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Biology Module 6 > Chapter 2 Patterns of inheritance > Flashcards

Chapter 2 Patterns of inheritance Flashcards

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1
Q

Definition of genotype?

A

Genetic makeup of an organism

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2
Q

Definition of phenotype?

A

Visible characteristic of an organism

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3
Q

Genome definition?

A

Total DNA content of a cell or an individual organism

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4
Q

What is meant by polygenic?

A

Determined by several genes

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5
Q

What are some physical mutagenic agents?

A
  • X-rays
  • Gamma rays
  • UV light
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6
Q

What are some chemical mutagenic agents?

A
  • Nitrous acid
  • Mustard gas
  • benzopyrene (tobacco smoke)
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7
Q

What are some biological mutagenic agents?

A
  • Some viruses
  • Transposons (remnants of viral nucleic acid)
  • Food contaminants such as mycotoxins from fungi
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8
Q

What are the 5 types of chromosome mutations that occur during meiosis?

A
  • deletion
  • inversion
  • translocation
  • duplication
  • non-disjunction
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9
Q

What is the chromosome mutation inversion?

A

A section of a chromosome breaks off, turns 180 degrees and join again. Some genes may be too far away from their regulatory nucleotide sequences to be properly expressed

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10
Q

What is the chromosome mutation deletion?

A

Deletion - part of a chromosome (containing genes and regulatory sequences) is lost

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11
Q

What is the chromosome mutation translocation?

A

A piece of one chromosome breaks off and become attached to another chromosome.

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12
Q

What is the chromosome mutation duplication?

A

A piece of a chromosome may be duplicated. Too many of certain proteins may disrupt metabolism

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13
Q

What is the chromosome mutation non-disjunction?

A

One pair of chromosomes/ chromatids fails to separate, leaving one gamete with an extra chromosome.

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14
Q

What is meant by aneuploidy?

A

When a chromosome number is not an exact multiple of the haploid number for that organism (e.g. trisomy).

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15
Q

What is meant by polyploidy?

A

When a diploid gamete is fertilised by a haploid gamete or 2 diploid gametes are fused, resulting in more than 2 sets of chromosomes.

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16
Q

What does genetic variation result from during meiosis?

A
  • Allele shuffling during crossing over in prophase 1 (swapping of alleles between non-sister chromatids)
  • Independent assortment of chromosomes during metaphase 1/ anaphase 1
  • Independent assortment of chromatids during metaphase 2/ anaphase 2
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17
Q

What is meant by monogenic?

A

Determined by a single gene

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18
Q

What is meant by dihybrid?

A

Involving 2 gene loci

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19
Q

What is an allele?

A

Different versions of the same gene

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20
Q

What is co-domidance?

A

Where both alleles present in the genotype of a heterozygous individual contribute to the individual’s phenotype

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21
Q

What are some examples of codominance?

A
  • ABO blood group (phenotypes - A,B,AB,O, where A and B are codominant and O is recessive)
  • Coat colour in rabbits
  • Sickle-cell anaemia (codominant if type of haemoglobin is the phenotype)
  • Flower colour
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22
Q

What are some examples of multiple alleles?

A
  • ABO blood group
  • coat colour in rabbits
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23
Q

What are autosomal chromosomes?

A

All chromosomes except sex chromosomes

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24
Q

How many genes does the X chromosome carry?

A

1000

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25
Q

What are some examples of sex-linked characteristics?

A
  • Haemophilia A (blood is unable to clot)
  • Red-green colour blindness
  • Duchenne muscular dystrophy
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26
Q

What is autosomal linkage?

A

Two genes are located on the same autosome and are more likely to be inherited together because they are less likely to be separated during crossing over.

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27
Q

When there is autosomal linkage between two genes, how many possible combinations of alleles are there in the gametes?

A

2

28
Q

What is epistasis?

A

Interaction of non-linked genes where one masks the expression of the other

29
Q

What is meant by complementary and antagonistic epistasis?

A

Antagonistic epistasis refers to when a gene is inhibiting expression of another. Complementary epistasis refers to when a gene is encouraging expression of another.

30
Q

Which is the epistatic gene?

A

The gene that is suppressing/ affecting another gene

31
Q

Which is the hypostatic gene?

A

The gene that is being suppressed/ affected in epistasis

32
Q

What is meant by recessive epistasis?

A

Presence of a homozygous recessive genotype prevents the expression of the second gene

33
Q

What is meant by dominant epistasis?

A

Presence of a homozygous dominant or heterozygous genotype prevents the expression of the second gene

34
Q

What is an example of:
a) recessive epistasis
b) dominant epistasis
c) complementary epistasis

A

a) Salvia plant flower colour
b) Feather colour in chickens
c) Coat colour in mice

35
Q

What is the chi-squared test used for?

A

To find out if the difference between observed and expected data is significant or due to chance.

36
Q

What is discontinuous variation?

A

Genetic variation producing discrete phenotypes - two or more non-overlapping categories

37
Q

What is continuous variation?

A

Variation that produces phenotypic variation where the quantitative traits vary by very small amounts between one group and the next

38
Q

What are some factors affecting allele frequencies within populations?

A
  • population size
  • mutation rate
  • migration
  • natural selection
  • changes to the environment
  • genetic drift
  • founder effect
  • non-random mating
39
Q

What are the 3 main types of natural selection?

A

Stabilising, directional and disruptive

40
Q

What is disruptive/ diversifying selection?

A

Selection pressure toward the extremes creates two modal values. It favours extreme phenotypes.

41
Q

What is stabilizing selection?

A

Natural selection leads to constancy within a population. Intermediate phenotypes are favoured.

42
Q

What is directional selection?

A

An environmental change favours one extreme, resulting in a change in population mean.

43
Q

What is an example of stabilizing selection?

A

Human birth weight

44
Q

What is an example of directional selection?

A

Antibiotic resistance

45
Q

What is an example of disruptive selection?

A

Rabbits are black, white or agouti. Black and white rabbit have advantages so agouti is less common.

46
Q

Definition of gene pool?

A

All the genes and alleles of the breeding individuals in a population at a particular time.

47
Q

What is genetic drift?

A

Neither allele has an advantage/ disadvantage, so evolution is down to chance and occurs due to random events such as natural disasters or diseases rather than selection pressures.

48
Q

What is a genetic bottleneck?

A

A sharp reduction in size of a population due to environmental catastrophes, which also reduces genetic diversity. As the population expands it is less genetically diverse than before.

49
Q

What are possible causes of genetic drift?

A

A genetic bottleneck or the founder effect.

50
Q

What is the founder effect?

A

When a small sample of an original population establishes in a new area. It’s gene pool is not as diverse as that of the parent population.

51
Q

What is the definition of population?

A

Members of a species living in the same area at the same time, that can interbreed.

52
Q

What does the Hardy-Weinberg model assume?

A
  • Mating in the population occurs at random
  • The population is experiencing no selection
  • The population is large enough to make sampling error negligible
  • The population has no mutation, migration or genetic drift
53
Q

What are the 2 equations that show allele frequencies determine genotype frequencies?

A

p^2 +2pq + q^2 = 1
p + q = 1

54
Q

What is speciation?

A

The splitting of a genetically similar population into 2 or more populations that undergo genetic differentiation and eventually reproductive isolation, leading to the evolution of 2 or more new species.

55
Q

What is allopatric speciation?

A

Formation of 2 different species from one original species, due to geographical isolation.

56
Q

What is sympatric speciation?

A

Formation of 2 different species from one original species, due to reproductive isolation, while the populations inhabit the same geographical location.

57
Q

What is geographical isolation?

A

Occurs when physical barriers divide a population so isolated populations experience different selection pressures and each population becomes adapted to their environment (allopatric speciation).

58
Q

What is reproductive isolation?

A

Biological or behavioural changes preventing 2 populations from successfully breeding together (sympatric speciation).

59
Q

Examples of changes leading to reproductive isolation?

A
  • Change in chromosome number may prevent gamete fusion, make zygotes less viable or produce infertile hybrid offspring
  • Changes in courtship behaviour, e.g. time of year mating occurs
  • Changes in animal genetalia or flower structure
60
Q

What is artificial selection?

A

Selectively breeding organisms; involves humans choosing desired phenotypes and interbreeding those phenotypes individually.

61
Q

What is the selecting agent for artificial selections?

A

Humans

62
Q

What is a negative affect of artificial selection?

A

Interbreeding depression - The genetic diversity in the gene pool of the selected breed is reduced so the chances of an individual inheriting 2 copies of a recessive harmful allele are increased.

63
Q

What can breeders do to avoid interbreeding depression?

A

Hybrid vigour - Outcross individuals belonging to two different varieties, to obtain individuals that are heterozygous at many gene loci.

64
Q

What are gene banks and some examples?

A

They store genomes, but in their organisms, e.g.
- rare breed farms
- seed banks
- sperm banks
- wild populations of organisms
- botanic gardens
- zoos

65
Q

What are some ethical considerations of artificial selection?

A
  • domesticated animals retain many juvenile characteristics, making them less able to defend themselves and easy pray
  • Livestock are selected to have less fat so might succumb to low temperatures during winter if not housed
  • Some dog breeds have susceptibility to disease
  • Some coat colours of dogs would fail to camouflage them
  • Some selected dog traits might put them at a selective disadvantage if they had to survive in the wild
66
Q

What is the selecting agents for natural selection?

A

Environment

67
Q

What is the phenotypic ratio likely to be if two genes are autosomally linked?

A

A higher proportion will have the same genotypes to parents. Alleles are not completely re-mixed.

Biology Module 6 (6 decks)

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