Regulation Of Eukaryotic Gene Expression

Question 1

role of histone acetylases

Answer 1

favor gene expression by actetylating certain lysyl residues …decreasing the positive charge ….weakening the interaction with DNA

Question 2

what are enhancers and silencers

Answer 2

enhancers in the DNA are the binding site for activator proteins.

silencers in the DNA are the binding site for repressor proteins.

Question 3

where are enhancers located

Answer 3

may be located upstream, downstream , or within an intron of the gene they control.

Question 4

what are the 2 domains present on transcription factors

Answer 4

1. DNA binding domain

2. activation domain

Question 5

name some common DNA binding domains of transcription factors

Answer 5

ZINC FINGERS::steroid hormone receptor

LEUCINE ZIPPERS::cAMP dep TF

HELIX- LOOP -HELIX

HELIX -TURN -HELIX::homeodomain proteins encoded by homeotic/ homeobox genes

Question 6

role of activation domain

Answer 6

bind to other TFs and coregulators

interacy with RNA pol2 to stabilise the formation of initiation complex

recruit chromatin modifying proteins such as histone acetylases / deacetylases

Question 7

homeodomain proteins

Answer 7

TFs that bind to DNA and regulate gene expression during development

helix turn helix– DNA binding domain

Question 8

steroid receptors

Answer 8

these are TFs that binds to HRE response element on DNA and induce steroid response.

DNA binding domain – Zn fingers

Question 9

whivh TFs have Zinc fingers as DNA binding domain

Answer 9

steroid receptors

peroxisome proliferator activated receptors PPARs

Question 10

fxn of PPARs (TFs)

Answer 10

1. regulaye multiple aspects of lipid metabolism

2. activated by fibrates and thiozolidenediones

Question 11

NFkappaB role

Answer 11

TF which regulates expression of many genes in immune system

Rel domains

Question 12

cAMP response element binding (CREB)protein fxn

Answer 12

TFs which bind to CRE and response to cAMP

leucine zipper

Question 13

general and specific TFs

Answer 13

GENERAL TFs–:
bind to promoter to allow RNAP II to bind and form initiation complex at the start site for trancription.

eg:TFIID, SP-1, NF-1

SPECIFIC TFs–:
bind to enhancer regions or in some cases silencers and modulate the formation of initiation complex, this regulating the rate of initiation of transcription.

eg:steroid, PPARs, NFkB, homeodomain

Question 14

PPARs activated by

Answer 14

fatty acids

PG derivatives

fibrates

thiozolidenediones

Question 15

Zellweger syndrome defect

Answer 15

genetic ds caused by a mutation in any one of the several gene(locus heterogeneity) involved in peroxisome biogenesis.

accum of long chain f.a. and abnormal f.a.

aka hepatocerbrorenal syn

Question 16

eg of how response elements effect metabolism

Answer 16

pathway of gluconeogenesis.

activated by glucagon and cortisol

GLUCAGON: memb ass receptor that increase cAMP ..activate protein kinase A..CREB

CORTISOL:binds to intracellular receptor which binds DNA via Zn fingers(permissive action)

both lead to transcription of PEPCK(phosphoenol pyruvate carboxykinase)
which is the rate limiting step in gluconeogensis.

Question 17

klein waardennburg syndrome

Answer 17

dvelopmental disorder resulting from a mutation in PAX(paired box) gene.

HOX and POX genes are req proper tissue and cell differentiation during embryonic period.

Question 18

features of klein waardenburg syndrome

Answer 18

K-looks like X so mutation in PAX3
L-limb abnormalities
E-eyes coloured(heterochromia  of iris)
I-inner canthus displaced laterally
N-neural crest cells mutated

W-white blaze of frontal hair
A-abnormal upper limbs
A-altered pigmentation
R-root of nose depressed
D-deafness

Question 19

what is the cause of holoprosencephaly HPE

Answer 19

haploinsufficiency of SHH(sonic hedgehog)

develpmental anomaly of forebraina nd face where there is failure of separation of cerebral hemisphere

Question 20

major exceptions to the rule of codominance

Answer 20

barr body

in the Ig heavy and light chain loci(ensuring that only one B cell makes only one type of Antibody)

in the T cell reveptor loci.