Gene Structure Function - Lecture 9

Question 1

What information does a gene contain?

Answer 1

○ Structural
○ Temporal
○ Positional
○ Inducible

Question 2

What does structural information refer to?

Answer 2

Coding DNA

Question 3

What does temporal information refer to?

Answer 3

Developmental - when a gene switches on

Question 4

What does positional information refer to?

Answer 4

Tissue/cell specific - where a gene switches on e.g. insulin production

Question 5

What does inducible information refer to?

Answer 5

Nutrients. stress, hormones - switching a gene on/off depending on the environment

Question 6

In prokaryote genes, what does the promoter do?

Answer 6

○ Defines transcription start site and it’s direction
○ Where RNA polymerase binds

Question 7

In prokaryote genes, what is a leader/spacer?

Answer 7

A section of DNA which is not translated

Question 8

In prokaryote genes, what is a cistron?

Answer 8

○ Coding regions
○ Segments of DNA corresponding to one polypeptide
○ Have a start and stop codon

Question 9

In prokaryote genes, what is a terminator?

Answer 9

Tells RNA polymerase to stop at that point

Question 10

What does transcription of prokaryotic gene produce?

Answer 10

○ Polycistronic mRNA
○ Promoter not transcribed

Question 11

What does translation of prokaryotic gene produce?

Answer 11

Polypeptides

Question 12

How can several proteins be made?

Answer 12

○ Using multiple stop and start signals
○ Transcriptions start/stop sites are not the same as translation start/stop sites

Question 13

In eukaryotic gene, what does the promoter do?

Answer 13

Same function as prokaryotes

Question 14

In eukaryotic gene, what does the enhancer do?

Answer 14

○ Binding sites for transcription factors to boost activity of the gene
○ Can be anywhere on the gene

Question 15

In eukaryotic gene, what are exons?

Answer 15

Include the mature mRNA

Question 16

In eukaryotic gene, what are introns?

Answer 16

In primary transcript but removed from the mature transcript

Question 17

What is splicing?

Answer 17

Introns removed and exons joined together

Question 18

What does the mature mRNA include in eukaryotes?

Answer 18

○ 5’ UTR
○ Translated region
○ 3’ UTR

Question 19

What is the size difference between eukaryotic and prokaryotic genes?

Answer 19

○ Eukaryotic genes can be quite large but most is non-coding
○ Lower eukaryotic genes and prokaryotic genes are small and equate more to the size of the polypeptides they produce

Question 20

What is the coding strand?

Answer 20

○ Sense 5’ - 3’
○ Same direction that RNA polymerase travels
○ Has same sequence as RNA product

Question 21

What is the template strand?

Answer 21

○ Antisense 3’ - 5’
○ RNA polymerase reads the template strand and uses it as a guide
○Sequence is complementary to RNA product

Question 22

What happens in the transcription bubble?

Answer 22

○ RNA polymerase binds to DNA
○ Melts double strand
○ Polymerises 5’ to 3’ direction
○ RNA produced is a copy of the coding strand and complementary to template strand

Question 23

What is the Pribnow box?

Answer 23

○ A conserved DNA sequence (TATAAATG) found in bacterial promoters
○ Located 10 nucleotides to the left of the transcription start site
○ Helps RNA polymerase to initiate transcription