DNA structure

Question 1

explain sanger DNA sequencing

Answer 1

A DNA strand is copied with a DNA polymerase in the presence of inhibitors that arrest DNA synthesis
specifically at A, C, G or T.The
DNA strands are separated by length on a polyacrylamide gel. If the DNA or incorporated inhibitor is radioactive or fluorescent, the DNA
bands can be visualised and the sequence read. 700-1000 bases per read.

Question 2

describe E.coli DNA

Answer 2

it is circular and comprises of 3x10^6 base pairs
it is super coiled-the DNA ribbon itself is twisted in space
the supercoiling is caused by the enzyme gyrase
e.coli genome is organised into approximately 50 independently supercoiled domains.

Question 3

how many chromosomes does human DNA have?

Answer 3

23 chromosomes - 22 autosomes and 1 sex chromosome

Question 4

How many DNA base pairs are there per cell in humans

Answer 4

there are 3 billion base pairs per cell in humans

Question 5

UV light produces what?

Answer 5

thymine dimers that cause skin cancer

Question 6

what does ionising radiation do to DNA

Answer 6

it breaks chromosomes to cause leukamia

Question 7

what is DNA supercoiling in simple terms

Answer 7

this refers to the over or umder winding of a DNA strand and is an expression of strain on that strand. DNA supercoiling is important in compacting DNA.

Question 8

importance of DNA repair

Answer 8

DNA repair ensures the survival of a species by enabling parental DNA to be inherited as faithfully as possible by offspring

it ensures genome stability. mutations in DNA can lead to cancer and other inherited diseases

Without DNA Repair, Spontaneous DNA Damage Would Rapidly Change DNA Sequences