Genetics Ch.16

Front 1

Mutation

Back 1

alteration in the DNA sequence

Front 2

Spontaneous mutation

Back 2

happen naturally and randomly and are linked to normal biological or chemical processes in the organism

Front 3

Induced mutations

Back 3

results from the influence of an extraneous factor, either natural or artificial

Front 4

Somatic mutations

Back 4

occur in any cell except germ cells and are not heritable

Front 5

Germ-line mutations

Back 5

occur in gametes and are in herited

Front 6

Autosomal mutations

Back 6

occur within genes located on the autosomes

Front 7

X-linked mutations

Back 7

occur within genes located on the X chromosome

Front 8

Recessive autosomal mutations

Back 8

unlikely to result in a detectable phenotype

Front 9

Dominant autosomal mutations

Back 9

will be expressed phenotypically in the first generation

Front 10

X-linked recessive mutations

Back 10

arise in the gametes of a homogametic female; may be expressed in hemizygous male offspring

Front 11

Point mutations

Back 11

base substitutions in which one base pair is altered

Front 12

Frameshift mutations

Back 12

result from insertions or deletions of a base pair; occurs when any number of bases are added or deleted, except multiples of three, which would reestablish the initial fram of reading.

Front 13

Missense mutations

Back 13

change a codon resulting in an altered amino acid within a protein-coding portion of a gene

Front 14

Nonsense mutations

Back 14

changes a codon into a stop codon and results in premature termination of translation

Front 15

Silent mutation

Back 15

alters a codon but does not result in a change to the amino acid at that position of the protein

Front 16

Transition

Back 16

if a pyrimidine replaces a pyrimidine or a purine replaces a purine

Front 17

Transversion

Back 17

if a purine and a pyrimidine are interchanged

Front 18

Classifications based on phenotypic effects

Back 18

loss of function, gain of function, morpholigical, nutritional, behavioral, regulatory

Front 19

Lethal mutations

Back 19

interrupt an essential process and result in death

Front 20

Conditional mutations

Back 20

expression depends on the environment in which the organism finds itself.

Front 21

Temperature-sensitive mutations

Back 21

example of a conditional mutation

Front 22

Neutral mutations

Back 22

the vast majority of all mutations, occur in the large portions of the genome that do not contain genes and therefore have no effect on gene products

Front 23

Slippage

Back 23

during replication can lead to small insertions or deletions.

Front 24

Tatutomeric shifts

Back 24

in nucleotides can result in mutations due to anomalous base pairing.

Front 25

Depurination

Back 25

one of the most common causes of spontaneous mutation

Front 26

Deamination

Back 26

one of the most common causes of spontaneous mutation

Front 27

Oxidative damage

Back 27

DNA may suffer this by the by-products of normal cellular processes.

Front 28

Transposons

Back 28

Integrating these into new genomic locations can act as naturally occurring mutagens.

Front 29

Mutagens

Back 29

nautural or artificial agents that induce mutations

Front 30

Base analogs

Back 30

substitute for purines or pyrimidines during nucleic acid replication

Front 31

Alkylating agents

Back 31

donate an alkyl group to amino or keto groups in nucleotides to alter base-pairing affinity

Front 32

Acridine dyes

Back 32

casue frameshift mutations by intercalating between purines and pyrimidines

Front 33

UV radiation

Back 33

creates pyrimidine dimers

Front 34

Pyrimidine dimers

Back 34

distort the DNA conformation in such a way that errors tend to be introduced during DNA replication.

Front 35

Ionizing radiation

Back 35

in the form of X rays, gamma rays, and cosmic rays are mutagenic/

Front 36

Muscular dystrophy

Back 36

results from mutation in the gene encoding dystrophin.

Front 37

DMD

Back 37

typically the result from a frameshift mutation in the dystrophin gene, which leads to a nonfunctional truncated protein.

Front 38

BMD

Back 38

primarily due to alteration of the protein sequence

Front 39

Trinucleotide repeat sequences

Back 39

responsible for :
fragile X syndrome
huntington disease
myotonic dystrophy
spinobulbar muscular atrophy

Front 40

Genetic anticipation

Back 40

the number of repeats may increase in each subsequent generation in affected individuals

Front 41

Ames test

Back 41

uses any of a dozen strains of salmonella typhimurium selected for their increased sensitivity to mutagens and their ability to reveal the presence of specific types of mutations

Front 42

Proofreading

Back 42

recognizing and correcting errors in replication

Front 43

Mismatch repair

Back 43

corrects errors that remain after proofreading

Front 44

Postreplication repair

Back 44

occurs when DNA replication skips over a lesion and requires homologous recombination mediated by the RecA protein.

Front 45

SOS repair system

Back 45

allows DNA to become error prone

Front 46

Photoreactivation repair

Back 46

removes thymine dimers casue by UV light.

Front 47

Photoreactivation enzyme

Back 47

photoreactivation repair depends on the activity of this protein

Front 48

Base excision repair

Back 48

three steps:
- removal of hte mutation by a nuclease
- gap filling by DNA polymerase
- sealing of the nick by DNA ligase
involves:
- recognition of the erroneous base by DNA glycosylase
- cutting cuting of the DNA backbone by AP endonuclease

Front 49

Nucleotide excision repair

Back 49

repairs bulky lesions and involves the uvr genes.

Front 50

Xeroderma pigmentosum

Back 50

have lost the ability to undergo nucleotide excision repair

Front 51

DNA double-strand break

Back 51

repair is activated when both DNA strands are cleaved.

Front 52

End joining

Back 52

repairs double-stranded breaks but does not require a homologous region of DNA during repair.

Front 53

Homologous recombinational repair

Back 53

fixes a double-strand DNA break by digesting back the 5' ends of the broken helix to leave overhanging 3' ends that interact with a region of an undamaged sister chromatid to allow DNA polymerase to copy the undamaged DNA sequence into the damaged strand.