Controlling Gene Expressions

Question 1

Why is controlling gene expression and regulating genes important

Answer 1

Required for cells to specialise and work in a coordinated way

Question 2

What are the different ways to regulate genes

Answer 2

1) transcriptional - switch genes on and off
2) post transcriptional- mRNA is modified which regulates translation and proteins produced
3) translational- translation can be stopped or started
4) post translational - proteins can be modified after synthesis changing their functions

Question 3

Describe what transcriptional level does

Answer 3

• alters the conditions of the gene to allow rna polymerise to bind and switch genes on

Question 4

Describe transcriptional level in eukaryotes (histone modification)
Cell division ——-> interphase
Heterochromatins——> euchromatins

Answer 4

1) heterchromatins: tightly wound dna so rna polymerase cannot access the genes to bind
2) has to be converted to euchromatin by acelyation and phosphorylation as opposites attract
3) rna polymerase cannot access now bind to genes and switch gene on
4) if we want reverse, methylation so cell division can occur

Question 5

Describe transcriptional level in prokaryotes ( lac operon)

Answer 5

1) regulatory gene codes for repressor protein
2) repressor protein binds to operator gene which prevents rna polymerase from binding to promotor
3) lactose then binds to repressor protein causing conformational change of he protein therefore revealing binding site
4) rna polymerase can bind to promotor therefore enabling transcription to make lactase enzyme

Question 6

What is an operon

Answer 6

Group of genes that are under the control of same regulatory mechanism and expressed at the same time

Question 7

What are structural genes

Answer 7

Genes that are not involved in regulatory mechanism and code for structure

Question 8

Describe what post transcriptional level does

Answer 8

1) pre mRNA made in transcription needs to be modified
2) pre mRNA contains introns and exons so need to remove introns so it contains genes that code for protein
3) do this by splicing to produce mature mRNA
4) to protect the mature mRNA, add adenine tail and a cap to the nucleotide and prevent degradation

Question 9

Describe what happens in translational level if we don’t want the proteins coded for

Answer 9

1) mature mRNA arrives at ribosomes
2) if we don’t want proteins made degradation of mRNA occurs
3) inhibitory proteins bind to mRNA to prevent binding to ribosomes so no proteins synthesised

Question 10

Describe translational level if we do want the protiens synthesised

Answer 10

1) avtivate initiation factors which allows mRNA to bind
2) activate protein kinase by cAMP which then catalysing addition of phosphates

Question 11

Describe post translational

Answer 11

1) Modifications of any protiens synthesised
2) by adding non protien groups like carbohydrates
3) modifying amino acids and formation of bonds
4) folding or shortening protiens
5) modifiyng cAMP