gene expression

Question 1

what are the 2 stages of gene expression?

Answer 1

transcription and translation.

Question 2

what are the 3 types of RNA

Answer 2

mRNA, rRNA, tRNA

Question 3

what are the 3 differences between DNA and RNA?

Answer 3

DNA is double stranded whereas RNA is single stranded, inits bases, RNA has uracil instead of thymine and finally RNA has ribose sugar whereas DNA has deoxyribose sugar.

Question 4

what does mRNA do?

Answer 4

carries a copy of the DNA code from the nucleus to the ribosome?

Question 5

what is an intron?

Answer 5

a non coding region of DNA

Question 6

what is an exon?

Answer 6

a coding region of DNA

Question 7

what happens to introns during RNA splicing?

Answer 7

they are removed from the primary transcript

Question 8

what happens if introns are not removed?

Answer 8

then extra amino acids will be coded for and this may cause the protein to fold incorrectly and not work.

Question 9

what is tRNA’s job

Answer 9

to carry its specific amino acid to the ribosome for translation.

Question 10

what are the at the 2 ends of a tRNA molecule?

Answer 10

at one end is an anti codon (an exposed triplet of bases) and at the other there is an attachment site for specific amino acids.

Question 11

why is tRNA folded?

Answer 11

due to the complementary base pairings.

Question 12

what is the role of RNA polymerase in transcription?

Answer 12

it firstly unwinds the DNA’s double helix and breaks the hydrogen bonds, separating the base pairs. Then once the free RNA nucleotides form complementary base pairs with one of the exposed strands, RNA polymerase then synthesises a primary transcript from the RNA nucleotides by complementary base pairings.

Question 13

what does RNA splicing do?

Answer 13

forms a mature transcript.

Question 14

what happens to exons during RNA splicing

Answer 14

they are joined together to form the mature transcrpt.

Question 15

where does transcription take place?

Answer 15

the nucleus

Question 16

wheres does translation take place?

Answer 16

the ribosome.

Question 17

what is the end goal of translation?

Answer 17

to translate mRNA into a polypeptide

Question 18

where does translation start and stop?

Answer 18

it starts at a start codon and finishes at a stop codon.

Question 19

what is a codon?

Answer 19

each triplet of bases on mRNA

Question 20

how can more different proteins be expressed from one gene?

Answer 20

alternative RNA splicing

Question 21

how does alternative RNA splicing work

Answer 21

because different mature transcripts can be produced from the same primary transcript depending on what exons are retained.

Question 22

polypeptide chains fold to form the three-dimensional shape of a protein, held together by hydrogen bonds and other interactions between individual amino acids, this means that….

Answer 22

proteins have a wide variety of shapes which determines their function.

Question 23

what is phenotype based upon?

Answer 23

proteins produced as a result of gene expression.

Question 24

what else can affect phenotype?

Answer 24

environmental factors, such as poor diet, for example someone who has inherited genes to be tall may not reach their potential height due to not eating right.

Question 25

explain why the primary mRNA is so much shorter than chromosomal DNA.

Answer 25

because the primary mRNA only codes for 1 protein