Question

31 cell cycle that associates Which of the following a synthesized at specific times during the B) PDGF with a kinase is protein complex? to form a catalytically active C) protein kinase D) cyclin E) Cdk What is the function of topoisomerase? A) relieving strain in the DNA ahead of the replication fork B) elongating new DNA at a replication fork by adding nucleotides the existing chain to C adding methyl groups to bases of DNA D) unwinding of the double helix stabilizing single-stranded DNA at the replication fork Red-green color blindness is a sex-inked recessive trait in humans.Two people with normal color vision have a color-blind son. What are the genotypes of the parents? XX C) KCXC and Xcy Calico cats are female because A) the males die during embryonic development. B) a male inherits only one of the two X-linked genes controlling hair color. C) the Y chromosome has a gene blocking orange coloration. D) only females can have Barr bodies. E multiple crossovers on the Y chromosome prevent orange pigment production. Two plants are crossed, resulting in offspring with a 3: ratio for a particular trait. What does this suggest? A) that the parents were true-breeding for contrasting traits B) that the trait shows incomplete dominance C that a blending of traits has occurred D) that the parents were both heterozygous for a single trait which of the following is a protein maintained at constant levels throughout the cell cycle 36. active? that requires cyclin to become catalytically A) PDGF B) MPF C) protein kinase D) cyclin E) Cdk

Answer 1

Please find the answers below:

Part 31: Choice D (Cyclins are those cell-cylce proteins which are synthesized just prior the cell undergoes division and hence play a crucial role in regulating cell cycle and division by their close association with cyclin dependent kinases.)

Part 32: Choice A (Topoisomerase is the enzyme which relieves the rotational stress experienced by the unwound DNA in the forward and reverse direction of the DNA replication fork in eukaryotes. A prokaryotic counterpart of topoisomerase also exists and has similar function. In absense of this enzyme, the DNA forward to the replication fork will go over-winding due to rotational stress of opened DNA strand in the replication fork.)

Part 33: Choice E (If CX represents the affected gene, it can be clearly seen from the choice E that only the mother would be a normal carrier for this allele and the father would be non-affected since he does not carry this allele. Only in this case, the offspring (male) can be affected by the disease)

Part 34: Choice B (The fur color is controlled by X-linked recessive gene. The males have a single X-chromosome and thus cannot be recessive for this allele and hence only females are generally calico in color)