Question

6.) During meiosis, when crossing-over occurs between two homologous chromosomes, it does not happen at a single point, but rather two points with a stretch of DNA in between. a. What are the two junction points called? b. What is the region between the two points called and what is different about this region compared to how double-stranded DNA usually is? c. If the region described in b.) is located within a gene and the two homologues have different alleles of this gene, what might happen that is a direct violation of Mendel's first law? (Describe the process with 2-3 sentences of detail.) 7.) A form of “homologous recombination" can also occur in somatic cells. a. When might this happen? b. Describe two main differences between the recombination that occurs in meiosis and that which happens in somatic cells. (2-3 detailed sentences.)

Answer 1

(6. o During Crossing over the chiasma is a structure that forms between a pair of Homologous choomarome by crossover Ofecombination during meisis in Pachytene stage. Chiesmata (P.) are the visible expression of co.of gent This region is known as Holliday junction, cross- Shaped structure that forms during the process of genétic ofecombination. 'The Holliday Junction travel along the ANA duplex by "unzipping” one strand and deforming the Hydrogen bonds in the and strand. along the holenduplex This Holliday Jmétiens involves the heteroduplex double - stranded DNA essential for ope combination. Holliday showlany os . Endonuclease? MOS I ligation (C) Holliday gunetim located within a gene arnd the two acetes homologous have different allele of this gene known as partial linkage occus a l l over the Parental No parental linkage In case of while linkage according genee assort independently v to the lit law of regregation

that known as law of purity of gan organism, segrega ac gemete that was hut after at thomas the allele which was guen before by the great scientist Mendel also two alleles in each gametes formed, me abiele goes into but after rediscovery of mendelian law done by Thomas Hunt Morgan explained The segregation of allele into gametes can be enfuenced by linkage in which genes that are located physically close to each other on the same # (chromozome) are more likely to be inherited as a pair. The garden per has y chromosome. Mendel was lucky that the genes he picked up were not located on separate chromosomes it is possible that he Almply did 'not obsene linkage because of the extensive shuffling effects of gecombination. . r on the as a pale Cay In Somatic cells, Homologous fecombinatim CHR) is a weare event caused by eventual ONA double standed breaks CDsBs) whale' frequently leads to nm- cross over Djecombinatim HB oceuss frequently at innate (G1), motif during mitosis in normal somatic cells in tro. (at microsatellite) .. Microsatellite are prone to DSBs during genome replicar - . © HR duringsmatie cell. HR during mėsosis It applies m epgenelite sjeopone per mother tematiche e verwelyn to DNA damage Non-cross oves stecombit Result in cross over between Homologous charmosome. essentia for faéttfet segregation, at merosis ] • It leads to natim