2D: changes in DNA sequences and spontaneous mutations

Question 1

what are mutations?

Answer 1

changes to nucleic acid sequences (DNA or RNA) that may be heritable (germline) or not (somatic) and can be small (gene level) or large (chromosomal)

Question 2

what is a germline mutation?

Answer 2

a mutation of the DNA/RNA of gametes (spem/egg cells). heritable

Question 3

what is a somatic mutation?

Answer 3

a mutation of the DNA/RNA of the cells of the body (NOT germ cells). not inherited by offspring

Question 4

what are chromosomal mutations?

Answer 4

any change from the normal structure or number of chromosomes in a cell

Question 5

what are 4 type of chromosomal mutations?

Answer 5

➝　deletion
➝　duplication
➝　translocation
➝　inversion

Question 6

define deletion mutation (chromosomal)

Answer 6

when a segment breaks off of a chromosome and is lost

Question 7

define duplication mutation (chromosomal)

Answer 7

when a segment is broken off of one chromosome and inserted into its homologue (identical twin chromosome). in the receiving homologue, the alleles are added to the ones that are already there

Question 8

define translocation mutation (chromosomal)

Answer 8

when a segment broken off of one chromosome attaches to a different, non-homologous chromosome

Question 9

define inversion mutation (chromosomal)

Answer 9

when a segment breaks off a chromosome and reattaches to the same chromosome from which it was lost but in reversed orientation

Question 10

what is the impact of a deletion mutation? (chromosomal)

Answer 10

may cause severe issues if the deleted genes were essential for normal development or cellular functions

Question 11

what is the impact of a duplication mutation? (chromosomal)

Answer 11

increases gene expression of duplicated genes. may be harmful or beneficial, depending on what gene is duplicated. some have been important sources of evolutionary change

Question 12

how can chromosomal duplication mutations have been a source of evolutionary change?

Answer 12

since there is now more than one copy of the gene, one form of the gene can mutate into new forms without seriously affecting the function of the organism

Question 13

what is the impact of a translocation mutation? (chromosomal)

Answer 13

genes may be broken internally, and therefore not be functional, or may be transferred to a new location, where the effect can range from beneficial to harmful. many cancers have chromosomal mutations, and the most common one is translocation

Question 14

what is the impact of a inversion mutation? (chromosomal)

Answer 14

essentially the same effects as translocations: genes may be broken internally by the inversion, with loss of function, or they may be transferred intact to a new location within the same chromosome, producing effects that range from beneficial to harmful.

Question 15

define mutations at the gene level

Answer 15

changes in the double-stranded sequence of bases in genetic material

Question 16

define missense mutation

Answer 16

a sense codon is changed to a different sense codon that specified a different amino acid. also called nonsynonymous mutation

Question 17

define nonsense mutation

Answer 17

a sense codoon is changed to a nonsense codon (stop codon). also called premature stop mutation

Question 18

define silent mutation

Answer 18

a sense codon is changed to a different sense codon, but the codon specifies the same amino acid as the original (no change)

Question 19

define frameshift mutation

Answer 19

a single base-pair deletion or insersion in the coding region of a gene alters the reading frame, resulting in all of the codons following the insertion/deletion being affected

Question 20

define base substitution mutation

Answer 20

single nucleotide base change as a result of point mutations

Question 21

define insertion mutation

Answer 21

one or more base pairs added in sequence during DNA replication

Question 22

define deletion mutation

Answer 22

one or more base pairs skipped during DNA replication

Question 23

do all deletion/insertion mutations result in a shifted reading frame?

Answer 23

no. if multiples of 3 are inserted/deleted, the reading frame remains the same

Question 24

define transition

Answer 24

purine-to-purine or pyrimidine-to-pyrimidine changes

Question 25

define transversion

Answer 25

purine-to-pyrimidine or pyrimidine-to-purine changes

Question 26

what type of mutation causes sickle cell anemia?

Answer 26

missense mutation (base substitution)

Question 27

define spontaneous mutation

Answer 27

naturally occuring mutations (mainly caused by errors in DNA replication or repair)

Question 28

what are spontaneous lesions

Answer 28

naturally occurring mutation that involves depurination and deamination of bases

Question 29

define induced mutation

Answer 29

mutations caused by environmental (natural or artificial) agent/mutagen greatly increasing the rate of mutation

Question 30

define mutagen

Answer 30

agents that induce mutations by replacing a base, altering it so it mispairs, or damaging a base so it can no longer pair with anything

Question 31

define mutagenesis

Answer 31

production of mutations in a lab through exposure to a mutagen

Question 32

define thymine dimer

Answer 32

linking together (through covalent bonds) of adjacent thymine bases, due to exposure to UV radiation

Question 33

what happens when a cell tries to repair or replicate a thymine dimer?

Answer 33

leads to mutation

Question 34

define base analogue

Answer 34

a substance that has very similar structure to bases and therefore mimics them and incorporates into DNA

Question 35

what is an impact of base analogue incorporating into DNA?

Answer 35

it can result in mispairing during DNA replication

Question 36

what is 5BU?

Answer 36

5-Bromouracil is a base analogue for thymine that switches between forms that bind with G and forms that bind with A

Question 37

define allele

Answer 37

one of different forms of a gene (sequence variation), which can cause different phenotypes

Question 38

define wild-type allele

Answer 38

the normal form of the gene found in nature or the standard laboratory strain of a model organism

Question 39

define loss-of-function allele

Answer 39

mutations that reduce/eliminate gene function/expression

Question 40

define gain-of-function allele

Answer 40

mutations that enhance gene function/expression