chapter 17 learning curve

To discover the location of a genetic mutation that causes disease in humans, scientists use genetic mapping. Specifically, they look for genetic markers, or previously discovered DNA polymorphisms, that show statistical association with the disease gene. The statistical association means that the:

DNA polymorphism and the disease gene are linked.

Which one of the following statements about segregation of the sex chromosomes is false? In human males, segregation of the X chromosome from the Y chromosome occurs during anaphase I of meiosis. The secondary sex ratio of males to females at birth usually shows a slight excess of males. In humans, the sex at each birth is not a random process because there are often large families with either all girls or all boys. In humans, half of the fertilized eggs are expected to be male and half are expected to be female; this 1:1 ratio is characteristic of Mendelian segregation.

In humans, the sex at each birth is not a random process because there are often large families with either all girls or all boys.

Which of the following events occur during anaphase I of meiosis? Homologous chromosomes move as one unit. In males, the X chromosome is segregated from the Y chromosome. The chromosome number is doubled during this phase of meiosis. In females, the two X chromosomes remain together. The centromeres of the chromosomes divide.

In males, the X chromosome is segregated from the Y chromosome.

Which of the following statements is true regarding mitochondrial diseases in humans? Due to the larger size of sperm carrying X chromosomes, only females demonstrate mitochondrial diseases. Only the sons of a mother with a mitochondrial disease will themselves have the disease—daughters are rarely affected. Mitochondrial diseases predominantly show patterns of biparental inheritance, with mitochondria being inherited (equally) from either the mother or father. All the progeny of a father with a mitochondrial disease will themselves have the disease, given the pattern of paternal inheritance for mitochondria. None of the answer options is correct.

None of the answer options is correct.

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

The Y chromosome contains approximately 50 genes.

Which of the following statements explains why all of the F1 females from a cross between a red-eyed homozygous female fly and a white-eyed male fly are heterozygous?

The male parent provides them with a white-eye allele on the X, and the female parent provides them with a red-eye allele on the X.

Which one of the following statements about the sex chromosomes is false? In contrast to the approximately 1000 genes on the X chromosome, the Y chromosome contains only about 50 genes. Crossing over between the X and Y chromosomes allows the sex chromosomes to align correctly during metaphase I and separate from each other during anaphase I. The X chromosome has a gene density similar to most autosomes. Crossing over between the X and Y chromosomes occurs in very small regions of homology at the tips of the chromosomes. The relative size and gene content of the X and Y chromosomes is very similar across all animal species.

The relative size and gene content of the X and Y chromosomes is very similar across all animal species.

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?

Their daughters are expected be heterozygous for the associated gene.

Which of the following is a possible human genotype that could result from nondisjunction of the sex chromosomes in one of the parental gametes?

XXY XYY XXX XO

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.

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 affects the survival of female embryos in the womb.

false

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.

false

In fruit flies, daughters of a cross between a white-eyed male and a red-eyed female always have red eyes.

false

Recombination frequency is used to measure the distance between genes located on non-homologous chromosomes.

false

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

false

The inheritance patterns of both chloroplasts and mitochondria have no relationship to the amount of cytoplasm contained in gametes produced by either the female or male parent. Organelle inheritance is typically a random occurrence.

false

The small area near the centromere is the most likely location for recombination between two homologous chromosomes.

false

An X-linked ichthyosis is a recessive form of a family of skin diseases caused by a hereditary deficiency of the steroid sulfatase (STS) enzyme. A woman heterozygous for this mutation mates with the phenotypically normal man and produces an XXY son who suffers from the disorder. What kind of nondisjunction can explain this result?

nondisjunction in meiosis II in the mother

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

receive the recessive allele from their mothers and carry the recessive allele in their X chromosomes.

The group that represents a small proportion of the progeny, deriving from maternal gametes containing combinations of alleles not found in either X chromosome of the mother, is called the _____group.

recombinant

Recall from the text that there are four clusters of Y-chromosome haplotypes scattered across the globe. Where would you expect to find these clusters?

the Americas; Southeast Asia; Europe; Africa.

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

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

the size and gene content of sex chromosomes is very similar across all animal species

A single point mutation in a mitochondrial gene involved in protein synthesis that affects oxidative phosphorylation shows a maternal inheritance pattern that is characteristic of mitochondrial diseases.

true

Nondisjunction could be the reason that a red-eyed male is among the offspring of a cross between a red-eyed male fruit fly and a white-eyed female fruit fly.

true

The presence of a nonmutant gene in one chromosome often masks the effect of a mutant allele for that same gene in its homologous chromosome.

true

The tips of the arms of the X and Y chromosomes share small regions of homology. Genes located in these regions are inherited in the same manner as the ones found in autosomes.

true

Two genes, A and B, are found on the same chromosome. One chromosome has alleles A and B, while its homolog has alleles a and b. If genes A and B are so closely linked that the recombination frequency is 0 percent, only AB and ab gametes will be produced during meiosis.

true

Without the SRY gene, humans and other mammals would develop and retain the female sex organs and phenotype.

true

In humans, one reason why mitochondrial inheritance is strikingly different from nuclear inheritance is that:

unlike nuclear inheritance, both parents do not contribute mitochondrial DNA