molecular biology 3

Question 1

what are 3 differences in the structures between RNA and DNA

Answer 1

• RNA does not consistently fold in a base paired manner
• RNA contains a lot of pseudo knots and complex structures
• RNA structure is a lot less stable than DNA secondary structure

Question 2

5 functions of RNA

Answer 2

• genetic messenger
• guide RNA’s like telomerase
• adaptor RNA
• structural RNA
• catalyst

Question 3

what unwinds dna for transcription

Answer 3

RNA polymerase II

Question 4

what is the template for RNA

Answer 4

dna

Question 5

describe the transcription of RNA

Answer 5

• uses RNA polymerase from 5 - 3
• not as accurate as dna replication

Question 6

what are the 2 strands called in dna- rna transcription

Answer 6

template strand and coding strand

Question 7

what is the difference in the number of copies made for DNA and RNA transcription

Answer 7

DNA = just one
RNA = multiple chains will be developed because multiple RNA polymerase work together at the same time.

Question 8

what do promoters contain

Answer 8

specific DNA sequences that provide a secure initial binding site.

Question 9

what is the promoter region called for RNA polymerase II

Answer 9

TATA region
but TBP will distort DNA once bound (this is a transcription factor)

Question 10

what are transcription factors

Answer 10

they are proteins that regulate gene transcription

Question 11

what are the 3 types of RNA polymerase

Answer 11

RNA polymerase I- rRNA
RNA polymerase II - protein coding RNA
RNA polymerase III - tRNA

Question 12

what does the TATA region do and where will you find it

Answer 12

it facilitates RNA polymerase and transcription factors and you will find it in the minor groove

Question 13

what are house keeping genes

Answer 13

they are genes that are required for the basic cellular maintenance function

Question 14

what does the promoter region do

Answer 14

it is a sequence that tells RNA polymerase to start transcribing at a set position, it can recruit accessory proteins.

Question 15

what do enhancers do

Answer 15

• increase likelihood transcription will occur
• stables the transcription machinery
• they ensure conditions are right for RNA polymerase to initiate transcription

Question 16

what are the 2 domains of transcription factors

Answer 16

DNA binding domain
activation domain = facilitates other protein to protein interactions

Question 17

what does RNA polymerase require to become active

Answer 17

accessory proteins

Question 18

how does RNA polymerase know to stop transcribing

Answer 18

because there are also bases in the terminator area which tells RNA polymerase to stop transcribing and fall off

Question 18

what are enhancer opposed by

Answer 18

silencers

Question 19

what are the 2 ways chromatin is modified to allow RNA polymerase access?

Answer 19

• Histone modified enzyme
• chromatin remodelling complex remodels nucleosomes

Question 20

what are the 2 types of responses to extra cellular signalling molecules?

Answer 20

1- when the protein machinery is already there and it only has to be altered, it will take seconds
2- when the protein has to be made, translation and transcription, can take mins/hrs

Question 21

what are 6 different ways transcription can be activated?

Answer 21

• protein synthesised
• protein phosphorylated
• protein dephosphorylated
• ligand binding
• release from an inhibitor
• change of binding partner

Question 21

aniridia

Answer 21

this is when there is no iris in the eye caused by the lack of transcription factor PAX6

Question 22

what are 2 modifications of pre-messenger RNA

Answer 22

RNA capping = methyl G capping (RNA transcription normally starts with a G at 5’ end- this is what allows the mRNA through the nuclear pore)
polyadenylation = at the end of the pre messenger RNA 3’ end, polyadenylation is added which is a chin of repeating A bases

Question 23

what are 3 reasons for pre messenger RNA modifications?

Answer 23

• protect from exonuclease
• aids export into cytoplasm from nucleus for translation to occur
• to identify the strand as mRNA

Question 24

explain splicing

Answer 24

introns need to be removed in order to produce a mature mRNA which has an open reading frame that only contains exons.
the mature mRNA will then move to the cytoplasm fro translation

Question 24

difference between introns and exons

Answer 24

introns= regions that do not encode protein
exons = regions of DNA that do code for proteins

Question 24

what are responsible for splicing and how does it take place

Answer 24

• spliceosomes are responsible for RNA splicing
• these proteins carry snRNA which recognise the specific sequences at the intron-exon junction.

Question 25

what type of reaction is splicing

Answer 25

esterification

Question 26

what are the 2 steps in splicing

Answer 26

1- branch site attacks intron-exon junction which forms a free hydroxide group at the 3’end of the Xon and a lariat structure.
2- the hydroxide group then attacks another intron-exon junction in order to release the lariat junction which leaves the exon mRNA

Question 27

how are exons recognised in pre-mRNA

Answer 27

the sn-RNA region of the splicisome looks for the sequence in the intron exon junction and form a base pair with these sequences

Question 28

what can alternative RNA splicing do

Answer 28

it can cause exon skipping which means an exon is left out of the mature mRNA after splicing
resulting in the production of different mRNA transcripts that will make proteins with different functions.

Question 29

what is Frasier syndrome

Answer 29

a kidney disease that causes FSGS which where scar tissue forms in the kidney glomeruli.

Question 30

what is Frasier syndrome caused by

Answer 30

caused by a mutation in a tumour suppressor gene
different amount of +KTS (less of this) and -KTS which stems from exon 9

Question 31

what are 5 ways that different proteins can be made from the same gene

Answer 31

• alternative promoters
• alternative splicing
• alternative 3’ ends
• RNA editing
• translational control