Genetics Chapter 4

Only B is true all the others are false

A coefficient of coincidence of 0.36 implies which one or more of the following statements are true: a) the frequency of double crossovers is 36% b) the frequency of double crossovers was 36% of the number that would be expected if there were no interference c) There were .36 times as many single crossovers as double crossovers d) there were 0.36 times as many single crossovers in one region as there were in an adjacent region e) there were 0.36 times as many parental as recombinant progeny

From what is given we know that the parents have a heterozygous repulsion configuration of Ab/aB and the frequency of recombination is given at 0.2. With this, we can assume that 20% of the non-parental gametes will be AB and ab. With this information, we can figure that 20% of gametes that carry the A allele will also carry the B allele so the probability is 0.2.

A double heterozygote as the repulsion configuration A b/a B of two linked genes that have frequency recombination of 0.20. If a randomly chosen gamete carries A, what is the probability that it also carries B?

The data include 108 progeny with either both mutations or niter and 41+41=92 with one mutation or the other. The first of these groups consists of parental chromosomes and the second of recombinant chromosomes, and so the appropriate chi square test compares the ratio of 108 :92 against the expected 100 : 100 under the hypothesis of no linkage. The chi square value equals 1.28 and there is one degree of freedom, from which P equals approximately 0.26. There is no evidence of linkage even though both genes are in the X chromosome

A drosophila cross is carried out with a female that is heterozygous for both the y (yellow body) and bb (bobbed bristles) mutations. Both genes are located in the X chromosome. Among 200 male progeny, there were 49 wild type for both traits 51 with yellow body, 41 with bobbed bristles, and 59 mutant for both genes. Do these genes show evidence for linkage?

The presence of double crossovers can reduce the measurement of longer distances, so, the distance c-p (12) is actually less than the distance c-r (10) + distance r-p (3). So the distance p-s, which we are not given, is at least 5, but could be closer to 6.

Construct a genetic map of a chromosome from the following recombination frequencies between individual pairs of genes: r-c, 10; c-p. 12; p-r, 3; s-c, 16; s-r, 8. You will discover that the distances are not strictly additive. Why aren't they?

This is a test cross, so the phenotypes of the progeny reveal the ratio of meiotic products from the doubly heterozygous parent. The expected progeny are 82 percent parental (41 percent purple, crossveinless) and 18 % recombinant (9% purple and 9% crossveinless)

In Drosophila pseudoobscura, the eye-color mutation purple (pr) and the wing mutation crossveinless (cv) are located in chromosome 3 at a distance of 18 map units. What phenotypes and in what proportions would you expect in the progeny from the mating of pr+ cv+/ pr cv females with pr cv/ pr cv males?

recombination frequency = (# of recombinants/ total # of offspring) x 100 (7+4)/(98+91+7+4) x 100 11/200 x 100 = 5.5%

Two genes in chromosome 7 of corn are identified by the recessive alleles gl (glossy), determining glossy leaves and ra (samosa) determining branching of ears. When a plant heterozygous for each of these alleles, the progeny consisted of the following genotypes with the numbers of each indicated: Gl ra/ gl ra 98 gl Ra/ gl ra 91, Gl Ra/gl ra 7, gl ra/ gl ra 4 Calculate the frequency of recombination between these genes

Females produce gametes of types A B, ab, Ab and aB in the proportions (1 - 0.08)/2 = 0.46 and (1- 0.08)/2 = 0.46 for each of the non recombinant types 0.08/2 = 0.04 and 0.08/2 = 0.04 for each of the non recombinant types. Owing to the absence of crossing-over in male Drosophila, males produce gametes only of types AB and ab in the proportions of 0.5 and 0.5

What gametes and in what frequencies are produced by a female Drosophila of genotype A B / ab when the genes are present in the same chromosome and the frequency of recombination between the genes is 8% What gametes and in what frequencies, are produced by a male of the same genotype?