Unit 1.3: Gene Expression

Question 1

What are the 3 types of RNA and what are their functions?

Answer 1

1. mRNA - carry a copy of genetic code from DNA to ribosome
2. tRNA - carry amino acids from cytoplasm to ribosome
3. rRNA - take part in translation of mRNA to amino acid

Question 2

What is a codon?

Answer 2

A group of 3 bases on a mRNA molecule

Question 3

What is an anti-codon?

Answer 3

3 bases on a tRNA molecule that is complementary to the codon on the mRNA molecule

Question 4

What happens during transcription?

Answer 4

• Section of DNA uncoils
• RNA polymerase unwinds DNA and breaks hydrogen bonds
• RNA polymerase synthesises a primary transcript from RNA nucleotides
• Strand of mRNA released

Question 5

What is RNA splicing?

Answer 5

The primary transcript gets converted to a mature transcript by RNA splicing which removes the non-protein coding introns while keeping the protein coding exons gets spliced together

Question 6

Why is alternative RNA splicing useful?

Answer 6

• Alternative RNA splicing allows multiple different proteins to be produced from the same primary transcript due to different exons being spliced together

Question 7

What happens during translation?

Answer 7

• tRNA carrying amino acids specific to its anticodon which pairs with a complementary codon on mRNA
• Peptide bonds joint amino acids on top of tRNA
• The first tRNA is released and the ribosome moves along a codon
• The process is repeated until a polypeptide is formed

Question 8

What is the difference between a genotype and a phenotype?

Answer 8

Genotype - the alleles present in an organism

Phenotype - the appearance of an organism

Question 9

What is the environmental influence on phenotype?

Answer 9

Changes on the DNA that do not change its appearance but may affect the expression of the DNA