Answer:
Crossing over and random alignment are the events of meiosis-I that add new gene combinations to the gametes. Random fusion of male and female gametes is called random fertilization.
Explanation:
During the pachytene stage of meiosis-I, part of the chromatids of each of the homologous chromosomes of a bivalent is broken apart and exchanged. This exchange of the genetic material between the members of a bivalent is called crossing over. The recombinant chromatids formed by crossing over have new allele combinations that were otherwise not present in the parental chromatids.
During metaphase I, the homologous pairs are aligned at the cell's equator in a random manner. This means that either the paternal or maternal chromosome of a pair may face one or the other pole of the cell. The arrangement of chromosomes during metaphase-I determines whether the paternal or maternal chromosome of each pair would be distributed to one or the other pole of the cell. This random segregation creates new gene combinations in gametes.
All the gametes have equal chances of getting fused with a gamete from the opposite gender. This is called random fertilization and further adds variations.
Answer: A, through extensive testing and the accumulation of several lines of evidence
Explanation:
The correct matching of enzymes and their role in the process of DNA replication is A- 3, B- 5, C-1, D-2 and E-4.
Replication is the process of synthesis of two indentical copies of DNA from a single DNA molecule. It is catalyzed by a set of enzymes with the following function-
A. RNA primase synthesizes an RNA primer (short sequence of RNA) on the lagging strand complementary to the single stranded DNA which acts as template during DNA replication.
B. Ligase is involved in joining the okazaki fragments on the lagging strand together and sealing the nicks of the DNA strand.
C. Helicase separates the two DNA strands at the replication fork.
D. Polymerase synthesizes the complementary daughter strand by adding nucleotides to DNA.
E. Topoisomerase relaxes the highly coiled DNA by creating nick ahead of the replication fork in the phosphate backbone of DNA strands.
Answer:
There are four possible combinations of gametes for the AaBb parent. Half of the gametes get a dominant A and a dominant B allele; the other half of the gametes get a recessive a and a recessive b allele. Both parents produce 25% each of AB, Ab, aB, and ab.
Explanation:
