Gene expression

Question 1

What is gene expression?

Answer 1

Gene expression involves the transcription and translation of DNA sequences. Only a fraction of genes in the cell are expressed.

Question 2

Describe the structure of RNA:

Answer 2

• RNA is single stranded
• it is composed of nucleotides
• it consists of a phosphate, ribose sugar and a nitrogenous base
• the nitrogenous bases include, guanine, cytosine, adenine and uracil

Question 3

What are the three types of RNA?

Answer 3

• mRNA
• tRNA
• rRNA

Question 4

What does mRNA do?

Answer 4

it carries a complimentary copy of the DNA code from the nucleus to the ribosome. The mRNA is then transcribed from the DNA in the nucleus and translated into proteins in the cytoplasm.

Question 5

What is a codon?

Answer 5

A triplet of bases that codes for 1 specific amino acid.

Question 6

What does tRNA do?

Answer 6

The tRNA molecule carries its specific amino acid to the ribosome.

Question 7

What is the function of rRNA?

Answer 7

rRNA and proteins from the ribosome.

Question 8

What is the process of transcription?

Answer 8

RNA polymerase moves along DNA unwinding the double helix and breaking the hydrogen bonds between bases.
RNA polymerase synthesises a primary transcript of mRNA from RNA nucleotides from the complimentary base pairing.

Question 9

What is the process of RNA splicing?

Answer 9

Regions known as introns, or non-coding regions, are removed from the primary transcript and the exons or coding regions remain and are spliced together. The exons when spliced together form the mature (mRNA) transcript.

Question 10

Whats the process of translation?

Answer 10

Translation starts at a START codon and ends at a STOP codon. The ribosome exposes one codon on the mRNA transcript which allows the tRNA to bring a specific amino acid to the ribosome. The correct anticodon on the tRNA will complementary base pair with the codon on the mRNA, bringing the correct specific amino acid with it. The ribosome exposes the next codon where another tRNA and its amino acid will complementary base pair with that codon.

Question 11

What forms a polypeptide chain?

Answer 11

amino acids that are bonded together by peptide bonds.

Question 12

What does alternative RNA splicing produce?

Answer 12

Depending on the exons cut and spliced together, there can be a variety of different proteins produced from the same mRNA transcript.

Question 13

What is a phenotype?

Answer 13

it is a physical expression of a gene/characteristic. It is determined by the protein produced as a result of gene expression.