3.9 DNA replication

Question 1

Why does DNA need to replicate?

Answer 1

• cell division- new cells need dna for growth and repair
• Reproduction-gametes reuire DNA to pass on genetic info

Question 2

How does DNA replicate?

Answer 2

1. DNA helicase breaks down the H bonds between the polynucleotide strands ‘unzips’
2. the original strand acts as a template for a new strand of free nucleotides to join the exposed bases by complemetary base pairing
3. these nucleotides are joined together by help of DNA polymerase catalysing the formation of the sugar-phosphate backbone
4. Hydrogen bonds form between the bases and it coils into a double helix

Question 3

why do we refer dna replication as

semi conservative?

Answer 3

Two new molecules are produced each consisting of one old and one new strand

Question 4

what are the two enzymes involved with DNA replication

Answer 4

• DNA helicase
• DNA polymerase

Question 5

what is the role of ……. in dna replication

DNA helicase

Answer 5

catlyses the breakdown of the H-bond between bases ‘unzipping’

Question 6

what is the role of ……. in dna replication

DNA polymerase

Answer 6

catalyses the formation of the phosphodiester bond between nucleotides

Question 7

comment on

DNA replication acccuracy?

Answer 7

• very accutate to make sure genetic info is conserved each time dna in a cell is replicated
• mutations:dont always affect but somealter sequence and lead to abnormal protein wich can be of advantage or disadvantage

Question 8

genetic code is a triplet code broken into…..

Answer 8

codons

Question 9

whats a

codon

Answer 9

3 bases wich code for one amino acid

Question 10

whats a

gene

Answer 10

section of dna that contains a complete sequence of codons to code for an **entire protein **

Question 11

what is meant by

degernate code

Answer 11

there are more codons than amino acids so many are coded from more than one codon

Question 12

what is meant by

universal geneitc code?

Answer 12

the same codons code for the same amino acid in all living organisms

Question 13

how mutations of a gene can occur so that the protein is not produced

Answer 13

• give a premature stop codon so resulting in a shortened product
• deletion with loss of allele a dif product made

Question 14

preventing the spread of malaira

Answer 14

reduce mosquito numbers
stock ponds with fish (Gambusia) to eat larvae; R kill mosquitoes
oil on surface;
spray bacteria (Bacillus thuringiensis) to kill mosquito larvae;
DDT / pesticide spray;
release of sterile male mosquitoes;
draining, ponds / bodies of water;
avoid being bitten by mosquitoes
wear insect repellent;
long sleeved clothes;
sleep under nets;
nets soaked in, insecticide / repellent;
sleep with, pigs / dogs;

Question 15

HIV transmission not sexual activity

Answer 15

shared needles or surgical instruments / needles, reused without sterilisation;
A contaminated needles reused
(mother to child) across placenta / at birth;
breast milk / breastfeeding;
blood products / blood transfusion;