Exam 4 (CH 18)

What are the three general steps in DNA repair mechanisms?

1. one or more proteins in the system detect an irregularity in DNA structure 2. the abnormality is removed by DNA repair enzymes 3. normal DNA is synthesized by DNA replication enzymes

During which event (2-words) does expansion of TNREs occur?

DNA replication

What are frameshift mutations? How many amino acids are altered? And what is the likely effect on protein function?

Mutation involving the addition or deletion of a number of nucleotides that is not divisible by THREE. This alters many amino acids. This has an inhibitory effect on proteins.

Whats the difference between "mutation rate" and "mutation frequency"?

Mutation rate is the likelihood that a gene will be altered by a new mutation. # new mutations per cell generation. Mutation frequency is the # of mutant genes/total # copies of that gene in a population

Explain how mutant tRNA's may act as nonsense and missense suppressors

The first mutation could put a stop codon into the protein encoding gene, then the second mutation could alter the anticodon region of the tRNA so that the anticodon recognizes a stop codon but inserts an amino acid.

What are somatic cells????

all cells of the body exculding the germ-line cells.

What genetic phenomenon (one word) describes a feature of some TNRE diseases in which there is progressively worsening severity of related disease features in subsequent generations?

anticipation

A mutation that changes a codon into a stop codon is a a. missense mutation. b. nonsense mutation. c. frameshift mutation. d. neutral mutation

b

What is the difference between induced mutations caused by chemical agents and those caused by physical agents?

chemical agents are chemical substances that changes the DNA structure. Physical agents are things such as UV light and X-rays

In the case of the TNRE diseases listed, where is the repeat unit located in the gene?

in the coding sequences

What is a deleterious mutation?

mutation that decreases the chances of survival and reproduction.

What is base substitution?

mutation where one base is substituted for another in DNA (NOT RNA like in transcription......DNA! so you can still use the table, EX: If non-template DNA is %'-TAA-3' then the RNA would be UAA put this question in thread for him to answer. NOTE: this is the NONTEMPLATE STRAND)

what are autosomal cells?

none sex chromosomes

___________ (2 words) extract is added to the suspected mutagen during the Ames test because cellular enzymes may be required to mimic its actions in animals.

rat liver

What type of mutation (one word) is needed for the auxotrophic strain of bacteria to grow in the Ames test?

reversion

what is the difference between a spontaneous mutation and an induced mutation?

spontaneous mutations are changes in DNA structure that result from natural biological or chemical processes. Induced mutations are caused by environmental agents (chemical or physical agents)

What is the ames test?

test that monitors the rate at which the second mutation occus, which indicates whether an agent increases the mutation rate above the spontaneous rate

What are the two ways a chromosomal rearrangement can cause a position effect?

translocation may move a gene next to a heterochromatic region of another chromosome and thereby diminish its expression OR it could be moved next to a euchromatic region and increase its expression. translocation may move the gene next to a new promoter or regulatory sequences that may now influence the gene's expression.

What is TNRE?

trinucleotide repear expansion. This is a mutation where a repeating sequence of three nucleotides can increase in number from one generation to the next.

can a missense mutation be a beneficial mutation?

yes, but its very unlikely

Lactose permease is encoded by the lacY gene of the lac operon. A mutation at codon 64 changes glycine to valine. Lactose permease is unable to function. A second mutation, on codon 50, changes the alanine to threonine, and restores function. are the following terms appropriate to describe this second mutation? a. reversion b. intragenic suppressor c. intergenic suppressor d. missense mutation

A. Not appropriate, because the second mutation is at a different codon. B. Appropriate. C. Not appropriate, because the second mutation is in the same gene as the first mutation. D. Appropriate, because it changes the amino acid

Is the following transition, transversion, addition, or deletion if the coding DNA strand is as shown: 5'-GGACTAGATAC-3' A. 5'-GAACTAGATAC-3' B. 5'-GGACTAGAGAC-3' C. 5'-GGACTAGTAC-3' D. 5'-GGAGTAGATAC-3'

A. transition B. transversion C. deletion D. transversion

A chromosomal rearrangement may affect a gene because a chromosomal ________ occurs within a gene.

Breakpoint (chromosome pieces break and rejoin other chromosome pieces)

Which of the following mutations is NOT and example of a spontaneous mutation? a. caused by error in DNA replication b. cause by tautomeric shift c. caused by UV light d. none

C

Is it better to use haploid or diploid organisms for mutagen testing? Why?

Haploid cells are more sensitive to mutation because they have only a single copy of each gene. Therefore, recessive mutations that inhibit cell growth are easily detected

A mutation in one gene that reverses the phenotypic effects of a mutation in a DIFFERENT gene is: a. intergenic suppressor b. intragenic suppressor c. up promoter mutation d. position effect

a

Which of the following examples is/are likely to be caused by a somatic mutation (can be more than one)? a. purple flower with small white patch b. albino child in family of seven c. tree blooming 2 weeks earlier than other trees in its orchard d. smoker developing lung cancer

a and d

What is a beneficial mutation?

enhances survival or reproductive success of an organism

What is the random mutation theory?

genetic variation exists as a random chance, and natural selection selects those that are better adapted to their environments. (compared to the mutations occurring as a result of the environment)

What type of point mutation is responsible for sickle cell anemia? What amino acid is altered to what?

missense mutation. the 6th amino acid, glutamic acid, is changed to valine

What is a germ-line mutation?

mutation in sperm or egg cell, or mutation in cell that produces the gamete.

What is a lethal mutation?

mutation that results in death to a cell or organism.

What are missense mutations?How many amino acids are altered? And what is the likely effect on protein function?

mutations where the base substitutions change the amino acid. (EX: sickle cell) One amino acid is altered. This mutation has a neutral (no effect) or inhibitory effect.

Which two of the four point mutations within the coding sequence can be concidered a "neutral" mutation?

silent mutations and missense mutations (occasionally)

What are the four point mutations that can occur in the coding sequence?

silent, missense, nonsense, and frameshift mutations

How does TNRE occur?

the triplet repeat forms a hairpin or stemloop. The hairpin spreads out and the gab is repaired through DNA synthesis

Which are more harmful: spontaneous or induced mutations?

they are both harmful........one isn't more harmful over the other

If the rate of mutation for a gene is 10^-5 per cell generation, how many new mutations per gene would you expect in a population of 1 million bacteria?

10

Which of the following is an example of a somatic mutation? a. mutation in embryonic muscle b. mutation in sperm cell c. mutation in adult nerve cell d. both a and c

D

What bacterial species is used in the Ames test? Which amino acid can strains of this species not produce? Separate the two answers by one space.

Salmonella typhimurium histidine

What is a mutagen?

agent that alters the structure of DNA, which then causes a mutation (this is in induced mutations)

Explain the TNRE caused huntington disease (i.e. numbers of repeats in affected and unaffected individuals, patterns of inheritance, and anticipation)

number of repeats in unaffected individuals=6-37 number of repeats in affected individuals=27-121 inheritance= autosomal dominant anticipation=from father

Explain the TNRE caused Fragile X syndrome (i.e. numbers of repeats in affected and unaffected individuals, patterns of inheritance, and anticipation)

number of repeats in unaffected individuals=6-53 number of repeats in affected individuals= over 200 inheritance= X-linked anticipation=from mother/none (type A/E)

What are the differences in effects of germ-line versus somatic mutations?

when the mutation is a germ-line mutation, the mutation is found throughout the entire body and talk the games of the offspring will carry the mutation. When theres a somatic mutation only a patch of the body is affected and NONE of the gametes will carry the mutation.

TNRE disorders are caused by ___ (number) base-pair repeats that expand due to formation of a _____ (one word) with CG base pairing. Separate the number and the word by one space.

3 hairpin

In the replica-plating experiments of the lederbergs, bacterial colonies appeared at the same locations in each of the two secondary plates because: a. T1 phage caused the mutation to happen b. mutations occurred on the master plate prior to T1 exposure and prior to replica plating c. both d. none

B

can a somatic mutation be passed to offspring?

NO, only germ-line mutations can be passed from parent to offspring

What is a position effect?

Position effect means that the expression of a gene has been altered due to a change in its position along a chromosome (ex: if inversion happens on a chromosome and a gene is moved next to a regulatory sequence for a difference gene, or translocation of the gene to a condensed and inactive/active heterochromatic chromosome (can lead to variegated))

What are up promoter mutations vs. down promoter mutations?

Up promoter mutations that increase transcription. Down promoter mutations cause the promoter to be different than consensus sequence, decreasing transcription rate.

What are suppressor mutations?

a second mutation suppresses the phenotypic expression of the first mutation. (Ex: mutation causing small growth, second mutation restores normal growth)

what is a reversion?

a second mutation that, counters the first mutation, and restores the wildtype phenotype.

What is a hairpin?

a stem loop structure caused by CG base pairing

Are the following silent, missense, nonsense or frameshift mutations if the original DNA is as shown: 5'-ATGGGACTAGATACC-3' A. ATGGGTCTAGATACC B. ATGCGACTAGATACC C. ATGGGACTAGTTACC D. ATGGGACTAAGATACC

a. silent b. missense c. missense d. frameshift

Describe how mutations within the coding sequence of a gene may alter a polypeptide's structure.

can alter the code, which change which amino acids are produced, which changes the structure of the polypeptide.

Explain how mutations within noncoding sequences may alter gene function.

can alter transcription rate (core promoter mutation), regulation (regulatory element/operator site mutation), translatability of mRNA (5'-UTR/3'-UTR mutation), and ability of pre-mRNA to be spliced (splice recognition sequence mutation).

What are germ line cells?

cells taht give rise to gametes (eggs and sperm)

Define point mutation

change in a single BASE PAIR within the DNA

a point mutation can be caused by a. depurination b. deamination c. tautomeric shift d. all the above

d

one way that TNRE may occur involves the formation of _____________ that disrupts_________ (DNA structure/DNA replication).

hairpin, DNA replication

In the ames test, a __________ number of colonies is observed if a substance ___________ a mutagen, compared with the control that is not exposed to the suspected mutagen.

high, is

an autosomal dominant mutation. 1,422,000 babies, 31 of them mutants. AMong the 31 mutants, 18 had one parent with the mutation. what is the mutation frequency? what is the mutation rate?

if there are 1,422,000 babies, there are 2,844,000 copies of this gene. The mutation frequency is 31/2,844,000= 1.09 × 10^-5 There are 13 babies who did NOT have a parent with mutation; thus, thirteen is the number of new mutations. Mutation rate= 13/ 2,844,000= 4.6 ×^ 10-6 .

What are intragenic suppressors vs. intergenic suppressors?

intragenic suppressor is when the second mutant site is within the same gene as the first mutation. intergenic suppressors is when the second mutation is on a different gene than the first mutation.

Explain how changes in chromosome structure may affect gene expression

inversions or translocation may cause some genes to become inactive due to position effect

What The earlier the somatic mutation occurs during development, the ______(larger, smaller) the affected region.

larger

A down promoter mutation causes the promoter of a gene to be _______ (more/less) like the consensus sequence and _________ (stimulates/inhibits) transcription.

less inhibits

What are silent mutations? What part of the codon do these type of mutations occur? How many amino acids are altered? And what is the likely effect on protein function?

mutations that do not alter amino acid sequence of the polypeptide even though the nucleotide sequence has changed. These mutations occur in the third base. They do not affect any amino acids. There is no effect on protein function.

What are nonsense mutations? How many amino acids are altered? And what is the likely effect on protein function?

mutations which involve a change from a normal codon to a stop codon. Many amino acids are altered due to termination. The effect is it inhibits protein function.

Explain the TNRE caused Mytonic muscular dystrophy (i.e. numbers of repeats in affected and unaffected individuals, patterns of inheritance, and anticipation)

number of repeats in unaffected individuals=5-37 number of repeats in affected individuals= over 200 inheritance= autosomal dominant anticipation= from mother

what is replica plating? How did Joshua and ester lederberg use this technique.

technique where a replica of bacterial colonies is transferred to a new petri plate. MUST HAVE AN ORIENTATION MARKER on plate, to compare location of growth between plates They used this to put bacteria onto plate with T1 Phage. Only mutants (resistant to phage) survived. THE COLONIES on the two different plates with T1 were in the SAME LOCATION (as they were transferred using the same velt peice).

What is the difference between a transition mutation and a transversion mutation? Which is more common?

transition is mutation when a purine switches with a purine or a pyrimidine switches with a pyrimidine (C to T or A to G). TRANSITIONS ARE MORE COMMON. Transversion is when a purine and pyrimidine interchange.

What is anticipation or dynamic mutation?

when a TNRE can progressively worsen its severity in future generations.