Linkage & Mapping

Chromosome Linkage & Mapping

In Principle:

Loci that are physically linked on the same chromosome will not show independent assortment.
          The characteristic gametic ratios will be different according to how close they are situated.
           Several gender-associated characters are linked on the sex chromosomes
                These are called sex linked

The gametic ratios produced by linked loci permit construction of physical maps of chromosomes

Loci that occur on the sex chromosomes are sex-linked
     Gender is determined by genes on the X and Y sex chromosomes
            Female mammals are XX: they have two alleles for any sex-linked locus
            Male mammals are XY: they have a single allele for any sex -linked locus
      Genes that occur on the X chromosome are linked to gender
            Ex.:, haemophilia and color-vision deficiency (OMIM303800) are more common in males than females
                    Sex-linked characters have distinctive pedigrees

          X-linked genes are inherited in characteristic patterns that differ between sexes
          Y-linked genes are expressed only in males