Unit 1.3 - Gene Expression

Question 1

What does gene expression involve?

Answer 1

The transcription and translation of DNA sequences

Question 2

What is the phenotype determined by?

Answer 2

The proteins produced as a result of gene expression

Question 3

What can result from alternative RNA splicing?

Answer 3

Different proteins can be expressed from one Gene.

Question 4

Only a fraction of genes in a cell are what?

Answer 4

Expressed

Question 5

What are the characteristics of RNA?

Answer 5

It’s single-stranded, it contains the base uracil instead of thymine, and it contains the sugar ribose instead of deoxyribose

Question 6

What are the complimentary base pairs in RNA?

Answer 6

Guanine + Cytosine

Uracil + Adenine

Question 7

Describe translation?

Answer 7

Translation begins at a start codon and ends at a stop codon
Anti codons bond to codons by complementary base pairing, translating the genetic code into a sequence of amino acids
Peptide bonds join the amino acids together
Each tRNA then leaves the ribosome as the polypeptide is formed.

Question 8

What does mRNA do?

Answer 8

Messenger RNA carries a copy of the genetic code on DNA to the nucleus to the ribosome

Question 9

Why does tRNA fold?

Answer 9

Due to complementary base pairing

Question 10

What does tRNA carry?

Answer 10

A specific amino acid to the ribosome

Question 11

What are ribosomes composed of?

Answer 11

Ribosomal RNA and proteins

Question 12

What are the regions of the primary transcript called?

Answer 12

Coding regions - exons

Non - coding regions - Introns

Question 13

What does the production of mature mRNA by RNA splicing involve?

Answer 13

It involves the removal of introns and the joining together of exons.
This forms the mature transcript. The order of exons is unchanged during splicing.

Question 14

What does RNA splicing form?

Answer 14

A mature mRNA transcript

Question 15

What’s the role of RNA polymerase in transcription?

Answer 15

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

Question 16

What translates mRNA into a polypeptide and where does it occur?

Answer 16

tRNA translates mRNA into polypeptide and it occurs at the ribosome

Question 17

How can different mature mRNA transcript be produced from the same primary transcript?

Answer 17

It depends on which exons are retained.

Question 18

What determines a proteins function?

Answer 18

It’s shape

Question 19

What can also influence phenotype?

Answer 19

Environmental factors

Question 20

What happens to mRNA?

Answer 20

• mRNA is transcribed from DNA in the nucleus
• It’s translated into proteins by ribosomes in the cytoplasm
• Each triplet of bases on the mRNA molecule is called a codon and codes for a specific amino acid

Question 21

What does a tRNA molecule have?

Answer 21

An anticodon at one end and an attachment site for a specific amino acid at the other end

Question 22

Describe the three dimensional structure of proteins?

Answer 22

• Amino acids are linked by peptide bonds to form polypeptides
• Polypeptide chains fold to form the three dimensional shape of a protein held together by hydrogen bonds and other interactions between individual amino acids.