitosis and/or meiosis? Anaphase I of meiosis Prophase I of meiosis Anaphase I and anaphase II of meiosis Prophase II of meiosis Prophase of mitosis

Prophase I of meiosis Correct! Crossing over produces intrachromosomal recombination and occurs in prophase I of meiosis.

An allele for red flower color (R) is dominant to an allele for white flower color (r). Heterozygotes for red exhibit 50% penetrance. The following cross is carried out: Rr x rr. What proportion of the progeny will be red? 1 0.5 0.125 0.25 0

The percentage of red offspring will be 0.5 x 0.5 = 0.25.

In the XX-XO sex determination system which of the following is true? The ratio of the number of X chromosomes divided by the number of haploid sets of autosomes determines the sex of the offspring. The presence of the Y chromosome determines the male sex, while the absence of the Y chromosome determines the female sex. The presence of only a single X chromosome determines the female sex, while the presence of two X chromosomes determines the male sex. The temperature during embryonic development determines the sex of the offspring. The presence of only a single X chromosome determines the male sex, while the presence of two X chromosomes determines the female sex.

The presence of only a single X chromosome determines the male sex, while the presence of two X chromosomes determines the female sex. Correct! In the XX-XO system, males have the XO chromosome constitution.

A twin study of a trait revealed that the concordance for monozygotic twins was 15% but was 85% for dizygotic twins. What would you conclude from the study? The trait has both a significant genetic basis and a significant environmental basis. The trait is mainly genetic in nature with very little environmental basis. The trait is mainly environmental in nature with very little genetic basis. The trait is probably caused by a single gene pair, and it is inherited in an autosomal dominant fashion. The results make no sense and can't be explained, except to assume that the study was flawed.

The results make no sense and can't be explained, except to assume that the study was flawed.

In the nondividing pancreatic cells of a human male, how many sex chromosomes would you expect to see? None One Two Four Correct answer not given

Two

Which individuals should be crossed to carry out a complementation test? An individual heterozygous for both mutations and an individual homozygous for both mutations. Two individuals heterozygous for different mutations. Two individuals homozygous for the same recessive mutations. An individual that is wild-type and an individual homozygous for a recessive mutation. Two individuals homozygous for different mutations

Two individuals homozygous for different mutations

When referring to twin studies, the term "discordant" means what? When the twins are monozygotic twins When one member of a twin pair has the trait or disorder and the other one does not When both members of the twin pair have the trait or disorder When both members of the twin pair do not have the trait of disorder When the twins are dizygotic twins

When one member of a twin pair has the trait or disorder and the other one does not

A man with a hereditary skin condition has 10 children with a phenotypically normal woman who is homozygous for the normal allele: 5 of the children are normal boys and 5 are girls who all have the same skin condition as their father. Which of the following is the most likely genetic basis for the skin condition? Autosomal recessive Autosomal dominant X-linked recessive X-linked dominant Y-linked

X-linked dominant

An affected father and a phenotypically normal woman have a son who is affected with the same trait as the father. Which of the following modes of inheritance can be excluded for this trait? Autosomal recessive X-linked recessive Autosomal dominant X-linked dominant Y-linked

X-linked dominant Correct! Males do not pass their X chromosome to their sons, so affected males would not have affected sons.

X inactivation is controlled by the _____ gene. SRY androgen insensitivity female-determining XIST None of the above answers is correct.

XIST

A man and a woman who both have normal vision have a daughter with the sex-linked recessive condition of red-green colorblindness. The daughter is also short and has folds of skin on the neck. A chromosome analysis of the daughter would likely reveal that she has which of the following chromosome constitutions? XX XXX XO XY XXY

XO

A man who is heterozygous for a sex-linked recessive condition such as red-green colorblindness is likely to have which of the following chromosome constitutions? XXY XXX XY XYY XO

XXY Correct! The male must have two X chromosomes to be heterozygous.

Individuals with the most common form of androgen insensitivity syndrome have which sex chromosomes? XXY XX XO XYY XY

XY

In birds, females have which sex chromosomes? XO ZZ ZW XX XY

ZW Correct! Birds have the ZZ, ZW sex determining system.

A bird that is heterozygous for a sex-linked trait is most likely to have which of the following chromosome constitutions? ZZ XY ZW WW XO

ZZ

Linked genes are those that ________. code for traits involved in sex and reproduction are located close together on the same chromosome code for linked steps in a biochemical pathway code for the same phenotypic traits are located on more than one chromosome

are located close together on the same chromosome

In a three-point cross, the double-crossover progeny can be identified because they

are the least numerous progeny.

The process of dosage _____ equalizes the amount of protein produced by X-linked genes in the two sexes. imbalance inactivation compensation activation None of the above is a correct answer.

compensation

To determine whether mutations occur at the same or different loci, one could use a _____ test. dominance complementation chi-square litmus penetrance

complementation

If both members of a twin pair exhibit a trait of interest, the twins are said to be dizygotic discordant fetal monozygotic concordant

concordant

Characteristics that exhibit many overlapping phenotypes are called _____ characteristics. recessive dominant polygenic discontinuous continuous

continuous

Traits encoded by genes located on mitochondrial DNA exhibit _____ inheritance. ribosomal nuclear cytoplasmic X-linked chloroplast

cytoplasmic

For single crossovers, the frequency of recombination is half the frequency of crossing over because each crossover takes place between only two of the four chromatids of a homologous pair. a test cross between a homozygote and heterozygote produces ½ heterozygous and ½ homozygous progeny. the frequency of recombination is always 50%. crossovers occur in about 50% of meioses. each crossover involves all four chromatids but this only occurs in half the meiotic events.

each crossover takes place between only two of the four chromatids of a homologous pair. Correct! For single crossovers, the frequency of recombination is only half of the recombination frequency because each single crossover takes place between only two of the four chromatids.

A three-point testcross is often used to determine whether mutations occur at the same or at different loci determine if chromosome mutations are present do a complementation test isolate mutations affecting a particular trait efficiently map genes

efficiently map genes

Dosage compensation is a mechanism that ensures that the amount of protein produced by a Y-linked gene is the same as the amount produced by an X-linked gene. ensures that a dose of a drug is the same for males and females. equalizes the effects of X-linked genes relative to autosomal genes. equalizes the amount of protein produced by X-linked genes in the two sexes. equalizes the effects of Y-linked genes relative to autosomal genes.

equalizes the amount of protein produced by X-linked genes in the two sexes.

The degree to which a character is expressed is known as the dominance characteristic expressivity codominance lethality

expressivity

A 13:3 ratio is produced by codominant alleles gene interaction dominance at a single locus imprinting incomplete dominance

gene interaction

A gene at one locus affecting the expression of a gene at a different locus is termed dominance multiple alleles variable expressivity gene interaction independent assortment

gene interaction

Chromosome maps constructed using recombination frequencies are called _____ maps. coupling genetic physical complementation crossing

genetic

In sequential _____, each individual animal is both male and female, but not at the same time. genic sex determination XX-XO sex determination hermaphroditism XX-XY sex determination ZZ-ZW sex determination

hermaphroditism

A(n) ____ gene is suppressed by the effect of another gene at a different locus. lethal epistatic hypostatic dominant maternal

hypostatic

Dosage compensation in human cells is achieved by doubling the activity of genes on the single X chromosome of males. halving the activity of genes on both X chromosomes of females. inactivating one X chromosome of females. All of the above None of the above

inactivating one X chromosome of females.

The patchy distribution of black and orange fur in tortoiseshell cats is caused by X deletion addition disjunction inactivation reactivation

inactivation

The Barr body is assumed to be the Y chromosome. structure that allows the X chromosome to pair with the Y chromosome at meisosis. inactive X chromosome. location of the SRY gene. pseudoautosomal region of the X chromosome.

inactive X chromosome.

Sex- _____ characteristics are encoded by autosomal genes that are expressed differently in males and females. linked determined limited dominant influenced

influenced

The degree to which one crossover interferes with additional crossovers in the same region is the interference recombination frequency mapping function linkage disequilibrium haplotype

interference

A sex- _____ characteristic is encoded by autosomal genes that are expressed only in one sex. linked influenced limited determined dominant

limited

Traits encoded by genes located on the Y chromosome are termed Y-_____ traits. disjoined labeled dissociated linked None of the above is a correct answer.

linked

Genetic _____ are variable genes or DNA sequences with easily observable allelic differences. centiMorgans haplotypes heterokaryons cell lines markers

markers

Characteristics affected by many genes and environmental factors are called multifactorial pleiotropic discontinuous phenocopies continuous

multifactorial

The Lyon hypothesis states that in females of most mammals males get their X chromosome from their fathers. one of the two X chromosomes is inactivated in each cell (which one becomes inactive is random). the Y chromosome is inactivated. the genes on both X chromosome are partially reduced in express so that they will equal the expression of these genes in males who only have one copy. the genes on certain autosomes are inactivated.

one of the two X chromosomes is inactivated in each cell (which one becomes inactive is random).

Incomplete _____ occurs when the genotype does not always produce the expected phenotype. dominance penetrance lethality genic interaction heterozygotes

penetrance

The percentage of individuals having a particular genotype that express the expected phenotype is the degree of dominance -expressivity -genotypic ratio -penetrance -allele frequency

penetrance

The term sex refers to an organism's sexual interests chromosomes genotype phenotype behavior

phenotype

In biology, the sex (male or female) of an organism is defined in reference to its phenotype. presence or absence of two X chromosomes ability to have offspring genotype presence or absence of a Y chromosome

phenotype.

Characteristics encoded by genes at many loci are termed polygenic characteristics phenocopies dominant characteristics pleiotropic characteristics epigenetic characteristics

polygenic characteristics

The person from whom a pedigree is initiated is called the __________ and is usually designated by an arrow. Correct term not given above the paternal (male) founder of the family carrier the maternal (female) founder of the family proband

proband

A rare ____________ trait is more likely to appear in a pedigree when two people who are closely related mate. dominant recessive Y-linked mitochondrial All of the above answers are correct.

recessive

Gametes that contain new combinations of alleles not present in the parents are called _____ gametes. restricted recombinant haplotype nonrecombinant repulsion

recombinant

When one wild-type allele and one mutant allele are found on each chromosome ( ), the genes are said to be in _____ configuration. association coupling equilibrium repulsion recombinant

repulsion

Chromosomes that differ between males and females are called ____ chromosomes. monoecious heterogametic pseudoautosomal autosomal sex

sex

The fundamental difference between males and females across all organisms is the size of the gametes: Males produce small gametes, and females produce larger gametes presence or absence of a Y chromosome presence or absence of two XX chromosomes presence or absence of a penis ability to nurture its offspring

size of the gametes: Males produce small gametes, and females produce larger gametes

Anticipation is the effect of environmental factors on the expression of a genetic trait stronger or earlier expression of a trait as it is passed from generation to generation. proportion of individuals with a genotype that express the expected phenotype sudden appearance of a genetic disease in a family without any prior history of the disorder prediction of genetic risk by examination of the DNA

stronger or earlier expression of a trait as it is passed from generation to generation.

A three-point cross is a testcross for three genes cross involving genes on three different chromosomes testcross with genes that are 3 map units apart testing for genetic differences among three individuals cross involving three different parents

testcross for three genes

Newborns are generally screened for genetic diseases when a close relative is known to be affected. that are irreversible or untreatable disorders. when heterozygous parents are affected. that are fatal by one year of age. that are treatable or preventable.

that are treatable or preventable. Correct! The goal of newborn screening is provide early treatment to affected children to improve their lives.

In a three-point cross, the nonrecombinant progeny can be identified because they are homozygous for all three loci. the progeny with recessive phenotypes the most numerous progeny the least numerous progeny the only progeny

the most numerous progeny

Lod (logarithm of odds) scores are used to determine the interference among genes whether the observed number of progeny in a genetic cross differs significantly from the expected number the probability that two genes are linked the chi-square value for independent assortment whether two alleles are in the repulsion configuration or the coupling configuration

the probability that two genes are linked

Direct-to-consumer genetic tests have been of concern to public health officials because they can provide information about an individual's ancestry. they can provide information about an individual's genotype. the results may be difficult to interpret without the involvement of appropriate genetic counseling they sometimes require that a blood sample be given. they often involve DNA analysis, and an individual will have to develop the laboratory skills to do this analysis.

the results may be difficult to interpret without the involvement of appropriate genetic counseling

Two genes have been both assigned to chromosome 12 by somatic-cell hybridization analysis. However when lod-score analysis is performed, the genes appear to be assorting independently. The most likely reason for the different results is that it is difficult to do lod score analysis with genes that are on chromosome 12. the two genes have multiple alleles. chromosome 12 is often lost in somatic-cell hybridization experiments, so the results from these experiments are not reliable. the lod-score analysis likely resulted in a high lod-score value in this experiment. the two genes are far apart on chromosome 12.

the two genes are far apart on chromosome 12. Correct! Genes that are far apart on a chromosome will assort independently and linkage will not be detected by lod-score analysis.

Females exhibiting an X-linked recessive trait inherited it from their mother only their father only their mother or their father their mother and their father their sisters

their mother and their father Correct! Females inherit one X from their mother and one from their father.

XY males inherit genes for an X-linked recessive trait from their father only their mother only. their mother and their father their mother or their father usually their father but occasionally from their mother

their mother only. Correct! Males inherit their single X chromosome from their mother.

A three-point testcross is performed to obtain data for gene mapping. A coefficient of coincidence of 2.0 is obtained. A coefficient of coincidence of 2.0 means that no parental progeny were obtained in the offspring. twice the number of double crossover progeny were obtained in the offspring compared to the number expected based upon probability. no double crossover progeny were obtained at all in the progeny. crossover interference was high and a crossover in one gene region suppressed the frequency of a crossover occurring in the adjacent region. only half the number of double crossover progeny were obtained in the offspring compared with the number expected based upon probability.

twice the number of double crossover progeny were obtained in the offspring compared to the number expected based upon probability. Correct! This would mean that twice the number of double crossover offspring were obtained than were expected to occur based upon probability.

Consider the following cross: Aa Bb x aa bb. If these genes assort independently, what proportion of the progeny will have genotype Aa Bb? ¾ ¼ ½ 1/8 1

¼ Correct. The probability of genotype Aa Bb progeny is ½ (the probability of Aa) x ½ (the probability of Bb) = ¼.

Genes A and B are linked. When a single crossover occurs in an individual with genotype Aa Bb, what proportion of the resulting gametes will be recombinant? 1 ½ ¼ 0 The answer will vary depending uon how far apart the two gene are.

½