1.3 Gene Expression

Question 1

Transcription

Answer 1

Synthesis of mRNA from section of DNA

Question 2

Translation

Answer 2

Synthesis of protein using instructions from mRNA

Question 3

mRNA

Answer 3

Carries copy of DNA code from the nucleus to ribosome

Question 4

tRNA

Answer 4

Folds (complementary base pairing), each molecule carries specific amino acid to ribosome

Question 5

rRNA

Answer 5

It and proteins form ribosome

Question 6

DNA structure

Answer 6

Double stranded

Deoxyribose sugar

Cytosine-Guanine

Adenine-Thymine

Question 7

RNA structure

Answer 7

Single stranded

Ribose sugar

Cytosine-Guanine

Adenine-Uracil

Question 8

Transcription stages

Answer 8

Nucleus

RNA polymerase moves along DNA and unwinds strand

Breaks hydrogen bonds between bases

RNA polymerase synthesises a primary transcript of mRNA from RNA nucleotides

Forms hydrogen bonds with exposed DNA strand by complementary base pairing

RNA polymerase continues synthesising mRNA molecule until sequence of stop codons is reached

mRNA strand separates from DNA- primary mRNA transcript

Introns- non-coding regions of primary mRNA transcript, removed

Exons- coding regions, spliced forming mature mRNA transcript

Question 9

Translation stages

Answer 9

Ribosome

Mature mRNA transcript attaches to ribosome in cytoplasm

Start codon begins protein synthesis

Complementary tRNA anticodons attach to mRNA strand, brings specific amino acid to form molecule

Peptide bonds form between amino acids

Each tRNA molecule leaves ribosome once amino acids are attached

Ribosome moves along mRNA molecule and polypeptide chain gets longer

Stop codon ends protein synthesis

Question 10

Alternative RNA splicing

Answer 10

Same gene makes several different proteins, (uses different regions as introns or exons)

Different mature mRNA transcripts can be produced from same primary mRNA transcript, depends on which exons retained