chapter 11 part 1

Question 1

what are germ-line mutations?

Answer 1

mutations that occur in germ-line cells giving rise to sperm & egg

Question 2

can germ line mutations be passed on from one generation to the next?

Answer 2

yes

Question 3

what are somatic mutations?

Answer 3

mutations not in the germ line cells

Question 4

what are cells not in the germ line called?

Answer 4

somatic cells

Question 5

will somatic mutations be passed on?

Answer 5

they will only be passed on to direct descendants of the original mutated cell
they divide my mitosis

Question 6

what do gene mutations do to one or more DNA base pairs?

Answer 6

substitute, add, or delete one or more base pairs

Question 7

what are point mutations and where do they occur

Answer 7

they are localized mutations that occur at a specific, identifiable position in a gene

Question 8

what are genes with elevated mutation rates called?

Answer 8

mutation hotspots
-large gene size, regions rich in CpG dinucleotides, long stretches of trinucleotide repeats

Question 9

what is the DYS gene associated with?

Answer 9

Duchenne muscular dystrophy

Question 10

what is the NF1 gene associated with?

Answer 10

neurofibromatosis are large genes each with a mutation rate of about 10^-4

Question 11

what is a base pair substitution mutation from purine to purine or pyrimidine to pyrimidine called?

Answer 11

transition

Question 12

what is a base pair substitution mutation from pyrimidine to purine and vise-versa called?

Answer 12

transversion

Question 13

what are the types of base-pair substitution mutations>

Answer 13

silent (synonymous) mutation
missense mutation
nonsense mutation

Question 14

silent (synonymous) mutation

Answer 14

a type of bp mutation where there is no amino acid change

Question 15

missense mutation

Answer 15

a type of bp mutation where there is a change in amino acid

Question 16

nonsense muation

Answer 16

a type of bp mutation where a stop codon is created

Question 17

what is a frameshift mution

Answer 17

insertion or deletion of one or more base pairs altering the reading frame of the message

Question 18

what are frame shift mutations also called

Answer 18

INDEL mutions
-INsertion or DELetion mutations

Question 19

what results from a frameshift mutation?

Answer 19

the wrong amino acid sequence is produced downstream of the altered nucleotides
-premature stop codons are commonly encountered

Question 20

what are promoter mutations

Answer 20

mutations that alter consensus sequence nucleotides of promoters

Question 21

what do promoter mutations interfere with?

Answer 21

interfere with efficient transcription initiation

Question 22

what is a splicing mutation?

Answer 22

when the specific splicing sequence is altered due to a mutation

Question 23

what requires specific sequences at either end of the intron?

Answer 23

splicing
efficient splicing of introns from mRNA requires specific sequences at either end of the intron

Question 24

what do splicing mutations result in?

Answer 24

result in splicing errors & the production of mutant proteins due to the retention of intron sequences in the mRNA

Question 25

what do some base-pair substitutions do?

Answer 25

they produce new splice sites that replace or compete with authentic splice sites during mRNA processing

Question 26

what are cryptic splice sites?

Answer 26

when a base-pair substitution mutation results in a new splice site that replaces or competes with the authentic splice sites during mRNA processing

Question 27

polyadenylation mutations

Answer 27

mutations of the polyadenylation signal sequence at the 3’ end of eukaryotic mRNA can block the proper 3’ processing of mRNA

Question 28

where do we know of that polyadenylation mutations occur?

Answer 28

in a rare mutant form of the human beta globin gene, leading to severe reduction in functional beta globin protein produced

Question 29

forward mutation

Answer 29

convers a wild-type allel to a mutant allele

Question 30

reverse mutations are also called what

Answer 30

reversion mutations

Question 31

reverse mutation

Answer 31

converts mutant alleles to wild-type or near wild-type

Question 32

true reversion

Answer 32

wild-type DNA sequence (or amino acid sequence) is restored by a second mutation with the same codon

Question 33

intragenic reversion

Answer 33

occurs through mutation elsewhere in the same gene

Question 34

second site reversion

Answer 34

occurs by mutation in a different gene & together the two mutations restore the organism to wild-type

Question 35

what are second site mutations also known by and why?

Answer 35

suppressor mutations since the second mutation “suppresses” the mutant phenotype caused by the first mutation

Question 36

spontaneous mutations

Answer 36

arise in cells without exposure to agents capable of inducing mutation (mutagens)

Question 37

how do spontaneous mutations primarily arise?

Answer 37

through errors in DNA replication or spontaneous changes in the chemical structure of a nucleotide base

Question 38

does DNA replication have high or low fidelity?

Answer 38

very high do to the DNA polymerases ‘proofreading’ ability as well as their accuracy & efficiency of mismatch repair

Question 39

what rate do mismatches due to replication errors occur?

Answer 39

about 1 x 10^-9 in wild type e.coli & about the same in eukaryotes

Question 40

what does alteration in number of DNA repeats occur via?

Answer 40

strand slippage

Question 41

strand slippage

Answer 41

the DNA polymerase of the replisome temporarily dissociates from the template & a portion of the newly replicated DNA forms a temporary hairpin
-resumption of replication leads to re-replication of some of the repeats & an overall increase in the number of repeats on the daughter strand

Question 42

what are trinucleotide repeat disorders?

Answer 42

a special class of mutations causing some hereditary diseases in humans & other organisms
-wild-type alleles of the genes in question have a characteristic number of DNA trinucleotide repeats
-increases in the number of repeats beyond a certain threshold causes the disorders

Question 43

what is depurination

Answer 43

the loss of a purine from a nucelotide by breaking the covalent bond linking the nucleotide base to the sugar

Question 44

what is a lesion of depurination called?

Answer 44

apurinic sitte

Question 45

are most apurinic sites repaired before replication?

Answer 45

yes

Question 46

what happens if apurinic sites are left unrepaired?

Answer 46

DNA polymerase will usually compensate by putting adenine into the site during replication

Question 47

what is deamination?

Answer 47

the loss of an amino group (NH2) from a nucleotide

Question 48

what happens when cytosine is deanimated?

Answer 48

an oxygen atom usually takes its place, converting the cytosine to uracil
-DNA mismatch repair removes the uracil from the DNA & replaces it with cytosine, restoring the wild-type sequence

Question 49

what happens when methylated cytosine is deaminated?

Answer 49

a thymine base is produced, which is now base-paired with guanine
-mismatch repair system can restore the wild-type G-C pair
-if repair does not occur, replication will produce two sister chromatids, one with mutant A-T pair & one with the wild-type G-C pair