Ch 19 - Genetics - UNIT 2 EXAM
what are the three steps in a DNA repair mechanism?
1) one or more proteins in DNA repair detect the irregularity 2) abnormality is removed by action of DNA repair enzymes 3) normal dna is synthesized via DNA replication enzymes
experimental protocol?
1) place individual cells onto growth medium 2) incubate overnight to allow the formation of bacterial colonies - master plate 3) press velvet cloth onto master plate and lifted to obtain a copy of each colony secondary plates had t1 phage * non mutant cells are lysed and killed on these plates
how does position effect alter gene expression?
1) the gene could be moved next to silencers or enhancers that express that of the relocated gene 2) a chromosomal rearrangement may reposition the gene from less condensed to very highly condensed heterochromatic
what is measured or tested the most by researchers in order to measure the amount of oxidative stress in a sample?
8-oxoG
A mutation in one gene that reverses the phenotypic effects of a mutation in a different gene is: an intergenic suppressor. an intragenic suppressor. an up promoter mutation. a position effect.
A
point mutation is what?
A change in a single base pair within the DNA
DNA repair System - Direct Repair
An enzyme recognizes an incorrect alteration in DNA structure and directly converts the structure back to the correct form.
In the replica-plating experiments of the Lederbergs, bacterial colonies appeared at the same locations on each of two secondary plates because: T1 phage caused the mutations to happen. the mutations occurred on the master plate prior to T1 exposure and prior to replica plating. Both a and b are true. Neither a nor b is true.
B
A mutation changes a codon that specifies tyrosine into a stop codon. This type of mutation is a: missense mutation. nonsense mutation. frameshift mutation. neutral mutation.
B nonsense mutation
One way that TNRE may occur involves the formation of _________ that disrupts ____________. a double-strand break, chromosome segregation an apurinic site, DNA replication a hairpin, DNA replication a free radical, DNA structure
C
Which of the following is not an example of a spontaneous mutation? A mutation caused by an error in DNA replication A mutation caused by a tautomeric shift A mutation caused by UV light All of the above are spontaneous mutations.
C
A down promoter mutation causes the promoter of a gene to be _______ like the consensus sequence and _________ transcription. less, stimulates more, stimulates less, inhibits more, inhibits
C - less and inhibits
A point mutation could be caused by: depurination. deamination. tautomeric shift. any of the above.
D
Which of the following is an example of a somatic mutation? A mutation in an embryonic muscle cell A mutation in a sperm cell A mutation in an adult nerve cell Both a and c are examples of somatic mutations.
D
Anticipation does not occur in all TNRE disorders and usually depends on whether disease is inherited from?
Mother or Father
are naturally produced as unwanted by-products of energy production in mitochondria?
ROS
mutation frequency?
a gene is a number of mutant genes divided by the total number of copies of that gene within the population
what causes sickle cell disease to occur and where in the amino acid sequence does it take place ?
a missense mutation and in the sixth amino acid has a missense occur and cause glu to become val
errors in DNA replication - spontaneous mutation
a mistake by DNA polymerase may cause the base pair to mismatch
conditional mutants
a mutant whose phenotype depends on environmental conditions
intergenic suppressor
a mutation that is in a different gene then the one that originally carries the gene
somatic mutations affect how much of the body?
a portion
transversion
a purine is interchanged for a pyrimidine
chromosomal break points?
a region where two chromosome pieces are broken and rejoin with other chromosome pieces - occurs in the gene
wild type
a relatively prominent genotype in a population
somatic mutation occurs in?
a single somatic cell
aberrant recombinant - spontaneous mutation
abnormal crossing over leading to deletions, duplications, translocations, and inversions
aberrant segregation -spontaneous mutation
abnormal segregation due to aneuploidy or polyploidy
If a mutant gamete participates in in fertilization, what happens to the cells it produces?
all of the cells produced will contain the mutation
some TNRE disorders have the unusually feature of progressively worsening in future generations
anticipation
a covalent bond between deoxyribose and a purine base is somewhat unstable and occassionally undergoes a spontaneous reaction with water called?
apurinic site
reactive oxygen products
are products of oxygen metabolism in all aerobic organisms
missense mutations
are substitutions for which the amino acid change does result
frameshift mutations?
are the addition or the deletion of a number of nucleotides and they are not divisible by 3
silent mutations
are those that do not alter the amino acid sequence of the polypeptide even though the base sequence has changed
A mutagen that is a base analog is ethyl methanesulfonate (EMS). 5-bromouracil. UV light. proflavin.
b
Nitrous acid replaces amino groups with keto groups, a process called alkylation. deamination. depurination. crosslinking.
b
In the Ames test, a ____________ number of colonies is observed if a substance ________ a mutagen, compared with the number for a control sample that is not exposed to the suspected mutagen. significantly higher, is significantly higher, is not significantly lower, is significantly lower, is not
c
chemical agents - induced mutations
can cause changes in the structure of DNA
transposable elements-spontaneous mutation
can insert themselves into the sequence of a gene
germ line mutation
can occur directly in a sperm or egg cell, or can occur in a precursor cell that produces the gametes
induced mutations
caused by environmental agents
down promoter sequence?
causes the promoter to become less like the consensus sequence decreasing affinity of transcription factors
hot spots
certain regions of the gene likely to mute more than others
reversion?
changes a mutant allele back to a wild type allele
spontaneous mutations
changes in the DNA structure due to natural biological or chemical processes
silent mutations can occur in bases in their ____ codon and the ______ is unchanged?
codon and amino acid is not changed
results of this experiment?
colonies on the plates were in the same locations and therefore the cells on the master plate were grown randomly since these cells remained in the same place
deamination-spontaneous mutation
cytosine or 5-methylcytosine can spontaneously dominate to create uracil or thymine
deleterious mutation?
decreases the chances of survival and reproduction
TNRE
diseases are caused by an unusually mutation in which a repeated sequence of three nucleotides can inc in number from one generation to the next
beneficial mutation
enhances the survival or reproductive success of an organism
mutations are a foundation for what?
evolutionary change
Sturtevant 1928?
first to notice the chromosomal rearrangements in flies can influence phenotypic expression
an individual with somatic regions that differ genotypically from each other are called?
genetic mosaics
random mutations are more likely to be?
harmful
mutation
heritable change in the genetic material
a break point in the middle of the gen causes what to happen?
inhibit gene function
when the second mutation is in the same gene as the first, what is it called?
intragenic suppressor
why are oxidized bases harmful?
it base pairs with adenine during DNA replication and causes mutations in which GC becomes a TA base pair - transversion mutation
random mutation theory
it can occur in any gene and does not require the exposure of an organism to an environmental condition that causes specific types of mutations to happen
if a gene is moved to a heterochromatic region what happens to the expression of the gene?
it may be turned off
5' UTR --> 3' UTR
may alter the ability of mRNA to be translated or be less stable
splice recognition sequence
may alter the ability of the mRNA to be properly spliced
regulatory element
may disrupt the ability of then to properly regulated
promoter?
may inc or dec the rate of transcription
alkylation?
methyl or ethyl groups are covalently attached to the bases
Agents known to alter the structure of DNa and thereby cause mutations are called?
mutagens
an allele that is created by altering a wild type allele by mutation
mutant allele
when an individual with a germ line mutation produces gametes what can happen?
mutation can be passed along to future generations of offspring
what was their hypothesis?
mutations are random events
when a missense mutation has no detectable affect it is called a what?
neutral mutation
replica plating - Lederberg Experiment
no selective agents used, velvet cloth used to pick up a few colonies, and replicas were then trasferred to secondary plates - the secondary plates had T1 bacteriophages to lyse the wild type cells
base substitutions?
one base is submitted for another
What can happen if ROS over accumulate
oxidative dna damage can occur - causing changes to the DNA structure
physical agents - induced mutations
physical phenomena such as uv might and x rays can damage dna
the change in gene location is said to have a?
position effect
germ line
refers to cells that give rise to the gametes like eggs and sperm
oxidative stress
refers to the imbalance between the production of ROS and an organisms ability to break them down
lethal mutation?
results in the death of a cell or organism
what is an example of a missense mutation?
sickle cell disease
tautomeric shifts-spontaneous mutation
spontaneous changes in base structure can cause mutations if they occur immediately prior to dna replication
what is the key aspect of TNRE formation?
stem loop structure due to CG base pairs
what is a second site mutation called?
suppressor mutations
what test is used to test mutagenicity?
the Ames test
nonsense mutations?
the changing of a normal codon to a stop codon
depurination-spontaneous mutation
the linkage between a purine and a deoxyribose can spontaneously break
toxic metabolic products-spontaneous mutation
the products of normal metabolic processes that may be chemically reactive agents that can alter the structure of DNA
the Ames test measures?
the rate at which the second mutation occurs.
conditional mutants are usually studied in temperature sensitive mutants. why is this a good example?
the ts grows normally in one temperature range but has defective growth outside of permissive range
Lamarck?
theory of inherited traits
some genes mutate at much higher levels than the of other genes, why?
this happens because some genes are larger than others and provides greater chance for mutation
ROS are produced by the immune system to do what?
to kill pathogens and some are useful in cell signaling
change of a pyrimidine to another pyrimidine (like c to t ) is call what?
transition
T OR F: mutations can occur within some somatic cells at early or late stages of development
true
random variation exists n a population as a matter of random chance. T or F?
true
mutations that increase transcription are called?
up promoter mutations
mutations can occur at other sites in the genome not just the gene
yeah