9.1- GENE MUTATION

Question 1

What is a mutation?

Answer 1

any change to quantity or base sequence of DNA of organism

Question 2

What mutations may be inherited?

Answer 2

mutations occurring during formation of gametes, often producing sudden + distinct differences between individuals

Question 3

What is a gene mutation?

Answer 3

any change to one/more nucleotide base, or change in sequence of bases in DNA

Question 4

How can gene mutations arise?

Answer 4

arise spontaneously during DNA replication + include base substitution + base deletion

Question 5

What is a base substitution mutation?

Answer 5

nucleotide in DNA molecule replaced by another nucleotide that has different base

Question 6

What does a base substitution mutation cause?

Answer 6

change in triplet code for different amino acid

polypeptide produced will differ in single amino acid

Question 7

What will the significance of base substitution mutation depend on?

Answer 7

depend upon precise role of original amino acid

Question 8

What happens if the original amino acid was important in forming bonds that determine tertiary structure of final protein? (base substitution mutation)

Answer 8

replacement amino acid many not form same bonds

Question 9

What happens as the replacement amino acid many not form same bonds? (base substitution mutation)

Answer 9

protein may then be different shape + so not function properly

Question 10

What happens if there is a base substitution mutation with an enzyme?

Answer 10

its active site may no longer fit substrate + will no longer catalyse reaction

Question 11

What happens if the mutation codes for the same amino acid? (base substitution mutation)

Answer 11

no change in polypeptide produced + mutation will have no effect

Question 12

When does a gene mutation by deletion arise?

Answer 12

when nucleotide lost from normal DNA sequence

Question 13

Why would deletion of a base cause a polypeptide not to function correctly?

Answer 13

as sequence of bases in DNA read in units of three bases (triplet)
one deleted nucleotide causes all triplets in sequence to be read differently as each has been shifted to left by one base

Question 14

What are chromosome mutations?

Answer 14

changes in structure or number of whole chromosomes

Question 15

How do chromosome mutations arise?

Answer 15

can arise spontaneously

Question 16

What two forms can chromosome mutations take?

Answer 16

changes in whole sets of chromosomes

changes in number of individual chromosomes

Question 17

When do changes in whole sets of chromosomes occur?

Answer 17

when organisms have three or more sets of chromosomes rather than usual two

Question 18

What is the condition called when organisms have three or more sets of chromosomes rather than usual two?

Answer 18

polyploidy

Question 19

Where does polyploidy mostly occur?

Answer 19

in plants

Question 20

What do individual homologous pairs of chromosomes fail to do sometimes? (changes in number of individual chromosomes)

Answer 20

fail to separate during meiosis

Question 21

What is it called when individual homologous pairs of chromosomes fail to separate during meiosis? (changes in number of individual chromosomes)

Answer 21

non-disjunction

Question 22

What does non-disjunction usually result in? (changes in number of individual chromosomes)

Answer 22

usually results in gamete having either one more or one fewer chromosomes

Question 23

What happens at fertilisation between a normal complement of chromosomes and gamete having one more/fewer chromosomes?

Answer 23

resultant offspring have more/fewer chromosomes than normal in all their body cells

Question 24

What is an example of non-disjunction in humans?

Answer 24

Down’s syndrome- individuals have additional chromosome 21