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Biology 4 > Changes in genetic makeup of populations > Flashcards

Changes in genetic makeup of populations Flashcards

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1
Q

What did Charles Darwin recognise?

A

If evolutionary change was to occur in a population, it could only do so if inherited variation was present in that population.

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2
Q

What is an adaption?

A

Any heritable trait that suits an organism to its natural function in the environment.

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3
Q

What is fitness?

A

Mathematical measure of contribution an organism makes to the next generation.
An observed fitness value for a phenotype is not fixed, but applies under a particular set of environmental conditions.

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4
Q

What did Darwin and Wallace propose?

A

That new species could develop by a process of natural selection.

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5
Q

What does polymorphic refer to?

A

When several discrete inherited variations are present in the members of a population
Polymorphic traits are encoded by one gene with 2 or more alleles.

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6
Q

What is a selective advantage?

A

Relative higher genetic fitness of a phenotype compared with other phenotypes controlled by the same gene.

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7
Q

What is a discrete trait?

A

Non-overlapping variants which are controlled by a single gene.

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8
Q

Explain what variation due to a single gene involves?

A

The inherited traits will exist as 2-3 discrete variants.

Often these genses will be controlled by two common alleles.

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9
Q

What is discontinuous variation?

A

Describes variation within a population that consists of a few discrete non-overlapping phenotypes.

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10
Q

What does monomorphic refer to?

A

Refers to a population in which all members are identical with regard to a particular phenotypic trait.

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11
Q

What is continuous variation?

A

Within a population, describes variation that forms a continuum of phenotypes, differing to a small degree from one another
Eg. the heights of adult human males.

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12
Q

What is continuous variation controlled by?

A

Polygenes.

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13
Q

Define polygenes.

A

A group of several genes in which each acts in a small but cumulative manner on a trait.

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14
Q

What would a greater number of polygenes infer?

A

Greater the number of polygenes, the greater the number of possible variants, therefore greater variation.

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15
Q

True or false?
For traits controlled by polygenes, the variation seen in members of a population falls into a few non-overlapping classes.

A

False .

The variation does not fall into a few non-overlapping classes. Variants are distributed across a continuous range

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16
Q

What is polyploidy?

A

Polyploidy refers to a condition in which an organism has more than two matched sets of chromosomes.

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17
Q

Is polyploidy more common in animals or plants?

A

More common in plants, very rare in animals.

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18
Q

What is autopolyploidy?

A

Organism with more than two sets of chromosomes derived from the genome of one species.
A polyploid individual will have additional complete sets of chromosomes from its own species

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19
Q

What is allopolyploidy?

A

Organism with more than two sets of chromosomes derived from the genomes of at least two different species.
Additional chromosome sets in a polyploidy may come from another species
Usually display superior qualities.

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20
Q

How can polyploidy occur?

A
  • duplication of chromosome number

- hybridisation

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21
Q

What is an aneuploid?

A

Cell or organism in which the total number of chromosomes is not an exact multiple of the haploid number owing to a missing or an additional single chromosome.

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22
Q

Are aneuploid changes usually tolerated by an organism?

A

Aneuploid changes in chromosome numbers are generally poorly, if at all, tolerated in animals but can be tolerated in polyploidy plants.

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23
Q

What is a gene pool?

A

Sum total of genetic information present in a population.

They are described by by the frequencies (proportions) of the alleles of each gene present.

24
Q

How can allele frequencies be changed in a populations gene pool? (5)

A
  • mutations (point, frameshift, block) source of new alleles
  • chromosomal abnormalities: aneuploidy and polyploidy
  • environmental selection pressures on phenotypes as the mechanism for natural selection
  • gene flow
  • genetic drift: bottleneck and founder effect
25
Q

Define evolution.

A

Is the genetic change in a gene pool of a population over time.

26
Q

Explain what the hardy-Weinberg principal.

A

Concept that allele frequencies in a population remain constant from one generation to the next unless an agent of change acts on the population.

27
Q

What are the conditions that apply in a population if allele frequencies are to remain constant over generations? (5)

A
  • population must be large.
  • members must mate at random
  • all matings are equally fertile, producing equal numbers of viable offspring at same rate
  • the population must be closed, no migration into or out
  • no mutations
28
Q

What agents can cause allele frequencies to change over time? (3)

A
  • selection
  • gene flow or migration
  • chance, as seen in genetic drift, bottlenecks and founder effects.
29
Q

Define natural selection.

A

The process by which new heritable traits, whether morphological, physiological or behavioural, evolve and persist in a population in the wild.

30
Q

Define selecting agent.

What are the three types, provide examples?

A

Any factors that affect the survival or fertility of members of a population such that variation is produced in different phenotypes.

  • chemical agent: pollutants in soil or water.
  • physical agent: climate change or food shortages
  • biological agents: infectious diseases, predation or competition
31
Q

When does natural selection occur?

A

Occurs when any selecting agent acts on a population in the wild and produces differences in the survival and reproduction rates of variants in that population.

32
Q

What is differential reproduction?

A

Occurs when different inherited varieties in a population vary in their rates of production of viable offspring.

33
Q

What are the two levels of selection which act on phenotypes? Provide an explaination.

A
  • Complete selection: occurs when any organism with a given phenotype cannot reproduce because of death before reproductive age is reached or because of sterility.
  • Partial selection: occurs when matings involving that phenotype produce on average fewer viable and fertile offspring relative to other matings.
34
Q

What is gene flow?

A

The movement of individuals or the genes they carry (through interbreeding) from one population to another.

35
Q

What is allele frequency?

A

The relative frequency a particular version of a gene (allele) has within a population.

36
Q

What are the 4 types of chromosomal abnormality?

A
  • Aneuploidy: individual possesses an abnormal number of chromosomes.
  • Monosomy: An organism has a diploid number, but one is missing its homologous partner
  • Trisomy: An organism has a diploid number, but one has an extra homologous pair
  • Polyploidy: Where an individual carries 3 or more complete sets of chromosomes (e.g. 3n)
37
Q

What is genetic drift?

Provide 2 examples.

A

The change in allele frequency over time, caused by random events. Extreme examples of this are the founder effect and the bottleneck effect.

38
Q

Explain what the bottle neck effect is.

A

Random, drastic reduction in a population (e.g. due to a natural disaster), which changes the gene pool.
The gene pool is limited to the alleles the survivors had. not include population reductions as a result of environmental changes (this would be natural selection).

39
Q

Is the reduction of a population due to environmental changes an example of the founder effect?

A

No, this would be natural selection.

40
Q

Explain what the founder effect is.

A

Where members of a larger population establish a new population in a new (biologically) isolated area. The gene pool of the new population is limited to those the founders carried.

41
Q

For each of the following state whether the variation within a population would increase/ decrease:

a) mutations
b) genetic drift
c) natural selection
d) gene flow

A

a) mutations: increase
b) genetic drift: decrease
c) natural selection: decrease
d) gene flow: increase

42
Q

For each of the following state whether the variation between a population would increase/ decrease:

a) mutations
b) genetic drift
c) natural selection
d) gene flow

A

a) mutations: increase
b) genetic drift: increase
c) natural selection: increase
d) gene flow: decrease

43
Q

Does natural selection result in the change of allele frequencies?

A

Due to the differential survival and reproduction of genotypes within a population, allele frequencies will change.

44
Q

Does natural selection act on the genotype of phenotype?

A

Phenotype.

45
Q

Define sexual selection.

A

Sexual selection occurs whenever there is a trait giving some individuals a preferential advantage in mating and in producing offspring.

46
Q

Define species.

A

A group of closely related organisms that are capable of interbreeding to produce viable, fertile offspring.

47
Q

What is selective breeding?

A

Artificial (human) selection of traits that appeal to us. The deliberate selection by a breeder of specific animals to provide the genetic material for the next generation

48
Q

What is the difference between aneuploidy and polyploidy?

A

Aneuploidy refers to the condition in which an organism has a chromosome number that differs by a small number from the standard chromosome number for its species. Polyploidy refers to a condition in which an organism has more than two matched sets of chromosomes.

49
Q

What is the difference between continuous and discontinuous variation?

A

Continuous variation is the variation seen, in members of a population, that does not fall into a few non-overlapping classes. Instead, the variants are distributed across a continuous range. Discontinuous variation is the variation seen, in members of a population, that falls into two or a small number of distinct groups. There are no overlapping classes.

50
Q

What is the difference between autopolyploid and allopolyploid organisms?

A

Autopolyploidy exists when a polyploid individual has additional complete sets of chromosomes from its own species. Allopolyploidy exists when a polyploid individual has additional chromosome sets from another species.

51
Q

Would a triploid plant be expected to be fertile?

A

Infertile.
Chromosomes may have difficulty ‘pairing’ during prophase 1 of meiosis, and viable gametes are less likely to be produced.

52
Q

Identify what is key between a genotype and a gene pool.

A

The genetic information in an individual is a genotype, while the genetic information in a population is a gene pool.

53
Q

In a plant population, some phenotypes survive periods of drought better than other phenotypes. What might be expected if this population was exposed to drought conditions for several generations?

A

It is reasonable to predict that continuous exposure of this population to drought over several generations would result in selection of those plants that are physiologically better adapted to drought conditions. These plants would survive and reproduce, whereas plants lacking alleles coding for drought-resistance would reproduce less well and, in many cases, would not survive to reproduce. It may be predicted that, over several generations, if drought conditions persisted, the frequency of alleles conferring drought resistance in this population would increase.

54
Q

What are the similarities between the bottleneck effect and the founder effect?

A

Both bottleneck events and founder effects are examples of genetic drift. Both are likely to cause a decrease in genetic diversity.

55
Q

What are the differences between the bottleneck effect and the founder effect?

A

A founder effect involves individuals from one population migrating to a new area and a new population being established. A bottleneck does not involve individuals migrating but rather the death of a large number of individuals within a population.

56
Q

Identify two consequences for AI when technology allowed semen to be successfully frozen.

A
  • the fertilisation of females located hundreds or thousands of kilometres distant from the stud animal, because its frozen sperm can be easily transported
  • the fertilisation of female animals and the production of offspring long after the stud animal’s death.

Biology 4 (9 decks)

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