Genetic code and transcription

Question 1

What are the 4 nucleotides that make up amino acids?

Answer 1

Adenine (A), Cytosine (C), Guanine (G) and Thymine (T)

Question 2

What is a reading frame?

Answer 2

A sequence of codons starting with ATG (methionine)

Question 3

What is a frame-shift mutation?

Answer 3

Code shifts by one letter causing the wrong amino acid to be read

Question 4

What does the genetic code not apply to?

Answer 4

Chromosomes and mitochondria in some eukaryotes

Question 5

Gene expression

Answer 5

Information stored in a gene is made into a functional product

Question 6

Gene regulation

Answer 6

The ability of a cell to control the expression of each gene

Question 7

What is transcription?

Answer 7

DNA is copied into RNA using RNA polymerase (enzyme) to go from a gene to mRNA

Question 8

What is DNA separated into?

Answer 8

Coding strand and template strand

Question 9

Coding strand

Answer 9

Contains codons

Question 10

Template strand

Answer 10

Copied by RNA polymerase

Question 11

What are the 3 classes of RNA transcriptions in eukaryotes?

Answer 11

• Ribosomal RNA (rRNA)
• Messenger RNA (mRNA)
• Transfer RNA (tRNA)

Question 12

What is the promoter?

Answer 12

Encourages RNA polymerase to synthesise to DNA

Question 13

Non-coding DNA

Answer 13

Junk RNA

Question 14

Coding DNA

Answer 14

Important RNA (information)

Question 15

Why is transcription termination needed?

Answer 15

Because RNA can become elongated causing problems for RNA synthesising with DNA

Question 16

How is RNA synthesis prevented in prokaryotes?

Answer 16

The RNA forms a hairpin loop and a uracil poly-tail

Question 17

How else can RNA synthesis be prevented?

Answer 17

A protein termination factor (Rho) in the cytosol

Question 18

How is RNA synthesis prevented in eukaryotes?

Answer 18

Transcripts are cleaved and poly-tail is added in the nucleus and cytosol

Question 19

What is post-transcriptional gene silencing (PTGS)?

Answer 19

Triggers production of small RNA fragments of gene to be suppressed and induces mechanism to destroy complimentary RNA.

Question 20

What are transgenes?

Answer 20

Genes which are artificially introduced into the genome of another organism

Question 21

What is the purpose of transfer RNA (tRNA)?

Answer 21

Carries specific amino acids and decodes codons

Question 22

Structure of tRNA

Answer 22

4 arms (only 2 are important): acceptor arm (attaches to amino acid) and anticodon arm (carries 3 nucleotides)

Question 23

Eukaryotic translation

Answer 23

Requires mRNAs, ribosomes and tRNAs

Question 24

Why are ribosomes needed in translation?

Answer 24

tRNAs can’t make proteins without them

Question 25

What is a Svedberg (S)?

Answer 25

A unit of weight

Question 26

What is the eukaryotic mRNA structure?

Answer 26

5’cap, 5’ UTR, coding region, 3’ UTR and a poly tail

Question 27

What is the UTR?

Answer 27

The untranslated region where RNA bases pair up

Question 28

What occurs in the translocation phase?

Answer 28

Charged tRNAs enter at the A site, then shift to the P site, and then finally to the E site for removal

Question 29

What occurs in the termination phase?

Answer 29

Translation is ended via the release of mRNA from the ribosome

Question 30

Control of translation

Answer 30

Rapid method of altering protein levels in the cell