Genetics, Populations, Evolution & Ecosystems 3.7 Flashcards

1
Q

Populations in ecosystems (AO1)

Define abiotic factor

A

A non-living / physical / chemical factor

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2
Q

Populations in ecosystems (AO1)

Examples of abiotic factors

A

soil pH
temperature
salinity (concentration of salt)
carbon dioxide concentration
humidity
light intensity

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3
Q

Populations in ecosystems (AO1)

Define biotic factor

A

Living / biological factor

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4
Q

Populations in ecosystems (AO1)

Examples of biotic factors

A

predator
prey / food
disease
presence of opposite sex

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5
Q

Populations in ecosystems (AO1)

Define population

A

Groups of organisms of the same species living in the same habitat / ecosystem at the same time;

They have the potential to interbreed;

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6
Q

Populations in ecosystems (AO1)

TRUE OR FALSE

Organisisms of the same species that make up a population have the potential to interbreed

A

TRUE

They will produce fertile offspring

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7
Q

Populations in ecosystems (AO1)

Define community

A

All the populations of the different species in the same habitat / ecosystem at the same time

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8
Q

Populations in ecosystems (AO1)

Define ecological niche

A

The role played by an organism in a
habitat/ecosystem governed by adaptations to biotic/abiotic factors

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9
Q

Populations in ecosystems (AO1)

Explain the advantage of different species occupying different niches (1 mark)

A

Reduced (interspecific) competition for food/resources

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10
Q

Populations in ecosystems (AO1)

Define carrying capacity

A

Certain size of population of a species that can be supported by the ecosystem

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11
Q

Populations in ecosystems (AO1)

What can reduce carrying capacity?

A

Habitat loss;

Reductions in food availability;

Increases in the number of predators;

Disease

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12
Q

Populations in ecosystems (AO1)

An ecosystem supports a certain size of population of a species, called the [1] capacity. There are often numerous habitats within an ecosystem. Within a habitat, a species occupies a [2] governed by an adaption to both [3] and biotic conditions. Populations of different species form a [4].

A

[1] carrying

[2] niche

[3] abiotic

[4] community;;

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13
Q

Populations in ecosystems (AO1)

Ecosystem definition

A

The interaction between a community and the abiotic components of the environment

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14
Q

Populations in ecosystems (AO1)

Competition between organisms of the same species is known as _________________ competition

A

intraspecific

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15
Q

Populations in ecosystems (AO1)

Competition between organisms of different species is known as _________________ competition

A

interspecific

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16
Q

Populations in ecosystems (AO1)

What term describes populations of different species living in the same habitat?

A

Community

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17
Q

Populations in ecosystems (AO1)

Describe and explain what typical patterns emerge when plotting the population sizes of predators and their prey over time (3 marks).

A

As prey populations increase, there is an increased availability of food for the predator population;

This causes a (delayed) increase in predator population;

Due to the increase in predators, the prey population
will decline;

A decline in prey populations leads to a shortage of food for the predators, and over time their population will also decline;

This decline reduces the predation on the prey population, allowing for interbreeding and an increase in the population size

(and repeat)

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18
Q

Populations in ecosystems (AO1)

In northern India, there is a conflict of interests between farmers of livestock (eg cows) and people trying to conserve ibex (a type of wild goat).

When livestock are given extra food, their populations can grow too large and compete with ibex.

Name the type of competition between livestock and ibex.

A

Interspecific

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19
Q

Populations in ecosystems (AO1)

Random sampling reduces __________

A

bias

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20
Q

Populations in ecosystems (AO1)

Random coordinates are produced using a ________________________

A

random number generator

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21
Q

Populations in ecosystems (AO1)

Measurements made within quadrat(s)

A

Number of individuals;
% cover;
Species richness;
Index of biodiversity;

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22
Q

Populations in ecosystems (AO1)

Why use percentage cover rather than frequency / number of individuals to count algae.

A

Difficult / too many to count / individual organisms not identifiable / too small to identify/count / grows in clumps;

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23
Q

Populations in ecosystems (AO1)

The sundew is a small flowering plant, growing in wet habitats such as bogs and marshes.

Describe how you could estimate the size of a population of sundews in a small marsh (4 marks).

A

1. Use a grid;

2. Use random number generator for random coordinates (for quadrats);

3. Large sample of quadarts (20 or more);

4. Add the total number/frequency in a quadrat and divide by number of quadrats;

5. Valid method of calculating total number of sundews, e.g. mean number of plants per m^2 multiplied by number of m^2 in marsh;

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24
Q

Populations in ecosystems (AO1)

Describe how you would determine the mean percentage cover for beach grass on a sand dune (3 marks).

A

1. Use random number generator for random coordinates (for quadrats);

2. Large number of quadrats (20 or more);

3. Divide total percentage by number of quadrats;

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25
Q

Populations in ecosystems (AO1)

Outline a method the ecologists could have used to determine the plant species richness at one site (3 marks).

A

1. Use random number generator for random coordinates (for quadrats);

2. Large number of quadrats (20 or more);

3. Count number of different plant species (in each quadrat)

Reject refs to % cover, or counting individuals

Species richness = all the different species (AS content)

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26
Q

Populations in ecosystems (AO1)

In addition to a quadrat, what piece of equipment do you need to undertake systematic sampling?

A

Line / belt transect

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27
Q

Populations in ecosystems (AO1)

In systematic sampling, quadrats are placed on a transect at ____________ intervals

A

regular

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28
Q

Populations in ecosystems (AO1)

What type of analysis can systematic sampling using a line or belt transect allow you to undertake?

A

The impact of an environmental gradient on a population size.

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29
Q

Populations in ecosystems (AO1)

Lettuce is classified in the same family as dandelions. Dandelions commonly grow on roadside verges and may accidentally be sprayed with salt when salt is added to the road in winter.

Describe how you could use a transect to investigate whether the distribution of dandelions changed with increased distance from the road (4 marks).

A
  1. Lay tape / rope at right angle / perpendicular to road;
  2. Take samples at regular intervals;
  3. Using a quadrat;
  4. Count numbers / percentage cover of dandelions;
  5. Use several transects;
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30
Q

Populations in ecosystems (AO1)

Suggest one precaution needed when marking the pine martens (during mark, release & recapture) to make sure the estimate of the number of pine martens is valid (1 mark).

A

(Marking) does not affect survival/predation/recapture (of the pine marten);

OR

Mark does not rub/wash off/is non-toxic.

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31
Q

Populations in ecosystems (AO1)

What are the assumptions made when using the the mark-release-recapture method to make valid estimates of population size?

A

1. The population size does not change between the two capture times.
* There should be no increase in predation of the marked organism
* There should be no migration

2. The marked organisms have enough time to (randomly) disperse/distribute into the rest of the population

3. The marking should not rub off or be lost

4. Sample population is large enough

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32
Q

Populations in ecosystems (AO1)

Mark, release, recapture equation

A

You must be able to recall and apply this equation

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33
Q

Populations in ecosystems (AO1)

Anolis sagrei is a species of lizard that is found on some of the smallest Caribbean islands.

Describe how you could use the mark-release-recapture method to estimate the number of Anolis sagrei on one of these islands (3 marks).

A

1. Capture sample, mark and release;

2. Method of marking does not make it more visible to predators (i.e. does not affect survivial the lizards);

3. Leave sufficient time for lizards to (randomly) distribute (on island) before collecting a second sample;

4. (Population =) number in first sample × number in second sample divided by number of marked lizards in second sample / number recaptured.

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34
Q

Populations in ecosystems (AO2)

A

20

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35
Q

Populations in ecosystems (AO2)

The scientists used the mark-release-recapture method to determine the number of pine martens in one area of forest. They captured, marked and released a first sample of 25 pine martens. A week later, they captured a second sample of 35 pine martens from the same area of forest. The scientists calculated that there were 125 pine martens in that area of forest.

Using the information provided, calculate how many pine martens in the second sample were marked.

A

7 pine martens

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36
Q

Populations in ecosystems (AO2)

Blue tits are small birds that live in woods. An ecologist estimated the size of the blue tit population visiting gardens near a wood in November.

  • She trapped 28 blue tits. She marked all of these birds with small metal rings on their legs.
  • Two weeks later, she trapped another sample of blue tits. Of these birds, 18 were marked and 20 were not marked.

Use the data to estimate the size of the blue tit population.

A

59

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37
Q

Succession (AO1)

Hostile environments such as rock and sand are colonised by ______________

A

pioneer species

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38
Q

Succession (AO1)

Pioneer species example

A

Lichen

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39
Q

Succession (AO1)

TRUE or FALSE:

Lichen are microorganisms

A

TRUE

Lichen are a symbiotic association between a fungus and algae and/or cyanobacteria

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40
Q

Succession (AO1)

Characteristics of pioneer species

A

Photosynthesise;

Fix nitrogen;

Asexual reproduction;

Tolerance to hostile environments;

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41
Q

Succession (AO1)

At each stage in [1], certain species may be recognised which change the [2] so that it becomes more suitable for other species with different adaptations. The new [3] may change the environment in such a way that it becomes less suitable for the previous species.

A

[1] succession
[2] environment
[3] species

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42
Q

Succession (AO1)

Succession occurs in natural ecosystems.

Describe and explain how succession occurs (5 marks).

A

1. (Colonisation by) pioneer (species);
2. Change in environment / example of change caused by organisms present e.g. adds more humus;
(humus = is the formation of a thin / basic layer of soil)
3. Enables other species to colonise / survive;
4. Increase in biodiversity;
5. Stability increases / less hostile environment;
6. Climax community;

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43
Q

Succession (AO1)

Final stage of primary succession

A

Climax community

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44
Q

Succession (AO1)

Features of a climax community

A

1. Same species present (over long time) / stable community (over long time);

2. Abiotic factors (more or less) constant (over time)

3. Populations stable (around carrying capacity)

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45
Q

Succession (AO1)

What happens to the pioneer species as succession progresses to the next stage?

A

They are outcompeted;

by species better adapted to the less hostile environment;

(This is a form interspecific competition)

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46
Q

Succession (AO1)

The species that are present change during succession. Explain why (2 marks).

A
  1. Species / plants / animals change the environment / less hostile (habitat);
    e.g. add humus / nutrients etc.
  2. New species / plants that colonise this environment outcompete original species (e.g. pioneer species);
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47
Q

Succession (AO2)

A

Crabgrass

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48
Q

Succession (AO2)

A

1. Beach grass is the pioneer (species);

2. Pioneers/named species change the (abiotic) environment/habitat/conditions/factors;

Accept example of change e.g. more humus

3. (So) less hostile for named species OR
(So) more suitable for named species;

4. Conifer/hardwood trees represent climax community;

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49
Q

Succession (AO2)

Explain the advantage to a plant that colonises 50 years after the pioneer species of having a high rate of photosynthesis at low light intensities.

A

Plant will grow / survive in the shade / when overshadowed (by taller plants) / when receiving less light;

Note that taller trees are a key feature of a climax community

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50
Q

Succession (AO1)

Reasons for conserving rainforests

A

1. Conserve / protect
species / plants / animals / organisms

OR For (bio)diversity;

2. Conserve / protect habitats

OR Provides / many habitats ;

3. Reduces climate change;

4. Source of medicines/drugs/wood;

5. Reduces erosion/eutrophication;

6. (For) tourism;

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51
Q

Succession (AO2)

Explain why conservation of habitats frequently involves management of succession.

A

Prevents a climax community from forming;

Habitats in earlier stage ofsuccession may be better for some species;

E.g. ground nesting birds on heather moorland

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52
Q

Inheritance (AO1)

Phenotype

A

Expression of genetic constitution / genotype / allele(s);

AND its interaction with the environment;

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53
Q

Inheritance (AO1)

Dominant allele

A

Is always expressed / shown
in the phenotype;

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54
Q

Inheritance (AO1)

Recessive allele

A

Requires both alleles to be present - homozygous recessive genotype - to be expressed / show in the phenotype.

55
Q

Inheritance (AO1)

Genotype

A

The genetic constitution of an organism.

In other words, all the alleles it contains

e.g. Heterozygous OR homozygous recessive

56
Q

Inheritance (AO1)

Define a gene

A

A sequence of DNA bases that codes for a protein

57
Q

Inheritance (AO1)

Define an allele

A

Different versions of the same gene

These are typically created by random mutations

58
Q

Inheritance (AO1)

There may be many _____________ of a single gene.

A

alleles

59
Q

Inheritance (AO1)

In a diploid organism, the alleles at a specific __________ may be either homozygous or heterozygous.

A

locus

60
Q

Inheritance (AO1)

Define locus

A

The location/position of a particular gene on a chromosome

61
Q

Inheritance (AO1)

If there the two copies of a gene are the same allele in a genotype, this is known as __________________

A

homozygous

62
Q

Inheritance (AO1)

If there the two copies of a gene are different alleles in a genotype, this is known as __________________

A

heterozygous

63
Q

Inheritance (AO1)

What is the expected phenotypic ratio if your cross heterozygous parents (i.e. they carry the recessive allele) in a monohybrid cross?

A

3 : 1

Where 1 represents the phenotype from the homozygous recessive genotype

64
Q

Inheritance (AO2)

A breeder crossed a black male cat with a black female cat on a number of occasions. The female cat produced 8 black kittens and 4 white kittens.

Explain the evidence that the allele for white fur is recessive.

A

Parents are heterozygous;

Accept carriers / carries white allele

Kittens receive white allele from parents / black cat;

65
Q

Inheritance (AO2)

A breeder crossed a black male cat with a black female cat on a number of occasions. The female cat produced 8 black kittens and 4 white kittens.

Predict the likely ratio of colours of kittens born to a cross between this black male and a white female.

A

1:1

A Bb (Black) x bb (White) cross will produce Bb and bb offspring

66
Q

Inheritance (AO1)

A
  1. Bb / suitable equivalent;
  2. Both parents have bar eyes, but have some offspring with round eyes, so parents must be carriers of recessive allele for round eyes;
67
Q

Inheritance (AO2)

A

Unaffected parents have affected children

e.g. 3 and 4 produce affected offspring (9 and 11);

Both 3 and 4 are carriers / heterozygous;

68
Q

Inheritance (AO2)

A

Evidence

3 and 4 / two Rhesus positives produce Rhesus negative child / children / 7 / 9;

Explanation

Both Rhesus positives / 3 and 4 carry recessive (allele) / are heterozygous / if Rhesus positive was recessive, all children (of 3 and 4) would be Rhesus positive / recessive;

69
Q

Inheritance (AO1)

A

Codominance

70
Q

Inheritance (AO1)

What is the expected phenotypic ratio if your cross heterozygous parents for a codominant phenotype.

A

1 : 2 : 1

71
Q

Inheritance (AO1)

In genetic crosses, the observed phenotypic ratios obtained in the offspring are often not the same as the expected ratios.

Suggest two reasons why.

A
  1. Small sample size;
  2. Fusion/fertilisation of gametes is random;
  3. Linked Genes;
  4. Epistasis;
  5. Lethal genotypes;
72
Q

Inheritance (AO2)

A
  1. Animal 2 / 5 has hair but offspring do not;
  2. So 2 / 5 parents must be heterozygous / carriers;

OR

  1. 4 / 7 / 8 are hairless but parents have hair;
  2. So 2 / 5 must be heterozygous / carriers;
73
Q

Inheritance (AO1)

Gametes produced by AaBb genotype.

The genes are on different chromosomes.

A

AB , Ab , aB , ab

74
Q

Inheritance (AO1)

Gametes produced by the AABb genotype.

The genes are on different chromosomes.

A

AB , Ab

There would be x2 AB and x2Ab following meiosis

75
Q

Inheritance (AO1)

Gametes produced by the ccdd genotype.

The genes are on different chromosomes.

A

cd

There would be x4 cd gametes following meiosis

76
Q

Inheritance (AO1)

Expected phenotypic ratio of offspring if both parents are heterozygous in a dihybrid cross.

i.e. AaBb x AaBb

A

9 : 3 : 3 : 1

77
Q

Inheritance (AO1)

Mutation is one cause of genetic variation in organisms.

Give two other causes of genetic variation.

A

1. Crossing over;

2. Independent segregation
(of homologous chromosomes);

3. Random fusion of gametes

OR random fertilisation;

78
Q

Inheritance (AO1)

What process during meiosis 1 creates different combinations of alleles in the gametes?

A

Independent segregation

79
Q

Inheritance (AO2)

A

1. Large number of eggs / offspring / flies (therefore) improves reliability / can use statistical tests / are representative

2. Small size / (breed) in small flasks / simple nutrient medium (therefore) reduces costs / easily kept / stored;

3. Size / markings / phenotypes (therefore) males / females easy to identify;

4. Short generation time / 7 - 14 days / develop quickly / reproduce quickly (therefore) results obtained quickly / saves times / many generations;

80
Q

Inheritance (AO1)

Meiosis results in cells that have the haploid number of chromosomes and show genetic variation. Explain how (6 marks).

A

(Crossing over)
1. Homologous chromosomes pair up / bivalents form;

  1. Crossing over / chiasmata form;
  2. Produces new combination of alleles;

(Independent segregation)
4. Homologous chromosomes separate;

  1. At random;
  2. Produces varying combinations of chromosomes / genes / alleles;
  3. Sister chromatids separated at meiosis II;
81
Q

Inheritance (AO1)

If two genes are linked on the same chromosome, what gametes would be produced by the AaBb genotype?

A

AB , ab

These are the known as the ‘parental’ gametes

82
Q

Inheritance (AO1)

If two genes are linked on the same chromosome, what gametes would be produced by the AABb genotype?

A

AB , Ab

These are the known as the ‘parental’ gametes

83
Q

Inheritance (AO1)

Which process during meiosis 1 produces recombinant gametes?

A

crossing over

84
Q

Inheritance (AO1)

If two genes are linked on the same chromosome but crossing over occurs, what gametes would be produced by the AaBb genotype?

Also, identify which gametes that would be produced in higher numbers.

A

More of the ‘parental’ gametes = AB & ab

Less of the ‘recombinant’ gametes = Ab & aB

85
Q

Inheritance (AO1)

For two linked genes on the same chromosomes, why are fewer recombinant gametes produced by crossing over?

A

Crossing over is a rare event

86
Q

Inheritance (AO1)

In fruit flies, the genes for body colour and wing length are linked. Explain what this means.

A

Genes are on the same chromosome

87
Q

Inheritance (AO2)

A

1. The two genes are linked;

2. No crossing over (occurs);

3. No Gl and no gL (recombinant gametes produced)

OR Only GL and gl (parental gametes produced);

OR No Ggll and no ggLl (offspring produced)

88
Q

Inheritance (AO1)

Alport syndrome results from a sex-linked mutation.

In a male with AS, where would the sex-linked mutation be located?

Tick (✓) one box.

A

Box 4 - The non-homologous section of an X chromosome

89
Q

Inheritance (AO2)

In fruit flies, males have the sex chromosomes XY and the females have XX. In fruit flies, a gene for eye colour is carried on the X chromosome. The allele for red eyes, R, is dominant to the allele for white eyes, r.

Male fruit flies are more likely than female fruit flies to have white eyes.

Explain why.

A

1. Males only have one allele

2. Females need two recessive alleles

OR Females must be homozygous recessive

OR Females could be heterozygous/carriers;

90
Q

Inheritance (AO2)

What typical pattern of inheritance would likely indicate that a gene is sex-linked?

Explain why.

A

Unaffected fathers have affected sons;

Explanation:
Sons inherit their x chromosome from their mother;

If mum is a carrier of a recessive allele, she will pass this onto her son who only needs 1 copy of allele for it to be expressed in the phenotype;

In family trees, it is more common for males to have the disease / affected phenotype;

91
Q

Inheritance (AO2)

Use evidence from the below diagram to explain that hairlessness is caused by a gene on the X chromosome.

A

Hairless males have fathers with hair OR

4 is hairless but 1 is hairy OR

7 and / or 8 are hairless but 6 is hairy OR

only males are hairless

This is an example of unaffected fathers have affected sons

92
Q

Inheritance (AO2)

How could you prove a dominant allele is NOT sex-linked?

Explain why.

CLUE = mums & sons

A

If the allele is sex-linked, homozygous recessive mothers will always have sons that show the recessive phenotype.

If, however, the sons show a dominant phenotype, there is no way he could have inherited this on the X chromosome from his mother.

The dominant allele must be on another chromosome.

93
Q

Inheritance (AO2)

How could you prove a recessive allele is NOT sex-linked?

Explain why.

CLUE = dads & daughers

A

If the recessive allele is sex-linked, unaffected fathers will always have unaffected daughters

The father will always pass on the dominant allele to his daughter who would therefore be unaffected.

If, however, the daugher does show a homozygous recessive phenotype, the recessive allele must be on another chromosome.

94
Q

Inheritance (AO2)

A
  1. (Individual) 2 has colour vision but 4 is colour blind / 10 has colour vision but 12 is colour blind

OR 4/12 is colour blind but parents have colour vision;

  1. So 2/10 must be heterozygous/carriers;
95
Q

Inheritance (AO2)

Explain one piece of evidence from the below diagram which shows that the gene is NOT on the X chromosome.

A

Evidence (Mums & Sons)

3 would not be / is Rhesus positive / would be Rhesus negative is sex-linked;

Explanation

3 would receive Rhesus negative (allele) on X (chromosome) from mother / 3 could not receive Rhesus positive (allele) from mother / 3 would not receive Rhesus positive (allele)

OR

Evidence (Dads & Daughters)

9 would be Rhesus positive / would not be / is Rhesus negative / 8 and 9 / all daughters of 3 and 4 would be Rhesus positive;

Explanation

As 9 would receive X chromosome / dominant allele from father / 3;

96
Q

Inheritance (AO2)

A
  1. Animal 2 / 5 has hair but offspring do not;
  2. So 2 / 5 parents must be heterozygous / carriers;

OR

  1. 4 / 7 / 8 are hairless but parents have hair;
  2. So 2 / 5 must be heterozygous / carriers;
97
Q

Inheritance (AO2)

A

Epistasis

98
Q

Inheritance (AO2)

A

Epistasis

99
Q

Inheritance (AO2)

A

Cannot make (active) enzyme A (which converts precursor to linamarin) / cannot make linamarin;

100
Q

Inheritance (AO2)

A

no enzyme coded for when no dominant / E allele;

phaeomelanin not converted – (remains yellow);

101
Q

Inheritance (Maths)

When to use the chi squared test?

A

If there is a significant difference between the observed AND expected numbers in an investigation with categorical data

102
Q

Inheritance (AO1)

Which statistical test could the scientist use to determine whether his observed results were significantly different from the expected results?

Give the reason for your choice of statistical test.

A
  1. Chi squared test;
  2. Categorical data.
103
Q

Inheritance (Maths)

What do the compontents of the chi squared equation represent?

A
104
Q

Inheritance (Maths)

A
105
Q

Inheritance (Maths)

When using the chi squared test, how do you calculate the degrees of freedom?

A

n - 1

Where ‘n’ represents the number of categories / groups / phenotypes

106
Q

Inheritance (Maths)

When using the chi squared test, how do you calculate the degrees of freedom?

A

n - 1

Where ‘n’ represents the number of categories / groups / phenotypes

107
Q

Inheritance (Maths)

There are 4 possible phenotypes with expected and observed results, calculate the degrees of freedom?

A

3

As degrees of freedom = n - 1

(where n represents the number of categories / phenotypes)

108
Q

Inheritance (Maths)

There are 3 possible phenotypes with expected and observed results. Use this information to determine the critical value from the table below.

A

2 degrees of freedom;

Critical value = 5.99
(when P = 0.05)

109
Q

Inheritance (AO3)

Following a genetic cross involving 4 possible phenotypes, researchers obtained a chi squared value of 2.32.

Use the table below to state what you can conclude from this data.

A

The chi squared value is SMALLER than the critical value of 7.82 (when P = 0.05);

There is NO SIGNIFICANT DIFFERENCE
(between the observed and expected values)

There is more than a 5% probability the differences are due to chance.

110
Q

Inheritance (AO3)

Following a genetic cross involving 2 possible phenotypes, researchers obtained a chi squared value of 4.07.

Use the table below to state what you can conclude from this data.

A

The chi squared value is LARGER than the critical value of 3.84 (when P = 0.05);

There is a SIGNIFICANT DIFFERENCE
(between the observed and expected values);

There is less than a 5% probability the differences are due to chance;

111
Q

Populations (AO1)

Define gene pool

A

All the alleles in a population

112
Q

Populations (AO1)

Define allele frequency

A

How often an allele occurs in a population.

Usually given as a percentage of the total population, e.g. 35%, or a decimal, e.g. 0.35.

113
Q

Populations (AO1)

What does the Hardy-Weinberg principle predict?

A

The frequency of alleles (of a particular gene);

Will stay constant from one generation to the next / over generations

Providing there are no mutations / no selection / population large / population genetically isolated / mating at random / no migration;

114
Q

Populations (AO1)

Hardy Weinberg equation
for allele frequency

A
115
Q

Populations (AO1)

If the frequency of a dominant allele is 0.72, what is the frequency of the recessive allele?

A

p + q = 1.0

0.72 + q = 1.0

q = 0.28

116
Q

Populations (AO1)

Hardy Weinberg equation
for genotype frequency

A
117
Q

Populations (Maths)

For a gene with two alleles, B and b. Consider a population of 1000 people, where 300 are homozygous dominant (BB), 500 are heterozygous (Bb) and 200 are homozygous recessive (bb).

Calculate the allele frequency of B and b.

A

The total number of alleles is: 1000 x 2 = 2000

The number of B alleles: (300 x 2) + (500 x 1) = 1100
Frequency of the B allele: 1100 / 2000 = 0.55

The number of b alleles is: (200 x 2) + (500 x 1) = 900
Frequency of the b alleles: 900 / 2000 = 0.45

p + q = 1.0
0.55 + 0.45 = 1.0

118
Q

Populations (AO2)

The scientists concluded that the observed frequencies of the phenotypes differed significantly from the expected frequencies.

Use your knowledge of the Hardy–Weinberg principle to suggest two reasons why.

A
  1. Selection (against/phenotype/allele);
  2. (High rate of) mutation;
  3. Immigration/emigration;
  4. No random mating.
119
Q

Populations (AO2)

In mice, one type of disease is inherited as a dominant allele. Would the Hardy–Weinberg principle hold true for a population of mice, some of which had this disease?

Explain your answer

A

(No)
1. Mice with disease will be unlikely
to reproduce/survive
OR Mice with disease will be selected against;

2. Will not pass on allele (for disease)
OR Allele frequency (for disease) will reduce;

(Yes)
3. As long as the disease did not
affect the mice’s ability to reproduce/survive;

4. The allele frequency will remain constant/not
change;

120
Q

Populations (Maths)

A
121
Q

Populations (Maths)

A population of fruit flies contained 64% grey-bodied flies (Genotype is GG or Gg).

Use the Hardy–Weinberg equation to calculate the percentage of flies heterozygous for gene G.

A
122
Q

Populations (Maths)

A
123
Q

Populations (Maths)

A
124
Q

Evolution may lead to speciation (AO1)

Define gene mutation

A

1. Random change in the base sequence of DNA.

2. Results in the formation of a new allele.

125
Q

Evolution may lead to speciation (AO1)

TRUE or FALSE:

Mutations arise spontaneously during DNA replication

A

TRUE

126
Q

Evolution may lead to speciation (AO1)

Random mutations are changes to the DNA base sequence that produce new ___________.

A

alleles

127
Q

Evolution may lead to speciation (AO1)

Types of mutation

A

Substitution
Addition
Deletion
Inversion
Non-disjunction
Translocation

128
Q

Evolution may lead to speciation (AO1)

Primary souce of genetic variation

A

random mutations

129
Q

Evolution may lead to speciation (AO1)

TRUE or FALSE:

Creating new combinations of alleles does not contribute to genetic variation

A

FALSE

130
Q

Evolution may lead to speciation (AO1)

Processes that create new combinations of alleles (and therefore genetic variation)

A

Independent segregation;

Crossing over;

Random fusion of gametes

131
Q

Evolution may lead to speciation (AO1)

Describe and explain which processes - other than mutations - that result in increases in genetic variation within a species (4 marks).

A

1. Independent segregation of homologous
chromosomes/pairs;

2. Crossing over between homologous
chromosomes/pairs (non-sister chromatids);

3. Random fertilisation of gametes;

4. (Produces) new combinations of alleles;

132
Q

Evolution may lead to speciation (AO1)

Variation which is caused predominantly by genetic factors produces [1] data and is usually caused by a [2] gene.

A

[1] categorical

[2] single*

*The single gene may have multiple alleles

133
Q

Evolution may lead to speciation (AO1)

TRUE or FALSE:

Individuals within a population show a wide range of variation in phenotype due to genetic AND environmental factors.

A

TRUE

134
Q

Evolution may lead to speciation (AO1)

Phenotypes that are controlled by more than one gene and environmental factors typically produce a __________ distribution.

A

normal