Unit 1 (K3) - Gene expression

Question 1

What is RNA (ribonucleic acid) composed of?

Answer 1

Nucleotides containing ribose sugar, a phosphate and 1 of 4 bases.

Question 2

What are the 4 bases found on RNA?

Answer 2

Cytosine, Guanine, Adenine, and Uracil.

Question 3

What is Uracil complimentary to on RNA?

Answer 3

Adenine

Question 4

Is RNA single-stranded or double-stranded?

Answer 4

Single-stranded

Question 5

What is essential for mRNA synthesis?

Answer 5

RNA polymerase, ATP

Question 6

What does mRNA do?

Answer 6

mRNa carries copy of the genetic code from the nucleus to the ribosome.

Question 7

What are the triplets of bases called on mRNA?

Answer 7

Codons

Question 8

What do codons do?

Answer 8

Code for a specific amino acid.

Question 9

What does rRNA (Ribosomal RNA) do?

Answer 9

Carries a specific amino acid to the ribosome from the cytoplasm.

Question 10

What is the structure of rRNA?

Answer 10

rRNA is folded due to complimentary bases on the same single strand, forming hydrogen bonds. rRNA has anticodons and a specific amino acid attachment site.

Question 11

What are the exposed triplet of bases on rRNA called?

Answer 11

Anticodons.

Question 12

What do codons on mRNA bind to?

Answer 12

Anticodons on tRNA.

Question 13

What is the first stage of gene expression called?

Answer 13

Transcription

Question 14

What is the second stage of gene expression called?

Answer 14

Translation

Question 15

Explain the process of Transcription

Answer 15

1. RNA polymerase unwinds the double helix breaking the hydrogen bonds between the bases.
2. RNA polymerase synthesises a primary transcript of mRNA.
3. It adds free RNA nucleotides to the forming strand by complimentary base pairing.
4. RNA splicing forms a mature mRNA transcript.
5. Mature mRNA transcript travels from the nucleus into the cytoplasm where it becomes translated into a sequence of amino acids.

Question 16

Explain the process of Splicing

Answer 16

This is when introns (non-coding regions) of the primary transcript is removed. the exons (coding regions) are spliced together to form the mature mRNA transcript.

Question 17

What is Alternative RNA Splicing?

Answer 17

This is where different proteins can be expressed from one gene.

Question 18

What is the process of Alternative RNA Splicing?

Answer 18

This is where different mRNA transcripts are produced from the same primary transcript depending on which exons are retained.

Question 19

Explain the process of Translation in brief steps

Answer 19

1. Mature mRNA travels from nucleus to the ribosome in the cytoplasm.
2. mRNA carries genetic code in the form of sets of 3 bases called codons.
3. Anticodons on tRNA carrying a specific amino acid are matched to complimentary codons on mRNA.
4. tRNA returns to the cytoplasm to collect another specific amino acid.
5. The amino acids are joined together in a chain by peptide bonds.
6. This forms a polypeptide chain.

Question 20

What is a stop and start codon on mRNA?

Answer 20

Start codons act as a starting point for translation and when the stop codon is reached the ribosome disassociates and the polypeptide chain is released.