Consider the following two human genes, each with two possible alleles. The PIP

Question

Consider the following two human genes, each with two possible alleles. The PIP gene coding for prolactin-inducible protein, is known to be on the short arm of chromosome 7 The location of the KEL gene which codes for a specific red Wood cell is unknown Consider the pedigree shown below Inheritance of alleles KEL1 and KEL2 was determined by assaying for the production of KEL1 and KEL2 antigens The PIP1 and PIP2 alleles were studied with a Southern blot analysis of endonuclease Taq1 cut DNA where PIP1 shows a 6 kb fragment hybridizing to the probe while PIP2 shows a 4 kb fragment hybridizing to the probe The results are shown below. a. List the genotypes for all individuals shown in the pedigree on the next page Refer to individuals by the numbers given in the figure, eg III-2 b. Is the KEL gene on chromosome 7? Explain your decision by giving specific examples from the genotypes you derived in part a.

Explanation / Answer

a. List of genotypes of all individuals shown in the pedigree is as follows:

Individual

Genotype

I - 1

KEL 1, KEL 2

PIP 1, PIP 2

I - 2

KEL 2, KEL 2

PIP 1, PIP 1

II - 1

KEL 2, KEL 2

PIP 1, PIP 1

II - 2

KEL 1, KEL 2

PIP 1, PIP 2

III - 1

KEL 2, KEL 2

PIP 1, PIP 1

III - 2

KEL 1, KEL 2

PIP 1, PIP 2

III - 3

KEL 1, KEL 2

PIP 1, PIP 2

III - 4

KEL 1, KEL 2

PIP 1, PIP 2

III – 5

KEL 2, KEL 2

PIP 1, PIP 1

b. Yes, KEL gene is located on chromosome 7. Inheritance pattern of alleles for PIP and KEL genes is same for an individual ie, both the gene alleles are either homozygous or heterozygous in an individual. KEL 2 allele is transmitted with PIP 1 allele while KEL 1 allele is transferred along with PIP 2 allele thus suggesting that there is a tight linkage between KEL and PIP alleles. PIP is located on chromosome 7 and since there is a linkage between PIP and KEL, KEL should also be located on chromosome 7.

Individual

Genotype

I - 1

KEL 1, KEL 2

PIP 1, PIP 2

I - 2

KEL 2, KEL 2

PIP 1, PIP 1

II - 1

KEL 2, KEL 2

PIP 1, PIP 1

II - 2

KEL 1, KEL 2

PIP 1, PIP 2

III - 1

KEL 2, KEL 2

PIP 1, PIP 1

III - 2

KEL 1, KEL 2

PIP 1, PIP 2

III - 3

KEL 1, KEL 2

PIP 1, PIP 2

III - 4

KEL 1, KEL 2

PIP 1, PIP 2

III – 5

KEL 2, KEL 2

PIP 1, PIP 1

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