Bio 210A - Genetics Problems Part 2

Front 1

One of two major forms of a human condition called neurofibromatosis (NF 1) is inherited as a dominant gene, although it may range from mildly to very severely expressed. If a young child is the first in her family to be diagnosed, which of the following is the best explanation?

Back 1

One of the parents has very mild expression of the gene.

Front 2

What is the genotype of the deceased individual in generation II?

Back 2

heterozygous for a gene for colon cancer

Front 3

In each generation of this family after generation I, the age at diagnosis is significantly lower than would be found in nonfamilial (sporadic) cases of this cancer (~ 63 years). What is the most likely reason?

Back 3

Hereditary (or familial) cases of this cancer typically occur at earlier ages than do nonfamilial forms.

Front 4

From this pedigree, how does this trait seem to be inherited?

Back 4

as an autosomal dominant

Front 5

The affected woman in generation IV is thinking about her future and asks her oncologist (cancer specialist) whether she can know whether any or all of her children will have a high risk of the same cancer. The doctor would be expected to advise which of the following?

Back 5

I. genetic counseling
II. prenatal diagnosis when/if she becomes pregnant

Front 6

If 1,000 F2 offspring resulted from the cross, approximately how many of them would you expect to
have red, terminal flowers?

Back 6

190

Front 7

Among the F2 offspring, what is the probability of plants with white axial flowers?

Back 7

3/16

Front 8

Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.
49) These results indicate which of the following?

Back 8

epistasis is involved

Front 9

How many genes must be responsible for these coat colors in Labrador retrievers?

Back 9

2

Front 10

51) In one type cross of black × black, the results were as follows: 9/16 black
4/16 yellow
3/16 brown
The genotype aabb must result in which of the following?

Back 10

yellow

Front 11

Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant characteristic.
52) If true-breeding red long radishes are crossed with true-breeding white oval radishes, the F1 will be
expected to be which of the following?

Back 11

purple and long

Front 12

In the F2 generation of the above cross, which of the following phenotypic ratios would be expected?

Back 12

6:3:3:2:1:1

Front 13

The flower color trait in radishes is an example of which of the following?

Back 13

incomplete dominance

Front 14

Drosophila (fruit flies) usually have long wings (+) but mutations in two different genes can result in
bent wings (bt) or vestigial wings (vg).
55) If a homozygous bent wing fly is mated with a homozygous vestigial wing fly, which of the following offspring would you expect?

Back 14

all +bt +vg heterozygotes

Front 15

56) If flies that are heterozygous for both the bent wing gene and the vestigial wing gene are mated, what is the probability of offspring with bent wings only?

Back 15

3/16

Front 16

Tallness (T) in snapdragons is dominant to dwarfness (t), while red (R) flower color is dominant to white
(r). The heterozygous condition results in pink (Rr) flower color.
57) A dwarf, red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F1 individuals?

Back 16

TtRr—tall and pink

Front 17

58) If snapdragons are heterozygous for height as well as for flower color, a mating between them will result in what ratio?

Back 17

6:3:3:2:1:1

Front 18

Skin color in a certain species of fish is inherited via a single gene with four different alleles.
59) How many different types of gametes would be possible in this system?

Back 18

4

Front 19

One fish of this type has alleles 1 and 3 (S1S3) and its mate has alleles 2 and 4 (S2S4). If each allele confers a unit of color darkness such that S1 has one unit, S2 has two units, and so on, then what
proportion of their offspring would be expected to have five units of color?

Back 19

1/2

Front 20

Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all.
61) The relationship between genes S and N is an example of

Back 20

epistasis

Front 21

A cross between a true-breeding sharp-spined cactus and a spineless cactus would produce

Back 21

A) all sharp-spined progeny.

Front 22

63) If doubly heterozygous SsNn cactuses were allowed to self-pollinate, the F2 would segregate in which of the following ratios?

Back 22

E) 9 sharp-spined:3 dull-spined:4 spineless

Front 23

Feather color in budgies is determined by two different genes, Y and B, one for pigment on the outside and one for the inside of the feather. YYBB, YyBB, or YYBb is green; yyBB or yyBb is blue; YYbb or Yybb is yellow; and yybb is white.
64) A blue budgie is crossed with a white budgie. Which of the following results is not possible?

Back 23

green and yellow offspring

Front 24

65) Two blue budgies were crossed. Over the years, they produced 22 offspring, 5 of which were white. What are the most likely genotypes for the two blue budgies?

Back 24

yyBb and yyBb

Front 25

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
66) Which of the following is a possible partial genotype for the son?

Back 25

IBi

Front 26

Which of the following is a possible genotype for the mother?

Back 26

Iai

Front 27

Which of the following is a possible phenotype for the father?

Back 27

B positive

Front 28

If both children are of blood type M, which of the following is possible?

Back 28

Each parent is either M or MN.

Front 29

Humanoids on the newly explored planet Brin (in a hypothetical galaxy in ~50 years from the present) have a gene structure similar to our own, but many very different plants and animals.
70) One species of a small birdlike animal has an extremely variable tail length, which is a highly polymorphic trait. Geneticists have come to realize that there are eight separate genes for tail length per haploid genome, with each gene having two alleles. One allele for each gene (a, b, and so on) increases the length by 1 cm, whereas the other allele (a2, b2, and so on) increases it by 0.5 cm. One bird was
analyzed and found to have the following genotype:
a1a1b2b2c1c2d1d2e2e2f1f2g1g1h1h2 What is the length of its tail?

Back 29

12 cm

Front 30

71) One species of green plant, with frondlike leaves, a spine-coated stem, and purple cup-shaped flowers, is found to be self-pollinating. Which of the following is true of this species?

Back 30

Some of the seeds would have true-breeding traits.

Front 31

If the environmental parameters, such as temperature, humidity, atmosphere, sunlight, and so on, are mostly Earthlike, which of the following do you expect of its types of leaves, stems, and flowers?

Back 31

Phenotypes would be selected for or against by these environmental factors.

Front 32

73) Marfan syndrome in humans is caused by an abnormality of the connective tissue protein fibrillin. Patients are usually very tall and thin, with long spindly fingers, curvature of the spine, sometimes weakened arterial walls, and sometimes ocular problems, such as lens dislocation. Which of the following would you conclude about Marfan syndrome from this information?

Back 32

It is pleiotropic.