23. When a cell of genotype F/f; G/g; H/h having all the genes on separate chrom

Question

23. When a cell of genotype F/f; G/g; H/h having all the genes on separate chromosome pairs divides mitotically, what are the genotypes of the daughter cells? a) F/F; G/G; H/H and f/f; g/g; h/h b) F/f; G/g; H/h and F/f; G/g; H/h c) F/f; G/G; H/h and F/f; g/g; H/h d) F/F; G/g; H/h and f/f; G/g; H/h e) all of the above are possible 24. A man has freckles, whereas his wife does not have freckles. Their first child, a boy, has freckles. If the difference in freckle phenotype is assumed to be due to two alleles of a single gene, which of the following statements cannot be true? a) the allele for freckles is recessive, and the wife is homozygous b) the allele for the lack of freckles is dominant, and the gene is sex-linked c) the allele for freckles is recessive, and the gene is sex-linked d) the allele for freckles is dominant, and the gene is autosomal e) the allele for the lack of freckles is recessive and the gene is autosomal 25. Your are trying to identify the region of a gene associated with a particular cancer. The table below gives LOD score values for different levels of recombination for five markers on Chromosome 17. Which marker is likely to be closest to the putative cancer gene? RF 0.001 0.01 0.05 0.10 0.20 0.30 D17S250 D17S579 D17S588 NME1 D17S574 11.9 1.4 8.2 1.4 39.1 -8.9 1.6 11.4 0.8 31.7 1.2 8.6 18.4 6.0 13.3 12.1 21.3 8.7 2.7 7.3 12.6 20.2 9.1 6.3 6.7 9.2 14.8 6.8 7.5 a) D17S250 b) D17S579 c) D17S588 d) NME1 e) D17S574

Explanation / Answer

23.

Option B is correct.

Daughter cells produced by mitotic division are identical to the parent cell.

The mitotic division does not involve recombination or mixing of chromosomes.

24.

Option B is correct.

Freckles phenotype is dominant.

Parental cross: FF or Ff X ff

Progeny: Ff or ff

Since the child has freckles, he must be Ff.

25.

Option B is correct.

The LOD score compares the likelihood of genetic linkage between two loci.

Positive LOD score = Linked loci (The greater positive value means the given loci are tightly linked)

Negative LOD score = Unlinked loci

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