4) Concisely, describe the particular festures of Creighton\'s and McClintock\'s

Question

4) Concisely, describe the particular festures of Creighton's and McClintock's experiment that allowed them. io prove Morgan's hypothesis that coupling and repulsion results from the physia exchange of DNA between homologous chromosomes? 5) What factors make mitochondrial DNA particularly useful for determining ancestory 6) The father of Mr. Spock, first officer of the starship Enterprise, came from the planet Vulcan. Mr. Spock's mother came from Earth. Pure-bred Vulcans like Mr. Spock's father have pointed ears (P), no adrenal glands (A), and a right-sided heart (R) and are homozygous for all of these alleles. These Vulcan alleles are dominant over normal earthling alleles. These three genes are autosomal, and they are linked as shown in this map: P 15 map itsA 20 map unitsR If Mr. Spock marries a woman from Earth, what is the likelihood (expressed as a percentage or as a decimal) that their children would: a) have Vulcan traits for all three of these characteristics?

Explanation / Answer

4. Creighton’s and McClintock’s use maize as a model organisms. They use a maize plant which possess an alternation (an extra knob) at its 9th chromosome, which is also undergo a reciprocal translocation with the 8th chromosome. This plant is heterozygous for the color (C) and waxy endosperm (wx) that is Cwx/cWx. Cwx was carried on the knobbed chromosome and cWx was located on the knobless chromosome. This plant was testcrossed with a plant that is homozygous recessive for both the traits (cwx/cwx). This crossing may generate eight different types of progeny

Cwx/cwx – colored and waxy & cWx/cwx – colorless and nonwaxy

2. Four different types generated due to two independent single crossing over event (the knob and c gene and between c and Wx)

cWx/cwx -Colorless non-waxy, Cwx/cwx-colored waxy, Cwx/cwx-colored non-waxy, cwx/cwx- colorless waxy

3. Two different types generated due to double crossover event

cwx/cwx-Colorless waxy and CWx/cwx-colored nonwaxy

This experiment indicated that recombination of genes on the chromosome rely on the physical exchange of the segments of chromosome with its homologous pair.

Morgan in his experiment proposed that when the two linked genes are observed in the coupling or repulsion phase, it indicates that these two gene reside on either the same chromosome or in the different but the homologous pair of this chromosome, respectively. This phenomena is known as linkage, and the linkage strength is inversely proportional to the distance between two genes. This linkage is disrupted by the crossing over during meiosis. The frequency of crossing over is directly proportional to the distance between the two genes. This crossing over events again causes physical involvement of a segment of the two homologous chromosome. This exchange of physical segment of chromosome within the homologous pair is proposed by Creighton’s and McClintock’s through the previously mentioned experiment.

5. In contrast to nuclear DNA, which is transmitted from both parents, mitochondrial DNA is inherited only from the mother. In addition, no recombination or crossing over did not occur in the mitochondrial DNA, which makes the mitochondrial DNA stay the same over generations. Mitochondrial genomes is more frequently mutated compared to the nuclear genome. Single nucleotide polymorphism (SNP) is often observed in the mitochondrial genome, in which a particular nucleotide is mutated. By using a standard mitochondrial genome (Cambridge Reference Sequence), and by comparing the SNP profile of the mitochondrial genome of different individuals, they can predict about their ancestry.

6. Mr. Spoke's mother genotype was missing

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