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Biology - Module 6 > Patterns of inheritance > Flashcards

Patterns of inheritance Flashcards

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1
Q

what is phenotypic variation

A

difference in phenotypes between organisms of the same species

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2
Q

how does phenotypic variation occur

A

genetic + environmental factors

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3
Q

example of genes effecting phenotype

A

blood group

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4
Q

example of environment effecting phenotype

A

clones with different height due to environmental conditions

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5
Q

example of both genes + environment effecting phenotype

A

recessive allele that causes sickle cell anaemia has a high frequency in populations where malaria is prevalent due to heterozygous individuals being resistant to malaria

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6
Q

how can diet effect fruit flies

A

If the larvae of normal grey flies are given a diet of silver salts, they develop the yellow colour regardless of their genotype

flies that should be grey (according to their genes) can become yellow due to an environmental factor (their diet)

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7
Q

what is chlorosis

A

cells not producing normal amount of chlorophyll

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8
Q

how is chlorosis caused

A

normal genes – but environmental pressures

lack of light – plants turn off chlorophyll production – conserve resources

mineral deficiencies – lack of iron / magnesium

(iron – cofactor for enzymes that make chlorophyll)
(magnesium – centre of chlorophyll molecule)

virus infections – interfere with metabolism + cant support synthesis of chlorphyll

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9
Q

how is etiolation caused

A

Plants that are grown in the dark may also develop long stems with small, curled leaves even though, genetically, they should develop normally

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10
Q

when does crossing over occur

A

prophase 1

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11
Q

describe crossing over

A

homologous chromosomes pair up and are in very close proximity to each other

non-sister chromatids can cross over and get entangled

crossing points are called chiasmata

entanglement places stress on the DNA molecules

section of chromatid from one chromosome may break and re-join with the chromatid from the other chromosome

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12
Q

when does independent assortment occur

A

metaphase 1 + 2

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13
Q

what is independant assortment

A

different combinations of alleles in daughter cells due to the random alignment of homologous pairs along the equator of the spindle

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14
Q

how does independant assortment occur

A

Each pair can be arranged with either chromosome on top, this is completely random

The orientation of one homologous pair is independent / unaffected by the orientation of any other pair

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15
Q

what are the number of different combinations of cells resulting from independant assortment

A

2 to the power of n

n = number of chromosomes in haploid cell

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16
Q

summarise meoisis

A
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17
Q

draw a monohybrid cross for Gg

A
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18
Q

what is codominance

A

both alleles are dominant

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19
Q

how to represent codominance

A

one normal letter – two different superscripts

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20
Q

alleles for all blood groups

A
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21
Q

when is a dihybrid cross used

A

to show inheritance of 2 different characteristics – caused by 2 different genes

Could be on different pairs of homologous chromosomes

Could have multiple alleles

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22
Q

draw a dihybrid cross

A
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23
Q

draw a cross with sex linkage

A

HAVE TO SHOW ALLELE ON SEX CHROMOSOME ITS FOUND ON

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23
Q

why does sex linkage exist

A

Y chromosome much smaller then X chromosome

Number of genes on the X chromosome + aren’t matched on the same locus on Y

Y chromosome shorter

doesn’t have a homozygous pair

Only have 1 copy

Any characteristic caused by recessive allele on section of x chromosome (missing on the Y) occurs more frequently in males

Females – may also have dominant on other X

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23
recombinant frequency
23
what is autosomal linkage caused by
Genes found on same chromosome / autosome Inherited as one unit + no independent assortment Recombinant offspring – different combinations of alleles than either parents crossing over
23
what is epistasis
interaction of genes at different loci
24
example of epistasis
Lac operon
25
hypostatic vs epistatic
A gene affected by another gene – hypostatic Gene that affects the expression of another gene – epistatic
26
what is recessive epistasis
where the epistatic allele (the allele that masks another gene) is recessive two copies of epistatic alleles must be present for expression of hypostatic allele to be affected
27
what is dominant epistasis
epistatic allele is dominant only one copy of the epistatic allele must be present for expression of the hypostatic allele to be affected
28
gene
length of DNA that codes for single polypeptide
28
alleles
genes existing in two or more different forms
28
locus
position of genes on a chromosome
28
ratio - dihybrid unlinked
9:3:3:1
28
ratio - monohybrid
3:1
28
ratio - dominant epistatic
12:3:1
28
difference between continuous + discontinuous variation
28
ratio - recessive epistatic
9:3:4
28
ratio - dihybrid linked
3:1
28
what is continuous
differences between individuals of a species where the differences are quantitative (measurable)
29
at genetic level - continuous
Different alleles at a single locus have a small effect on the phenotype Different genes can have the same effect on the phenotype and these add together to have an additive effect If a large number of genes have a combined effect on the phenotype they are known as polygenes
29
what is discontinuous
differences between individuals of a species where the differences are qualitative (categoric
29
at genetic level - discontinuous
Different genes have different effects on the phenotype Different alleles at a single gene locus have a large effect on the phenotype Factor 8 - heamophillia
29
what is a selection pressure
environmental factors that effect chances of survival
30
Factors that affect the size of a population
Density – dependant factors = Dependant on population size = Competition / predation / parasitism / communicable disease Density-independent factors = Effect populations of all sizes in same way = Climate change / seasonal change / human activities – deforestation
30
Factors affecting evolution
mutation gene flow genetic drift genetic bottleneck founder effect
30
mutation
* Necessary for the existence of different alleles
31
gene flow
Movement of alleles between populations Immigration / emigration result in changes in allele frequency
31
genetic drift
Chance affects which individuals in population survive / breed + pass on alleles E.g – when population is small – chance can affect which alleles get passed onto the next generation Large populations – less likely - any chance variations in allele frequencies usually even out across the whole population
31
genetic bottlenecking
Occurs when previously large population suffers a dramatic fall in numbers Reduces genetic diversity = alleles are lost surviving individuals end up breeding and reproducing with close relatives genetic diversity greatly reduced
32
founder effect
extreme example of genetic drift occurs when only a small number of individuals from a large parent population start a new population made up of only a few individuals from the original population = only some of the total alleles from the parent population will be present not all gene pool present which alleles end up in new population = up to chance
33
what is stabilising selection
Natural selection that keeps allele frequencies relatively constant over time Average individuals favoured Very-low and very-high birth weights are selected against leading to the maintenance of the intermediate birth weights
33
what is directional selection
Natural selection that produces a gradual change in allele frequencies over several generations Individuals favoured in one direction Caused by change in environment / new allele that has appeared in population = advantageous
33
process of directional selection
Selection pressure that favours phenotype Phenotype is produced by specific alleles Individuals with favoured phenotype = fitter / more likely to pass on their alleles to offspring Frequency of advantageous allele increases
34
what is disruptive selection
Extremes are selected for
34
graphs - all selection types
34
what is the hardy-weinberg principle used for
to calculate allele frequencies in populations
34
what does the Hardy-Weinberg principle state
– in a stable population with no disturbing factors, the allele frequencies will remain constant from one generation to the next and there will be no evolution
35
conditions for hardy-weinberg principle
Organisms are diploid Organisms reproduce by sexual reproduction only There is no overlap between generations, i.e. parents do not mate with offspring Mating is random The population is large There is no migration, mutation, or selection Allele frequencies are equal in both sexes
35
hardy weinberg equations
35
35
what is speciation
formation of new species through process of evolution
36
events leading to speciation
Members of population becomes isolated – no longer interbreed – no gene flow between 2 populations Alleles within groups – random mutations – different selection pressures Accumulation of mutations + changes in allele frequency – large difference in phenotype over time
37
what is allopatric speciation
occurs as a result of geographical isolation most common type of speciation
38
describe allopatric speciation
occurs when populations of a species become separated from each other by geographical barriers creates two populations of the same species who are reproductively separated from each other no genetic exchange can occur between them If there are sufficient selection pressures acting to change the gene pools (and allele frequencies) within both populations then eventually these populations will diverge and form separate species changes in the alleles/genes of each population will affect the phenotypes present in both populations
39
what is sympatric speciation
takes place with no geographical barrier A group of same species living in the same place but in order for speciation to take place = exists two populations within that group and no gene flow occurs between them
40
how can sympatric speciation occur
via: Ecological separation Behavioural separation Polyploidy
41
what is ecological speciation
Populations are separated because they live in different environments within the same area
42
example of ecological separation
soil pH can differ greatly in different areas. Soil pH has a major effect on plant growth and flowering, so a population growing in soil with a slightly different pH may flower at a different time from another population leading to reproductive separation (and eventually genetic isolation) of the two populations
43
what is behavioural isolation
separated because they have different behaviours differences in feeding, communication or social behaviours = courting behaviours to attract a mate
44
examples of behaviours that lead to sympatric speciation
45
what is polyploidy
Occurs when an organism has more than two sets of homologous chromosomes
46
example of polyploidy
When a newly-arisen tetraploid (4n) plant tries to breed with its ancestral species (a backcross), triploid offspring are formed. These are sterile because they cannot form gametes with a balanced assortment of chromosomes. However, the tetraploid plants can breed with each other. So in one generation, a new species has been formed.
47
process of artificial selection / selective breeding
1. The population shows phenotypic variation - there are individuals with different phenotypes 2. A breeder selects an individual with the desired phenotype 3. Another individual with the desired phenotype is selected 4. two selected individuals should not be closely related to each other 5. The two selected individuals are bred together 6. The offspring produced reach maturity and are then tested for the desirable trait. Those that display the desired phenotype to the greatest degree are selected for further breeding 7. continues for many generations until all offspring display the desirable trait
47
example of selective breeding
farmers have selected female cows that have the highest milk yield and crossed them with male bulls related to high yield females economical benefit to farmers
47
what is artificial selection / selective breeding
- process by which humans choose organisms with desirable traits and selectively breed them together to enhance the expression of these desirable traits over time and over many generations
47
importance of maintaining a resource of genetic material for use in selective breeding including wild types.
important to maintain a resource of genetic material that includes types that are close to the original wild type (of the organism you are selectively breeding) This is important as it ensures that the gene pool for a particular species doesn't become too small (which can weaken the population by reducing variation)
47
ethics of selective breeding
lead to inbreeding results in a reduction in the gene pool an increased chance of: 1. Organisms inheriting harmful genetic defects - as there is a higher chance of harmful recessive alleles combining in an individual and being expressed in the phenotype 2. Organisms being vulnerable to new diseases - as there is less chance of resistant alleles being present in the reduced gene pool
48
examples of selective breeding in plants and animals

Biology - Module 6 (6 decks)

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