DNA replication

Question 1

before cell divides

Answer 1

chromosomes become shorter, thicker and more visible

Question 2

DNA replication

Answer 2

1. helicase enzyme separates 2 DNA strands at the replication fork
2. strand kept apart by SSB proteins
3. DNA polymerase reads sequence and add free-floating DNA nucleotides,
   complementary base to form new strands
4. DNA polymerase catalyses the joining of nucleotides with phosophodiester bond
5. DNA polymerase reads parent strand in 3’ to 5’ direcction, build leading strand in 5’ to 3’ towards replication fork, continuous
6. lagging strand is built away, 5’ to 3’, discontinuous, okazaki fragments
7. DNA ligase join okazaki fragments together

8.multiple replication forks along molecule, speed up replication, occurs in both direction

9.all individual segments of new strand meet up and join together

Question 3

Replication errors

Answer 3

Errors in replication of DNA occur around every 108 base pairs.

These errors occur randomly and spontaneously and are referred to as gene mutations or point mutations.

When this happens the genetic code could be changed. Not all mutations are harmful but some are fatal. Some provide neither
advantage nor disadvantage. Others may be advantageous, such as a
white coat for an animal in winter.

During replication there are enzymes that can proofread and edit out incorrect nucleotides which reduces the rate that mutations are produced.