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genetic info, variation and relationships between organisms > genetic diversity > Flashcards

genetic diversity Flashcards

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1
Q

Give 2 possible causes of variation that result from meiosis during gamete formation

A
  • Random segregation of chromosomes

* Crossing over and recombination of chromosomes

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2
Q

Explain what happens to chromosomes in meiosis

A
  • Chromosomes condense
  • Chromosomes undergo independent segregation and arrange themselves in homologous pairs
  • Crossing over and recombination of sections of chromosomes (this is rare)
  • Chromosomes join to spindles at the middle of the cell joined by the centromere
  • Homologous chromosomes are pulled apart to opposite poles (meiosis 1)
  • The pairs or chromosomes are then separated at the centromere in meiosis 2 producing 4 genetically unique gametes.
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3
Q

Describe how meiosis causes variation and explain the advantage of variation to the species

A
  • Crossing over
  • Independent assortment/segregation (Random assortment)
  • Some members of the species will be better adapted so may survive if the environment changes
  • So will be able to reproduce and pass on the advantageous alleles
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4
Q

What is the biological importance of reducing the chromosome number when the cell divides by meiosis?

A

As the diploid number is restored during fertilisation

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5
Q

State ways in which meiosis and mitosis are different

A
  • Meiosis reduces the chromosome number where as mitosis maintains the chromosome number
  • In meiosis chromosomes associate in pairs where as in mitosis chromosomes do not pair
  • In meiosis there are 2 nuclear divisions that produce 4 gametes where as in mitosis there is 1 nuclear division producing 2 body cells
  • Meiosis results in genetically unique daughter cells where as in mitosis the daughter cells are all genetically identical
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6
Q

Briefly go through the stages of meiosis 1

A
  1. Homologous chromosomes pair up randomly (independent segregation/assortment)
  2. Chromatids from each pair wrap around each other then crossing over and recombination of portions of chromatids occurs.
  3. One of each pair of chromosomes is randomly separated into 2 daughter cells.
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7
Q

Briefly go through the stages of meiosis 2

A
  1. Sister chromatids are pulled apart at the centromere by spindle fibres and separate into 4 haploid daughter cells
  2. Resulting gametes have varying combinations of alleles
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8
Q

Describe the role of the centromere in mitosis

A

It holds the chromatids together
It attaches the chromatids to the spindle and then splits the chromatids apart pulling them to separate poles of the cell

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9
Q

Homologous chromosomes carry the same genes but are not genetically identical. Why?

A

Homologous chromosomes have different alleles

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10
Q

Meiosis results in cells that have the haploid number of chromosomes and show genetic variation. How?

A
  • Homologous chromosomes pair up
  • Crossing over produces new combinations of alleles
  • Chromosomes separate at random
  • This produces varying combinations of chromosomes
  • Chromatids then separate at meiosis 2
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11
Q

Explain the role of independent segregation in meiosis

A
  • To provide genetic variation.
  • Allows different combinations of maternal and paternal chromosomes.
  • Produces haploid cells.
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12
Q

Identify the 2 ways that meiosis produces variation

A

crossing over

independent segregation

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13
Q

Name an event that occurs during division 1 of meiosis that does not occur in division 2

A

pairing up of homologous pairs, crossing over followed by their separation to either pole

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14
Q

How is mitosis similar to the second division of meiosis?

A

separation of sister chromosomes

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15
Q

Define mutation.

A

Any change to the quantity of bases or the base sequence of DNA in an organism.

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16
Q

Identify the 3 types of mutation that can occur.

A

Identify the 3 types of mutation that can occur.

  1. Base substitutions
  2. Base deletions
  3. Chromosome mutations
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17
Q

Describe how DNA nucleotide substitutions can lead to a non-functional protein.

A
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18
Q

Describe how DNA nucleotide deletions can lead to a non-functional protein.

A
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19
Q

Describe how DNA nucleotide deletions can lead to a non-functional protein.

A
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20
Q

What is a chromosome mutation?

A
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21
Q

What is the equation for calculating the possible chromosome combinations as a result of independent segregation during meiosis.

A
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22
Q

What is the equation for calculating the possible chromosome combinations as a result of independent segregation during meiosis AND random fertilisation of gametes.

A
23
Q

explain the difference in a cell that has under gone meiosis 1 and meiosis 2

A
24
Q

How is chromosome number halved in meiosis

A
25
Q

In down syndrome, people have an extra chromosome (trisomy) - how does this happen?

A
26
Q

define proteome

A
27
Q

Define ‘genetic diversity’

A

The number of different alleles of each gene (within in a population )

28
Q

Apart from genetic factors what other type of factors causes variation within a species

A

Environmental (biotic and abiotic) factors

29
Q

What is a species?

A

A group of organisms with similar features that can interbreed to produce fertile offspring

30
Q

Explain how crossing over can contribute to genetic diversity

A

Sections of chromatids are exchanged.

Different sections have different alleles so new combinations of linked alleles are made.

31
Q

What can different species not do?

A

They cannot breed to produce fertile offspring as they have different genes and may have a different number of chromosomes

32
Q

What is a population

A

A population is a group of the same species in the same place that can interbreed

33
Q

Go through the stages of natural selection

A
  1. A change in the environment causes a selection pressure
  2. Random mutations produce genetic diversity
  3. Some alleles provide an advantage
  4. Those individuals with the advantageous alleles survive and reproduce
  5. So the advantageous alleles are passed on
  6. This means the frequency of advantageous alleles in the population increases
34
Q

Who decides what is the advantageous alleles?

A

The environmental conditions (nature)

Humans if selective breeding

35
Q

What is a selection pressure?

A

An environmental change that affects a population resulting in the death of some individual and the survival of those that are better adapted (those with favourable alleles)

36
Q

What are the 2 types of variation and give examples

A
  • Continuous variation - a characteristic that an have a wide range of values shows continuous variation e.g. height, weight
  • Discontinuous variation - a characteristic with few possible values shows discontinuous variation e.g. blood group
37
Q

Monogenic characteristics often show which type of variation

A

Discontinuous

38
Q

Polygenic characteristics often show which type of variation

A

Continuous

39
Q

Describe and explain how selection can affect the genetic diversity of a species

A

The genetic diversity is reduced as alleles have been chosen and rejected

40
Q

What is selection?

A

Selection is the process by which organisms that are better adapted to their environment survive, reproduce and pass on their genes

41
Q

Other than hunting give 2 reasons why populations might show low levels of genetic diversity.

A
  1. population is small
  2. inbreeding
  3. population started with one pregnant female
42
Q

Index of diversity is higher in a hedge than a barley field - why?

A
  1. more plant species
  2. more food sources/variety of food
  3. more habitats
  4. More niches
43
Q

In a diploid organism phenotype (expressed characteristics) is determined by what?

A
44
Q

What is meant by a low genetic diversity?

A
45
Q

If there was no genetic diversity could natural selection occur?

A
46
Q

Define the term ‘gene pool’.

A
47
Q

What is directional selection and what does it result in?

A
48
Q

What is stabilising selection and what does it result in?

A
49
Q

When you plat continuous variation on a graph it will produce which type of curve?

A
50
Q

The 3 types of adaptations are…

A
51
Q

Give an example of an anatomical adaptation.

A
52
Q

Give an example of a physiological adaptation.

A
53
Q

Give an example of a behavioural adaptation.

A
54
Q

state 3 comparisons of genetic diversity

A

genetic info, variation and relationships between organisms (3 decks)

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