Mutations

Question 1

AT WHAT LEVELS CAN MUTATIONS OCCUR?

Answer 1

1. genome mutation –> Change in chromosome number
2. chromosomal mutations –> change in chromosomal structure
3. point mutation –> Change in DNA sequence

Question 2

in what cells can mutations occur in? what could the result be?

Answer 2

• somatic cells –> Could result in cancer

- in germ-line cells –> Could result in gametes and offspring with mutations

Question 3

what is the function of mutation in evolutionary change? what does mutation produce?

Answer 3

Ultimate source of evolutionary change
-Change in DNA sequence produces new alleles and allows for new combination of alleles to be passed
on to offspring

Question 4

what are Spontaneous mutations?

Answer 4

naturally occurring mutations, arise in all cells without external cause

Question 5

what are Induced mutations?

Answer 5

Induced mutations arise through the action of

certain agents called mutagens

Question 6

what are the 2 basic types of genome mutation? what is the most common cause to the change in chromosome number?

Answer 6

1. Changes in number of chromosome sets
2. Changes in parts of chromosome sets = extra
   chromosomes or missing chromosomes

-Nondisjunction –> the failure of homologous chromosomes or sister chromatids to separate properly during cell division

Question 7

what does Mitotic nondisjunction result in? what does it produce?

Answer 7

-in sections of the body having the wrong number of
chromosomes
-produces gametes with missing or extra chromosome(s) –> which Results in organisms with missing or extra chromosome(s)

Question 8

what are the 4 major classes of chromosomal mutations?

Answer 8

1. Chromosomal segment lost = deletion
2. Chromosomal segment doubled = duplication
3. Orientation of a segment within a chromosome
   reversed = inversion
4. Segment moved to non-homologous chromosome = translocation

Question 9

what is point mutation? where does it occur?

Answer 9

• Change of a single base pair of DNA or a small number of adjacent base pairs
• Can occur within a gene or between genes

Question 10

what are the 2 main types of point mutation?

Answer 10

1. Nucleotide Substitution = mutation in which one
   base pair is replaced by another
2. Nucleotide Insertion or Deletion = mutation in
   which one base pair is added or deleted

Question 11

what are 3 possible outcomes from substitution mutations in the protein-coding portion of a gene?

Answer 11

1. Synonymous mutations = silent mutation
2. Missense mutations = codon for one amino acid
   is changed into codon for another amino acid
3. Nonsense mutation = changes codon into
   translation-termination (stop) codon

Question 12

what do synonymous mutations (silent mutation) do?

Answer 12

-Mutation changes one codon for an amino acid into
another codon for the same amino acid

therefore Mutation in DNA does not change amino acid

Silent = no effect on amino acid sequence

Question 13

what is a missense mutation? does it effect the proteins function?

Answer 13

Missense = results in a single amino acid change in the sequence
-Some missense mutations DO NOT affect the function
of the protein, such as:
1. the mutation is not in an important part of the protein
2. the mutation is a conservative substitution

-Some missense mutations DO change a protein’s
shape and ability to function

Question 14

what is a conservative substitution? what is a non-conservative substitution? which is more likely to affect a protein’s structure and function?

Answer 14

• replacing one amino acid with a chemically similar amino acid
• this Alteration is less likely to affect protein’s structure and function severely

-amino acid replaced by chemically different amino acid
-this Alteration more likely to produce sever change in
protein’s structure and function

Question 15

what do nonsense mutations do? what does it have an affect on? if a nonsense mutation is close to the end of the gene, it’s more likely to produce what? what do most nonsense mutations produce?

Answer 15

-Causes premature termination of translation
-Nonsense mutations can have considerable affect
on a protein’s structure and function

Nonsense = changes an amino acid codon into a stop codon

-more likely to produce a protein with some biological activity
-Most nonsense mutations produce completely
inactive protein products

Question 16

what are Insertion and Deletion Mutations? what does it do to codons? what does it do to reading frame? when does this not happen?

Answer 16

• Insertion or deletion of one or more nucleotide pairs
• Changes all codons , and thus all amino acids, downstream of the mutation
• Often changes reading frame –> “frameshift mutation”
• Insertions or deletions in multiples of 3 base pairs does not cause a frameshift

Question 17

what can frameshift cause?

Answer 17

Frameshift can cause immediate nonsense (1 base-pair insertion) (termination)
Frameshift can cause extensive missense (1 base-pair deletion)
No frameshift, but one amino acid missing (3 base-pair deletion)