L6 Regulating Gene Expression 1

Question 1

Cell expression

Answer 1

Fibroblast -> bone cell (osteoblast/osteocyte), adipocyte, smooth muscle cell and cartilage cell (chondrocyte)

Question 2

Transcription importance

Answer 2

Control amount of RNAs that are made at a particular time

RNA amount is varied but proportional to the amount of protein

Question 3

RNA polymerase I

Answer 3

most rNA genes transcribed

Question 4

RNA polymerase II

Answer 4

protein-coding genes, miRNA genes plus genes for some small RNAs (spliceosomes)

Question 5

RNA polymerase III

Answer 5

tRNA genes, 5s rRNA gene and genes for small RNAs

Usually increases during cancer progression

Question 6

Alpha amanitin poisoning

Answer 6

Death cap (amanita phalloides)
Inhibits RNA polymerasell
Causes death by mass liver failure

Question 7

Transcription overview

Answer 7

Basal transcription factor binds first
RNA polymerase binds with other factors
C-terminal domain is initially un-phosphorylated
C-terminal domain is phosphorylated and RNA polymerase starts making RNA

Question 8

Transcription only starts

Answer 8

when the correct complex of transcription factors and other components come together
DNA may loop round for some regulatory transcription factors to bind
Transcription factors can be far from controlled gene sites

Question 9

Fragile X syndrome symptoms [6]

Answer 9

Large, protruding ears
Hyperextensible finger joints
Double-jointed thumbs 
macro-orchidism (large testes)
learning difficulties
autism.

Question 10

Fragile X syndrome observation

Answer 10

Expansion of CGG results in methylation of DNA in the promoter. This prevents the RNA polymerase complex assembling properly – no transcription

Risk of expansion of repeat region from premutation to full disease mutation if inherited maternally

Question 11

Alpha-thalassemia

Answer 11

Deficiency of alpha-globin
Mental retardation

ATRX is a protein that unwinds DNA - part of a large multiprotein complex that controls chromatin structure

Particularly associated with centromeres
Lack of ATRX shuts down transcription of a numner of genes including alpha-globin

Question 12

Primary transcript modification

Answer 12

C-terminal domain acts as an assembly line to co-ordinate modification of capping, splicing and polyadenylation

Question 13

Eukaryotic pre-mRNA may have many introns

Answer 13

many introns

Question 14

unspliced RNA is termed

Answer 14

pre-mRNA

Introns need to be spliced to convert to mRNA

Question 15

Introns removed from primary transcript

Answer 15

Introns removed by complex RNAs and spliceosomes proteins
Accurate removal of introns is very important
Accuracy is conferred by small nucleolar RNAs (snRNAs) within spliceosome

Occurs co-transcriptionally

Question 16

b -thalassemia

Answer 16

Anemia from about 6 months of age
Require frequent blood transfusions

Aberrant processing – introns not spliced out properly
Results in premature stop codons
lack of protein.

Question 17

alpha tropomyosin gene

Answer 17

mRNA: 
Striated muscle 
smooth muscle 
fibroblast 
brain