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adv biology > 2.3 variation and sexual reproduction > Flashcards

2.3 variation and sexual reproduction Flashcards

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1
Q

what environmental factors, other than temperature, can be used to determine the sex of an organism?

A

size, parasitic infection, competition

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2
Q

where is TSD most prevalent?

A

in reptiles

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3
Q

what is TSD?

A

where the temperature experienced during the incubation period of the embryo determines its sex

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4
Q

what is the main benefit of being a hermaphrodite?

A

their mate does not have to be of the opposite sex if they are struggling to find one

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5
Q

do hermaphrodites have partners to exchange gametes with

A

yes usually

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6
Q

what is a hermaphrodite?

A

a species that has both male and female reproductive organs, so can produce both types of gametes

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7
Q

what does x inactivation leave

A

only one active x chromosome in each cell of the female embryo

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8
Q

what does x inactivation mean for carriers?

A

they are less likes to be affected by deleterious mutations on the x chromosomes

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9
Q

what are two qualities of x inactivation

A

random in each cell
irreversible

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10
Q

what does x-inactivation prevent

A

female from presenting double the quantity of x linked gene products which could be harmful to cells

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11
Q

what happens during x inactivation

A

during embryonic development of every female, most of one of the two X chromosomes in each cell inactivates

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12
Q

what does heterogametic mean

A

females produce gametes with two possible combinations of chromosomes

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13
Q

what does homogametic mean

A

females produce gametes with the same combination of chromosomes

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14
Q

a male has a recessive allele on one X chromosome…

A

which has no copy to mask its effects

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15
Q

a female has a recessive allele on one X chromosome…

A

which can be masked by a dominant allele on the other X

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16
Q

what is the root cause of the pattern of inheritance called sex linkage?

A

the Y chromosome lacks many genes found on its homologous x chromosome

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17
Q

why are x and y homologous?

A

they pair up during meiosis I

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18
Q

what determines the development of male traits in most mammals?

A

the SRY gene on the Y chromosome

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19
Q

what do sex chromosomes do?

A

determine whether an individual is male or female

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20
Q

what are the four things we must remember about meiosis II?

A

single chromosomes line up at the equator
spindles contract and chromatids move to opposite poles
cytokinesis occurs
4 non-identical haploid gametes

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21
Q

what does a greater distance between linked genes mean?

A

there is a greater chances of crossing over, resulting in greater frequency of allele recombination

22
Q

what are linked genes?

A

genes on the same chromosome

23
Q

what are linked genes?

A

genes on the same chromosome

24
Q

what does independent assortment result in?

A

the production of gametes with varying combinations of maternal and paternal chromosomes

25
Q

how does meiosis I end?

A

cytokinesis occurs and two daughter cells are formed

26
Q

what happens fourth in meiosis I?

A

spindles contract and each homologous partner moves to opposite poles of the cell

27
Q

what is independent assortment?

A

homologous chromosomes line up at the equator independent of maternal and paternal origin

28
Q

what does crossing over result in?

A

recombination of alleles as info is shared between linked genes

29
Q

what happens third in meiosis I?

A

homologous chromosomes line up at the equator and independent assortment occurs

30
Q

what happens second in meiosis I?

A

chiasmata form at points of contact between non-sister chromatids and crossing over occurs

31
Q

what begins meiosis I?

A

chromosomes condense and homologous chromosomes pair up

32
Q

does meiosis occur in asexual reproduction?

A

no

33
Q

what are two examples of cells that undergo horizontal gene transfer?

A

bacteria and yeast cells (prokaryotes)

34
Q

what does horizontal gene transfer allow for?

A

gene transfer between individuals = increased variation and faster evolutionary change

35
Q

in which organisms can horizontal gene transfer occur?

A

asexually reproducing organisms

36
Q

what allows for natural selection and evolution to take place in asexually reproducing populations?

A

mutations can sometimes occur that allow for small degrees of variation

37
Q

where is parthenogenesis more common?

A

cooler climates with low parasite density

38
Q

what is parthenogenesis?

A

reproduction from a
female gamete without fertilisation.

39
Q

what are examples of asexual reproduction in eukaryotes include?

A

vegetative cloning in plants
parthenogenesis in lower plants and animals

40
Q

asexual reproduction involves one parent producing daughter cells - what does this allow?

A

an unlimited colony to be produced over time

41
Q

when can asexual reproduction be a particularly successful reproductive strategy?

A

in narrow, stable niches
recolonising disturbed habitats

42
Q

why does sexual reproduction remain the main reproductive method used?

A

the benefit of increased genetic variation outweighs the costs

43
Q

why is genetic variation vital?

A

provides the raw material required for adaptation
reduces the chance of parasitic infection

44
Q

what is the cost of asexual reproduction?

A

no variation

45
Q

what is the benefit of sexual reproduction?

A

variation = fundamental to evolution

46
Q

what are the costs of sexual reproduction?

A

males are unable to produce offspring
only half of each parent’s genome is passed on
disrupts successful genomes

47
Q

what are the benefits of asexual reproduction?

A

time-efficient
less energy required
only 1 parent required
increased number of offspring regularly

48
Q

what is asexual reproduction?

A

a mode of reproduction by which offspring arise from a single organism and inherit the genes from that parent only

49
Q

what are 2 problems arising from heterogametic males and homogametic females

A

males and females will have different inheritance patterns
female has a potential double dose effect from the 2 copies of the non-homologous section

50
Q

what is sexual reproduction?

A

the production of new living organisms by combining genetic information from individuals of different types

adv biology (13 decks)

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