RNA synthesis and Gene expression

Question 1

what is the central dogma

Answer 1

DNA replicates, it is then transcribed to RNA, which is translated to protein

Question 2

how much of the human genome actually encodes proteins

Answer 2

about 1%

Question 3

properties of DNA

Answer 3

much more stable than RNA,
deoxyribose,
double stranded
permanent of store of genetic information

Question 4

messenger RNA (mRNA)

Answer 4

transmits the info from the genes to the ribosomes where its translated into proteins.

Question 5

transfer RNA (tRNA)

Answer 5

ensures correct AA matches the codon specified mRNA (carries the AA to site of transcription)

Question 6

ribosomal rRNA (rRNA)

Answer 6

form part of the ribosome structure (made almost continuously)

Question 7

small nuclear RNA (snRNA)

Answer 7

helps align introns to be spliced out of primary transcripts

Question 8

what is transcription

Answer 8

is the synthesis of RNA molecule, which will be complementary to the DNA template strand but identical to the coding strand.

Question 9

examples of nucleotide triphosphate (used to synthesise RNA)

Answer 9

ATP,
CTP,
GTP,
UTP

Question 10

what does RNA polymerase i

Answer 10

transcribe rRNA genes

Question 11

What does RNA polymerase II

Answer 11

transcribes mRNA

Question 12

what does RNA polymerase III

Answer 12

transcribes tRNA and other small RNAs

Question 13

transcription process (6)

Answer 13

1) at 5’ end you have the promoter region and then downstream from that you have the transcription unit
2) the RNA polymerase is then recruited (in controlled process) by the promoter region
3) a local region of DNA will unwound, so there is an open strand (template strand) for RNA polymerase to copy
4) RNA synthesis then begins by RNA polymerase in the 5’ to 3’ direction
5) then there is elongation, with RNA polymerase moving along the DNA synthesising the RNA with the strand comping out from the end
6) when it gets to the en dot the gene there is termination and the RNA dissociates, this is the primary transcript

Question 14

how is the RNA transcript modified

Answer 14

capped at the 5’end
polyadenylated at the 3’ end
spliced - introns are removed

Question 15

what is the significance of the cap

Answer 15

tells the cell that mRNA is ready to be exported from the nucleus

Question 16

significance of the polyadenylated tail

Answer 16

mRNA molecule is ready to leave the nucleus,

increases stability of mRNA (longer the poly a the more stable the mRNA molecule)

Question 17

where do snRNPs bind to during splicing

Answer 17

DNA sequences at the ends of axons

Question 18

how does splicing occur

Answer 18

snRNPs bind to these regions on either side of the introns, which forms a splicosome which then uses out and removes the introns. exons are now side to side.

Question 19

intron

Answer 19

sequence in the gene DNA that is transcribed as part of the pirmary RNA transcript, but is removed to form the mature mRNA

Question 20

exon

Answer 20

sequence in the gene and primary transcript that is retained in the mature mRNA

Question 21

untranslated region

Answer 21

a sequence in the mature mRNA (so part of exon sequence) that does not code for amino acids.

Question 22

Tissue - specific gene expression

Answer 22

human cells all contain the same genes (genotype), the type of genes expressed will depend on the type of cell

Question 23

housekeeping genes

Answer 23

code from proteins needed by all cells (so expressed in all cells)

Question 24

inducible genes

Answer 24

only turn on when needed, e.g. steroid hormone triggers it

Question 25

tissue specific genes

Answer 25

alpha and beta globulins genes only expressed in red cell precursors.

Question 26

promoter region

Answer 26

sequence immediately 5' to the region to be transcribed - recruits RNA polymerase to the DNA - helps RNA polymerase bind

Question 27

Transcription factors

Answer 27

proteins that bind - DNA specific binding proteins, they recognise particular sequence on the DNA molecule - can also repress polymerase binding