03/04 mutations

Question 1

what was Darwin’s idea of genetic variation

Answer 1

he believed that variation always existed within individuals but the selectional pressure of the environment is what selected certain traits as favorable

Question 2

what was the idea behind use and disuse being the cause of genetic variation

Answer 2

they believed that the use of certain traits is what caused them to be passed down to offspring

Question 3

what is the idea behind mutations that occur by pre-selectional force?

Answer 3

these mutations occurred without the influence of selection and happened before the force was applied. it just so happened that the selectional force favored the mutation

Question 4

what is the idea behind mutations that occur by post-selectional force? is this idea correct?

Answer 4

this idea is not correct. the idea is that mutations occur with directionality and are caused by the selective force itself. the mutation occurs as a result of a selectional force.

Question 5

in the lederberg replica plating experiment, what were the results

Answer 5

the random mutation occured by pre-selective forces and the same mutated bacteria was transferred to each of the plates

Question 6

What if the physiological adaptation hypothesis was correct and you performed the lederberg replica experiment? what would you see on the plates

Answer 6

the mutation would not occur until the selective pressure was applied, when the bacteria were exposed to the T1 bacteriophage they begin to mutate as a means to survive, but the cells that will actually be successful will be random

the colonies would be randomly dispersed

Question 7

how does the lederberg replica plating experiment support pre-selective forces and the random mutation theory?

Answer 7

the mutation occured before the selective pressure was applied. The cells that were going to survive the bacteriophage were already preselected for and this was not influenced by the presence of the bacteriophage

Question 8

if the lamark theory of physiological adaption was true, what would the plates show in the lederberg experiment?

Answer 8

the mutation would occur after the selective force was applied, but it is unpredictable which cells will survive so the colonies that form will be random and non uniform

Question 9

what is the idea behind the random mutation theory

Answer 9

it aligns with darwins idea of mutation already existing prior to selection. It suggests that mutations occur randomly without selectional pressure

Question 10

what is the idea behind the physiological adaption theory

Answer 10

it suggests that the mutation occurs due to the selectional pressure

Question 11

describe the random mutation theory in the context of the fluctuation test

Answer 11

it predicts that the number of mutated (torR) bacteria will fluctuate in differential bacterial populations based on the timing of mutations

Question 12

why is it important that the number of bacteria fluctuated in the fluctuation test?

Answer 12

it tells us that the mutations occurred randomly throughout the replication cycles of the bacteria and some of the cells mutated earlier than others.

it also tells us that the mutation occured before the cells were plated (pre selection)

Question 13

what was the experimental question in the fluctuation test by Luria and Max Delburk?

Answer 13

How often does mutation occur given the experimental parameters and how does the number of mutations fluctuate

Question 14

in the fluctuation test, what was the idea of the physiological adaption theory

Answer 14

it predicted that the number of mutated bacteria will be in constant proportion or evenly distributed across the plates, indicating that all the bacterial cells mutated at the same time

Question 15

if the physiological adaption theory was correct, what would the plates look like

Answer 15

they would look like the control in the experiment with an evenly distributed amount of bacterial colonies

Question 16

what is a mutation rate

Answer 16

the likelihood that a gene will be altered by a mutation

Question 17

is the rate of mutation constant

Answer 17

no, it can be increased by the presence of mutagens and some genes may have a higher rate of mutation

Question 18

what is a hot spot?

Answer 18

it is a location in a chromosome or single gene that is more susceptible to mutation

Question 19

what is a spontaneous mutation

Answer 19

it is a mutation that occurs naturally and cannot be avoided

Question 20

what is an induced mutation

Answer 20

it is a mutation caused by outside factors that can be avoided

Question 21

what is a mutagen

Answer 21

it is a chemical or physical mutation agent

Question 22

what is the most common spontaneous mutation? why?

Answer 22

dupurination; it occurs due to a spontaneous reaction with water

Question 23

what is depurination

Answer 23

it is the removal of a purine (adenine and guanine) from DNA due to a spontaneous reaction with water at the apurinic site

Question 24

can apurinic sites be repaired? why does it matter how soon it is repaired?

Answer 24

yes they can, if they are not repaired before DNA replication, there is only a 1/4 chance of fixing the error and it is harder in subsequent rounds of replication

Question 25

what is deamination

Answer 25

it is when a amino group is removed from pyrimidines (usually cytosine)

Question 26

what happens if cytosine is deaminated in prokaryotes

Answer 26

it forms uracil

Question 27

if a deaminated cytosine forms uracil and is not corrected by a repair enzyme, what might occur in DNA replication

Answer 27

the U may be paired with an A in subsequent repair, the U may be replaced with a T instead of a C

Question 28

why is 5-methyl cytosine a hot spot for mutation?

Answer 28

when 5-methyl cytosine is deaminated, it forms thymine which is a base commonly found in DNA. In DNA replication, this thymine may be base paired with Adenine instead of guanine as intended

Question 29

in what types of cells are there 5-methyl cytosines

Answer 29

eukaryotic

Question 30

true or false? deamination and depurination will result in insertion and deletion mutations

Answer 30

false, it is a substitution

Question 31

true or false, deamination will cause a frameshift

Answer 31

false, only insertion and deletions will cause this

Question 32

what are tautomeric shifts? why are they a problem

Answer 32

they are changes in conformation, they can result in incorrect bond formations

Question 33

when in its common form, complementarity is followed in DNA replication. If it is in its rare tautomer form, what will occur?

Answer 33

rare bonds like AC and GT may form due to changes in the hydrogen bonding states

Question 34

for a tautomeric shift to cause a mutation, when must it occur

Answer 34

right before DNA replication

Question 35

if the rare tautomeric form of a nitrogenous base occurs but then returns back to its more common state before DNA polymerase converts it back into the new DNA, then it wont be a problem and cause a mutation true or false

Answer 35

true

Question 36

what was lamark's theory of the cause of mutations?

Answer 36

he believed in the idea of physiological adaptions and how the environment can drive a mutation to occur when a selective pressure is applied

Question 37

what is an example of a hot spot for mutation in eukaryotes

Answer 37

5-methyl cytosine, it is prone if deamination

Question 38

what type of mutation is 5-methyl cytosine prone towards

Answer 38

deamination to form thymine