DNA and protein synthesis

Question 1

What is a genome?

Answer 1

The complete set of genes in a cell (all of the cells DNA)

Question 2

What is a proteome?

Answer 2

The full range of proteins that a cell is able to produce

Question 3

What is the structure of mRNA?

Answer 3

• single-stranded
• variable length (length of gene)
• linear shape
• no binding site for amino acids

Question 4

What is the structure of tRNA?

Answer 4

• single-stranded
• around 80 nucleotides long
• base pairing
• clover shape
• binding site for amino acids
• 3 bases forming the anticodon

Question 5

What is the structure of rRNA?

Answer 5

• part of the structure of a ribosome

Question 6

What is transcription?

Answer 6

• During transcription, DNA helicase breaks hydrogen bonds between complementary base pairs in DNA, and the double helix unwinds, exposing the bases
• The antisense strand (only one strand) of DNA is used as a template.
• Free RNA nucleotides bind to complementary exposed bases on the antisense strand, and nucleotides join by RNA polymerase forming phosphodiester bonds, to form pre-mRNA
• In eukaryotic cells, the pre-mRNA is spliced meaning the introns are removed which forms mature mRNA which can leave the nucleus through pores to travel to the ribosomes

Question 7

What is translation?

Answer 7

• During translation, the mRNA attaches to a ribosome at the start codon
• The codon on mRNA will bind to a complementary anticodon on tRNA, which carries a specific amino acid. tRNA will line up along the mRNA to form a specific sequence of amino acids (determined by the sequence of codons)
• Between each amino acid, energy from ATP hydrolysis is used to form a peptide bond in condensation reactions and an enzyme catalyses this reaction
• Once a peptide bond has formed, the tRNA molecule will leave and the ribosomes will move along the mRNA to continue the sequence
• Once the amino acid sequence is complete, tRNA will bring a stop codon which will end the chain of amino acids, to form a complete polypeptide