Unit 2: DNA Mutations

Question 1

point mutation (nucleotide substitution) (2)

Answer 1

• mutation where a base pair is replaced by a different base pair
• the most frequent type of mutation

Question 2

single-nucleotide polymorphism (SNP) (2)

Answer 2

• site in the genome where the base pair that is present differs among individuals in a population
• result of point mutation

Question 3

why do many point mutations have no detectable effects on the organism?

Answer 3

• they occur in noncoding DNA

Question 4

synonymous (silent) mutation

Answer 4

• mutation resulting in a codon that does not alter the corresponding amino acid in the polypeptide

Question 5

amino acid replacement

Answer 5

• change in the identity of an amino acid at a particular site in a protein resulting from a mutation in a gene

Question 6

non-synonymous (missense) mutations

Answer 6

• point mutation that causes an amino acid replacement

Question 7

nonsense mutation (2)

Answer 7

• mutation that creates a stop codon, terminating translation
• nearly always has harmful affects as they are nonfunctional, unstable and quickly destroyed

Question 8

what happens when a deletion or insertion occurs in a noncoding DNA?

Answer 8

• mutations have little or no effect

Question 9

What happens when deletion or insertion occurs in groups of 3 nucleotides?

Answer 9

• deletion or addition of amino acids in the resulting polypeptide chain results

Question 10

what happens when deletions and insertions occur that are not in exact multiples of 3?

Answer 10

• can cause major changes in the amino acid sequence because they do not delete or insert entire codons

Question 11

frameshift mutations (2)

Answer 11

• mutation in which an insertion or deletion of some number of nucleotides that is not a multiple of 3 causes a shift in the reading frame of the mRNA changing all following codons
• mutant protein does not fold properly into its tertiary structure and becomes nonfunctional

Question 12

wild-type

Answer 12

• the natural state of an organism isolated in nature (“in the wild”)

Question 13

genotype

Answer 13

• the hereditary (genetic) information within an organisms genome

Question 14

phenotype

Answer 14

• resulting expression of the genotype within an organism resulting in observable traits

Question 15

mutant

Answer 15

• an organism with a changed genotype, usually in a specific location in the DNA

Question 16

mutation

Answer 16

• change in the genotype

Question 17

what can mutations arise from?

Answer 17

• incorrect DNA copying during replication
• chemical mutagens
• environmental damage

Question 18

A missense point mutation changes a base in the template strand only, how will this change phenotype?

Answer 18

• in the current cell and one of the daughter cells