Mutations

Question 1

Types of errors

Answer 1

Transcription error- mRNA and protein affected
Translation error- protein affected
DNA-replication errors DNA, RNA & protein affected

DNA may be passed on to other cells and cause permanent change in a population of cells

Question 2

Reading frames

Answer 2

3 bases per codon gives 3 ways of reading a nt sequences as a series of consecutive non-overlapping triplets

Only one of these will encode a protein known as an open reading frame

Question 3

Open reading frame

Answer 3

Part of a reading frame that has the potential to be translated
Continuous stretch of codons that contains a start codon and a stop codon
STOP CODONS:
1/4 of U at 1st
2/4 of A or G at 2
2/4 of A or G at 3

Question 4

Amino acid sequence

Answer 4

Linear sequence of consecutive non-overlapping triplets in mRNA read in 5’-3’

Question 5

Mutations

Answer 5

Spontaneous mutations- ultimate source of genetic variation, absence of mutagen

Induced- greater dose, more mutations, treatment with mutagen

Question 6

Point mutations

Answer 6

BASE SUBSTITUTIONS- one base pair is replaced by another
Transition- replacement of a base by another base of the same chemical category
Transversion- replacement of a base by another base of a different chemical category
Base insertions and deletions- insertion of deletion of nt pairs

Synonymous mutation (silent)- codon change results in same AA 
Missense mutation- Change in AA 
Nonsense- Codon for one AA changed to stop Codon
Frameshift-indel

Question 7

Other alterations

Answer 7

Environmental stress e.g. UV light, ionising radiation, chemicals=mutagens

UV induces condensation of 2 ethylene groups to form a cyclobutane ring.