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Advanced Higher Biology 2022 > Unit 2 - KA2.3 Variation and Sexual Reproduction > Flashcards

Unit 2 - KA2.3 Variation and Sexual Reproduction Flashcards

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1
Q

Give three disadvantages/costs of sexual reproduction

A

1 - Reproduction rate is much slower
2 - Males unable to produce offspring
3 - Successful parental genomes are disrupted as only half the genome is passed on

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2
Q

Give two disadvantages of needing males for sexual reproduction

A

1 - Males are unable to produce the offspring, so only half the population can reproduce
2 - Only half of each parent’s genome is passed on so disrupts successful parental genomes

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3
Q

List the three advantages of sexual reproduction

A

1 - Greater genetic variation
2 - Genetic variation allows sexually reproducing organisms a better chance of survival under changing selection pressures.
3 - Variation provides the raw material required to keep running in the Red Queen’s arms race between parasites and their hosts

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4
Q

List the three advantages of asexual reproduction

A

1 - Maintains the parent’s entire genome
2 - Advantage in re-colonising disturbed habitats
3 - Faster reproduction rates

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5
Q

Explain why maintaining the parental genome is an advantage in asexual reproduction.

A

In very narrow, stable niches it is advantageous as the offspring will be well adapted to this niche.

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6
Q

In what conditions is asexual reproduction beneficial?

A

1 - Very narrow and stable niche
2 - Recolonising disrupted habitats

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7
Q

Explain why the red queen hypothesis helps explain the persistence of sexual reproduction over time.

A

1 - Hosts better able to resist and tolerate parasitism have greater fitness.
2 - Parasites better able to feed, reproduce and find new hosts have greater fitness.
3 - If hosts reproduce sexually, the genetic variability in their offspring reduces the chances that all will be susceptible to infection by parasites

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8
Q

What are two examples of asexual reproduction in eukaryotes?

A

1 - Vegetative cloning in plants
2 - Parthenogenesis in some animals.

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9
Q

What is parthenogenesis?

A

Production of haploid offspring without needing males gametes to fertilise the female gamete.

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10
Q

Give conditions that parthenogenesis is common

A

1 - Cooler Climates
2 - Lower level of Parasitism

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11
Q

Name a mechanism used by bacteria to allow the exchange of genetic material between generations

A

Horizontal Gene Transfer (HGT)

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12
Q

What is the diploid number of chromosomes for humans?

A

46

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13
Q

Give characteristics that are the same in homologous chromosomes

A

1 - Same size
2 - Same centromere position
3 - Same genes at the same loci

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14
Q

What is a gametocyte?

A

Diploid cells located in the sex organs that produce the male and female sex cells.

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15
Q

What happens in the first stage in meiosis I?

A

The chromosomes, which have replicated prior to meiosis I, each consist of two genetically identical chromatids attached at the centromere. The chromosomes condense and the homologous chromosomes pair up.

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16
Q

What happens in the second stage in meiosis I?

A

Chiasmata form at points of contact between the non-sister chromatids of a homologous pair and sections of DNA are exchanged

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17
Q

What happens during crossing over?

A

Chromosomes touch at chiasmata which allows exchanging of DNA with homologous partner. Chromosomes in the gametes can have new combinations of alleles than the parent genome.

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18
Q

What is the process that allows chromosomes in the gametes to have new combinations of alleles?

A

Recombination due to crossing over.

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19
Q

What happens in the third stage in meiosis I?

A

Spindle fibres attach to the homologous pairs and line them up at the equator of the spindle

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20
Q

What happens in the fourth stage in meiosis I?

A

The chromosomes of each homologous pair are separated and move towards opposite poles

21
Q

What happens in the fifth stage in meiosis I?

A

Cytokinesis occurs and two daughter cells form

22
Q

What happens during the stages of meiosis I

A

1 - The chromosomes, which have replicated prior to meiosis I, each consist of two genetically identical chromatids attached at the centromere. The chromosomes condense and the homologous chromosomes pair up
2 - Chiasmata form at points of contact between the non-sister chromatids of a homologous pair and sections of DNA are exchanged.
3 - Spindle fibres attach to the homologous pairs and line them up at the equator of the spindle.
4 - The chromosomes of each homologous pair are separated and move towards opposite poles.
5 - Cytokinesis occurs and two daughter cells form

23
Q

What happens during the stages of meiosis II

A

Each of the two cells produced in meiosis I undergoes a further division during which the sister chromatids of each chromosome are separated. A total of four haploid cells are produced

24
Q

What is the site called where homologous chromosomes cross called?

A

Chiasma (plr. Chiasmata)

25
Q

What is Independent Assortment?

A

A way of producing variation between daughter cells due to the fact there is no control over which chromosomes of each pair goes to which side of the cell

26
Q

What are separated during Meiosis I?

A

Pairs of homologous chromosomes, e.g. X-X are separated NOT the chromatids that make up X

27
Q

What are separated during Meiosis II?

A

Sister chromatids, e.g. the chromatids that make up X are pulled apart NOT the homologous chromosomes X-X

28
Q

What are the two types of factors that can influence the sex of individual?

A

1 - Genetic Factors
2 - Environmental Factors

29
Q

Describe the work of the SRY gene

A

Acts as a master switch which triggers a cascade to activate all male genes in the genome

30
Q

What causes embryos to develop as male?

A

SRY gene

31
Q

What is the heterogametic sex in humans?

A

Male (XY)

32
Q

What is the homogametic sex in humans?

A

Female (XX)

33
Q

What is different about the Y chromosome compared to the X chromosome?

A

The Y chromosome lacks most of the corresponding homologous alleles that are on the X chromosome, so many genes only have one allele as opposed to two.

34
Q

What leads to sex linked patterns of inheritance?

A

The fact that X and Y chromosomes do not have homologous alleles

35
Q

Which sex is affected most by sex-linked disorders?

A

Males as they only have one copy of each gene due to the shorter Y chromosome.

36
Q

What is X inactivation?

A

Most of the genes on one X chromosome are inactivated so that cells have a single working copy of the X chromosome genes

37
Q

Why does X inactivation happen?

A

To prevent a double dose of gene products, which could be harmful to cells.

38
Q

What does X inactivation ensure?

A

The female has exactly the same level of gene products as a male and do not get a double dose of gene products

39
Q

What are hermaphrodites?

A

Organisms which individually have both male and female reproductive structures

40
Q

Describe the benefits of hermaphrodites?

A

If the chance of encountering a partner is an uncommon event it will increase reproductive success.

41
Q

How many alleles are needed for a male to express the deleterious allele?

A

1

42
Q

How many alleles are needed for a female to express the deleterious allele?

A

2

43
Q

Who is less likely to express the effect of a deleterious allele carried on an X chromosome?

A

Female

44
Q

What environmental factors have an effect on sex or sex ratio?

A

1 - Temperature
2 - Size
3 - Competition
4 - Parasitic Infection
5 - Resource Availability

45
Q

Give an example of a species where temperature effects the sex ratio and explain how it does that

A

Hermann’s Tortoise If eggs are incubated at less than 31 degrees - all males produced. If eggs are incubated at above 31 degrees - all females produced

46
Q

Give an example of a species where size effects the sex ratio and explain how it does that

A

Clown Fish live in groups, one large female and some smaller females. When the largest female is removed, the largest male becomes a female

47
Q

Give an example of a species where competition effects the sex ratio and explain how it does that

A

Lesser Mouse Lemur - If a solitary female detects urine of another female, she produces more male offspring

48
Q

Give an example of a species where parasite infection effects the sex ratio and explain how it does that

A

Insects infected by Wolbachia Bacteria. Bacterial infection of the eggs kills the males or feminises them

Advanced Higher Biology 2022 (3 decks)

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