20.1 Gene mutations

Question 1

a mutation is

Answer 1

any change to the quantity or structure of DNA

Question 2

a gene mutation is

Answer 2

any change to one or more nucleotide bases or any rearrangement of bases in DNA

Question 3

Substitution of bases is a gene mutation where

Answer 3

a nucleotide in a section of DNA is replaced by another nucleotide that has a different base

Question 4

substitution of bases consequence

1. formation of stop codon

Answer 4

production of the polypeptide stopped prematurely.

likely final protein significantly different and cn not perform normal function

Question 5

substitution of bases consequence

2. formation of a codon for a different amino acid

Answer 5

structure of polypeptide would differ in a single amino acid.
could affect the shape and not function properly.
e.g. enzyme active site

Question 6

substitution of bases consequence

3. formation of a different codon that produces same amino acid as before (genetic code is degenerate)

Answer 6

no effect of polypeptide

mutation has no effect.

Question 7

deletion of bases is a gene mutation where

Answer 7

there is a loss of a nucleotide base from DNA

Question 8

consequence of deletion of base

Answer 8

impact on phenotype can be enormous.
one deleted base creates a frame shift (to the left).
gene is now read in wrong 3 base groups.
most triplets will be different therefore amino acids will be different
could produce a non functional protein .
deletion of base towards end of sequence has less of an impact, less of triplets altered .

Question 9

addition of bases is where

Answer 9

extra base inserted in sequence

Question 10

consequence of addition of base

Answer 10

frame shift to the right
could alter whole sequence of triplets.
three bases added together- not as big a change. an extra amino acid

Question 11

duplication of base is where

Answer 11

one or more bases are repeated

Question 12

consequence of duplication of base

Answer 12

produces a frame shift to the right

Question 13

inversion of base is where

Answer 13

a group of bases become separated from the DNA sequence and rejoin at same position but in inverse order (back to front)

Question 14

consequence of inversion of base

Answer 14

base sequence for the portion reversed. effects amino acid sequence

Question 15

translocation of base is where

Answer 15

a group of bases become separated from the DNA sequence on one chromosome and become inserted into the DNA sequence of a different chromosome.

Question 16

consequence of translocation of base

Answer 16

often have significant effect on gene expression
abnormal phenotype
effects include development of certain forms of cancer and reduced fertility

Question 17

what are spontaneous mutations

Answer 17

permanent change in DNA occur with out any outside influence

arise in DNA replication

Question 18

what is the basic mutation rate increased by

Answer 18

outside factors known as mutagenic agents or mutagens

Question 19

High energy ionising radiation (mutagenic agent/ mutagens )

Answer 19

alpha and beta particles. short wave length radiation such as x-rays and uv light. can disrupt structure of DNA

Question 20

Chemicals (mutagenic agent/ mutagens)

Answer 20

such as nitrogen dioxide may directly alter structure of DNA or disrupt transcription.
Benzopyrene (in tobacco smoke) powerful mutagen. inactivates tumour-supressor gene TP53 leading to cancer