Four autosomal recessive Drosophila mutations were studied using an online Fly L

Question

Four autosomal recessive Drosophila mutations were studied using an online Fly Lab-yellow eyes, tan body, forked bristles, and curly wings. The results of all crosses that were performed are shown on the following pages. Crosses are labeled A-E. NOTE: Letters in the crosses represent a specified phenotype: + represents the wild type phenotype, Y - yellow eye color, T-tan body, F - forked bristles, and C-curly wings A. Results for yellow eye eolor and curty wings Parents (Female:+) x (Male: C;Y) F1 Offspring Number 1033 1033 Phenotype Total (FI female: +) x (Male: C;Y) F2 Offspring Phenotype.… Number 433 52 48 467 1000 Total B. Results for curly wings and forked bristles Parents (Female: +) x (Male: C.F) Fl Offspring Phenotype 998 998 Total (F1 Female:+) x (Male: C.F) F2 Offspring 347 155 142 346 990 C:F Total

Explanation / Answer

Answer:

11). d). A two point test cross

Explanation: A two-point testcross is done to determine the recombinant frequency between 2 linked genes.

12). a). Linked

Explanation:

A two-point testcross is done to determine the recombinant frequency between 2 linked genes. The classic Mendelian dihybrid cross ratio (round yellow and green wrinkled seeds) is 1:1:1:1, which shows that genes are not linked and located on different chromosomes. Any deviation from this ratio shows that genes are linked and located on same chromosomes, and the distance between them determines the recombinant frequency and chances of crossover during meiotic division. The results of F2 ratio is deviation from 1:1:1:1 ratio, so that the genes are said to be linked.

13).

A). 10 map units

Explanation:

Hint: Always recombinant progeny are in smaller number in linkage. So the recombinants are light and straw.

Recombination frequency (RF) = (number of recombinants/total progeny)100

RF = (52+48/1000)100 = 10%

RF (%) = Distance between the genes (map units)

b). 30 map units

Explanation:

RF = (297/990)100 = 30%

C). 49.5 map units

Explanation:

RF = (267+235/1014)100 = 49.5%

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