Biochemistry - Gene Regulation

Question 1

Housekeeping genes

Answer 1

Eukaroytic genes codiing for proteins maintaining metabolic activity.

Question 2

Example of housekeeping genes.

Answer 2

GAL1, GAL7 and GAL10 for galactosee metabolism to convert galactose to G1P.

Question 3

Monocistronic

Answer 3

Only one gene is contained for protein, also called a cistron

Question 4

Operon

Answer 4

Gene clusters transcribed together to give a single mRNA

Question 5

What regulates GAL7/1/10?

Answer 5

Galactose

Question 6

How does GAL80 repress galactose transcription?

Answer 6

Binds and inactivates the activator protein GAL4

Question 7

GAL4

Answer 7

Activates transcription of the GAL genes

Question 8

GAL3 mechanism in presence of galactose?

Answer 8

Binds galactoses with ATP and binds GAL80, restricting it to the cytoplasm.

Question 9

What happens when galactose is not present?

Answer 9

GAL80 is free to roam as GAL3 cannot repress it, GAL80 binds and represses GAL4 to prevent GAL synthesis.

Question 10

What are the two mechanisms of transcription activator protein?

Answer 10

Indirectly by interacting with transcriptional machinery components then recruiting it to the site or directly by inaitation transcription of a pre-assembled transcription complex

Question 11

What are the two ways TAP interact with DNA?

Answer 11

helix-turn-helix motif and zinc fingers

Question 12

TAP zinc finger mechanism..

Answer 12

Zinc has affinity for 17BP sequence either end of gene with CCG triplet codon it recognises.

Question 13

How does helix-turn-helix motif faciltiate its functiion?

Answer 13

Infiltrate dsDNA grooves.

Question 14

Where are enhancers found?

Answer 14

Intergenic regions or on introns within the gene.

Question 15

Example of a TAP?

Answer 15

Mammary tumour virus activated by glucocorticoid steroid hormones.

Question 16

Importance of enhancers?

Answer 16

Allow genes to be transcribed when certain proteins are present as well as alter amplification of syntheiss.

Question 17

Polycomb Group Proteins

Answer 17

Epigenetic regulators of transcription important in stem-cell identiy and differentiation.

Question 18

DNA looping

Answer 18

The binding of two sites of DNA.

Question 19

Mechanism of DNA looping

Answer 19

TAP interacts with transcriptionak complex to recruit it tto gene, formation begins with TFIID(contans TBP), binding TATA box promoter region and DNA minor groove bending it 80 degrees, a TAP links TFIID to enhancer, which also brings TBP into contact with tata box allowing RNAPII recruitment

Question 20

Why is DNA looping important?

Answer 20

Allws promoters to activate genes thousands of BP

Question 21

Structure of RNAP II

Answer 21

Consists of 12 subnuits found in the POL2 holoenzyme

Question 22

Chromatin-Remodelling Complexes

Answer 22

Multiprotein complexes that restructure chromatin to allow its transcription.

Question 23

Most common CRC?

Answer 23

Cytosine methylation and CpG islands.

Question 24

Methylation

Answer 24

Addition of a methyl group to 5’ carbon

Question 25

What does CPG methylation do?

Answer 25

Repress transcription activity.

Question 26

Example of methylation fucnctional importance...

Answer 26

Inactive X chromosome and in 60-70% somatic cell CCpG islands are methylaed

Question 27

Genomic Imprinting

Answer 27

Expression of one copy of a gene and supression of another.

Question 28

Wher edoes imprinting sex-specific silencing occur?

Answer 28

Prader-wili syndrome and Angelman syndrome

Question 29

What do PWS and AS share in common?

Answer 29

Deletions of 15q11

Question 30

What genes are deleted in 15q11?

Answer 30

SNRPN, necdin and UBE3A.

Question 31

Where are SNRPN, necdin and UBE3A imprinted?

Answer 31

SNRPN and necdin in the egg and UBE3A in the sperm.

Question 32

What happens to the 15q11 genes in germ line?

Answer 32

Males UBE3A imprinted on both homologs and necdin SNRPN in females

Question 33

What happens if wildtype imrpinted female implanted with sperm of 15q11 deletion?

Answer 33

Embryo have no active copy of SNRPN nor NECDIN resulting in PW

Question 34

Why might imprinting occur?

Answer 34

If a father supresses genes to conserve resources at expense of fetus, imeediate production will be maximuse.

Question 35

Alternative Splicing

Answer 35

Where splice sites in pre-mRNA are selected in alteranting combination to produce variably spliced mRNA

Question 36

What does Alternative Splicing allow for?

Answer 36

Varying quantites and different types from the same gene of an mRNA

Question 37

Example of alternative splicing?

Answer 37

Insulin in skeletal muscle cells has exon 11 removed whilst liver retains it

Question 38

Why is exon 11 removed frfom insulin in skeletal muscle cells?

Answer 38

Increases its affinity for insulin

Question 39

How does mRNA stability regulate mRNA?

Answer 39

Altering stability affects outcome of protines.

Question 40

Two type of mRNA stability?

Answer 40

Deadenylation dependent pathway Deadenylation independent pathway

Question 41

Deadenylation dependent pathway

Answer 41

Where poly-a tail is trimmed to about 25-60NT making it susceptible to cap removal