Nucleic acids 3-4

Question 1

What are housekeeper genes?

Answer 1

Genes that are expressed in every cell as they are needed for normal cell function.

Question 2

What is used instead of nucleotides in transcription?

Answer 2

Ribonucleotide bases

Question 3

What is the sense strand?

Answer 3

DNA strand that is the same as the new mRNA strand (apart from uracil in the place of thymine)

Question 4

What is the antisense strand?

Answer 4

DNA strand that is complementary to the new mRNA strand (template strand).

Question 5

What does RNA polymerase I do?

Answer 5

Transcribes rRNA.

Question 6

What does RNA polymerase II do?

Answer 6

Transcribes mRNA.

Question 7

What does RNA polymerase III do?

Answer 7

Transcribes tRNA and 5sRNA.

Question 8

What is a gene promoter?

Answer 8

DNA sequence that allows the initiation of transcription.

Question 9

What does TF-II D do?

Answer 9

Bind to the minor groove of DNA and unwinds it in preparation for transcription.

Question 10

What must bind between TF-II D?

Answer 10

TF-II A and B.

Question 11

What do accessory proteins (TF-II E, J, H and F) do?

Answer 11

Promote further unwinding.

Question 12

What factors determine rate of transcription? (8)

Answer 12

1) Hormones
2) Growth hormones
3) Mechanical stress
4) Heat
5) Cell contact
6) Touch
7) Light
8) Voltage

Question 13

What is the initial product of transcription and its alternate names?

Answer 13

mRNA

• Primary transcript
• Pre-mRNA
• Heterogenous nuclear RNA (hnRNA)

Question 14

Where does RNA processing take place?

Answer 14

Nucleus

Question 15

What happens during RNA processing?

Answer 15

Introns are moved and the adjacent axons are ligated together with DNA ligase to form mature mRNA which is then exported into cytoplasm to ribosomes for translation.

Question 16

What sequence marks the beginning of an intron?

Answer 16

GU

Question 17

What sequence marks the end of an intron?

Answer 17

AG

Question 18

What proteins are involved post-transcriptional modification?

Answer 18

Small nuclear ribonucleoproteins (snRNPs)

Question 19

What does the U1 snRNP do?

Answer 19

Recognises and binds to the AGGU splice donor site (beginning of the intron).

Question 20

What does the U5 snRNP do?

Answer 20

Binds to the splice acceptor site (end of the intron)

Question 21

How is the intron removed?

Answer 21

A residues form branch points between 5’ phosphate on G and 2’ OH on A branch point. Removed as a lariat structure.

Question 22

What is a 5’ cap?

Answer 22

Added to the 5’ end of mRNA to protect it and greatly enhance translation of strand.

Question 23

Which disease is associated with 5’ cap interference?

Answer 23

Polio - interferes with translation of certain mRNA strands.

Question 24

What is polyadenylation?

Answer 24

Addition of a poly A tail to the pre-mRNA. They are thought to add stability and used as a template as to how much the strand has been translated.

Question 25

Who does Duchenne muscular dystrophy affect?

Answer 25

Only males as mutated gene is carried by the Y chromosome.

Question 26

What happens in Duchenne muscular dystrophy?

Answer 26

79 exons make up the normal mRNA. One or more of these axons are deleted by alternative splicing in DMD, resulting in progressive muscle degeneration and weakness due to a lack of dystrophin.

Question 27

What is alternative splicing?

Answer 27

Regulated process whereby particular exons of a gene may be included or excluded into the final RNA.