DNA and genes, protein synthesis

Question 1

Differences between Eukaryotic + prokaryotic DNA

Answer 1

E = Longer, linear and associated with histones

P= Shorter, circular and not associated with histones

Question 2

Define gene

Answer 2

A base sequence of DNA that codes for the amino acid sequence of a polypeptide and a functional RNA

Question 3

Locus is …

Answer 3

the position of a gene on a chromosome

Question 4

3 features of a genetic code

Answer 4

1. Degenerate
2. Universal
3. Non-overlapping

Question 5

Genetic code being degenerate means…

Answer 5

more than one triplet of bases can code for the same amino acid

Question 6

Advantage of genetic code being degenerate

Answer 6

If mutation occurs even though the triplet of bases will be different , it may still code for the same amino acid and have no effect

Question 7

Genetic code being universal means…

Answer 7

same triplet of bases codes for the same amino acid in all organisms

Question 8

Genetic code being non - overlapping

Answer 8

Each base in a gene is only part of one triplet of bases that codes for one amino acid. Thus, each codon/triplet of bases is read as a discrete unit.

Question 9

Introns are

Answer 9

sections of DNA that do not code for polypeptides

Question 10

Exons

Answer 10

sequences of DNA that do code for amino acid

Question 11

Genome is…

Answer 11

an organisms complete set of genes in a cell (never changes unless mutation)

Question 12

Proteome is …

Answer 12

the full range of proteins that a cell is able to produce ( changes constantly)

Question 13

Process of transcription

Answer 13

1. DNA helicase unwinds DNA helix to expose the bases by breaking the hydrogen bonds.
2. One strand acts as a template. Free mRNA nucleotides in the nucleus align opposite exposed complementary DNA bases.
3. DNA polymerase joins together the RNA nucleotides to create a new RNA polymer chain

Question 14

What happens after transcription in eukaryotes

Answer 14

Introns are spliced out by splicesome

Question 15

Process of translation

Answer 15

1. mRNA leaves the nucleus and attaches to a ribosome in the cytoplasm. The ribosome attaches at the start codon,
2. tRNA with the complementary anticodon aligns opposite the mRNA.
3. Ribosome will move along one codon on the mRNA to enable another complementary tRNA to attach to the next codon on the mRNA
4. The two amino acids join to form a peptide bond. (Catalysed by an enzyme + ATP). tRNA then deattaches and leaves.
5. This continues to happen until it reaches the stop codon. Ribosome detaches+ translation ends