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George Biology > Patterns of inheritance and variation chp 20 > Flashcards

Patterns of inheritance and variation chp 20 Flashcards

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1
Q

what is an example of a condition in plants that can be brought about via environment and genotype

A

chlorosis

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2
Q

What are some environmental factors that can cause chlorosis in plants

A
  • lack of light (plants will turn off chlorophyll production reserve resources)
  • mineral deficiencies (lack or iron of Mg, they are needed in chlorophyll production)
  • virus infections (they can interfere with metabolism of cells and so cannot produce pigment)
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3
Q

what is the difference between alleles and genes within a species

A

all individuals within a species have the same genes but not necessarily the same alleles of these genes

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4
Q

what influences an individuals phenotype

A

the individuals mixture of alleles an organism inherits from its parents

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5
Q

what determines the combination of alleles within an organism

A

by sexual reproduction involving meiosis, the random fusion of gametes at fertilisation

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6
Q

how many alleles are inherited by an individual for most genes

A
  • 2
  • one from each parent
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7
Q

what is meant by genotype

A
  • the combination of alleles an organism inherits for a certain characteristic
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8
Q

what is meant by phenotype

A

the observable characteristics of an organism

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9
Q

what is meant by modifications in respect to phenotype

A

changes to a organisms phenotype caused by the environment not there genes

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10
Q

what is meant by a dominant allele

A
  • a version of the gene that will always be expressed if present in an organism
  • an individual showing the dominant characteristic could be homo- or hetro-zygous
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11
Q

what is meant by a recessive allele

A
  • will only be expressed if 2 copies of the alleles are present in an organism
  • an individual has a recessive phenotype, they will have a homozygous genotype
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12
Q

what are all the different terms that can be used to describe the genotype of an organism

A
  • homozygous dominant
  • homozygous recessive
  • heterozygous (no need for dominant or recessive as will also be dominant)
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13
Q

what is meant by continuous variation

A
  • a characteristic that can take any value within a range
  • example is height or weight
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14
Q

what is meant by discontinous variation

A
  • a characteristic that can only appear in specific values
  • examples include blood group
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15
Q

how many genes are involved with continuous variation

A
  • polygenic
    ^controlled by a number of genes
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16
Q

how many genes are involved with discontinous variation

A
  • 1 or 2 genes
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17
Q

what is meant by monogenic inheritance

A
  • the kind of inheritance whereby a trait is determined by the expression of a single gene or allele, not by several genes as in polygenic inheritance.
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18
Q

what are the steps to properly analyse a genetic cross diagram

A
  • 1) state phenotype of both parents
  • 2)state genotype of both parents. e.g Aa, A = dominant allele, a = recessive allele
  • 3)state gamete of each parent.
  • 4)use punnet square to show results of gamete
  • 5)state ratio/percentage/fraction of each genotype produced
  • 6) state the phenotype that would arise from each genotype
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19
Q

what is meant by true or pure breeding individual

A
  • there genotype is homozygous
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20
Q

what would be the product of breeding homozygous dominant and homozygous recessive individuals

A
  • all offspring heterozygous
  • offspring demonstrate the dominant allele phenotype
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21
Q

what is meant by F1 generation

A

the first generation of offspring produced by a set of parents

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22
Q

what is meant by codominance in reference to alleles

A

phenomenon in which two alleles are expressed to an equally dominant degree within an organism

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23
Q

what is an example of where codominance occurs within plants

A
  • the colour of snapdragon flowers
  • there is an allele that codes for red flowers and an allele than codes for white flowers, when mixed they can create pink flowers
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24
Q

how can codominance result in 3 different phenotypes in snapdragon flowers

A
  • 1)red flowers - plant is homozygous for the allele coding for the production of red pigment
  • 2)white flowers - plant is homozygous for the allele coding for no pigment
  • 3)pink flowers - plant is heterozygous, single allele present which codes for red pigmentation produces enough pigment to produce pink flowers
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25
Q

how are codominant alleles represented

A
  • a letter is chosen to represent gene
  • secondary letter then shown as superscript of gene letter. e.g. C^w for white flowers and C^r for red flowers
26
Q

what is an example of something in humans that is determined by genes with multiple alleles

A
  • blood group
27
Q

how many pairs of chromosomes do humans have

A
  • 23 pairs
  • 46 individual chromosomes
28
Q

what is the 23rd pair of chromosomes within males and females

A
  • males - XY
  • females - XX
29
Q

what is meant if a gene is described as sex linked

A
  • characteristics determined by genes carried on the sex chromosomes (X & Y, not really Y)
30
Q

why are males more susceptible to recessive conditions

A
  • Y chromosome is smaller than the X (doesnt contain all genes that X has)
  • there are genes in the X chromosome that males have only 1 copy of,
  • they only need one recessive allele to gain the recessive condition
  • females have to inherit 2 recessive alleles to gain it which is much rarer
31
Q

what is an example of a sex-linked genetic disorder

A
  • Haemophilia (recessive condition)
  • ^blood is slow to clot due to low level of clotting factors
32
Q

what is meant by dihybrid inheritance

A
  • the inheritance of 2 characteristics that are controlled by different genes at different loci
33
Q

what is the expected ratio for the F2 generation of dihybrid inheritance

A

9:3:3:1

34
Q

what can affect the ratio of actual offspring produced

A
  • fertilisation of gametes is random (more prominent in smaller sample sizes)
  • genes being studied are linked genes, if no crossing over occurs the alleles for the 2 characteristics will always be inherited together
35
Q

what is the formula for the chi-squared test
what does each thing represent

A
36
Q

what does the chi-squared test measure

A
  • measures the side of the difference between the results you actually get and those you expected (helps determine whether differences are significant or not)
37
Q

what do P values mean

A
  • p values = probability it was down to chance
  • smaller values means strong evidence (smaller value of chance)
  • larger values mean weak evidence (bigger value for chance)
  • if p value if greater than 0.5 results are likely to be down to chance and so must accept null hypothesis
38
Q

whats the formula for degree of freedom

A

DF= number of variables in experiment - 1

39
Q

what is meant by a critical value

A

the minimum value of a statistical test that gives a 5% probabilty its down to chance so the null hypo can be rejected

40
Q

what is epistasis

A

when the expression of one gene is controlled by the inheritance of alleles of another gene at a different loci

41
Q

what is a hypostatic gene

A

a gene that is affected by another gene

42
Q

what is recessive epistasis

A

when the inheritance of recessive alleles causes the hypostatic gene to be masked

43
Q

what is dominant epistasis

A

when the inheritance of dominant alleles causes the hypostatic gene to be masked

44
Q

how could the epistatic gene actually cause the hypostatic gene to be masked

A

is the epistatic gene coded for an enzyme that modifies a precursor molecule so that the next enzyme in the pathway will not form complexes

45
Q

what do the hardy-weinberg principle state

A

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

46
Q

what is the hardy-weinberg equation

A

p^2 + 2pq + q^2

47
Q

define gene pool

A

sum of total of all genes in a population at any given time

48
Q

define allele frequency

A

relative frequency of a particular allele in a population

49
Q

what factors affect evolution

A

mutation
sexual selection
gene flow
genetic drift
natural selection

50
Q

what are limiting factors

A

density-dependent factors
density-independent factors

51
Q

what are density-dependent factors

give examples

A

depend on pop size
e.g.
competition, predation, parasitism, communicable disease

52
Q

what are density-independent factors

A

affect pops the same no matter of size
e.g
climate change, natural disasters, season changes

53
Q

what is stabalising selection

A

extreme characteristics slected against and modal value selected for increase frequency of alleles coding for this

54
Q

what is directional selection

A

one of the extreme phenotypes is selected for and alleles coding for this become more frequent
occurs after change in environment

55
Q

what is disruptive selection

A

extremes are selected for, increase the allele frequncy that code for these, reducing ‘average’ allele frequency

56
Q

define speciation

A

formation of new species via process of evolution

57
Q

what events occur that lead to speciation

A

pops become isolated and no-longer interbreed (no gene flow)
random mutation accumilate
due to random mutations populations can no longer interbreed to make fertile kids

58
Q

what is allopatric speciation

A

populations become isolated via geogrphical barrier

59
Q

what is sympatric speciation

A

2 species in the same habitat interbreed to form fertile offspring that cannot form fertile offspring with either species and is a new species

60
Q

what is meantby the wild type

A

the allele coding for the most common charactersitic

61
Q

what is pre and post zygotic sympatric speciation

A

prevents species coming together to form zygote is pre
zygote is infertile is post

George Biology (71 decks)

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