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Biology > Module 6 patterns of inheritance > Flashcards

Module 6 patterns of inheritance Flashcards

1
Q

What processes is variation essential for?

A

natural selection and therefore evolution

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2
Q

What is genetic variation caused by?

A

-random fusion of gametes at fertilisation
-mutations
-during meiosis the genes on homologous chromosomes are reshuffled through a process called recombination which produces new combinations of genes
-independent segregation also creates genetic variation as pairs of homologous chromosomes are randomly separated

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3
Q

Define alleles

A

different versions of the same gene

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4
Q

What is the difference between environmental and genetic variation?

A

environmental isn’t inherited or past onto offspring

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5
Q

Give an example of environmental AND genetic variation in plants

A

chlorosis- leaves turn yellow due to the cells not producing enough chlorophyll which means the plant looses its ability to photosythesise

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6
Q

Define dominant allele

A

version of a gene that will always be expressed if present in an organism

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7
Q

Define recessive allele

A

only will be expressed if 2 copies are present in an organism

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8
Q

Define homozygous

A

have 2 identical alleles for 1 characteristic

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9
Q

Define heterozygous

A

have 2 different alleles present for a characteristic so the dominant allele will be expressed

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10
Q

Define phenotype

A

appearance of an organism/ physical characteristics

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11
Q

Define genotype

A

alleles present within an organism

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12
Q

Define gene pool

A

sum total of all the genetics in a population at a given time

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13
Q

Describe continuous variation

A

-characteristic that can take any value within a range
-cause of variation can be genetic or environmental
-controlled by a number of genes (polygenic)
-e.g height, body mass

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14
Q

Describe discontinuous variation

A

characteristic can only appear in specific (discrete) values
-mostly genetic
-one or 2 genes control
-blood group, shoe size, eye colour

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15
Q

What does independent assortment mean?

A

every possible combination of alleles is equally likely to happen

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16
Q

What does codominance mean?

A

both alleles for the same characteristic are simultaneously expressed in he heterozygote

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17
Q

Does co dominance influence phenotypic ratios?

A

yes

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18
Q

What are the 4 different blood groups determined by

A

3 alleles of a single gene for isoagglutinogen, I, on chromosome 9

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19
Q

Where does a characteristic caused by a recessive allele on the x chromosome happen most frequently?

A

in males as females will also have a dominant allele present in their cells

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20
Q

What genes are men functionally haploid for?

A

X linked genes

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21
Q

What is haemophilia?

A

Blood disorder that is X linked

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22
Q

How can females be carriers of haemophilia?

A

-if they are heterozygous for the coding gene

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23
Q

What are the other 22 pairs of chromosomes known as?

A

autosomes

24
Q

Structure of autosomes?

A

each pair is homologous, match in length and contain the same genes at the same loci

25
Q

When are genes likely to be inherited together?

A

when they are close to one another and on the same chromosome

26
Q

How are genes likely to be inherited together?

A

there’s no independent assortment during meiosis unless the alleles are separated by chiasmata

27
Q

How does a recombinant gamete form?

A

if crossing over occurs in prophase 1, alleles are exchanged between 2 sister chromatids

28
Q

What increases the chances of recombination?

A

the further away the genes are

29
Q

What is epistasis?

A

interaction of genes at different loci to produce the phenotype of an organism

30
Q

What is recessive epistasis?

A

-epistatic gene is recessive
-so 2 copies of the epistatic allele must be present for expression of the hypostatic allele to be affected

31
Q

What is dominant epistasis?

A

-epistatic allele is dominant
-so only 1 needs to be present to affect expression of the hypostatic allele

32
Q

What does epistasis often involve?

A

a pathway where expression of one gene is dependent on the function of another gene

33
Q

What does population genetics investigate?

A

how allele frequency within populations change over time

34
Q

Define allele frequency

A

relative frequency of a particular allele within a population
-the frequency in which an allele occurs isn’t linked to whether it codes for a dominant or recessive characteristic and is not fixed as it can change over time in response to changing conditions

35
Q

What does evolution involve in terms of allele frequency?

A

a long term change in the allele frequencies of a population e.g alleles for antibiotic resistance have increased in many bacteria populations overtime

36
Q

How does allele frequency increase?

A

if an allele is particularly advantageous for survival an individual that possesses it is more likely to survive and reproduce so the allele is more likely to be passed onto offspring and overtime this allele will increase in frequency.

37
Q

What does the hardy weinberg principle rely on?

A

-diploid breeding programme with 2 potential alleles
-population is stable
-population has no disturbing factors e.g mutations, migrations or emigrations
-no selective pressure for or against a specific genotype
-population size is infinite

38
Q

what does p^2, 2pq and q^2 each stand for in the hardy weinberg equation?

A

p^2=frequency of homozygous dominant genotype
2pq=frequency of the heterozygous genotype in the population
q^2=frequency of homozygous recessive genotype

39
Q

What is the chi squared test used for?

A

-to compare observed phenotypic ratios with expected phenotypic ratios

40
Q

Why will the observed results almost always differ from the expected?

A

due to chance

41
Q

What kind of data is needed in order for a chi squared test to be used?

A

-data is discontinuous
-data shows absolute numbers (whole numbers)

42
Q

What does the null hypothesis mean?

A

there is no significant difference and the difference is due to chance

43
Q

What do large chi squared values mean?

A

there is a significant difference and there must be a reason for this

44
Q

How do you work out the degrees of freedom?

A

number of categories-1

45
Q

Define gene flow

A

movement of alleles between different populations

46
Q

Where does genetic drift occur?

A

in small populations where there is a change in allele frequency due to the random nature of mutation

47
Q

Describe genetic bottle necks

A

-sudden reduction in genetic variation in a population
-can be caused by environmental factors like disease, flooding and famine
-a small gene pool means that genetic drift has more of an impact on these populations

48
Q

What is stabilising selection?

A

-natural selection favours an average phenotype
-the selection pressure selects against the extreme phenotypes
-only takes place in environments that change
-this reduces alleles at the extremes and increases the number of average alleles

48
Q

Describe the founder effect

A

-when a new population is founded, their genetic variation is only a subset of the original population
-when a population is founded by a small number of individuals their genetic variation is unlikely to be representative of the population they came from

49
Q

What is directional selection?

A

-natural selection favours the extreme phenotype
-the selection pressures select against all other phenotypes
-takes place after an environment has experienced a change

50
Q

Describe the process of speciation

A

-members of a population become reproductively isolated resulting in no gene flow between 2 groups
-the environment of each group may be different or change resulting in different selection pressures which drive the evolution of the 2 groups in different directions as different characteristics will be selected for and against
-the accumulations of mutations and changes in allele frequency over many generations eventually leads to significant changes in phenotype and are now not able to produce fertile offspring

51
Q

What is disruptive selection?

A

where the norms are selected against

52
Q

What is allopatric speciation?

A

-where 2 or more populations are geographically isolated from one another
-the environments of the 2 groups will most likely be different which will put different selection pressures on each population and drive evolution in separate directions
-if they are geographically isolated for a long time, their allele frequencies will change so much they will no longer be able to breed to produce fertile offspring

53
Q

What is sympatric speciation?

A

-occurs within populations that share the same habitat
-happens less frequently than allopatric
-more common in plants than animals
-2 different species breed together and form fertile offspring but it will not be able to breed with either parents population

54
Q

What is artificial selection?

A

-humans choose animals and crops to breed based on genetic characteristics
-offspring of this cross showing the best examples of desired traits are then selected to breed

55
Q

Advantages of selective breeding

A

-crops can be bred to increase disease resistance which increases yield
-domesticated dogs with caring nature to coexist with humans
-flowers made appealing to increase profit

56
Q

Disadvantages of selective breeding

A

-inbreeding causes inherited defects and make them susceptible to disease
-reduced variation so hard to adapt to environmental change

Biology (17 decks)

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