Chapter 19 Keyconcepts

Question 1

Why are intiation factors useful

Answer 1

• activiation of initiation factors that help mRNA bind to ribosomes
• the eggs of many organisms makes bare mRNA not needed until after fertilisation
• at fertil, intiation factors activated and translation happens

Question 2

What two types of gene mutations are frameshift mutations?

Answer 2

Insertion and deletion. This changes every successive codon from the point of mutation

Question 3

Importance of the triplet code

Answer 3

Sequence read in non overlapping windows

Question 4

Effects of different mutation can either be…

Answer 4

Neutral, have no effect
No effect on phenotype because normal functionitig proteins are still made

Damaging
Phenotype negatively affected because proteins aren’t made or are made but aren’t functional.
Can interfere with one or more essential processes

Beneficial
Rare. However one eg.Is people immune to HIV infection because mutation on protein in their csm so hiv can’t bind and enter

Question 5

Beneficial mutations

Answer 5

people immune to HIV infection because mutation on protein in their csm so hiv can’t bind and enter

Lactose tolerance. This prevents diseases like osteoporosis
Could’ve prevented individuals with the mutation from starving
Found in european populations who are likely to farm cattle. Has arisen spontaneously

Question 6

Pros of gene regulation in bacteria

Answer 6

Enables bacteria to respond to changes in the environment

Prevents vital resources being wasted

Question 7

Why are operon more common in pro than eukary?

Answer 7

Pro have smaller and simpler structured genomes

Very efficient way of saving resources cuz if gene product not needed, just switch their production off

Question 8

How to make the RNA polymerase transcribe more effiencently (lac operon)

Answer 8

Binding of cAMP receptor protein CRP.

Question 9

Describe RNA processing

Answer 9

Happens in the nucleus

After transcription you have pre-mRNA. A precursor molecule
This is modified to make mature mRNA which can then bind to a ribosome
Modified nucleotide cap added to 5 primes and tail added to 3 prime

Question 10

Why add the cap and tail to the mRNA

Answer 10

Add stability
Delay degradation in the cytoplasm
Cap aides binding of mRNA to ribosomes

Question 11

What is splicing and where does it happen

Answer 11

Happens in the nucleus

RNA cut at specific places. Introns removed and exons joined together

Question 12

What is RNA editing

Answer 12

Chaining the nucleotide seq of mRNA by base addition sub or deletion
Some effect as point mutations
Result in making different proteins with diff functions

Question 13

Pros of RNA edition

Answer 13

Increases range of proteins that can be made from a single mRNA molecule or gene

Question 14

Why use fruit flies

Answer 14

Easy to raise isn large numbers in the lab
Reproduce rapidly
Many of its mutations easy to see under low light maginification
Short life cycle
Small
Easy to keep
Reproduce on rotting fruit

Question 15

Example of how drugs effect regulatory genes

Answer 15

Thalidomide
Given to pregnant women in 1950 -60 to treat morning sickness
Prevented the normal expression of a particular hox gene so made babies with shortened limbs
Now used for treating some types of cancer to stop their development
Prevents the formation of capillary necessary for some tumours to grow and develop