Genetics Essay Example | Topics and Well Written Essays - 750 words - 5

Genetics - Essay Example This type of Down’s syndrome usually occurs in mothers who are less than 30 years of age. The Robertsonian translocation that leads to Down syndrome occurs between chromosomes 21 and 14. During meiosis, three possible pairing configurations can be observed between the 14 and 21 translocate chromosome and normal homolog (Crow and William 111). Think about how there pairings might occur and draw all possible pairing arrangements. You should draw your pairing arrangements with respect to the equator of the cell at metaphas This is because it helps us to determine whether genes are on the same or separate chromosomes. By calculating the frequency of crossing over, we obtain a measure of the map distance between the gene pairs (Crow and William 127). One genetic map unit (mu) is the distance between gene pairs for which one product of meiosis out of a hundred (100) is recombinant. 14. Perform a crossover between homologues 2 and 3 at the point indicated in the diagram below. If a second crossover occurs in the same region between the 2 genes, tell which chromatids would be involved to produce the following outcomes 15. Using the homologous chromosomes below, assume that a paracentric inversion occurs that involves genes B and C such that genes B and C are now inverted. The inversion occurs on only one homologue. During meiotic pairing of the inverted chromosome with the normal chromosome, a chiasma forms between B-C and crossing over