8. DNA, genes and protein synthesis

Question 1

how many bases code for one amino acid

Answer 1

3

Question 2

how many naturally occurring amino acids are there?

Answer 2

20

Question 3

why is genetic code described as;
degenerative?
non-overlapping?
Universal?

Answer 3

degenerative, most amino acids are coded by more than one triplet

non-overlapping, each sequence is only read once

Universal, same bases code for the same amino acid across different species

Question 4

what are introns?

Answer 4

non coding sequances

Question 5

what is a genome

Answer 5

complete set of genes in a cell

Question 6

what is a proteome

Answer 6

full range of proteins produced by genome

Question 7

how many tRNA molecules can attach to one mRNA

Answer 7

2

Question 8

what is pre-mRNA

Answer 8

mRNA that hasn’t been sliced

Question 9

what is a homologous chromosome

Answer 9

chromosomes that share the same structural features, the same genes at the sames loci.

Question 10

Describe the structure of tRNA

Answer 10

• single-stranded chain
• ‘clover-leaf shape’
• extended codon for amino acid
• anticodon loop on opposite side

Question 11

What is transcription

Answer 11

process of making pre-mRNA using part of the DNA as a template

Question 12

Explain the steps of transcription

Answer 12

• DNA unwound by DNA helicase exposing bases
• One chain acts as a template
• free mRNA nucleotides align with complementary bases on template
• RNA polymerase joins RNA nucleotides

Question 13

Give three differences between eukaryotic and prokaryotic DNA

Answer 13

eukaryotic is;
- longer
- linear (pro is circular)
- associated with histones (pro isn’t)

Question 14

What sets chloroplast and mitochondria DNA apart from other eukaryotic cells

Answer 14

they are;
- short
- circular
- not associated with histones.
(like prokaryotes)

Question 15

How many amino acids is a tRNA complementary to?

Answer 15

one

Question 16

Why is mRNA shorter than DNA?

Answer 16

able to carry section of genetic code to ribosome.

Question 17

What does DNA helicase do?

Answer 17

Breaks hydrogen bonds between bases

Question 18

What is a spliceosome? what does it do?

Answer 18

Protein that ‘splices’ out non-coding introns

Question 19

Do prokaryotes have introns?

Answer 19

no

Question 20

Explain the steps of translation.

Answer 20

• mRNA attaches to ribosome
• ribosome attaches at the start codon
• tRNA molecule complementary to the start codon aligns, held in place by the ribosome.
• ribosome moves along one codon, to enable another tRNA to join
• amino acids are joined by a peptide bond req. enzyme and ATP
• … until stop codon, ribosome detaches

Question 21

Where do proteins go after translation?

Answer 21

enter golgi body for folding and modification

Question 22

Give two key similarities in prokaryotic and eukaryotic DNA.

Answer 22

• made of DNA nucleotides
• nucleotides joined by phosphodiester bonds to make a polymer chain