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Gene Linkage

Gene Linkage. For each of the three cells what is the chance of producing a haploid gamete with the genotype AB. A XX a B XX b. A XX a XX. A XX a XX. B b. B b. Gene Linkage and Mapping.

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Gene Linkage

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  1. Gene Linkage

  2. For each of the three cells what is the chance of producing a haploid gamete with the genotype AB AXXa BXXb AXXa XX AXXa XX B b B b

  3. Gene Linkage and Mapping • If the genes are closer to one another, what happens to their recombination grequency? • If Gene A recombines 12% of the time with gene B, but 16% of the time with gene C, which gene is closer to gene A? • If gene B and C recombine with one another 28% of the time, what is the order of genes A, B C along the chromosome? • Answer the Interactive Question 15.4 on p. 113 in the study guide and then answer the genetics questions on p. 116.

  4. Sex Linkage • Why is crossing-over not as common with sex chromosomes? • What types of genes are on the sex chromosomes? • If there is a gene on the top portion of the X chromosomes and the males have an X and a Y, how many alleles do the have for that one locus? • Because of the lack of homology in the sex chromosomes, male only have one allele for some traits. What do we call a male genotype for these genes since he is neither homozygous or heterozygous?

  5. Pedigree Practice • Make a pedigree for the following family: • 3 generations, some members have the recessive trait of color blindness • Genotypes are written as XBXB – for female with normal vision, XBXb for a female who is normal but is a carrier for colorblind, and XbXb for a female who is colorblind; XBY for a male with normal vision and XbY for a male who is colorblind. • There are two sets of grandparents in the 1st generation • The 2nd generation has at least 8 people half are male and half are female • 2 people are married to each other in the 2nd generation. • The 3rd generation has at least 6 people, half are male and half are female. • The sex-linked trait of male color blindness is present through a heterozygous genotype (XBXb) in the grandmother of one side of the family and in the grandfather (XbY) of the other side of the family. • All phenotypes and genotypes should be depicted for all family members.

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