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why two crossovers are needed on one chromatid arm?
explain please
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- In the following schematic drawing of a Holliday junction,one chromatid is shown in red, and the homologous chromatidis shown in blue. The red chromatid carries a dominant allelelabeled A and a recessive allele labeled b, whereas the blue chromatidcarries a recessive allele labeled a and a dominant allelelabeled B. Where would the DNA strands have to be cut to produce recombinantchromosomes? Would they be cut at sites 1 and 3, or at sites2 and 4? What would be the genotypes of the two recombinantchromosomes?An initial crossover event will occur between A and B, as indicated in the corresponding image. After this initial event occurs, a second crossover event occurs (not illustrated) involving the products of the first crossover event. a. Given this chromosome organization, A B c, A b c, a B C, and a b C, which two chromatids of the bivalent were involved chromatid 1 chromatid 2 chromatid 3 chromatid 4 and between which genes gene A gene B gene C did the second crossover event occur to produce the indicated chromosomes? b. Returning to the original crossover depicted in the image, given this chromosome organization, A B C, A B C, a b c, and a b c, which two chromatids of the bivalent were involved chromatid 1 chromatid 2 chromatid 3 chromatid 4 and between which genes gene A gene B gene C did the second crossover event occur to produce the indicated chromosomes?why The chromatids formed byrecombination within the inversion loop of a pericentric inversionheterozygote are genetically unbalanced?
- Name the disorder with choromosome compliment 22 pairs of autosomes +XXY?Consider the following two meiocytes in metaphase I, with crossover positions as indicated for cell A. Solid black lines indicate spindle microtubules. Assume blue chromosomes represents paternal chromosomes and green maternal chromosomes. F G N R A B D e g a B d E Cell A Cell B i) How many chromosomes and chromatids were present in cell A during the G1 phase? Please clearly specify chromosomes and chromatids in your answer. ii) For cell A, list all the gametes that will be produced from this cell. Give the alleles of each gamete contained within a set of brackets. You may ignore independent assortment. iii) For cell B, list all the gametes that will be produced from this cell given independent assortment. Give the alleles of each gamete contained within a set of brackets. You may assume that no crossing over would take place.What would be the effect of crossing-over between two sister chromatids?
- A diploid species has 3 pairs of chromosomes in its somatic cells. In males, the first pair is large submetacentric[1]; the second is medium acrocentric[2], and the third is small telocentric[3]. In females, the first two pairs are like those of the males while the third is large metacentric[4][5], with satellite4 Illustrate the karyograms (drawing/picture of the chromosome) of the following: A triploid cell in females tetrasomic cell in males tetraploid cell in females [1] submetacentric --centrosome is just above the middle of the chromosome [2] acrocentric --centrosome is much higher location than submetacentric so that the “p” arm of the chromosome is much shorter than the q arm [3] telocentric --the centromere is at the end of the chromosome [4] metacentric --centrosome is in the middle of the chromosome; thus the “p-arm” and the “q-arm” or both arms of the chromosome are equal in length [5] satellite-a constriction in an arm of a chromosome, aside…Consider the following two meiocytes in metaphase I, with crossover positions as indicated for cell A. Solid black lines indicate spindle microtubules. Assume blue chromosomes represents paternal chromosomes and green maternal chromosomes. G N D t d Cell A Cell B i) How many chromosomes and chromatids were present in cell A during the G1 phase? Please clearly specify chromosomes and chromatids in your answer. ii) For cell A, list all the gametes that will be produced from this cell. Give the alleles of each gamete contained within a set of brackets. You may ignore independent assortment. iii) For cell B, list all the gametes that will be produced from this cell given crossing over. Give the alleles of each gamete contained within a set of brackets. You may assume that no crossing over would take place.During meiotic prophase in a eukaryotic cell, Spo11 initiates recombination by causing a double-strand break in DNA between Gene A and Gene B on one sister chromatid. Which of these events will occur prior to formation of a Holliday junction? A) A heteroduplex forms due to pairing of Gene A and Gene B. B) Resolvase cuts all four chromatids. C) Spo11 causes a double-strand break in a nonsister chromatid. D) Strand invasion causes one strand of the uncut chromatid to form a D loop. E) Branch migration lengthens the heteroduplex region to include Gene A and Gene
- a. Manually, using a pencil, draw a cell in anaphase II from an organism in which 2n = 2 and each chromosome is metacentric. b. Given that each G1 nucleus from this organism contains 16 picograms of DNA, how many picograms of chromosomal DNA would you expect in the cell shown here?Two nonhomologous chromosomes have the following segments, where * represents the centromere: *ABCDEFG , *RSTUVWX. Name the type of chromosomal rearrangements that would produce each of the following chromosomes. *ABABCDEFG , *ABCD , GFEDCBA*RSTUVWX , *RSWVUTX , *ABCWX , *RSTUVDEFG . Which of these types of abnormalities are most likely embryonic lethal and which ones are not usually a problem for the individual carrying them? Briefly explain why.Assume that the diploid number of a certain species is four chromosomes, two large and two small (2n=4). a) Of the following figures, which represents a 3n (triploid) cell in mitotic metaphase? b) For each of the wrong answers from part (a) above, explain briefly why it cannot represent a triploid cell in mitotic metaphase.