Ch 14 and 15

Question 1

What do we mean when we use the terms monohybrid cross and dihybrid cross?

Answer 1

A dihybrid cross involves organisms that are heterozygous for two characters and a monohybrid cross involves only one.

Question 2

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?

Answer 2

8

Question 3

Mendel was able to draw his ideas of segregation and independent assortment because of the influence of which of the following?

Answer 3

His reading of the scientific literature current in the field.

Question 4

In the cross AaBbCc x AaBbCc, what is the probability of producing the genotype AABBCC?

Answer 4

1/64

Question 5

Which of the following calculations require that you utilize the addition rule?

Answer 5

Calculate the probability of a child having either sickle-cell anemia or cystic fibrosis if parents are each heterozygous for both.

Question 6

Which of the following is an example of polygenic inheritance?

Answer 6

skin pigmentation in humans

Question 7

Which of the following provides an example of epistasis?

Answer 7

In rabbits and many other mammals, one genotype (cc) prevents and fur color from developing.

Question 8

Most genes have many more than two alleles. However, which of the following is also true?

Answer 8

There may still be only two phenotypes for the trait.

Question 9

An ideal procedure for fetal testing in humans would have which of the following features?

Answer 9

A procedure that can be performed at the earliest time in the pregnancy

Question 10

The frequency of heterozygosity for the sickle-cell anemia allele is unusually high, presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following?

Answer 10

Darwin’s explanation of natural selection

Question 11

Phenylketonuria (PKU) is a recessive human disorder in which an individual cannot appropriately metabolize a particular amino acid. The amino acid is not otherwise produced by humans. Therefore, the most efficient and effective treatment is which of the following?

Answer 11

Regulate the diet of the affected persons to severely limit the uptake of the amino acid.

Question 12

When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyes flies. Remarkably, all the white-eyes flies were male. What is the explanation for this result?

Answer 12

The gene involved is on the X chromosome.

Question 13

Which of the following is the meaning of the chromosome theory of inheritance as expressed in the early 20th century?

Answer 13

Mendelian genes are at specific loci on the chromosome and in turn segregate during meiosis.

Question 14

Males are more often affected by sex-linked traits than females because

Answer 14

males are hemizygous for the X chromosome.

Question 15

Cinnabar eyes is a sex-linked recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have cinnabar eyes?

Answer 15

100%

Question 16

Sex determination in mammals is due to the SRY region of the Y chromosome. An abnormality of this region could allow which of the following to have a male phenotype?

Answer 16

translocation of the SRY to an autosome of a 46, XX individual

Question 17

Which of the following statements is true of linkage?

Answer 17

The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.

Question 18

What is the reason that linked genes are inherited together?

Answer 18

Alleles are paired together during meiosis.

Question 19

Three genes are three loci are being mapped in a particular species. Each has two phenotypes, one of which is markedly different from the wild type. The unusual allele of the first gene is inherited with either of the other about 50% of the time. However, the unusual alleles of the other two genes are inherited together about 14.4% of the time. Which of the following describes what is happening?

Answer 19

The first gene is located 14.4 units apart from the other two.

Question 20

A nonreciprocal crossover causes which of the following products?

Answer 20

deletion and duplication

Question 21

Of the following human aneuploidies, which is the one that generally has the most severe impact on the health of the individual?

Answer 21

47, +21

Question 22

A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child’s condition?

Answer 22

One member of the couple underwent nondisjunction in gamete production

Question 23

A gene is considered to be non-Mendelian in its inheritance pattern if it seems to “violate” Mendel’s laws. Which of the following would be considered Mendelian?

Answer 23

a gene transmitted to males from the maternal line and from father to daughters

Question 24

Genomic imprinting is generally due to the addiction of methyl (-CH3) groups to C nucleotides in order to silence a given gene. If this depends on the sex of the parents who transmits the gene, which of the following must be true?

Answer 24

Methylation must be reversible in ovarian and testicular cells