Gene Expression Reg

Question 1

Steps at which gene regulation occur

Answer 1

chromatin structure, transcription initiation, transcript processing (RNA cap), mRNA stability

Question 2

Temporal Specificity Outline

Answer 2

Gene expressed at specific times. Eg HOX genes, only active during early dev (body structure eg head vs limb placement)

Question 3

What causes Stem Cell Differntiation

Answer 3

Bind to DNA specififc element regulating gene expression. Different levels of gene expression determine cell characteristics

Question 4

Constitutive Genes Outline

Answer 4

Genes essential for life that are continuously expressed (always being made). Level of gene expression is determined by vol TF bound. Aren’t imapcted by external/internal stimulants eg polymerase

Question 5

Inducible Genes Outline

Answer 5

Genes synthesised only when required. Responds to external/internal stimulants. Develop tissue selectively. Eg PDX1 insulin gene

Question 6

Inducible Genes Activation Steps

Answer 6

Extracellular stimulant (eg hormone) binds to TF, TF changes shapes and dimerises with other active TF, TF + stimulant complex translocates to nucleus, complex binds to specific site on DNA

Question 7

What Determines Extent of Gene Expression

Answer 7

Accessibility of gene (how tight it is around histone) and availability of transcription factors

Question 8

Chromatin Modification Outline

Answer 8

Regulating acessability of promoter. Have activators (HATs), acetylating histone tail, when gene is needed. When not needed repressors (HDAC) are activated

Question 8

Histone Modification

Answer 8

Tails on histones that aren’t contained in nucleosome. Contain + charged lysine residuals that attract DNA. Acetylation (COCH3) of lysine

Question 9

Promoters Def

Answer 9

DNA which act as regulatory elements upstream of gene’s start site

Question 10

How do repressors act

Answer 10

Prevents polymerase binding

Question 11

DNA Binding Domains Outline

Answer 11

Unique structural features that allow TF structures to recognise and bind DNA. Amino acid in DBD are specific to region of DNA where gen is (and primers). Gene is slightly further downstream. Eg; zinc fingers dimer & leucine zipper dimer

Question 12

Transcription Factor Activity

Answer 12

Binds specific DNA sequence (RE), promote RNA polymerase 2, bring in chromatin modifiers and bring in coactivators

Question 13

DNA Methylation Outline

Answer 13

Promotor sequence transcription repression. recruits silencer proteins, inhibits transcription factor binding. Catalysed by methyltransferase. Epigenetic mark (not inheritable)

Question 14

Main Post-Transcriptional Reg. Areas

Answer 14

mRNA stability and differential mRNA splicing

Question 15

Poly A Binding Protein (PABP) Outline

Answer 15

Binds to poly A tail, to prevent mRNA coding degradation

Question 16

Deadenylation Outline

Answer 16

The degradation of the poly A tail overtime. Increasing risk of protein coding mRNA degradation

Question 17

How much DNA is conserved across generations/species

Answer 17

5-10%

Question 18

How does DNA chains lengthen each gen

Answer 18

Transponons. Viral DNA is integrated with host’s after infection, transponons isn’t removed as it’s not harmful. Transponons are passed onto the next gen

Question 19

micro RNA Function

Answer 19

miRNAs attach to mRNA to down regulate the gen it’s expressing. miRNAs attract enzyme to break apart mRNA