General Genetics Exam 3 2020-2021

Consider the F2 generation from one of Mendel's monohybrid crosses. What is the probability that an F2 individual displaying the dominant phenotype is a homozygote? A) 1/3 B) 1/4 C) 1/2 D) 2/3 E) 3/4

A) 1/3

Consider a trihybrid cross involving three of Mendel's seven pairs of traits (stem height, flower color, and pea pod shape), where the dwarf height (d), white flower color (w) and constricted pod shape (c) alleles are recessive. What proportion of the progeny from the cross DdWwCc x DdWwCc will be dwarf plants with white flowers and constricted pea pods? A) 1/64 B) 3/64 C) 6/64 D) 9/64 E) 27/64

A) 1/64

Among the crosses below, which should produce offspring that all display the same phenotypes? A) CCdd x ccdd B) CcDd x CcDd C) CcDd x ccdd D) CcDD x ccDd E) Ccdd x ccDD

A) CCdd x ccdd

Albinism in ball pythons is a recessive Mendelian trait. Which of the following would you expect from a cross between two albino ball pythons? A) all of the offspring should be albino B) the offspring should display a 3:1 phenotypic ratio C) half of the offspring should be albino and half should be normally pigmented D) all of the offspring should be normally pigmented E) there is not enough information to predict the progeny phenotypes

A) all of the offspring should be albino

Sister chromatids: A) are joined together by a common centromere B) are part of non-homologous chromosomes C) undergo disjunction during anaphase I D) carry different genes E) both B and C are correct

A) are joined together by a common centromere

Which of the following is a common element of sex determination in both Drosophila and mammals? A) females are typically homogametic and males are typically heterogametic B) the SRY gene C) Barr body formation D) ZZ and ZW sex chromosomes E) none of the above

A) females are typically homogametic and males are typically heterogametic

Although he didn't know it at the time, Mendel's third postulate (segregation) is accounted for by which of the following cytological events? A) the separation of homologous chromosomes during anaphase I B) the separation of sister chromatids during mitotic anaphase C) the decondensation of chromosomes during telophase II D) exit from the cell cycle by cells entering the quiescent G0 stage E) crossing-over between non-sister chromatids during prophase I

A) the separation of homologous chromosomes during anaphase I

Consider the following cross: AabbCcDd x AaBbccDD. What proportion of the offspring would have the genotype AABbccDd? A) 1/64 B) 1/32 C) 1/16 D) 1/8 E) 1/2

B) 1/32

You are working with Drosophila, and cross females from a true-breeding strain with white eyes to males from a true-breeding strain with red eyes. You examine 200 offspring (100 males and 100 females) from this cross. Which of the following matches the expected outcome? A) 100 red-eyed females, 100 red-eyed males B) 100 red-eyed females, 100 white-eyed males C) 50 red-eyed females, 50 white-eyed females, 50 red-eyed males, 50 white-eyed males D) 100 red-eyed females, 50 red-eyed males, 50 white-eyed males E) 100 white-eyed males, 50 red-eyed females, 50 white-eyed females

B) 100 red-eyed females, 100 white-eyed males

A recessive allele in tigers causes a completely white coat. If two normally pigmented tigers are mated and produce a white cub, what percentage of their remaining offspring would be expected to display white coats? A) 0% B) 25% C) 50% D) 75% E) 100%

B) 25%

Among the crosses below, which should produce a 9:3:3:1 phenotypic ratio in the offspring? A) CCdd x ccdd B) CcDd x CcDd C) CcDd x ccdd D) CcDD x ccDd E) Ccdd x ccDD

B) CcDd x CcDd

Pea plants which are heterozygous for the tall and dwarf stem height alleles (Dd) will produce gametes of which of the following genotypes? A) DD, Dd, and dd B) D and d C) D only D) d only E) Dd only

B) D and d

Biological sex in humans is best understood as _______ . A) a strict binary where XX is always female and XY is always male, with no exceptions B) a spectrum that includes typical XY male and XX female development plus a number of variations including intersex conditions C) a haplodiploid system similar to ants and bees D) an example of isogamy E) both A and D are correct

B) a spectrum that includes typical XY male and XX female development plus a number of variations including intersex conditions

In complete dominance, the phenotype of the _____ allele is visible in a heterozygote, while the phenotype of the _____ allele is not visible in a heterozygote. A) recessive, dominant B) dominant, recessive C) haplosufficient, haploinsufficient D) loss of function, gain of function E) both A and D are correct

B) dominant, recessive

Which of the following events occurs during prophase I of meiosis? A) DNA replication occurs B) homologous chromosomes synapse to form tetrads C) sister chromatids separate from each other D) the chromosomes decondense into chromatin E) the chromosome number is reduced from diploid to haploid

B) homologous chromosomes synapse to form tetrads

Which of the following terms describes the condition where sexual reproduction involves two mating types that produce morphologically indistinguishable gametes? A) anisogamy B) isogamy C) hemizygosity D) genotypic sex determination E) both A and C are correct

B) isogamy

By observing the results of his dihybrid cross experiments, Mendel was able to determine that _______ . A) some of his traits exhibited complete dominance, while others did not B) two pairs of traits will be inherited independently in the same experiment C) the F2 generation of his dihybrid crosses always exhibited a 1:1:1:1 phenotypic ratio D) the round seed phenotype and the yellow seed phenotype will always be inherited together E) all of the above

B) two pairs of traits will be inherited independently in the same experiment

How many gamete types can be produced by an individual with the genotype DdEeFf ? A) 2 B) 4 C) 8 D) 16 E) 32

C) 8

Mendel crossed pea plants with yellow full pea pods to pea plants with green constricted pea pods. All F1 plants had pea pods that were green and full. He then self-crossed some of these F1 plants, and observed four different phenotypic classes in the F2. What proportion of these F2 pea plants would you expect to have green full pea pods? A) 3/4 B) 1/4 C) 9/16 D) 3/16 E) 1/16

C) 9/16

Why does X chromosomes inactivation occur in mammals? A) the X chromosome does not carry any genes and is not needed for development B) in males, the Y chromosome turns off the X so that the embryo does not develop as a female C) X-inactivation ensures that X-linked genes are expressed at similar levels in males and females D) the X chromosome carries lethal mutations that would kill the embryo if not inactivated E) none of the above; X-inactivation occurs in fruit flies, not in mammals

C) X-inactivation ensures that X-linked genes are expressed at similar levels in males and females

Sister chromatids separate during _______ . A) anaphase I of meiosis and anaphase II of meiosis B) metaphase of mitosis and anaphase of mitosis C) anaphase of mitosis and anaphase II of meiosis D) prophase I of meiosis and metaphase II of meiosis E) anaphase of mitosis, anaphase I of meiosis, and anaphase II of meiosis

C) anaphase of mitosis and anaphase II of meiosis

When carrying out a testcross for a single gene, if you observe two phenotypic classes in the progeny (one displaying the dominant phenotype, and one displaying the recessive phenotype), which of the following would you conclude? A) both of the parents in the testcross were heterozygous B) both of the parents in the testcross were homozygous C) the parent displaying the dominant phenotype was heterozygous D) the parent displaying the dominant phenotype was homozygous E) the parent displaying the recessive phenotype was heterozygous

C) the parent displaying the dominant phenotype was heterozygous

What makes two alleles of the same gene different from one another? A) they are found on different (non-homologous) chromosomes B) they are found at different locations (loci) on the same chromosome C) they have one or more DNA sequence differences D) nothing; two alleles of the same gene are always identical E) both B and C are correct

C) they have one or more DNA sequence differences

In Mendel's pea plant experiments, the seed color and seed shape traits were controlled by: A) a single gene with two different mutations B) a single gene with four different alleles C) two different genes, each with two alternative alleles D) four different genes, each with a single allele E) an unknown number of genes and alleles

C) two different genes, each with two alternative alleles

If a diploid cell containing six chromosomes (2n=6) undergoes mitosis, how many chromosomes will be present in one of the resulting daughter cells? A) 2 B) 3 C) 4 D) 6 E) 12

D) 6

A homozygote is __________ . A) a loss of function allele in a haplosufficient gene. B) a female individual. C) a haploid individual that displays a mutant phenotype. D) a diploid individual that carries two identical alleles of a gene. E) a synonym for dihybrid.

D) a diploid individual that carries two identical alleles of a gene.

Which of the following is true of Barr bodies? A) they are the result of X-inactivation B) they are produced via a reversible epigenetic mechanism C) they are never present in males D) both A and B are true E) A, B, and C are all true

D) both A and B are true

Meiosis II is described as a(n) ______ division because the number of chromosomes _______. A) reductional ; is reduced by half B) equational ; is reduced by half C) reductional ; remains equal D) equational ; remains equal E) both B and C are correct

D) equational ; remains equal

In a testcross, the tester parent is always _______ . A) homozygous dominant B) heterozygous C) of an uncertain genotype but displaying the dominant phenotype D) homozygous recessive E) a snake

D) homozygous recessive

In lions, ear size and tail length are Mendelian traits controlled by two different genes (neither of which is sex-linked). From a cross between a male lion with large ears and a short tail and a female lion with small ears and a long tail, all of the offspring exhibit small ears and a long tail. Which of the following statements are consistent with these results? A) the long tail and large ear phenotypes are both dominant B) long tail is recessive and small ears is dominant C) short tail is dominant and large ears is recessive D) the large ears and short tail phenotypes are both recessive E) you cannot determine dominance relationships from this scenario

D) the large ears and short tail phenotypes are both recessive

You have identified a novel recessive mutation in spiders that reduces the number of legs. However, the mutant phenotype is not always identical among individuals. In a collection of spiders that are all homozygous for the mutant allele, some spiders have four legs, some have five legs, and some have six legs. None of the homozygous mutants display the wild type phenotype of eight legs. Which of the following best describes this situation? A) X-chromosome inactivation B) polygenic inheritance C) incomplete penetrance D) variable expressivity E) anisogamy

D) variable expressivity

When parents from two different true-breeding strains are crossed with each other, the resulting F1 progeny _______ . A) will exhibit the dominant phenotype B) will be heterozygous C) can be described as monohybrids D) can produce two different gamete types E) all of the above

E) all of the above

For genes that are _______ , loss-of-function mutant alleles are often _______ relative to the wild type allele of the same gene. A) haplosufficient ; dominant B) haplosufficient ; recessive C) haploinsufficient ; dominant D) haploinsufficient ; recessive E) both B and C are true

E) both B and C are true

Which of the following occurs during metaphase of mitosis? A) the cell's DNA is replicated B) the DNA condenses into chromosomes C) crossing over happens between non-sister chromatids D) tetrads form and align near the middle of the cell E) none of the above

E) none of the above

In humans, red-green colorblindness is a trait that appears more frequently in males than in females. Which of the following explains why this is the case? A) red-green colorblindness is a result of X-inactivation, which only occurs in males B) the red-green colorblindness allele is carried on the Y chromosome C) red-green colorblindness only occurs in XXY individuals with Klinefelter syndrome D) in females, the X chromosome carrying the red-green colorblindness allele is always inactivated E) red-green colorblindness is caused by a recessive X-linked mutation

E) red-green colorblindness is caused by a recessive X-linked mutation