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biology paper 2 > 3.7.1 inheritance, population and evolutions > Flashcards

3.7.1 inheritance, population and evolutions Flashcards

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1
Q

what scientists studied inheritance?

A

gregor mendel (1822-1884)
used pea plant experiments
established many rules of inheritance

charles darwin was not aware of mendel’s work

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2
Q

what is a gene?

A

a section/region of a chromosome/length of DNA, sequence of nucleotides/base

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3
Q

what is an allele?

A

a version/form of a particular gene

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4
Q

what are homologous chromosomes?

A

pair of DNA molecules which contain information for the same genes, though each homologous chromosome may carry different genes

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5
Q

what is a genotype?

A

genetic constitution of an individual organism, collection of genes and alleles in an individual

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6
Q

what is a phenotype?

A

set of observable characteristics on individual organisms resulting from interaction of genotype + environment

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7
Q

what does homozygous mean?

A

genotypes where both alleles at a particular loci are the same

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8
Q

what does heterozygous mean?

A

genotypes where both alleles at a particular loci are different

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9
Q

what does dominant mean?

A

allele that is expressed in the phenotype when there is one copy

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10
Q

what does recessive mean?

A

allele is expressed in the phenotype if two copies are present

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11
Q

codominance

A

relationship between two alleles of a gene where allele is recessive + phenotypes are expressed

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12
Q

multiple alleles

A

population with two alleles

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13
Q

monohybrid inheritance

A

inheritance of a characteristic controlled by a single gene

if an organism is bred until they continually give rise to offspring with a given characteristic

pure breeding strains

organisms must be homozygous for that particular gene

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14
Q

F1 and F2 offspring

A

if two pure bred are crossed resulting in offspring = F1 generation

heterozygous plants cross F1 generation = gives F2 generation

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15
Q

describe the inheritance of pod colours in peas

A

Gregor Mendel - studied the colour of pea plants

Green pea pods are bred repeatedly with each other - pure breeding the character of green pea pods
Organisms are homozygous = two alleles

Green crossed with yellow pea pod - F1 generation (green pods)
Allele for green is dominant

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16
Q

what is the definition of dihybrid inheritance?

A

inheritance of two genes on different chromosomes that control different characteristics or influence the same characteristic

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17
Q

mendel

A

investigated the inheritance of two characteristics of pea plants at the same time

round (R) or wrinkled (r)
yellow (Y) or green (y)

crossed pure breeding homozygous dominant for both characteristics, with pure breeding plants homozygous recessive for both characteristics

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18
Q

FOIL

A

F = first
O = outside
I = inside
L = last

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19
Q

pedigree diagrams

A

family pedigree diagrams can be used to trace the pattern of inheritance of a specific trait

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20
Q

what do the symbols mean on pedigree charts?

A

male is represented by squares
female is represented by circles
shading within either shape indicates the prescence of a character
vertical lines show relationship between parent + child
romance numerals may be used to indicate generations
eldest child is always on the left, individuals are numbered

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21
Q

sex inheritance in humans

A

females = 2 X chromosomes, all the gametes are the same and contain an X chromosome
male = one X chromosome and one Y chromosome , they produce two different types of gamers, half have both an X and Y chromosome

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22
Q

autosomal vs sex linkage

A

any two genes that occur on the same chromosome are said to be linked

all the genes on a single chromosome are called autosomes

if two or more genes appear on autosome chromosomes they are said to be autosomal linkage

if two or more genes appear on the sex chromosomes they are said to be sex linked

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23
Q

X linked dominant

A

females are more frequently affected as they have a greater chance of receiving X chromones

females always inherit two copies of an X chromosome, males only inherit one so they are less frequently affected

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24
Q

describe haemophilia

A

haemophilia = disease in which the blood clots slowly, may be a slow and persistent internal bleeding

caused by a change to the DNA sequence resulting in a faulty protein being created

disease is always inherited from mother, as it it cannot be found on the Y chromosome

if mother doesn’t suffer from the disease but is heterozygous with the alleles she is a carrier

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25
Q

what is the frequency of X linked recessive?

A

females are less frequently affected as they can inherit an alternative unaffected allele

this one unaffected allele may produce enough normal protein to bring about an unaffected phenotype

males are more frequently affected as they inherit one copy

most common X linked recessive is red green colour blindness

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26
Q

what is codominance?

A

codominance = both alleles are expressed in the phenotype

multiple alleles = where there are more then two alleles, of which two may be present at the loci of an individuals homologous chromosomes

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27
Q

what is the relationship between codominance and sickle cell anaemia?

A

genetic disease resulting from a faulty gene encoding the B polypeptide chain in haemoglobin

mutant and normal alleles are codominant

Hb represents the gene locus for this chain in the haemoglobin molecule

normal = HbA
sickle cell = HbS

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28
Q

what is the sickle cell anaemia genotype + phenotype?

A

HbA HbA = normal haemoglobin

HbA HbS = half the haemoglobin is normal and half is sickle - sickle cell trait

HbS HbS = all sickle cell haemoglobin - sickle cell anaemia

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29
Q

describe sickle cell anaemia

A

sickle cell is common in parts of the world where malaria is present

caused by a single celled organism plasmodium

lives + breeds inside red blood cells

causes recurrent fevers

children who are born with sickle cell disease (HbS HbS) are likely to die before reproductive age = removes HbS allele from population

individuals with HbS HbA have sickle cell anemia but not susceptible to malaria, most likely to grow up and reproduce

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30
Q

what is incomplete dominance?

A

one allele codes for enzymes that catalyses the formation of pigments

one allele lacks the catalytic activity + no pigment

neither white/red is dominant

pink colour results from the blending of 2 alleles

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31
Q

what are multiple alleles and what do they code for?

A

multiple alleles can exist for a particular characteristic

more than two versions of that gene present with a population

1 individual within population will still only possess two alleles for one gene = maternal + paternal eg cat coat colour

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32
Q

what is epistasis?

A

interaction of different genes in different loci where the gene at one locus masks or surpresses the expression of another gene at a second locus

IF EXAM QUESTION MENTIONS INTERACTION, IT HAS TO BE EPISTASIS

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33
Q

what is dominant epistasis?

A

one gene masks the expression of alleles at a second gene locus

ratios = 12:3:1 and 13:3

eg summer squash fruits
presence at least one dominant allele B at the 2nd locus results in white fruits, no matter which alleles are found on the 1st locus

34
Q

genetics in summer squash

A

A = produces enzyme A that catalyses the formation of a yellow pigment
a = no enzyme is produced

B = produces protein B that prevents pigment from depositing
b = produces protein B that allows pigment from depositing

35
Q

what is recessive epistasis?

A

two recessive alleles at one gene locus masks the expression of alleles at a second gene locus

ratio = 9:3:4

eg labrador coat colour
gene 1 determines pigment = B, black and b = brown
gene 2 determines amount of pigment in the fur: E = dark pigment and e = no pigment

36
Q

what is complimentary epistasis?

A

presence of a particular allele at each locus is required for the expression of a particular phenotype

ratios = 9:7

eg sweet pea flower colour

37
Q

what is chi squared test used for?

A

chi squared (x2) is used to test a null hypothesis

38
Q

what is the relationship between chi squared test and null hypothesis?

A

null hypothesis states there is no sig difference between a set of observations + differences due to chance

used to examine results to test if there any deviations between expected and observed

39
Q

chi squared test
null hypothesis and sig difference

A

null hypothesis = states there is no sig difference between observed + expected results

sig difference = 95% probability sure the difference is not due to chance

40
Q

what is the chi squared test equation?

A

sum of = [ observed numbers (O) - expected numbers (E) ] 2 / expected numbers (E)

41
Q

describe population genetics

A

the number of individuals in a single species in particular area at a given time and that can potentially interbreed

all of the alleles of all the genes of all the individuals in a population at a given time are known as a gene pool

number of times an allele occurs within the gene pool is referred to as the alleles frequency

42
Q

what are the hardy-weinburg calculations?

A
  1. allele frequencies = p + q = 1
  2. genotype frequencies = p2 + 2pq + q2 = 1

p = dominant

q = recessive

43
Q

what are the breakdown of hardy-weinburg calculations?

A

p = frequency of the dominant allele
q = frequency of the recessive allele

p2 = frequency of AA (homozygous dominant)
2pq= frequency of A (heterozygous)
q2 = frequency of a (homozygous recessive)

44
Q

what are the assumptions of hardy-weinberg principle?

A
  1. no selection
  2. no mutations
  3. no migration
  4. large population
  5. random mating
45
Q

what are mutations?
what are meiosis?
what is random fertilisation of gametes?

A

mutations = sudden changes to genes and chromosomes that can passed on to the next generation are a main source of variation

meiosis = a special form of nuclear division that produces new combinations of alleles before they are passed onto gametes

random fertilisation of gametes = in sexual reproduction this produces new combinations of alleles and offspring are different

46
Q

what variations are due to genetic factors?

A

a few distinct forms

no intermediate types

usually controlled by a single gene (monogenic)

represented by a bar chart/pie graph

environmental factors have little influence on thus type of variation

47
Q

what variations are due to environmental factors?

A

the environment exists an influence on the way an organisms genes are expressed

an organisms gene sets an limit for a particular characteristic

largely determines where within that limit the organism lies

48
Q

what is the difference between polygenes and polygenic?

A

polygenes = a gene whose individual effect on a phenotype is too small to be observed, but can act together to produce observable variation

polygenic = characteristics that are controlled by many genes

eg height and mass

49
Q

what is the normal distribution of genetic mutations?

A

bell shaped curve

eg number of individuals vs height

50
Q

what are selective pressures?

A

every organism is subject to a process of selection based on it’s suitability for survival under the conditions that exists at the time

environmental factors that limit the population = selective pressures

eg predation, disease, competition, natural disasters

selective pressure varies from location and time

51
Q

what is the selective pressures affect on the gene pool?

A

selective pressure determines the frequency of all alleles within the gene pool

gene pool = total number of all the alleles of all the genes of all the individuals within a particular population at a given time

52
Q

how do organisms evolve through natural selection?

A
  1. organisms produce more offspring than can be supported by the available supply of resources
  2. genetic variety within populations of all species
  3. variety of phenotypes that selection operates against
53
Q

what is overproducing?

A

all species have the potential to increase their numbers but this is rare

death rate of slow breeding is high

high reproductive rates evolved to ensure a large population survives to breed and produce

compensates for selective pressures

some species have evolved lower reproductive rates and higher parental care

high reproductive rates ensures a sufficiently large population survives to breed and produces
increases infraspecific competition

greater the competition the greater the deaths

deaths aren’t random

54
Q

Sickle cell anaemia is a debilitating genetic disease that causes premature death but provides some resistance to the malarial parasite.

Explain how selection might affect the distribution of the gene causing sickle cell andemia in both malarial & non-malarial regions.

A

In malarial regions:
* The disadvantages of having the disease will be offset by the advantages of having resistance to malaria and so there will be little if any selection against the gene and its frequency will be relatively high.

In non-malarial regions:
* No advantage in having resistance to malaria so individuals with SCA will be at a disadvantage. They will be selected against and the frequency of the gene will be low.

55
Q

what is the genetic variety within populations?

A

whole process only works if individuals are genetically different

populations showing little genetic variation are more vulnerable

species must be capable of adapting

56
Q

how does natural variation cause genetic variation?

A

different species of grasses have a variety of forms with respect to copper tolerance

some varieties are very tolerant and grow readily, others have a low tolerance and do not survive

57
Q

what are the effects of the environment on variation?

A

environmental factors help to create variation within a population

these factors: agents of constant/change are dependant on fur length

58
Q

what are the effects of temperature on fur length variation?

A

hot = shorter hair is an advantage as body heat is lost easier

cold = long hair is an advantage as there is better insulation

both extremes survive as temperature fluctuates

average is favoured

59
Q

what is the relationship between disruptive selection and fur length?

A
  1. when there is a wide range of temperatures throughout the year there is continuous variation in fur length around a mean of 1.5cm
  2. when the summer temperature is static around 15 degrees and winter temperature is static around 5 degrees
    individuals with two distinct fur lengths are predominate
  3. after many generations two distinct sub-populations are formed = temporal isolation
60
Q

describe fur length in showing continuous variation

A
  1. When the average environmental temperature is 10°C, the optimum fur length is 1.5 cm. This then represents the mean fur length of the population.
  2. A few individuals in the population already have a fur length of 2.0 cm or greater. If the average environmental temperature falls to 5°C, these individuals are better insulated and so are more likely to survive to breed. There is a selection pressure favouring individuals with longer fur.
  3. The selection pressure causes a shift in the mean fur length towards longer fur over a number of generations. The selection pressure continues.
  4. Over further generations the shift in the mean fur length continues until it reaches 2.0cm - the optimum length for the prevailing average environmental temperature of 5°C. The selection pressure now ceases.
61
Q

what is evolution?

A

defined as the formation of new species from pre-existing species over time as a result from changes to gene pools and allele frequencies

natural selection causes the allele frequencies to change and characteristics of the species change

62
Q

what is the relationship between evolution and speciation?

A

the formation of new species via the process of evolution has resulted in greater diversity

theoretically, this would have been one species to begin with, this has evolved into separate species

evolution has led to countless number of speciation events
can take a long time

bacteria has a short generation time

population must be genetically and reproductively separated from previous populations
no longer can be an exchange of genes

63
Q

what causes reproductive separation?

A
  1. seasonal changes
  2. mechanical changes
  3. behavioural changes
64
Q

what are seasonal changes?

A

some individuals may develop different mating or flowering seasons

may be sexually active at different times of the year

reproductive timings no longer match

65
Q

what are mechanical changes?

A

some individuals may develop changes to genitalia that prevent them from mating successfully with individuals of the opposite sex

reproductive body parts no longer match up

66
Q

what are behavioural changes?

A

some individuals in a population may develop changes in courtship behaviour

can no longer attract opposite sex

ineffective mating

67
Q

what is genetic isolation?

A

two populations of the same species become reproductively isolated and eventually genetically isolated

no interchange of genes

groups evolve independently of each other
formation of two populations that cannot interbreed

speciation

68
Q

what is adaptive radiation?

A

when each population becomes adapted to it’s local environment by natural selection

changes allele frequencies within the population and results in different phenotypes from selective pressures

69
Q

what is genetic drift?

A

mechanisms of evolution referring to random fluctuations in frequencies of alleles

due to chance

can cause traits to disappear or become dominant

most pronounced in small populations

eg bottleneck effect

70
Q

what is allopatric speciation?

A

allopatric = different countries

describes speciation where populations have become geographically separated

may be the results of a physical barriers eg oceans, rivers, mountain ranges and deserts

barriers are species specific

occurs of the environment either side of the barrier differs

71
Q

what is sympatric speciation?

A

takes place with no geographical barrier

ecological separation = populations are separated because they live in different environments within the same area

behavioural seperations

72
Q

what do these terms mean:
temporal
mechanical
gametic
hybrid sterility

A

temporal = breeding seasons of different species

mechanical = anatomical differenced physically preventing mating

gametic = biochemical incompatibility of gametes

hybrid sterility = sterile hybrid animals are produced as hybrids cannot produce gametes

73
Q

what is required practical 12?

A

effect of different variables on species distribution

74
Q

list 3 abiotic factors

A

light intensity
temperature
water supply
nutrient supply
humidity
wind speed
day length
rainfall

75
Q

list 3 biotic factors

A

competition for resources
predation
disease

76
Q

how is percentage cover caluclated?

A

Use a quadrat with squares. Count how many squares the required species is present in.
Only count a square if more than half of the square is covered. Calculate the percentage of squares the species is present in.

77
Q

outline the procedure to this practical

A
  1. Choose an area to take samples from. Use a random number generator to generate 10 sets of random coordinates.
  2. Use two tape measures to create a set of axes off which coordinates can be read.
  3. Place the quadrat at each of the coordinates, placing the bottom left corner on the coordinate every time.
  4. Record the percentage cover for the chosen species.
  5. At each coordinate, a measure of the independent variable should be taken.
    Eg. record light intensity using a photometer at each location
78
Q

How can the results be used to determine the relationship between the chosen factor and the percentage cover?

A

Use a statistical test eg. Pearson’s linear correlation, Spearman’s rank

79
Q

why should a random number generator be used?

A

to avoid bias in random sampling

80
Q

state the formula for the mark-release-recapture method

A

population size = number in 1st sample x number in 2nd sample / number marked in second sample

81
Q

state the assumptions when using the mark release recapture method

A

No births, deaths or immigrations.

Random mixing of marked individuals with population.

Marking does not affect behaviour of individuals or make them more vulnerable to predators.

biology paper 2 (12 decks)

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