Essential Cell Biology 5th edition

Questions
689
C. Genotype and phenotype.
D. Dominant and recessive.
QUESTION 19–11
You have been given three wrinkled peas, which we shall call
A, B, and C, each of which you plant to produce a mature
pea plant. Each of these three plants, once self-pollinated,
produces only wrinkled peas.
A. Given that you know that the wrinkled-pea phenotype
is recessive, as a result of a loss-of-function mutation, what
can you say about the genotype of each plant?
B. How do you determine if each of the three plants carries
a mutation in the same gene or in different genes that
produce the phenotype?
QUESTION 19–12
Susan’s grandfather was deaf, and passed down a hereditary
form of deafness within Susan’s family as shown in
Figure Q19–12.
A. Is this mutation most likely to be dominant or recessive?
B. Is it carried on a sex chromosome? Why or why not?
C. A complete SNP analysis has been done for all of the 11
grandchildren (4 affected and 7 unaffected). In comparing
these 11 SNP results, how long a haplotype block would
you expect to find around the critical gene? How might you
detect it?
grandfather
QUESTION 19–14
In the pedigree shown in Figure Q19–14, the first born in
each of three generations is the only person affected by
a dominant genetically inherited disease, D. Your friend
concludes that the first child born has a greater chance of
inheriting the mutant D allele than do later children.
A. According to Mendel’s laws, is this conclusion plausible?
B. What is the probability of obtaining this result by
chance?
C. What kind of additional data would be needed to test
your friend’s idea?
D. Is there any way in which your friend’s hypothesis might
turn out to be right?
Figure Q19–14
children
grandchildren
great-grandchildren
QUESTION 19–15
Suppose one person in 100 is a carrier of a fatal recessive
mutation, such that babies homozygous for the mutation die
soon after birth. In a population where there are 1,000,000
births per year, how ECB5 many eQ19.14/Q19.14
babies per year will be born with
the lethal homozygous condition?
Figure Q19–12
Susan
QUESTION 19–16
Certain mutations are called dominant-negative mutations.
What do you think this means and how do you suppose
these mutations act? Explain the difference between
a dominant-negative mutation and a gain-of-function
mutation.
QUESTION 19–13
Given that the mutation ECB5 causing eQ19.12/Q19.12 deafness in the family
shown in Figure 19−26 is very rare, what is the most
probable genotype of each of the four children in
generation II?
QUESTION 19–17
Early genetic studies in Drosophila laid the foundation for
our current understanding of genes. Drosophila geneticists
were able to generate mutant flies with a variety of easily
observable phenotypic changes. Alterations from the fly’s
normal brick-red eye color have a venerable history because
the very first mutant found by Thomas Hunt Morgan was
a white-eyed fly (Figure Q19–17). Since that time, a large
brick-red
flies with other eye colors
white
Figure Q19–17