In mice, the allele C for colored fur is dominant over the...

In mice, the allele $C$ for colored fur is dominant over the allele $c$ for white fur, and the allele $V$ for normal behavior is dominant over the allele $v$ for waltzing behavior, a form of discoordination. Give the genotypes of the parents in each of the following crosses: (a) Colored, normal mice mated with white, normal mice produced 29 colored, normal and 10 colored, waltzing progeny. (b) Colored, normal mice mated with colored, normal mice produced 38 colored, normal, 15 colored, waltzing, 11 white, normal, and 4 white, waltzing progeny. (c) Colored, normal mice mated with white, waltzing mice produced 8 colored, normal, 7 colored, waltzing, 9 white, normal, and 6 white, waltzing progeny.

In mice, the allele $C$ for colored fur is dominant over the allele $c$ for white fur, and the allele $V$ for normal behavior is dominant over the allele $v$ for waltzing behavior, a form of discoordination. Give the genotypes of the parents in each of the following crosses:
(a) Colored, normal mice mated with white, normal mice produced 29 colored, normal and 10 colored, waltzing progeny.
(b) Colored, normal mice mated with colored, normal mice produced 38 colored, normal, 15 colored, waltzing, 11 white, normal, and 4 white, waltzing progeny.
(c) Colored, normal mice mated with white, waltzing mice produced 8 colored, normal, 7 colored, waltzing, 9 white, normal, and 6 white, waltzing progeny.

Key Concepts

Allelic Dominance

This concept refers to the hierarchical relationship between alleles, where one allele masks or suppresses the expression of another when both are present in an organism's genotype. In classical genetics, a dominant allele will determine the phenotype even in a heterozygous condition, while a recessive allele will only be expressed phenotypically when present in a homozygous state.

Genotype and Phenotype

Genotype represents the genetic makeup of an organism, essentially the combination of alleles it carries, whereas phenotype is the observable physical or behavioral trait resulting from the genotype and its interaction with the environment. Understanding the distinction between these concepts is essential when interpreting outcomes from genetic crosses and determining parental contributions.

Dihybrid Cross

A dihybrid cross involves two different genes, each with a pair of alleles, and examines the inheritance of two traits simultaneously. It highlights how alleles for different traits are assorted independently (assuming no linkage), leading to a variety of genotype combinations and corresponding phenotypic ratios in the offspring.

Punnett Square Analysis

The Punnett square is a visual tool that helps in predicting the possible genotypes and phenotypes of offspring from a cross. It systematically arranges the possible gametes of each parent and illustrates how these combine, making it an invaluable method to analyze the outcomes of dihybrid crosses and to infer the parental genotypes from the observed progeny.

Transcript

00:01 In this question, it says leo, uppercase c is color, lowercase c is white, uppercase v is normal behavior, and lowercase v is watson.

00:16 So let's look at one at a time.

00:20 In question a, it says the parent is a color, normal mice, that mated with white, normal mice, and it produced 29 color normal and 10 color watson progeny.

00:37 So i write down the possible genotype here, the one i put underscore here, that is unknown.

00:46 Looking at the f1 generations that both have uppercase, so they are both color, but we do know one of the parent is homozygous recessive, so that would mean that this one is a color leo as well.

01:13 By looking at the 3 to 1 ratio will make us guess that this is going to be a heterozygous right here, and let's double check if that's correct.

01:33 So in here, you will have a 2 pound square cross, and so for this one, we don't need to do it because that is 100 % of cc and nothing else.

01:57 So 100 % equal to 1.

02:00 Whereas here, you have heterozygous here, so it's homozygous, 2 dominant, heterozygous, heterozygous, and homozygous recessive.

02:21 And the ratio of this for color, i'm sorry, the normal versus bolzhin behavior is going to be 3 to 1.

02:41 So since you have this, it's 100%, so you will have 1 times 3 quarter versus 1 times 1 quarter, so this is the c of leo, this is the v of leo, c of leo, v of leo, so that is going to be a 3 to 1 ratio.

03:09 So here is the answer for the parent genotype.

03:16 In b, it says the parent, one of them is color normal and mate with another color normal mice.

03:33 And f1 generation has a ratio of 9 to 3 to 3 to 1.

03:39 We are familiar with that one, so i'm going to say the answer for this is going to be heterozygous, cc, vv, okc.

03:59 So now let's see if that will produce the f1 generation.

04:04 So we will do 2 pound square each one for each leo...

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