gene regulation & transcription factors

Question 1

define gene expression

Answer 1

process by which specific genes are activated to produce a required protein

Question 2

define gene regulation

Answer 2

the control of gene expression

Question 3

define epigenetics

Answer 3

studying changes caused by modification of gene expression rather than alteration of the genetic code itself

Question 4

state the 4 levels at which genes are regulated

Answer 4

• transcriptional
• post-transcriptional
• translational
• post-translational

Question 5

briefly describe the 4 levels at which genes are regulated

Answer 5

• transcriptional - genes can be turned on / off
• post-transcriptional - mRNA can be modified to regulate translation + types of proteins produced
• translational - translation can be stopped / started
• post-translational - proteins can be modified after synthesis to change their functions

Question 6

give an example of transcriptional control in eukaryotes and prokaryotes

Answer 6

• eukaryotes: chromatin remodelling by histone modification
• prokaryotes: operons (lac operon)

Question 7

give 2 examples of post-transcriptional control

Answer 7

• RNA processing
• RNA editing

Question 8

give 3 examples of translational control

Answer 8

• degradation of mRNA
• binding of inhibitory proteins
• regulation of translation initiation factors

Question 9

give 4 examples of post-translational control

Answer 9

• addition of non-protein groups
• modification of amino acids
• folding/shortening of proteins
• protein activation by cAMP

Question 10

what is chromatin?

Answer 10

complex of DNA and histones

Question 11

define heterochromatin

Answer 11

tightly wound DNA (makes it visible during cell division)

Question 12

explain the significance of heterochromatin in gene expression

Answer 12

transcription of genes is not possible when DNA is tightly wound bc RNA polymerase can’t access genes

Question 13

define euchromatin

Answer 13

loosely packed DNA

Question 14

explain the significance of euchromatin in gene expression

Answer 14

transcription of genes is possible - RNA polymerase can access genes

Question 15

explain how chromatin remodelling is useful in cell division

Answer 15

• genes in heterochromatin can’t be transcribed, genes in euchromatin can
• having DNA in heterochromatin during cell division prevents complex + energy-consuming process of protein synthesis from occurring

Question 16

explain how histone modification can affect gene expression

Answer 16

• DNA wraps around histones bc DNA is -itively charged, histones +itively charged
• acetylation/phosphorylation reduces +itive charge on histones + causes DNA to coil less tightly - certain genes can be transcribed
• methylation makes histones hydrophobic so bind more tightly to each other, causing DNA to coil more tightly - certain genes transcription prevented