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Human Biology > Mutations > Flashcards

Mutations Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are gene pools?

A

sum of all alleles in a population

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2
Q

Allele frequency

A

how many of each allele of a gene occur in the gene pool

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3
Q

What are Mutations? where can it occur

A

a change in the DNA that can affect a single gene (gene mutations) or all/part of a chromosome (chromosomal mutations)
- occur in body or sex cells

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4
Q

What are somatic mutations?

A
  • occurs in body cells
  • often involved in cancerous grwoths
  • not inherited
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5
Q

What are germinal mutations?

A
  • occur in gametes
  • don’t usually affect individual but may be passed onto next generation
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6
Q

Two main types of mutations? and describe

A
  1. Gene mutations
    - Changes in a single gene so that traits normally produced by that trait are changed.
    - Occur during DNA replication
  2. Chromosomal mutations
    - all or part of a chromosome is affected.
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7
Q

What are causes of mutations?

A
  • Agents known to increase rate of mutation called mutagenic agents or mutagens - called induced mutations
  • Spontaneous mutations – random error in biological process-
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8
Q

What is a type of gene mutation?

A

Point mutation

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9
Q

What is point mutation?

A
  • change in only one base that could alter a protein, have no effect at all, or prevent the protein being produced
  • Within genes, the sequence of the bases in DNA is the code for amino acids used to build a protein.
  • If DNA of particular gene is altered, the protein it codes for could be missing or abnormal.
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10
Q

What are the 3 mechanisms of point mutation?

A
  • Inserted – new nucleotide added to DNA strand
  • Substituted – existing nucleotide is replaced with a different base
  • Deleted – a nucleotide is removed from the DNA strand
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11
Q

2 Examples of point mutation?

A

Albinism – mutation in gene for melanin production
- Effects: absence of pigment from hair, skin, eyes

Duchene muscular dystrophy – arises from mutation in mother which can be passed onto sons, or in male zygote
- Effects: wasting of leg muscles and later arms, shoulders and chest.
- Death occurs within failure of respiratory muscles

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12
Q

What is a Lethal recessive allele? what do they cause? and example

A
  • Most gene mutations produce a recessive allele called Lethal Recessive
  • They are recessive mutations which are lethal if not masked by dominant allele
  • Cause death of embryo or foetus, or early death of child
  • Eg. Tay Sachs Disease
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13
Q

What are chromosomal mutations?

A

Involve all or part of chromosome and affect a number of genes
- Cause abnormalities so severe, miscarriage often occurs in early pregnancy.

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14
Q

5 Types of chromosomal mutations

A

Deletion: part of chromosome lost
Duplication: section of chromosome occurs twice.
- Can happen when part of chromatid breaks off and joins to wrong chromatid.
Inversion: break occurs and broken piece joins back on wrong way around.
- Change order of gene and may disrupt pairing of homologous pairs in meiosis.
Translocation: part of chromosome breaks off and re-joined to wrong chromosome.
Non-disjunction: chromosome pair does not separate during meiosis and one daughter cell has extra chromosome while the other has one less.
- Aneuploidy – change in chromosome number

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15
Q

What are 3 examples of chromosmal mutation?

A
  • Trisomy: three copies of a chromosome (three copies instead of two)
    -eg Trisomy 21(Down Syndrome)
  • 3 of chromosome 21.
  • Result of non-disjunction
  • Intellectual disability, developmental delay
  • Monosomy: individual missing a chromosome (one copy instead of two)
  • eg Turner’s syndrome
  • Monosomy X (and no Y chromosome)
  • Females, short in stature, lack secondary sexual characteristics, infertile.
  • Partial trisomy/monosomy: part of extra chromosome/part of one chromosome missing
  • eg Cri-du-chat syndrome
  • Partial monosomy
  • Missing portion of chromosome 5
  • Problem with larynx and nervous system
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16
Q

What is frameshift?

A

when bases have been added or removed -> can affect the outcome for all the DNA from that point on

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17
Q

What are the 4 mutations that can be classified by effect?

A
  • Missesne mutations: cause a change in amino acid (and therefore, protein)
  • Nonsense mutations: change in the base sequence to code STOP, stopping protein synthesis and producing protein unable to function
  • Neutral mutations: cause change to amino acid, however, does not change the structure of protein enough to affect protein’s function
  • Silent mutation: does not change the amino acid (or protein).
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18
Q

What is evolution?

A
  • the change in characteristics of a species over time.
  • It is gradual and occurs over a number of generations.
  • reflects the changes in allele frequencies in populations, not individuals
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19
Q

Change in alleles present in a population may be due to…

A
  • New alleles forming due to mutation or introduced due to migration
  • Frequency of alleles changing due to selective pressures in natural selection or by chance in genetic drift.
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20
Q

3 Mechanims through which evolution occurs

A

Migration
Natural selection
Genetic drift

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21
Q

What is migration?

A

individuals moving between populations- enables gene flow

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22
Q

What is gene flow?

A
  • movement of genetic material from one population to another.
  • Individuals moving between populations (migration) enable gene flow.
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23
Q

What are barriers to gene flow and the types?

A

Barriers inhibit/hinder interbreeding between populations leading to separate gene pools forming.
- Barries classified by cause:
- Geographical barriers
- Sociocultural barriers:

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24
Q

What is Geographical barriers?

A

E.g. oceans, mountain ranges, deserts, expansive ice
Most common barrier for early humans.
E.g. First Nations people of Australia isolated by oceans as sea levels rose.

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25
Q

What is Sociocultural barriers?

A

developed as humans people more culturally complex
Language and religious groups, economic status, educational background and social position.
E.g. Basque people of Pyrenees (France & Spain) have unique language which has preserved culture and gene pool.

26
Q

What is Natural Selection?

A
  • the process by which a species becomes better adapted to its environment
  • individuals with favourable characteristics have a survival advantage and pass characteristics to next generation
  • there must be struggle for existence and those best suited to environment were more likely to survive (survival of the fittest).
  • environmental factor acting is selective agent
27
Q

What is sickle cell anaemia? how is it caused?

A
  • an example of natural selection operating in human operations
  • results when homozygous for a particular recessive allele of the HBB gene on Chromosome 11.
    →Point mutation changes amino acid from glutamic acid to valine altering the shape of the haemoglobin molecule
28
Q

What does sickle cell anaemia result in?

A
  • Results in sickle-shaped (crescent) red blood cells which:
  • Die early resulting in anaemia
  • Are inflexible and can become stuck in blood vessels causing blockages.
  • Complications include fatigue, jaundice, organ damage, high blood pressure, heart failure.
  • Often fatal.
  • found to provide resistance to malaria and therefore maintained in the gene pool in areas where malaria exists.
29
Q

What are the 3 effects of sickle cell anaemia of allele frequency/gene pools?

A
  • Heterozygotes for the sickle-cell trait were also found to be less susceptible to malaria and usually only affected by sickle-cell anaemia at low O2 conditions.
  • Having only one sickle-cell allele provides individuals living in malaria-prone areas a survival advantage = heterozygote advantage.
  • Presence of malaria acts as a selective agent.
30
Q

What are the 3 basic observations the theory of natural selection based on?

A
  • Variation: all members of a species vary and variation could be passed onto next generation.
  • Birth rate: all living organisms reproduce at rate greater than food supply and other resources increase.
  • Nature’s balance: although high birth rate, species numbers relatively constant.
31
Q

6 Summary points of natural selection?

A
  • There is variation of characteristics within a population
  • More offspring are produced than can possibly survive to maturity
  • Because of excessive birth rate and limited resources, there is struggle for existence (competition for survival).
  • Individuals with characteristics best suited to environment have more chance of surviving and reproducing – survival of the fittest.
  • Favourable characteristics are passed onto next generation.
  • In gene pool, proportion of alleles that produce favourable characteristics gradually increase
32
Q

2 Examples of Natural selection in humans

A
  • Features of human body correlate well with environments they occur in:
  • Long bodies and short limbs = smaller surface area for heat loss
    -> Inuit people indigenous to Arctic regions
  • Short bodies and long limbs = larger surface area for heat loss.
    ->People in very hot parts of Africa.
33
Q

What is Random genetic drift?

A
  • The random non directional change in allele frequency between generations that occurs by chance
  • allele that is rare in large populations can become frequent in small populations -> making it significant
34
Q

Two types of genetic drift

A
  • founder effect
  • bottleneck effect
35
Q

Founder effect

A

a small group (not representative of the original population) moves away from the homeland and establishes a community which later expands
- Because of size, chance can cause new groups to have:
- Different allele frequency
- Decreased genetic variation

36
Q

Bottleneck effect

A

occurs when a large population is reduced in size and the alleles present in the new gene pool are random -> survival not due to a specific trait

37
Q

What is Speciation

A
  • the process of new species evolving
  • not a mechanism for evolution, it can be a result of these changes (evolution) over a very long period of time.
38
Q

Explain the 4 steps to speciation?

A
  • Variation: a range of varations (Allele frequencies) exists within population, sharing a common gene pool

-Isolation: barrier has formed, diving population, no interbreeding occurs between two populations, each population has separate gene pool

  • Selection: diff selection pressures act on populations over a no. of generations, changes gene frequencies of each gene pool, leaf to evolution of diff sub species
  • Speciation: over a long period of time, change in gene frequencies may be great enough to prevent the production of fertile offspring between two populations = two species exist.
39
Q

What is a fossil

A
  • Any preserved trace left of an organism – including footprint, burrows, faeces, or impressions of all or part of animal or plant (e.g. teeth, bones, etc.)
  • Usually bones, teeth or footprints in case of humans, artefacts
40
Q

What are artefacts?

A

an object made or modified by humans

41
Q

How are fossils formed?

A
  • Parts of organisms buried by drifting sand, mud deposited by rivers, volcanic ash (not lava – too hot), collapsing caves, or other organisms.
  • Rapid burial slows/prevents decay.
42
Q

Where are fossils found?

A
  • human ancestors often found at edges of ancient lakes and river systems, caves or in volcanically active areas
  • cus the organism can be buried rapody, preventing devompsoiton.
  • lakes and rivers build up sentiments when flooding occurs or when water low slows rapidly.
43
Q

What are the 4 conditions requried for fossils to form?

A
  • quick burial
  • presence of hard body parts
  • absence of bone decay
  • long period of stability
44
Q

Fossilisation of bone

A
  • Wet, acidic soil dissolved bones - unless containing no oxygen (e.g. peat), then it may occur.
  • Alkaline soil produces best fossils – minerals in bones not dissolved.
  • New minerals (lime/iron oxide) deposited in pores petrifying it (turning to rock) while maintaining its structure.
45
Q

What is dating of fossils and types?

A
  • Dating: Determining the age of fossil/artefacts
    Able to provide:
  • Absolute dates: actual age of specimen in years
  • Relative dates: determine if one object older than another.
  • Age of fossils given in years ‘before present time’ – e.g. 45 000 years BP.
46
Q

4 Absolute dating fossils technqiues

A
  • Potassium-argon technique
  • Radiocarbon (carbon-14) dating
  • Accelerator mass spectrometry (AMS) radiocarbon dating
  • Dendrochronology (tree-ring dating)
47
Q

What is an isotope

A

different forms of same element with different number of neurons

48
Q

What is decay

A

emission of particle from nucleus

49
Q

What is potassium argon technique?

A

based on decay of radioactive potassium to form calcium and argon
- radioactive potassium-40(isotope) decays to calcium-40 and argon-40
→occurs slowly but at a constant rate
- amounts of potassium-40 and argon-40 in rock used to determine age of rock
- suitable rocks 100 000 - 200 000 years or older
→ usually produced in volcanic eruptions
material used: volcanic deposits

50
Q

What is radiocarbon dating?

A

based on decay of carbon-14 to nitrogen
- for every one carbon-14 atom, there is million million carbon-12 atoms
→ incorporated into plant tissue and then animal tissue when consumed
→ intake stops at death and then decays at fixed rate
- amount of radiation from sample measured to estimate carbon - 14 to carbon -12 radio and determine age
- Carbon dating cannot be used for samples older than 60 000 years – no carbon-14 left in sample.

51
Q

What is Accelerator mass spectrometry (AMS) radiocarbon dating?

A
  • more refined used to date smaller sample (~100 micrograms)
  • Involves breaking sample into atoms so number of each carbon isotope can be counted.
  • Became possible to date cave paintings accurately from tiny samples of pigment (made from charcoal, honey, milk, blood, seed oil, etc.)
  • material used: carbon compounds
    LIMITATIONS:
  • Carbon dating cannot be used for samples older than 60 000 years – no carbon-14 left in sample.
  • Sample must contain organic matter
52
Q

What is Dendrochronology

A

aka tree dating
- Concentric rings within a tree trunk examined – particular rings produced during exceptional weather conditions used as markers.
- By comparing living trees with timber taken from ancient human structures, dates of building can be determined.
- material used: wood
- dating can be used for samples that are up to 9000 yrs old

LIMITATIONS:
- Timber rarely preserved more than a few thousand years

53
Q

2 relative dating techniques?

A
  • Stratigraphy
  • Fluorine dating
54
Q

What are index fossils

A

common/widely distributed/only present at particular time -> used to compare strata in different locations

55
Q

What is stratigraphy?

A

study of layers, or strata.
- principle of superposition: younger layers of rock at the top
- Correlation of strata: matches rocks in different areas by matching rock and fossils it contains.
- Fossilised pollen grain: can be used as index fossils and allow botanists to determine vegetation through time

56
Q

What is fluorine dating?

A
  • When bone is left in soil, fluoride ions from water and soil replace some of the ions in the bone.
  • Older fossils will contain more fluoride.
  • Concentration of fluoride varies between places so unable to determine absolute age
57
Q

What are problems with the fossil record?

A
  • correct conditions don’t always occur making fossils a chance occurrence
  • small portion of fossils testing have been discovered
  • dating fossils can be problematic
  • unusual to find fossil of an entire organism -> often only a few fragments of bone
58
Q

What are phylogenic trees?

A
  • Represents Probable evolutionary relationships between organisms derived from common ancestor
  • Ancestral organism forms ‘base’ of the tree and organisms which arise are placed on ends of ‘branches’.
  • Closely related organisms are closer together.
  • Useful for showing evolutionary pathways.
59
Q

Biomedical evidence for evolution: Protein sequences

A
  • by comparing the type and sequences of amino acids in a similar proteins from diff species, the degree of similarity can be established
  • the degree of diff between proteins enables an estimate to made of the amount of evolution that has taken place since two species developed from common ancestor.
  • longer the period of time, greater number of amino acids diff
60
Q

What are ubiquitous proteins?

A

one of a group of proteins that appear to be in all species, called ubiquitin - present in all types of cells
- perform basic, essential tasks
- eg cytochrome C

Human Biology (6 decks)

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