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Molecular and Experimental Genetics > Mutations: origin, patterns and implications > Flashcards

Mutations: origin, patterns and implications Flashcards

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Biology 101 flashcards
1
Q

What is a mutation?

A

A heritable change in the base sequence of DNA

May affect the structure and function of a protein when it occurs within a gene

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2
Q

What are gene mutations?

A

Relatively small change in DNA structure that affects a single gene

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3
Q

What are chromosome mutations?

A

Changes in chromosome structure (aneuploidy)

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4
Q

What are genome mutations?

A

Changes in chromosome number (translocation/inversion)

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5
Q

What are spontaneous mutations?

A

Result from abnormalities in cellular/biological processes

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6
Q

Give some examples of spontaneous mutations

A 
Errors in DNA replication
Aberrant recombination
Aberrant segregation
Transposable elements
Depurination
Deaminations
Tautomeric shifts
Toxic metabolic products
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7
Q

What is depurination?

A

The removal of a purine (guanine or adenine) from the DNA.
This is termed an apurinic site
If the repair system fails, then a mutation may result during rounds of DNA replication

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8
Q

What are induced mutations?

A

Mutations caused by environmental agents:
Physical
Chemical
Biological/infectious

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9
Q

What are mutagens?

A

Agents that are known to alter DNA structure

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10
Q

What is a teratogen?

A

Any environmental factor that can produce a permanent abnormality in structure or function, restriction of growth, or death of the embryo or fetus

(eg. sodium valproate)

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11
Q

What is a carcinogen?

A

Any agent capable of causing cancer in humans or animals.

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12
Q

What is a genotoxic and non-genotoxic carcinogen?

A

Genotoxic - if the mutagen binds covalently to DNA

non-genotoxic - non DNA reactive, metabolic effects

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13
Q

What are epigenetic carcinogens?

A

Do not damage DNA directly.

may induce expression of enzymes that metabolise carcinogens to DNA reactive forms.

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14
Q

What are clastogens?

A

Mutagen that can cause breaks in chromosomes leading to sections of the chromosome being deleted, added or rearranged

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15
Q

What are Aneugens?

A

Mutagen that causes a daughter cells to have an abnormal number of chromosomes or aneuploidy

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16
Q

What is the Ames test?

A

Biological assay which uses bacteria to assess the mutagenic (and therefore carcinogenic) potential of chemical compounds.

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17
Q

Why is the Ames test used?

A

Often used as one of the initial screes for potential drugs to indicate possible carcinogens.

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18
Q

What are the main physical mutagens?

A

Ionising radiation
Non-ionising radiation
Heat

19
Q

What are some ionising radiation mutagens?

A

X-rays / gamma rays / corpuscular radiation.

Has short wavelengths and high energy so they can penetrate deeply into biological molecules creating chemically reactive molecules (free radials) that break covalent bonds.

20
Q

What mutations can ionising radiation cause?

A 
Damage to base and sugar residues
Base deletions
Oxidise bases
Single nicks in DNA strands
Cross-linking
Chromosomal breaks
21
Q

What type of non-ionising radiation is a mutagen?

A

UV light.

Has less energy and cannot penetrate as deeply into biological molecules.

22
Q

What does UV radiation cause?

A

formation of cross-linked thymine dimers.

Thymine dimers may cause mutations when that DNA strand is replicated.

23
Q

What are the different types of chemical mutagens?

A

Base analogues
Base altering chemicals
Intercalating agents
Agents altering DNA structures

24
Q

What are base analogue mutagens?

A

Structurally resemble purines and pyrimidines and may incorporate into DNA in place of normal bases
(eg. Bromouracil will incorporate into DNA and pair with A due to being similar to thymine residues)

25
Q

What are base modifying mutagens?

A

Chemicals that alter structure and pairing properties of bases

26
Q

What are deaminating agents?

A

base modifying mutagens:
Nitrous acid formed by digestion of nitrites in food, causing C to U, C to T and A to hypoxanthine deaminations leading to baes transitions

27
Q

What are Hydroxylating agents?

A

Base modifying mutagens:

add OH- groups to C

28
Q

What are alkylating agents?

A

Base modifying mutagens:

add methyl or ethyl groups to bases

29
Q

What are intercalating agents?

A

Plate-like, multiple ringed molecules which interact with DNA bases and insert between them. This causes stretching of DNA duplex causing DNA polymerase during replication to insert bases resulting in frameshifts.

30
Q

Give some examples of intercalating agents

A

Acridine orange, Proflavine, ethidium bromide

31
Q

What are transposon mutagens?

A

Insert into DNA and disrupts the gene structure

32
Q

What are Viral mutagens?

A

virus DNA may be inserted into the genome and disrupt genetic function.

33
Q

What is aetiology?

A

the cause, set of causes or manner of causation for a disease or condition.

34
Q

What are bacterial mutagens?

A

May cause DNA damage and reduce the efficiency of DNA repair systems, therefore increasing mutations rate
(eg. Helicobacter Pylori)

35
Q

What are mutational signatures?

A

Mutational signatures are characteristic combinations of mutation types arising from specific mutagenesis processes

36
Q

What are germline mutations?

A

Mutations that occur directly in a sperm or egg cell, or in one of their precursor cells.
This mutation will be inherited

37
Q

What are somatic mutations?

A

Mutations that occur directly in a body cell or in one of its precursor cells.
This mutation will not be inherited

38
Q

What is a polymorphism?

A

Genetic alteration that occur in more than 1% of the population and therefore are considered a normal variation in the DNA

39
Q

What are polymorphisms responsible for?

A

Responsible for many of the normal differences between people such as eye colour, hair colour and blood type.

40
Q

How do mutations correspond with genetic variation?

A

Mutations provide allelic variation.

For every gene there are many different alleles in a population thus the combination makes you unique.

41
Q

Define evolution

A

Genetic change in a population over time.

42
Q

What example is there for the duplication of genes?

A

Ancestral Globin gene was duplicated into alpha and beta types and thus later transposed to different chromosomes and followed further subsequent duplications and mutations

43
Q

Who has a higher mutation rate?

A

Men have a higher substitution mutation rate

Females have a higher deletion mutation rates

Molecular and Experimental Genetics (10 decks)

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