20.1 — gene mutation

Question 1

what are gene mutations?

Answer 1

permanent changes in the DNA sequence that make up a gene — involved in one or more DNA base within a gene

Question 2

what are the differences between mutations in body cells and gametes?

Answer 2

1. mutations in body cells can disrupt normal functions, like cell division, potentially causing cancer
2. mutations in gametes can be inherited by offspring whilst body cell mutations cannot

Question 3

what are mutagens?

Answer 3

external factors that increase the rate of mutations significantly

Question 4

what are the main types of mutations?

Answer 4

ionising radiation and chemical mutagens

Question 5

what is an example of ionising radiation?

Answer 5

x-rays

Question 6

what is an example of a chemical mutagens?

Answer 6

the benzopyrene in cigarette smoke

Question 7

what are the possible effects of ionising radiation?

Answer 7

can break DNA strands or alter its structure

Question 8

what are the possible effects of chemical mutagens?

Answer 8

can modify DNA bases or interfere with DNA metabolism

Question 9

how can mutations be detrimental?

Answer 9

they can lead to production of abnormal proteins and disease phenotypes, including cancer

Question 10

when do substitution mutations occur?

Answer 10

when one DNA base is replaced by another’s within the gene’s sequence

Question 11

what are the possible outcomes of substitution mutations?

Answer 11

1. may create one of three stop codons
2. may create a codon for a different amino acid
3. may create a codon for the same amino acid

Question 12

what happens when a substitution mutation creates one of the three stop codons?

Answer 12

polypeptide synthesis is prematurely terminated — the protein’s structure may be significantly changed and in turn be non functional

Question 13

what happens when a substitution mutation creates a codon for a different amino acid?

Answer 13

the protein’s amino acid sequence will be changed along with possibly its shape and function

Question 14

what happens when a substitution mutation creates a codon for the same amino acid?

Answer 14

no effect to the protein product or phenotype — due to the degenerate nature of the genetic code

Question 15

aside from substitution, what are the types of gene mutation?

Answer 15

1. inversion
2. duplications
3. translocations

Question 16

what is the inversion mutation?

Answer 16

when a segment of DNA becomes detached and then reattaches in the wrong direction

Question 17

in inversion mutations, what occurs in relation to the sequence of codons?

Answer 17

the sequence of codons is inverted, and in turn, so is the amino acid sequence

Question 18

what is the duplication mutation? what occurs in relation to the sequence of codons?

Answer 18

when one or more DNA bases are repeated.

Question 19

in duplication mutations, what occurs in relation to the sequence of codons?

Answer 19

the frame of the codons is altered and causes a frame shift to the right

Question 20

what is the translocation mutation?

Answer 20

when a segment of DNA is moved from one chromosome to another.

Question 21

in translocation mutations, what occurs in relation to the sequence of codons?

Answer 21

gene expression and regulation can be interfered with and can lead to certain types of cancer