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