Question

1. What would the complementary strand of DNA be for these strands of DNA? (1 point each; 5 points total)

a. 5’ – AGCTTGCATGGCTATT – 3’

b. 3’ – GCAATGGGCGCT – 5’

c. 3’ – AAATCCGATGCGCTA – 5’

d. 5’ – GCAGCAGCATTGCA – 3’

e. 3’ – GCAATCGCCGGTGCAC – 5’

3 During what portion of the cell cycle does DNA replicate? How many times does DNA replicate before mitosis? How many times does DNA replicate before meiosis? (3 points)

4 What is a primer? What are they made out of during DNA replication? Why does the process of DNA replication require the use of a primer? (4 points)

Answer 1

Ans.1- Complementary strand of DNA for this template strands would be:

a. 3'-TCGAACGTACCGATAA -5'

b. 5'- CGTTACCCGCGA -3'

c. 5'- TTTAGGCTACGCGAT - 3'

d. 3'- CGTCGTCGTAACGT - 5'

e. 5' - CGTTAGCGGCCACGTG - 3'

Adenine (A) always pairs with thymine (T) with two hydrogen bonds and Guanine (G) always pairs with Cytosine (C) with three hydrogen bonds. DNA double helix show antiparallel strands means if one strand run towards 5' to 3' direction then it's complementary strand run towards 3' to 5' direction.

Ans.3- DNA replication occurs during Synthesis ( S phase) of the interphase of cell cycle. Interphase ( S phase ) is the stage when DNA replication occurs. Both mitosis and meiosis contains only one interphase that means DNA replicates once in either mitosis or meiosis.

Ans.4- A primer is a short nucleic acid sequence that provides starting point for DNA synthesis. DNA replication process require primer to extend their strands. DNA polymerase uses primer for DNA synthesis because they cannot replicate DNA template without primers. Hence, the process of DNA replication cannot be initiated without primer. Primers are the complementary to the existing DNA template strand.