Chi-Square Analysis for Gene Segregation in Black and Brown Rabbit Crosses

[TECHXHEAD]

I have no idea where to start on this and would appreciate some help:

Homework Statement

In the rabbit the dominant gene B specifies black hair pigment and its recessive allele b specifies brown hair pigment. Alleles of the albino locus, chinchilla (cch) and Himalayan (ch) affect the distribution of pigment in the coat. True-breeding (homozygous) black chinchilla rabbits are crossed with true-breeding brown Himalayan rabbits. The progeny, which are black chinchilla, are crossed to brown Himalayan rabbits: the phenotypes are given elow.

Phenotype of F2/Number of F2:

Black Chinchilla/191
Brown Chinchilla/138
Black Himalayan/147
Brown Himalayan/184

a. What is the map distance between these two genes (without using the mapping function)?

b. Could the numbers seen in the F2 progeny be explained by segregation of unlinked genes?

Use Chi-Square Analysis to estimate the probability for this segregation pattern.

 

[nate808]

I am happy to help you with this problem. Let's break it down step by step.

First, it's important to understand the terminology being used. In this problem, we are dealing with genes and alleles. Genes are units of heredity that determine specific traits, and alleles are different versions of a gene. In this case, the gene in question is responsible for hair color in rabbits, and there are two alleles - B and b - which determine whether the rabbit will have black or brown hair.

Next, we need to understand the concept of dominance and recessiveness. In genetics, dominant alleles are expressed over recessive alleles. This means that if a rabbit has one copy of the dominant allele B and one copy of the recessive allele b, it will have black hair because B is dominant over b.

Now, let's look at the cross between the true-breeding black chinchilla rabbits and brown Himalayan rabbits. True-breeding means that these rabbits are homozygous, meaning they have two copies of the same allele (either BB or bb). When these two types of rabbits are crossed, all of the F1 (first generation) offspring will have black chinchilla coats because B is dominant over b.

In the second part of the problem, we are looking at the F2 (second generation) progeny. This time, the black chinchilla rabbits from the F1 generation are crossed with brown Himalayan rabbits. This cross produces four different phenotypes: black chinchilla, brown chinchilla, black Himalayan, and brown Himalayan. The numbers given for each phenotype tell us how many rabbits of each type were produced.

Now, let's move on to the actual questions. The first question asks for the map distance between the genes B and cch. Map distance is a measure of the distance between two genes on a chromosome. In this problem, we can calculate the map distance by looking at the proportion of offspring that have recombined genes. Without using the mapping function, we can estimate the map distance to be approximately 25 units.

The second question asks if the numbers seen in the F2 progeny could be explained by segregation of unlinked genes. This means that the genes in question are located on different chromosomes and do not affect each other's inheritance. In this case, we can use a Chi-Square Analysis to determine the probability of this segregation pattern. Based on the given numbers, the

 

[Blueshift5]

I am familiar with Chi-Square Analysis and its use in genetic studies. In this scenario, we are examining the gene segregation of black and brown hair pigment in rabbits. The first step would be to calculate the map distance between the two genes, which can be done by dividing the number of recombinants (black Himalayan and brown chinchilla) by the total number of progeny. This will give us an estimate of the distance between the two genes.

To answer the second question, we would need to perform a Chi-Square Analysis to determine if the observed numbers in the F2 progeny could be explained by segregation of unlinked genes. This analysis compares the observed data to the expected data based on Mendelian ratios. If the p-value is less than 0.05, we can reject the null hypothesis that the observed and expected data are the same and conclude that the genes are likely linked.

In this case, the expected data would be a 9:3:3:1 ratio of black chinchilla, brown chinchilla, black Himalayan, and brown Himalayan rabbits. We can calculate the expected numbers by multiplying the total number of progeny by the expected ratios. We can then use the Chi-Square formula to calculate the p-value and determine if the observed data fits the expected ratios.

In conclusion, Chi-Square Analysis can be used to estimate the probability of gene segregation in this rabbit cross and determine if the observed data is consistent with Mendelian ratios. It is an important tool in genetic studies and can provide valuable insights into the inheritance patterns of different traits.