Chapter 5 genetics

1. In Drosophila, the genes y, f, and v are all X-linked. y f v females are crossed to wild-type males and the F1 females are test-crossed. The F2 are distributed as follows:

y f v 3210 y f + 72 y + v 1024 y + + 678 + f v 690 + f + 1044 + + v 60 + + + 3222 10,000

10. The Q gene locus is 10 map units from the R gene locus which is 40 map units from the S gene locus: Q——10 mu——R——40 mu——S Which interval would likely show the higher ratio of double to single chiasmata? A. Q-R B. R-S C. The ratios would be the same in the two intervals. D. Two chiasmata never occur in the same interval.

B. R-S

4. Which statement(s) below apply to the concept of gene linkage? A. The different alleles of two or more genes that are on a chromosome are inherited in an manner inconsistent with Mendel's Second law B. Recombination between homologous chromosomes during meiosis results in different combinations of alleles for different genes C. Recombination between sister chromatids during meiosis results in different combinations of alleles for different genes A. A only B. B only C. C only D. A and B E. A, B, and C

D. A and B

9. Recombination frequencies near 50% suggest that A. two genes are on different chromosomes. B. two genes lie very close together on the same chromosome. C. two genes are on the same chromosome but lie very far apart. D. two genes are on different chromosomes, or two genes are on the same chromosome but lie very far apart. E. none of the choices are correct.

D. two genes are on different chromosomes, or two genes are on the same chromosome but lie very far apart.

2. Which of the following linkage maps correctly shows the order and distance between the y, f, and v genes? A. f——35 mu——y——15 mu——v B. f——22 mu——y——15 mu——v C. y——35 mu——f——22 mu——v D. y——22 mu——v——15 mu——f E. y——15 mu——v——22 mu——f

E. y——15 mu——v——22 mu——f

2. Plant t, r, w Genes root In peas, tall (T) is dominant to short (t), red flowers (R) is dominant to white flowers (r), and wide leaves (W) is dominant to narrow leaves (w). A tall, red, wide-leaved plant is crossed to a short, white, narrow-leaved plant and the progeny are as follows:

tall, red, wide 381 tall, white, wide 122 short, red, wide 118 short, white, wide 379 total 1000 Plant t, r, w Genes parental genotype

5. The R and S genes are linked and 10 map units apart. In the cross Rs/rS × rs/rs what fraction of the progeny will be RS/rs?rev: 02_11_2015_QC_CS-7192 A. 5% B. 10% C. 25% D. 40% E. 45%

A. 5%

8. Suppose the L and M genes are on the same chromosome but separated by 100 map units. What fraction of the progeny from the cross LM/lm × lm/lm would be Lm/lm? A. 10% B. 25% C. 50% D. 75% E. 100%

B. 25%

What is the genotype of the tall, red, wide-leaved parent? A. Tt Rr Ww B. Tt Rr WW C. TT RR WW D. TT Rr Ww E. TT RR Ww

B. Tt Rr WW

3. Plant t, r, w Genes root In peas, tall (T) is dominant to short (t), red flowers (R) is dominant to white flowers (r), and wide leaves (W) is dominant to narrow leaves (w). A tall, red, wide-leaved plant is crossed to a short, white, narrow-leaved plant and the progeny are as follows: tall, red, wide . 381 tall, white, wide 122 short, red, wide 118 short, white, wide 379 total . 1000 If two or more of the genes are linked, what map distance separates them? A. 4 mu B. 12 mu C. 24 mu D. 50 mu E. None of the genes are linked to each other.

C. 24 mu

7. In Drosophila, singed bristles (sn) and cut wings (ct) are both caused by recessive, X-linked alleles. The wild type alleles (sn+ and ct+) are responsible for straight bristles and intact wings, respectively. A female homozygous for sn and ct+ is crossed to a sn+ct male. The F1 flies are interbred. The F2 males are distributed as follows sn ct 13 sn ct+ 36 sn+ ct 39 sn+ ct+ 12 What is the map distance between sn and ct? A. 12 m.u. B. 13 m.u. C. 25 m.u. D. 50 m.u. E. 75 m.u.

C. 25 m.u.

6. If the map distance between genes A and B is 10 map units and the map distance between genes B and C is 25 map units, what is the map distance between genes A and C? A. 15 map units B. 35 map units C. either 15 map units or 35 map units, depending on the order of the genes D. The map distance between A and C can not be predicted from these data.

C. either 15 map units or 35 map units, depending on the order of the genes