7.2 transcription and gene expression

Question 1

transciption direction

Answer 1

5’ to 3’

Question 2

strcutrure of nucleosomes

Answer 2

• eukaryotic DNA wrapped around 8 histone proteins
• histone proteins have protruding tails – determine how tigthly the DNA is packaged
• histone tails pos charge, associate w neg charge DNA

Question 3

modification of histone tails to increase transcription

Answer 3

add an acetyl group to the tail = neutralises charge = DNA less tightly coiled

Question 4

modification of histone tail to reduce transcription

Answer 4

add a methyl grp to tail = maintain pos charge = more coiled DNA

Question 5

2 types of chromatin

Answer 5

• hetero chromatin (methylation)
  supercoiled DNA, not accessible for transcription
• eu chromatin (acetylation)
  DNA is loosely packed, accessible for transcription machinery

Question 6

increased direct methylation of DNA

Answer 6

decreases gene expression
(prevents binding of transcription factors)
- genes that r not transcribed exhibit more dna methylation

Question 7

possible causes of changes to DNA methylation

Answer 7

• parental genes
• maternal diet during pregnancy
• environmental
• infant exposure to microbes
• diet
• lifestyle
• old age related changes

Question 8

define epigenetics

Answer 8

the study of CHANGES in PHENOTYPE as a result of VARIATION in GENE EXPRESSION LEVEL

Question 9

epigenetic analysis shows … point+3

Answer 9

DNA methylation patterns may change over the course of a lifetime
- influcened by heredity
- diff cell types diff DNA m patterns
- environmental factors

Question 10

transcription defintiion

Answer 10

process by which DNA sequence is copied into a COMPLEMENTARY RNA sequence by RNA POLYMERASE

Question 11

3 stages of transcription

Answer 11

1. inititation
2. elongation
3. termination

Question 12

transcription 1st stage initiation

Answer 12

RNA polymerase binds to the promoter and causes the unwinding and separating of the DNA strands (in rep its helicase)

Question 13

transcription 2nd stage elongation 4

Answer 13

• RNA polymerase moves along the coding sequence
  – Free nucleotides exist in the cell as ribonucleoside triphosphates (NTPs), which line up opposite their complementary base partner
  – RNA polymerase covalently binds the NTPs together in a reaction that involves the release of the two additional phosphates
  – Synthesising RNA in a 5’ → 3’ direction

Question 14

transcription 3rd stage termination

Answer 14

RNA polymerase reaches the terminator, both the enzyme and nascent RNA strand detach and the DNA rewinds

Question 15

the literal only thing that is used in transcription

Answer 15

RNA polymerase

Question 16

template strand in transcription: read from

Answer 16

3’ to 5’

Question 17

syntesis of RNA strand from template strand in transcirtion:

Answer 17

5’ to 3’
- 5’ phosphate linked to 3’ end of growing mRNA strand

Question 18

3 post transcriptional events to form mature mRNA

Answer 18

1. Capping
2. Polyadenylation
3. Splicing
   CHILD PROTECTIVE SERVCEIS

Question 19

post transcriptional dolling up! capping – what is it and which end

Answer 19

• Addition of a methyl group to the 5’-end of the transcribed RNA

Question 20

function of methylated cap in capping

Answer 20

• Provides PROTECTION against degradation by exonucleases
• Allows the transcript to be RECOGNISED by the cell’s TRANSLATIONAL machinery (e.g. nuclear export proteins and ribosome)

Question 21

post transcriptional modification like a car vroom: poly ade nylation WHAT and WHERE

Answer 21

• Addition of a long chain of adenine nucleotides (a poly-A tail) to the 3’-end of the transcript

Question 22

FUNCTION of poly-a tail (poly ade nylation)

Answer 22

• Improves the STABILITY of the RNA
  transcript
• FACILITATES the EXPORT of RNA transcript from the nucleus

Question 23

splicing?? in post trascriptional hee hees. hint its what it says on the tin

Answer 23

• non coding sequences (introns) must be removed
• coding regions (exons) fuse tgt to form continuous after introns removed
• introns = intruding sequences VS exons = expression sequences

Question 24

alterantive splicing uh oh

Answer 24

• selective removal of specific exons !!! (coding/expressing sequence)
  = formation of diff polypeptide

Question 25

what are coding genes and non coding genes called (in splicing after transcription)

Answer 25

exons (expressing sequences)
introns (intruding sequences)

Question 26

gene expression can be regulated by proteins that …

Answer 26

theres TWO groups sike
they mediate binding of RNA poly (the thing that does transcripton) to the promoter
- transcription factors (promotor)
- regulatory proteins (outside proomotr)

Question 27

how do transcription factors regulate gene expression

Answer 27

these bitches are proteins by the way. they are helpful! they kick start transcription i think
- they form a complex with RNA polymerase at the promotor – cannot initiate transcription without them

Question 28

how do regulatory proteins regulate gene expression. there are 2 types

Answer 28

bind to sequences OUTSIDE the promoter, INTERACT w transctiption factors its buddy ol pal
- ACTIVATOR proteins bind to ENCHANCER sites – incr (mediating complex formation
- REPRESSOR proteins bind to SILENCER sequences – decr (preventing complex formation)

Question 29

regulatory proteins their 2 types and their repsectve binding sequcens

Answer 29

Activator – enchancer sites

repressor – silencer sites

Question 30

what are control elements

Answer 30

DNA sequences that regulatory proteins and transcription factors bind to
- some close to promotor (proximal elements), some far (distal elements)
- most genes have multiple – tightly controlled and coordinated gene expression

Question 31

regulatory proteins bind to which control element and transcription factors bind to which

Answer 31

reg – distal
tf – proximal

closeness to promotor

Question 32

3 components of a gene

Answer 32

1. promotor (non coding)
2. coding sequence
3. terminator

Question 33

what is a promoter and where is it located

Answer 33

The non-coding sequence responsible for the initiation of
transcription

The core promoter is typically located immediately upstream of the gene’s coding sequence

Question 34

function of promoter + how its affected

Answer 34

Functions as a binding site for RNA polymerase
– binding of RNA poly to promoter mediated and controlled by array of transcription factors
– These transcription factors bind to either proximal control elements (near the promoter) or distal control elements (at a distance)

Question 35

what is the coding sequence of DNA in transcription

Answer 35

• The region of DNA that is transcribed by RNA polymerase

this is the TEMPLATE STRAND

Question 36

what is the terminator on a sequence of DNA being trasncribed

Answer 36

• RNA polymerase will transcribe DNA until reaches a terminator sequence
• mechanism for transcriptional termination differs between prokaryotes and eukaryotes

Question 37

antisense vs sense strand

Answer 37

• strand transcribed (template) // strand not transcribed (coding)
• complementary to RNA // identiacal to RNA (T not U tho)

Question 38

what triggers changes within the cell to moderate its gene expression

Answer 38

chemical signals –> changes in levels of reg proteins or trans factors (in response to stimuli)

Question 39

some examples of environment having impact on gene expression

Answer 39

• hydrangeas flower colour change depending on soil pH
• some fish change gender (mate availiabiliy)
• humans diff amts of melanin (dep. on light exposure)