Unit 2-Variation And Sexual Reproduction Flashcards

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1
Q

Give three disadvantages of sexual reproduction

A

High metabolic cost, gametes are made by special type of cell division
Reproduction rate is much slower
Only half of the population can actually produce offspring

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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

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

A

Horizontal Gene Transfer (HGT)

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4
Q

Give examples of vegetative cloning methods in plants

A

Bulbs - Daffodils
Tubers - Potato
Rhizomes - Ginger
Spores - Fungi

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5
Q

What is parthenogenesis?

A

Production of haploid offspring without needing males or fetilization

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6
Q

Give conditions that parthenogenesis is common

A

Cooler Climates
Lower level of Parasitism

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7
Q

In what conditions is asexual reproduction beneficial?

A

Very narrow and stable niche
Recolonising disrupted habitats

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8
Q

Give an example of an area where asexual reproduction is beneficial

A

Butter cups using stolons to spread into flower beds with clear soil, gaining a competitive advantage

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9
Q

What is the diploid number of chromosomes for humans?

A

46

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10
Q

Give characteristics that are the same in homologous chromosomes

A

Same size
Same centromere position
Same genes at the same loci

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11
Q

What is the first stage in meiosis?

A

Long uncoiled chromosomes replicate to form two identical chromatids
Chromosomes coil up and become visibile

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12
Q

What is the site called where homologous chromosomes cross called?

A

Chiasma (plr. Chiasmata)

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13
Q

What are seperated during Meiosis I?

A

Pairs of homologous chromosomes (Not actually any chromosomes, its the pairs)

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14
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

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15
Q

How many different combinations of chromosomes is there in the resulting haploid cells where n is the number of homologous pairs?

A

2^n

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16
Q

What does Chiasmata allow?

A

The chromosomes to exchange DNA with their homologous partner

17
Q

What happens during crossing over?

A

Chromosomes touch at chiasmata
Allows exchanging of DNA with homologous partner
Chromosomes in the gametes can have new combinations of alleles

18
Q

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

A

Recombination

19
Q

The further apart genes are on a chromosome the more likely _____?

A

they are to have a chiasma form between them, leading to new allele combinations in the gametes

20
Q

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

A

Genetic Factors
Enviromental Factors

21
Q

What are hermaphordites?

A

Organisms which individually have both male and female reproductive structures

22
Q

What is the heterogametic sex in humans?

A

Male (XY)

23
Q

What causes embryos to develop as male?

A

SRY gene

24
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

25
Q

What is the default pathway for embryos?

A

To develop as a female

26
Q

What leads to sex linked patterns of inheritance?

A

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

27
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

28
Q

What is X inactivation an example of?

A

Dosage Compensation

29
Q

What does dosage compensation 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

30
Q

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

A

1

31
Q

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

A

2

32
Q

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

A

Female

33
Q

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

A

Temperature
Size
Competition
Parasitic Infection

34
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

35
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

36
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

37
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

38
Q

What type of cell undergoes meosis?

A

Gamete mother cell