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Biology > M6 C20: patterns of inheritence > Flashcards

M6 C20: patterns of inheritence Flashcards

1
Q

how does variation occur?

A

mutations

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2
Q

why is variation important?

A

natural selection and evolution

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3
Q

what is chlorosis?

A

when leaves of plants look pale yellow due to cells not producing the right amount of chlorophyll

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4
Q

what is an effect of chlorosis?

A

reduces ability to make food in photosynthesis

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5
Q

what can cause chlorosis?

A

environmental factors such as:
lack of light
mineral deficiencies
virus infections

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6
Q

how can genetic factors contribute to animals body mass?

A

mutations in genes on chromosome 7 can cause fat deposition in the body to be altered causing more chance of weight gain

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7
Q

what are different versions of a gene called?

A

allele

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8
Q

what is a genotype?

A

genetic make-up of an organism

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9
Q

what is a phenotype?

A

observable characteristics of an organism

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10
Q

what is a modification?

A

when an environmental factors changes an phenotype of an organism

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11
Q

what is a dominant allele?

A

when present is always expressed

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12
Q

what is a recessive allele?

A

only expressed if 2 copies of it are present

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13
Q

what does homozygous mean?

A

two identical copies of an allele

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14
Q

what does heterozygous mean?

A

has 2 different alleles for a characteristic

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15
Q

what is continuous variation?

A

characteristic that can have any value within a range

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16
Q

what is the cause of continuous variation?

A

genetic and environmental

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17
Q

what is an example of continuous variation?

A

skin colour
animal mass

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18
Q

how is continuous variation genetically controlled?

A

polygenes- mutlipled genes

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19
Q

what is discontinuous variation?

A

characteristic that is only in discrete categories/ values

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20
Q

how is discontinuous variation genetically controlled?

A

one or 2 genes

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21
Q

what is the cause of discontinuous variation?

A

mostly genetic

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22
Q

what is an example of discontinuous variation?

A

blood group

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23
Q

what is monogenic inheritance?

A

inheritance of a single gene

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24
Q

what is codominance?

A

when 2 different allele for a gene, both of which are equally dominant

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25
how can multiple alleles code for a characteristic/
when there are more than 2 versions of a gene. however only 2 are present in an organism
26
what is a characteristic coded for by multiple alleles?
blood group
27
what are the co dominant and recessive alleles in blood groups?
Ia and Ib and dominant Io is recessive
28
what is the 23rd pair of chromosomes?
the sex chromosomes
29
what is meant by sex linked characteristics?
determined by genes of the sex chromosome
30
how are males more likely to display sex linked characteristics?
Y chromosome is shorter, therefore an recessive allele on the X chromosome aren't masked by a dominant allele on the Y chromosome so are expressed.
31
why are females less likely to display sex linked characteristics?
in females both X chromosomes are the same length so a recessive allele likely has a dominant allele on the other X chromosome
32
what are some examples of sex linked genetic disorders?
haemophillia
33
what will happen if a male inherits the recessive allele for a genetic disorder on his X chromosome/
it will be expressed and he will have the disorder as there is no dominant allele on the Y chromosome to mask this
34
what are females called who carry the recessive allele on one of their X chromosomes?
known as carriers as they are hetrozygous for the recessive gene may pass this gene on to their sons who could be affected
35
what is dihybrid inheritence?
inheritance of two different characteristics caused by two genes which may be located on different pairs of homologous chromosomes
36
why may the 9:3:3:1 ratio differ in offspring, when looking at dihybrid inheritence?
random fertilisation of gametes if genes being studied are on the same chromosome these are known as linked genes, if no crossing over these are more likely to be inherited together
37
what are linked genes?
genes that are likely to be inherited together as 1 unit because they are physically close to one another on the same chromosome.
38
what is epistasis?
when one gene masks or suppresses the expression of another
39
what is recessive epistasis?
presence of two copies of the recessive allele at the first locus prevents the expression of another allele at a second locus.
40
what is dominant epistasis?
dominant allele masks the expression of both dominant and recessive alleles at another locus
41
what can a deviation from expected phenotypic ratios suggest?
genes are linked epistatic genes
42
how do you work out recombination frquencey?
number of recombinant offspring divided by total number of offspring
43
what does recombinantion frequencey measure?
the amount of crossing over that has occured in meosis
44
why is chi squared used when looking at expected frequencey? | eg by looking at expected ratios and comparing to normal
it shows if differences are due to chance or if they are due to another reason (significant)
45
In biology, what hypotheris do we accept if thr O value is greater than the critical value?
A factor other than chance is causing the difference The null hypothesis can be rejected
46
what hypothersis do we accept if f the chi-squared value is smaller than the critical value?
Any differences are due to chance The null hypothesis is accepted no significant difference between observed and expected values
47
what are some factors affecting evolution?
mutations sexual selection gene flow (allele freq) genetic drift natural selection
48
what is genetic drift?
Genetic drift is a process that changes the frequency of an existing allele in a population due to random chance. It can result in the loss of beneficial alleles or the fixation of harmful alleles. When the allele itself is not responsible for the change in its frequency in a population,
49
what are the 2 factors that can influence the size of a population?
density indepepndent density dependent
50
what are density dependent factors?
dependent on population size, include competition, predation, paratism, disease
51
what are density independent factors?
affects all popualtion sizes includes climate change, natural disatsers, seasonal change, human activites
51
what is a founder effect?
when small populations arise due to establishment of new colonies from a few isolated individuals
52
is there high genetic diversity in populations that have experienced the founder effect?
display less genetic variation smaller gene pool
53
what is stabilizing selection?
the average is selected for and the extremes are selected against reduction in alleles that result in extremes
54
what is direcrtional selection?
when a change occurs and the most common phenotype is no longer the average. organisms with the less common and extreme phenotype are positively selected for
55
what is disruptive selection?
extremes are selected for and norm is selectted against
56
what is speciation?
formation of a new species through process of evolution
57
how does speciation occur?
members become isolated and no longer interbreed with the rest of the population so no gene flow occurs
58
what is allopatric speciation?
when members of a group are seperated by a physical barrier (geographically)
59
why does allopatric speciation occur?
the environments are different resulting in different selection pressures, which result in different physical adaptations
60
what is sympatric speciation?
occurs within species that share the same habitat but there is two populations within that group and no gene flow occurs between them
61
how can sympatric speciation occur?
Ecological separation- live in different environments within the same area Behavioural separation- Populations are separated because they have different behaviours
62
what is artificial selection?
AKA selective breeding humans identify and breed plants and animals for specific desirable traits. This involves selecting breeding pairs to produce offspring that exhibit these traits, enhancing and perpetuating them in future generations.
63
what is inbreeding?
breeding of closely related organisms
64
what are some problems caused by inbreeding?
limited gene pool reduced genetic diversity genetic disorders- recessive alleles have a higher freq in inbred population

Biology (23 decks)

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