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BIO HL > D1.3 Mutation and gene editing > Flashcards

D1.3 Mutation and gene editing Flashcards

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Biology 101 flashcards
1
Q

what is a gene mutation

A

a change in the sequence of bases of a particular gene

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2
Q

when can gene mutations occur

A

they are more likely to occur at certain times in the cell cycle than other times
such as when DNA polymerase fails to proofread errors during replication

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3
Q

what are factors that can change the sequence of bases in DNA

A

ionising radiation
UV
Chemicals

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4
Q

what is a point mutation

A

a change in one base in the gene sequence
can change the amino acid being coded by the gene

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5
Q

what is substitution mutation

A

change of one base to a different base copied by incorrect copying of DNAw

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6
Q

what is insertion mutation

A

additional base/s are added to the DNA

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7
Q

What is deletion mutation

A

removal of a base/s from DNA

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8
Q

what are frameshift mutations

A

mutations in DNA where the number of nucleotides removed or inserted arent in a multiple of 3, leading to every codon afterwards to be read incorrectly during translation
happens due to deletions/insertions

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9
Q

what are nonsense mutations

A

codes for a stop codon meaning the rest of the code isn’t read

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10
Q

what is missense mutation

A

results in a different amino acid being coded for

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11
Q

what is a sense mutation

A

when the mutation has no effect due to degeneracy of the genetic code

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12
Q

what happens if the substitution occurs in a non coding region

A

the mutation may have a neutral effect on the proteome of the cell

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13
Q

what are single nucleotide polymorphisms

A

they are the result of base substitution mutations

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14
Q

what is the result of mutations

A

they increase the likelihoods of polypeptides not functioning properly

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15
Q

what is an example of an insertion mutation

A

Huntingtons disease

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16
Q

Explain Huntington’s disease

A

Insertions can result in repeating base sequences of three nucleotides, which lead to abnormal number of triplet repeat sequences
In huntington’s there is an abnormality in the HTT gene
A DNA segment (CAG trinucleotide repeat) is repeated multiple times in a row (10-35)
mutation leads to a higher number of these causing degenerative effects

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17
Q

what is the result of Huntington’s disease

A

neurodegenerative disease
progressive mental deterioration
involuntary muscle movements

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18
Q

Explain the delta 32 mutation in relation to HIV

A

the delta 32 mutation is a deletion mutation which prevents the production of CCR5 protein which is a receptor. Without this receptor, HIV finds it harder to bind to the cell and enter
people who have two copies of the mutation are less susceptible to infection

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19
Q

what is a mutagen

A

a factor capable of causing a mutation

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20
Q

explain ionising radiation as a mutagen

A

X rays and radiation can damage ions inside the nucleus leading to breakup of DNA

21
Q

explain non ionising radiation as a mutagen

A

UV light
less penetrating but if absorbed, can cause adjacent bases on DNA strand to bind to each other instead of opposite base

22
Q

explain bacterial infection as a mutagen

A

specific bacterial infections can trigger cancers

23
Q

explain chemicals as a mutagen

A

can be carcinogenic. prolonged exposure to chemicals can trigger cancer

24
Q

explain virus infection as a mutagen

A

specific infections that may trigger DNA mutations
some can insert part of the virus genome into the host and produce proteins that alter the cell cycle
leads to uncontrolled replication of cells

25
Q

how is natural selection related to random mutation

A

is a process that selects features of favourable alleles that have been generated by random mutation

26
Q

What is a transition substitution mutations

A

swaps between bases of similar shapes ( between purines or between pyrimidines)
they are less likely to affect the protein and usually dont have any phenotypic effects

27
Q

what is a transversion substitution mutation

A

swaps between a purine and a pyrimidine base

28
Q

what are possible reasons for ‘hot spots’ in mutations

A

variations in the superstructure of DNA
Regions where accessory proteins are less common, leading to an increased localised error that exceeds the correct rate

29
Q

what are germ line mutations

A

mutations occurring in ovaries or testes
they give rise to mutated gametes resulting in inherited diseases

30
Q

what happens to mutations in somatic cells

A

they are only passed to the immediate descendant of that cell, and disappear when organisms die

31
Q

are mutations in somatic cells inheritable

A

they are not
but they may lead to cancer

32
Q

how do changes in environment affect mutation and evolution

A

some individuals in a population may have a selective advantage with increased chance of survival, ultimately lead to changes in the gene pool of a species

33
Q

what is gene knockout

A

it produces an organism with one non-functional gene, allowing researchers to investigate the function of that gene

34
Q

what are examples of model organisms

A

mice, bacteria, plants

35
Q

what makes the use of model organisms possible

A

universality of the genetic code and commonality of basic biological process performed by almost all living organisms
allows prediction of similar effects

36
Q

how do prokaryotes defend themselves against infection

A

their response is based on a region of DNA sequences called CRISPR

37
Q

what is CRISPR

A

Clustered regularly interspaced short palindromic repeats
sequences in the genome of some prokaryotes that act as a genomic record of a previous viral attack

38
Q

what works alongside CRISPR

A

the Cas9 enzyme are bacterial endonuclease that form a double strand break in DNA at a specific target site within a larger recognition sequence
With both, bacteria uses the sequences to recognize and deactivate future invading viruses

39
Q

what are the steps of CRISPR and Cas9

A

after bacteria is infected, CRISPR system used to cut up the invading viral DNA and insert pieces of it into their own genome as a memory
Bacteria transcribe the spacers into RNA, forming a complex with the Cas9 enzyme. They monitor the cell for any DNA sequence complementary to the RNA. When complementary DNA sequence is located, the Cas9 enzyme is activated
If matching DNA is encountered, the complex binds and cuts the viral DNA at specific locations to prevent it from replicating

40
Q

what have scientists been able to do with CRISPR and Cas9

A

develop precise genome editing technology

41
Q

Why is CRISPR so useful

A

due to its precision, there are many opportunities to modify any gene on interest with a reduced risk of accidentally affecting other genes
can be used to edit out gene defects

42
Q

how can CRISPR be used to treat gene defects

A

by removing diseased cells, fix them using CRISPR and then return them to patients to treat the gene condition

43
Q

How can CIRSPR be used to treat sickle cell anaemia

A

by editing a gene from bone marrow so cells would produce a certain type of haemoglobin

44
Q

what are conserved genetic sequences

A

they are identical or similar sequences in nucleic acids across species or a group of species
they are a way of providing evidence about the structure and function of first life on earth

45
Q

what are the hypotheses behind the mechanism for conserved sequences

A

functional requirement for the gene products
slower rates of mutation than the background mutation rate

46
Q

what shows lower mutation rates than less expressed genes

A

highly transcribed genes

47
Q

what can the impact of gene expression on mutation rate may be due to

A

enhanced proofreading and repair mechanisms for the section of DNA

48
Q

where are highly conserved sequences contained

A

in non coding regions

BIO HL (23 decks)

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