DNA, protein synthesis and mutations Flashcards
messenger RNA (mRNA) is used during translation to form polypeptides.
describe how mRNA is produced in the nucleus of a cell. [6 marks]
DNA helicase unwinds the DNA breaking H-bonds
exposes template strand- with desired gene
RNA nucleotides form comp base pairs with exposed DNA nucleotides
EG: adenine on DNA <3 uracil on mRNA
RNA polymerase then joins adjacent RNA nucleotides by phosphodiester bonds producing pre-mRNA
pre-mRNA is then subject to RNA splicing by enzymes to remove introns.
describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation. [3 marks]
tRNA brings specific amino acid
anticodon binds to codon
amino acids join to form peptide bond (using ATP)
describe the role of a ribosome in the production of a polypeptide.
do not include transcription.
[3 marks]
mRNA binds to ribosome
tRNA with anticodons bind to codons on mRNA
formation of peptide bond between amino acids
moves along mRNA to next codon
describe two differences between the structure of a tRNA molecule and the structure of an mRNA molecule. [2 marks]
tRNA = “clover leaf shape” whilst mRNA is linear
tRNA has anticodons whilst mRNA has codons
explain how a mutation can result in the production of a non-functional protein receptor? [4 marks]
mutation in DNA base sequence
change in amino acid sequence
alters position of hydrogen bonds
change in tertiary structure of receptor.
