Mutations/evolution 2 Flashcards

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1
Q

Define evolution

A

Change in characteristics of a species overtime due to changes in allele frequencies

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2
Q

Distinguish difference between genotypes and phenotypes

A

phenotype: observable characteristics in an individual resulting from expression of gene

genotype: genetic makeup of an organism (specific alleles inherited for particular trait)

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3
Q

Define population

A

group of organisms of same species living together in a particular place at particular time

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4
Q

Define gene pool

A

sum of all alleles in a given population

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5
Q

Define allele frequency. What can be determined by allele frequency variation

A

how common an allele is in a given population. Variation in allele frequencies reflect differences in characteristics

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6
Q

Define mutation. What are the two main types

A

Change in the DNA sequence of an organism leading to new characteristics in said organism
- Chromosomal; effect multiple genes, therefore, all/part of chromosome affected. May change chrom. structure/number
- Gene; changes in single gene so traits normally produced by gene are destroyed/changed

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7
Q

Explain the causes of organism mutations.
Include examples

A

May often occur spontaneously due to random errors in meiosis/mitosis or…
Mutagenic agents/mutagens- environmental agents that increase the rate of/induce mutation e.g. mustard gas, xrays

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8
Q

How are mutations classified

A

1.Induced or spontaneous
2.Hereditary or not
3.Effect
4.Extent of mutation

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9
Q

Define somatic mutations

A

Occur to all somatic/body cells excluding gametes.
Cannot be passed onto offspring
Only tissues derived from the mutated cell are effected i.e. cancer

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10
Q

Define germinal/germline mutations

A

Occur in gametes/reproductive cells
can be passed onto offspring/inherent
Every cell in entire organism will be effect
e.g. PKU(phenylketonuria-prevent AA phenylalanine breakdown

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11
Q

What are the effects of protein mutations

A

Missense: change in the amino acid and therefore protein production

Nonsense: change in base sequence to code to STOP (synthesis of protein will stop=short, less well functioning strand)

Neutral: change in amino acid (same type) does not change the protein’s structure enough to alter it’s function

Silent: do not cause any change in amino acid and therefore protein produced

All substituted nucleotide

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12
Q

Define point mutation. What are the three changes in DNA as a result of gene mutation

A

Due to change in single nucleotide (one base changed)
Substitutions-existing nucleotide replaced with another one, with different base
Insertion-new nucleotide added to DNA strand
Deletion-nucleotide removed from DNA strand

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13
Q

Define frameshift. How does it occur

A

Result form point mutations-occurs when base is inserted/deleted and changes the way codons are read from point in DNA

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14
Q

What changes in long DNA segments/chromosomes come as a result of chromosomal mutation

A

Duplication: section of chromosome occurs twice
Deletion: piece of DNA is removed
Inversion: breaks occur in a chromosome and the broken piece joins back in, but wrong way around
Translocation: part of chromosome breaks off and is re-joined to wrong chromosome
Non-disjunction: during meiosis, chromosome pair does not separate and so one daughter cell has extra chromosome and one daughter cell has one less than normal number (aneuplody)

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15
Q

Conditions caused by gene mutation

A

Duchenne muscular dystrophy
Cystic fibrosis: inherited from both parents only. Salty skin taste, coughing, wheezing
Tay-sachs disease (lethal recessive)- fatal, inherant condition lethal if not masked by dominant allele. Death in early childhood due to disorder of lipid metabolism

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16
Q

Conditions caused by chromosomal mutation

A

Trisomy (result of non-disjunction) failure of one or more chromatid separations in second division of meiosis=down syndrome or trisomy-21, child has three of chromosome-21
Monosomy missing a chromosome either full or partially.

17
Q

Define gene flow. Attachment to migration?

A

movement of alleles from one population to another through migration

18
Q

What are the barriers of gene flow? Include examples

A

Inhibit interbreeding between populations due to enforced isolation
Geographical: oceans, mountain ranges, large lake systems, deserts and expansive ice sheets.
Sociocultural: economic status, educational background, social position, religion and language, ethnic origin

19
Q

Define species

A

group of organisms that shares similar characteristics and are able to interbreed to produce fertile offspring

20
Q

Define geneticists

A

specialise in studying inheritance

21
Q

Define allele

A

alternate form of same gene

22
Q

Describe Darwins observations

A

Variation: all individual in species vary
Birth rate: organisms reproduce at a rate greater than that at which food supply and other resources increase
Natures balance: species numbers remain at a constant level despite high birth rate

23
Q

Define variation

A

The differences that exist between individuals of a population or species

24
Q

Describe survival of the fittest

A

Organisms with favourable characteristics will survive, while those with unfavourable died before reproducing and passing on trait

25
Q

Describe struggle for existence

A

due to larger birth-rate to resources and food available for all organisms, there is competition for resources

26
Q

Define selective agent

A

Any factor that cause death of organisms with certain characteristics, but which has no effect on individuals without those characteristics

27
Q

Define the principles of evolution/natural selection

A
  1. Variation within species
  2. More offspring produced than can survive till adulthood
  3. Struggle for existence
  4. Individuals with favourable characteristics will survive and reproduce
  5. Favourable characteristics passed onto offspring
  6. Proportion of favourable alleles gradually increases
28
Q

Provide and example of evolution due to natural selection
(e.g. body stature?)

A

Body stature
- long bodies and short limbs have smaller SA to body volume ratio
-less heat loss in cold environments
-survival advantage
Sickle cell anaemia
-immunity to malaria

29
Q

Explain how the incidence of sickle-cell alleles increase in areas prone to malaria

A
  1. Variation in genes
  2. More offspring than can survive adulthood
  3. Struggle for existence
  4. Individuals heterozygous for sickle cell anaemia were less susceptible to malaria = heterozygote advantage
  5. Presence of malaria acted as selective agent for the sickle cell allele, where heterozygous individuals had selective advantage
30
Q

What are the symptoms and effects of sickle cell anaemia
What is it’s population frequency

A

Inflexible, crescent shaped sickle cell red blood cells cause blockage of blood vessels, fatigue, jaundice, heart failure, etc
-black african community

31
Q

What causes speciation? Describe the steps involved

A

Isolation prevents reproduction between two populations (no gene flow as a result), causing them to be regarded as separate species overtime
1. Variation: Variation between individuals of a species
2. Isolation: Populations of same species are isolated without gene flow (barriers w/examples)
3. Selection: no two environments same therefore each population is subjected to different selective agents
4. Speciation: Allele frequency changes until they become so different that the two groups no longer are able to interbreed and produce fertile offspring

32
Q

Define genetic drift. Differentiate it’s presence in opposingly sized populations.

A

Random, non-directional change in allele frequencies between generations, usually more noticeable in smaller populations.
Rare allele in large population can become frequent in small

33
Q

Describe founder effect (genetic drift) providing an example

A

When small groups move away from homeland to establish new, smaller population which later expands. Causes
- different allele frequency from original population
- decreased genetic variation

Bentley glass and dunkers
-religion opposed outside of group marriage, causing isolated breeding within population causing certain characteristics to become more common in comparison to surrounding society

34
Q

Describe bottle effect (genetic drift) providing an example

A

When population is sharply reduced due to an event such as a natural disaster.

Pingelap typhoon , population reduced to 20. One individual was heterozygous for achromatopsia. Due to isolated breeding, 5% population shares similar trait while surrounding society only 0.0033%

35
Q

What causes changes to allele frequencies

A

Selection pressures, random assortment, non-disjunction, crossing over, random fertilisation, mutation

36
Q

Define selection pressures

A

Factors that affect an organisms ability to survive within the environment

37
Q

Using Tay-Sachs disease as an example, outline what a lethal recessive is

A

fatal, inherant condition lethal if not masked by dominant allele. Death in early childhood due to disorder of lipid metabolism

38
Q

Describe Thalassemia and it’s population frequency

A

an autosomal recessive gene mutation (inherited disorder) caused when the body doesn’t make enough of a protein called hemoglobin
-mediterranean coast and S.E. africa