Grey brown and yellow are coat colors. Individuals showing coat colors (not nece
ID: 7119 • Letter: G
Question
Grey brown and yellow are coat colors. Individuals showing coat colors (not necessarily from pure lines) were intercrossed:Progeny:
Cross: brown grey yellow
1. brown X brown 20 0 0
2. yellow X yellow 0 0 20
3. grey X brown 10 10 0
4. grey X yellow 0 10 10
5. grey X grey 5 10 5
a. How many genes are involved, and how many alleles of each gene?
b. Assign symbols to the various genes and alleles. What genotype will give rise to each phenotype?
brown _________________ grey ________________ yellow __________________
c. What are the genotypes of the parents in cross 4?
Explanation / Answer
There is one gene involved in this cross (the gene coding for coat colour).
There are two alleles associated with attaining a certain coat colour include a dominant allele, B (representing brown coat colour), and a recessive allele, b (representing yellow coat colour). You can assign any letter you want to the alleles, but I just chose uppercase and lower case B's (e.g. B and b, G and g, A and a, etc.)
The genotypes (the genetic allele combinations - BB, Bb, and bb) that will give rise to each phenotype (physical expression of the gene, in the form of different coat colours) are as follows:
Brown: BB
Grey: Bb
Yellow: bb
In cross 4, the parents' genotypes are Bb and bb, as illustrated in the following Punnet square:
Parents: Grey (Bb) x Yellow (bb)
B b
b Bb bb
b Bb bb
Progeny Genotypic Ratios: 2/4 Bb and 2/4 bb
Progeny Phenotypic Ratios: 50% or 0.50 grey and 50% or 0.50 yellow
Hopefully this helps you! If you have any problems understanding, feel free to comment back!
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