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Example of a two allele determination of linkage

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A female animal with genotype A/a B/b is crossed with a double recessive male (a/a b/b). Their progeny include 442 A/a B/b, 458 a/a b/b, 46 A/a b/b and 54 a/a B/b. This problem is explained.

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The ratio of genotypes observed for the progeny is not the typical 1:1:1:1 that one would normally expect (ie, the law of independent assortment states that the segregation of alleles of ...

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An example of a two allele determination of linkage is included.

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See Also This Related BrainMass Solution

Six Genetics Problems on sex linkage, alleles, patterns of inheritance and dosage compensation.

1. G6PD is an enzyme found in human white blood cells. It is made by a gene that has 2
alleles, A and B. In females, cells either make the A type or the B type, but never both.
This is very different from most other enzymes, where all cells in a heterozygote make
both types of enzyme. What is the most reasonable explanation for this unusual
behavior of G6PD?

2. In humans, red-green color blindness is recessive and X-linked, while albinism is
recessive and autosomal. What types of children can be produced as the result of
marriages between two homozygous parents, a normal-visioned albino woman and a
color-blind, normally pigmented man? (Give your answer separately for males and
females)

3. Suppose that a mutation occurred in the SRY gene on the human Y chromosome,
knocking out its ability to produce the testis-determining factor. Predict the
phenotype of an individual who carried this mutation and a normal X chromosome?

4. Sex determination in Gryllus campestris (cricket) is by the XO method. The somatic
cells of a cricket are analyzed and found to contain 29 chromosomes.
A. What sex is this individual?
B. What is the diploid number of the opposite sex?

5. Ichthyosis hystrix gravior (a greatly thickened horny condition of the skin) is a rare
human condition, but in the single extensive pedigree which has been studied it occurs
only in males. All the sons of each affected father have the condition. Females are
not only unaffected, but never transmit the gene for this defect. Can you suggest a
possible explanation for this curious and unusual type of inheritance?

6. Dosage compensation is only found in organisms that have sex chromosomes. What is
dosage compensation? Briefly describe how dosage compensation is achieved in
Drosophila and humans.

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