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Biology > Patterns of inheritance > Flashcards

Patterns of inheritance Flashcards

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1
Q

What is continuous variation?

A

Characteristics that can take any value in a range.

Affected by genes and the environment, polygenic, quantitative.
eg. height

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2
Q

What is discontinuous variation?

A

Characteristics that can only appear in specific values.

Affected by genes only, monogenic, qualitative.
eg. blood type

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3
Q

What is a locus?

A

A position on a chromosome where a certain allele is found.

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4
Q

What is an allele?

A

A copy or variant of a gene.

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5
Q

What is variation and what causes it?

A

A difference in characteristics of organisms of the same species. It is when genetic mutations cause new alleles.
Can be due to genetics or the environment or both.

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6
Q

What are examples of variation?

A

Body mass - due to both. Large variations in species because of their environments.
Chlorosis in plants - lack of light, mineral deficiencies or a viral infection.

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7
Q

What causes genetic variation?

A

Sexual reproduction, as gametes are randomly fertilised. Crossing over and independent assortment during meiosis to form gametes.

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8
Q

What is codominance?

A

Both alleles are expressed as the organism is heterozygous.

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9
Q

What is monogenic inheritance?

A

It shows 2 alleles of the same gene being inherited.

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10
Q

What happens when multiple alleles are present?

A

More than 2 alleles are possible for any gene, so a gradient of dominance is observed in phenotypes.
eg. hair colour, skin colour

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11
Q

What is dihybrid inheritance?

A

When an individual inherits 2 characteristics that are controlled by different genes.

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12
Q

Who investigated dihybrid inheritance?

A

Mendel, with pea plants.

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13
Q

What is epistasis?

A

An allele at a certain locus masks the expression of alleles of other genes.

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14
Q

What are the 2 types of epistasis?

A

Recessive - 2 recessive alleles at 1 locus mask another
Dominant - 1 dominant allele masks another

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15
Q

What is an autosome?

A

Any chromosome that is not a sex chromosome.

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16
Q

What is autosomal linkage?

A

2 genes located on the same autosome, close together. It is very likely they are inherited together on the same chromosome.
Recombinant chromosomes do form, but they are rare.

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17
Q

Why does the observed ratio differ from the expected ratio?

A

Alleles are linked, so certain gametes are more likely to be made.
Therefore these genotypes are the most common in the offspring.
Crossing over makes some recombinant gametes, just less than expected.

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18
Q

What is sex linkage?

A

When certain genes are found on 1 sex chromosome only. Genetic inheritance can be sex linked if it depends on only the sex chromosome to be passed on.

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19
Q

Why do men have more sex linked genetic conditions?

A

Y chromosome is shorter, so it does not carry some genes. Recessive alleles are more likely to be expressed on their X chromosome.

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20
Q

What is a hypostatic gene?

A

A gene that can be masked by an epistatic gene.

21
Q

How does epistasis work?

A

If a trait is determined by the interaction of 2 genes, gene B encodes for an enzyme or an inhibitor. This stops the enzymes working so there is no colour change.

22
Q

What statistical test is used?

A

Chi squared

23
Q

What is polygenic inheritance?

A

Multiple genes are present at different loci. Alleles interact and give an additive effect on the phenotype. So it varies continuously in a quantitative way.

24
Q

What is evolution?

A

The frequency of an allele within a population over time.

25
Q

How does evolution occur?

A

Genetic drift and natural selection.

26
Q

What are the steps for evolution?

A
  • Species shows genetic variation due to genetic mutation
  • Competition for abiotic/biotic factors lead to selection pressures
  • Some have beneficial alleles which are passed on
  • This frequency increases over time
27
Q

What are the 3 types of selection?

A

Stabilising - middle phenotype selected for.
Directional - 1 extreme phenotype will live.
Disruptive - 2 distinct groups as both extremes live.

28
Q

What is a species?

A

Organisms that can reproduce to produce fertile offspring.

29
Q

What is a gene pool?

A

All alleles for all genes in a breeding population.

30
Q

What is the allele frequency?

A

Proportion of a particular allele within a gene pool.

31
Q

What is genetic drift?

A

Chance dictates which alleles are passed on. With a small population, it is more likely alleles are lost as have bigger effect.

32
Q

What is the bottleneck effect?

A

A dramatic decrease in population size, decreasing genetic variation. Remaining organisms have different allele frequencies. eg. overhunting. `

33
Q

What is the founder effect?

A

New population is established from a very small number of organisms from a parent population - different allele frequencies.

34
Q

How can genetic diversity be measured?

A

Polymorphism.

35
Q

What factors affect allele frequency?

A
  • genetic drift
  • environmental changes
  • mutation rate
  • migration
  • non random mating
  • gene flow
36
Q

What is the Hardy-Weinberg principle?

A

Predicts that allele frequency will not change between generations.

37
Q

What are the assumptions of the Hardy-Weinberg principle?

A
  • no selection, mutation or migration
  • large population
  • random mating
  • no genetic drift
38
Q

What is speciation?

A

Splitting of a genetically similar population to form 2+ populations. Undergo genetic differentiation and reproductive isolation to form 2+ species.

39
Q

What is allopatric speciation?

A

Geographical isolation.
2 environments on either side of the barrier -> separate gene pools.
Mutation leads to variation so they can no longer interbreed. There is no gene flow between groups.
Allele frequencies change over many generations.

40
Q

What is sympatric speciation?

A

Reproductive isolation.
Genetic mutations are rare because of genetic recombination and it is hard to isolate without a barrier.

41
Q

What are the mechanisms of sympatric speciation?

A

Temporal (active different times), behavioural, gametic (incompatible), different courting rituals.

42
Q

What is assertive mating?

A

Between more similar members of a population to form 2 separate breeding populations.
No longer interbreed.

43
Q

What is artificial selection?

A

Humans select organisms with desired characteristics and interbreed them for particular characteristics.

44
Q

What are examples of artificial selection?

A

Animals - increased yield, docile natures, aesthetics
Plants - bigger fruit, increased yield, drought/pest resistant, big seeds.

45
Q

How does hybrid vigour work to reduce inbreeding depression?

A

If related individuals interbred, inbreeding depression occurs. Likelihood of inheriting 2 recessive alleles for harmful characteristics.
Outcross to increase heterozygosity = hybrid vigour.

46
Q

What are gene banks?

A

Store unusual gene variants to:
- rebuild rare populations
- increase genetic diversity
- prepare crops for climate change
- preserve cells with unusual alleles

47
Q

Evaluation for artificial selection?

A

POSITIVE: very high yields, select for service animal traits.
NEGATIVES: increased genetic problems, not survive in the wild, not enough fat for insulation.

48
Q

What is stored in gene banks?

A

Semen, blood, embryos, seeds, blood, stem cells.

Biology (32 decks)

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