Recently, on an isolated island, a researcher found a colony of cats with very i
ID: 147709 • Letter: R
Question
Recently, on an isolated island, a researcher found a colony of cats with very interesting coat patterns: tartan (plaid), striped, and checkered. She determined that three alleles of a single gene cause these different coat patterns. Now she wants to determine the order of dominance for the three alleles (C tartan, C striped, Ch checkered). She has the following information: Cross Parental Phenotypes Offspring Phenotypic Ratios 2 3 Tartan x tartan | Checkered x checkered | Checkered x striped 75% tartan, 25% striped 75% checkered, 25% striped 50% checkered, 50% striped Tartan x checkered 100% tartan 1. What is the order of dominance for the three alleles? (2 pt) 2. Identify the genotypes of the parents in the following crosses. (4 pts) a. Cross 3 b. Cross 4Explanation / Answer
1) In tartan x tartan, 75% progeny is tartan and 25% is striped. This is typical to the monohybrid phenotypic ratio of 3:1. The trait striped is hidden in the parents but is observed in some progeny , it means that parents with tartan pheontype are heterozygous Ct Cs.
Ct Cs x Ct Cs
Progeny : CtCt (tartan), CtCs (tartan), CtCs (tartan), CsCs ( striped)
75% tartan and 25% striped
Major proportion of progeny is tartan phenotype. Therefore we can conclude that tartan Ct allele is dominant over striped Cs allele.
In cross 2 checkered x checkered, 75% progeny is checkered and 25% is striped. In this case major proportion is of checkered progeny. Therefore checkered Cch allele is dominant over striped Cs.
In cross 4 tartan x checkered 100% progeny is tartan which suggest that tartan Ct is dominant over checkered Cch allele.
Therefore the order of dominance is Ct > Cch > Cs
2. a) In cross 3 checkered x striped, the striped cat should be homzygous as all other alleles are dominant over it , therefore the striped cat is Cs Cs. Checkered cat genotype can he homozygous or heterozygous. It can have CchCS or CchCch. However it cannot be CchCt as Ct is dominant over Cch.
Now the progeny of cross 3 is 50% checkered and 50% striped. In order to produce a striped progeny both parents (checkered and striped) must contribute one CS allele each. In this case the genotype of checkered parent should be heterozygous CchCS.
Answer : Checkered CchCsx striped Cs Cs
50% checkered and 50% striped
2. b) In cross 4 Tartan x checkered all progeny is tartan. Only the dominant phenotype is expressed in the progeny i.e tartan. This suggest that parents are homozygous.
CtCt x CchCch
Progeny : CtCch ( all tartan )
Gametes Cs Cs Cch CchCs (checkered) CchCs (checkered) Cs CsCs ( striped) CsCs (striped)Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.