Question 1

The pedigree shown here pertains to a trait due to a rare, X-linked recessive mutation.  Individual 1 has an affected grandfather, but the genotypes and phenotypes of individuals 1-4 are unknown. What is the probability that individual 1 is heterozygous? What is the probability that individual 3 is heterozygous? What is the probability that individual 4 is affected?

Accepted Answer

The answer of The pedigree shown here pertains to a...

Question 2

The pedigree shown here pertains to a trait due to a rare, X-linked recessive mutation.  Individual 1 has an affected brother, but the genotypes and phenotypes of individuals 1-4 are unknown. What is the probability that individual 1 is heterozygous? What is the probability that individual 3 is heterozygous? What is the probability that individual 4 is affected?

Accepted Answer

The answer of The pedigree shown here pertains to a...

Question 3

A restriction-fragment length polymorphism at a site in the X chromosome has three alleles, A₁, A₂, and A₃. The gel below is the DNA fingerprint for two girls who have the same parents. What is the genotype of the mother? Of the father?

Accepted Answer

The answer of A restriction-fragment length polymorphism at a site...

Question 4

A restriction-fragment length polymorphism at a site in the X chromosome has three alleles, A₁, A₂, and A₃. The gel below is the DNA fingerprint for two prospective parents (Mo and Fa) as well as DNA types that may (or may not) correspond to their possible offspring. What are the possible phenotypes of sons from this mating?

Accepted Answer

The answer of A restriction-fragment length polymorphism at a site...

Question 5

Which one of the following statements regarding the human Y chromosome is TRUE?

Accepted Answer

The human Y chromosome is relatively small and contains about 50-60 genes, which is significantly fewer than most other chromosomes, including the X chromosome. This makes option C the correct answer.

Question 6

For an X-linked gene, which of the following genotype options is possible?

Accepted Answer

Females have two X chromosomes, so they can be either homozygous or heterozygous for an X-linked gene. Males, having only one X chromosome, can only have one allele for an X-linked gene, making them hemizygous, not heterozygous or homozygous.

Question 7

All organisms have either an X or Y chromosome, as these chromosomes are solely responsible for determining the sex of an individual. Mendel's failure to identify X and Y chromosomes in his pea plants invalidated a portion of the data he collected.

Accepted Answer

This statement is false. Mendel's failure to identify X and Y chromosomes in his pea plants did not invalidate any portion of the data he collected, as these chromosomes are not relevant to pea plant genetics. Mendel's laws of inheritance still hold true and are widely used in genetics today.

Question 8

A cross involving an autosomal gene versus a sex-linked gene would differ in that:

Accepted Answer

The phenotype outcomes of females compared to males could be different in a cross involving an autosomal gene versus a sex-linked gene. This is because females have two copies of the autosomal gene, while males have only one copy of the sex-linked gene. Therefore, the expression of the gene may differ between males and females in a cross involving an autosomal gene versus a sex-linked gene.

Question 9

Considering a rare X-linked recessive trait, which of the following statements is/are TRUE?

Accepted Answer

The answer of Considering a rare X-linked recessive trait, which...

Question 10

A restriction-fragment length polymorphism at a site in the X chromosome has three alleles, A₁, A₂, and A₃. The gel below is the DNA fingerprint for two girls who have the same parents. What is the genotype of the mother? Of the father?

Accepted Answer

The bands in the gel correspond to the alleles A₁, A₂, and A₃. Each individual has two alleles at this locus. The two girls have identical band patterns, suggesting that they are homozygous at this locus. The only way for them to be homozygous for the same allele is if each parent contributed one of the same alleles to each daughter. This means that the genotypes for the parents are A₁/A₃ for the mother and A₂/A₃ for the father.

Question 11

A woman at a train station sees a family with five boys. The occurrence of five boys in this family is likely the result of a mutation in one of the X chromosomes of the mother that impacts the survival of female embryos in the womb.

Accepted Answer

The statement is not accurate. The occurrence of five boys in a family can happen due to chance and is not necessarily related to a mutation in the X chromosome of the mother. The probability of having five boys in a row is (1/2)^5 or 3.125%, which is a rare but possible occurrence.

Question 12

Segregation of X and Y chromosomes in males happens during anaphase II of meiosis.

Accepted Answer

The answer of Segregation of X and Y chromosomes in...

Question 13

Considering an X-linked dominant trait, if an unaffected woman and an affected man decide to have children, which of the following statements is TRUE about the possibilities for their children?

Accepted Answer

In X-linked dominant inheritance, an affected man will pass the dominant allele to all of his daughters, making them heterozygous and affected, while his sons will inherit his Y chromosome and will not be affected.

Question 14

Genes located along the X chromosome:

Accepted Answer

Genes located along the X chromosome are called X-linked genes. They are not necessarily recessive and are not solely contributed by the female parent. There is no complementary set of alleles on the Y chromosome.

Question 15

Which of the following statements regarding sex ratios is TRUE?

Accepted Answer

Sex ratios are dynamic and can change over time; the ratio of males to females at birth may be different from that during adolescence and adulthood. Option A is incorrect because sex ratios can change over time due to various factors. Option B is incorrect because although the ratio at birth is slightly skewed towards females, this is not always the case in other age groups. Option C is incorrect because the ratio of males to females during adolescence is about 1:1. Option D is incorrect because the sex ratio becomes increasingly skewed towards females at advanced ages due to higher female life expectancy.

Question 16

X-linked inheritance does not follow the inheritance patterns of which of Mendel's discoveries?

Accepted Answer

X-linked inheritance does not follow the principle of equivalence of reciprocal crosses because the expression of traits differs between males and females due to the presence of a single X chromosome in males and two in females.

Question 17

Which one of the following statements about the sex chromosomes is FALSE?

Accepted Answer

The relative size and gene content of the X and Y chromosomes vary significantly across animal species. In some species, the X chromosome is much larger and contains more genes than the Y chromosome, while in others, the two chromosomes are similar in size and gene content.

Question 18

Which one of the following statements about segregation of the sex chromosomes is FALSE?

Accepted Answer

In humans, the sex at each birth is actually a random process and can be determined by the chance of a sperm carrying either an X or Y chromosome fertilizing the egg. While it is true that there can be families with all boys or all girls, this is still due to chance rather than any predetermined factor. Therefore, statement D is false.

Question 19

When X-linked traits are recessive, males who express the trait:

Accepted Answer

Males have one X and one Y chromosome, so they express X-linked recessive traits if they inherit the recessive allele on their X chromosome, which they can only get from their mothers since fathers pass on the Y chromosome to their sons.

Question 20

Which of the following statements regarding both the X and Y chromosomes is TRUE?

Accepted Answer

The statements A, B, C, and D are not universally true across all species. Not all organisms have X and Y chromosomes as their sex-determination system (e.g., birds use a ZW system, and some reptiles use temperature-dependent sex determination). The presence of a Y chromosome does not universally determine maleness across all species, and the size and similarity of X and Y chromosomes can vary significantly between species. Therefore, E is correct because it states that none of the other options is universally correct.

Quiz 17: Inheritance of Sex Chromosomes, Linked Genes, and Organelles

A restriction-fragment length polymorphism at a site in the X chromosome has three alleles, A1, A2, and A3. The gel below is the DNA fingerprint for two girls who have the same parents. What is the genotype of the mother? Of the father?

Which one of the following statements regarding the human Y chromosome is TRUE?

For an X-linked gene, which of the following genotype options is possible?

All organisms have either an X or Y chromosome, as these chromosomes are solely responsible for determining the sex of an individual. Mendel's failure to identify X and Y chromosomes in his pea plants invalidated a portion of the data he collected.

A cross involving an autosomal gene versus a sex-linked gene would differ in that:

Considering a rare X-linked recessive trait, which of the following statements is/are TRUE?

A restriction-fragment length polymorphism at a site in the X chromosome has three alleles, A1, A2, and A3. The gel below is the DNA fingerprint for two girls who have the same parents. What is the genotype of the mother? Of the father?

A woman at a train station sees a family with five boys. The occurrence of five boys in this family is likely the result of a mutation in one of the X chromosomes of the mother that impacts the survival of female embryos in the womb.

Segregation of X and Y chromosomes in males happens during anaphase II of meiosis.

Considering an X-linked dominant trait, if an unaffected woman and an affected man decide to have children, which of the following statements is TRUE about the possibilities for their children?

Genes located along the X chromosome:

Which of the following statements regarding sex ratios is TRUE?

X-linked inheritance does not follow the inheritance patterns of which of Mendel's discoveries?

Which one of the following statements about the sex chromosomes is FALSE?

Which one of the following statements about segregation of the sex chromosomes is FALSE?

When X-linked traits are recessive, males who express the trait:

Which of the following statements regarding both the X and Y chromosomes is TRUE?

A restriction-fragment length polymorphism at a site in the X chromosome has three alleles, A₁, A₂, and A₃. The gel below is the DNA fingerprint for two girls who have the same parents. What is the genotype of the mother? Of the father?

A restriction-fragment length polymorphism at a site in the X chromosome has three alleles, A₁, A₂, and A₃. The gel below is the DNA fingerprint for two girls who have the same parents. What is the genotype of the mother? Of the father?