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Biology > Genetic Diversity > Flashcards

Genetic Diversity Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Gene mutations involve a change in the ____ sequence of _________. They can arise spontaneously during DNA ________ and include base deletion and base substitution

A

base, chromosomes, replication

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2
Q

What increases rate of mutation?

A

mutagenic agents

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3
Q

what is silent substitution?

A

Due to the degenerate nature of the genetic code, not all base substitutions cause a change in the sequence of amino acids

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4
Q

what is non-disjunction?

A
  • failure of chromosomes to separate during anaphase

- produces abnormal no. of chromosomes

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5
Q

give 2 examples of chromosome mutations

A

non-disjunction, polyploidy

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6
Q

what is polyploidy?

A
  • changes to whole sets of chromosomes

- have 3 or more sets of chromosomes rather than 2

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7
Q

give an example of gene substitution

A

sickle cell anemia (1 nucleotide substitution in haemoglobin gene)

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8
Q

Meiosis produces daughter cells that are…..

A

genetically different from each other

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9
Q

which cells does meiosis occurs?

A

germline cells

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10
Q

how many daughter cells are produced after 2 meiotic divisions?

A

4

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11
Q

why is meiosis necessary?

A

halving of a diploid cell to become haploid by meiosis (allows the fusion of gametes via sexual reproduction)

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12
Q

why are daughter cells genetically different?

A

independent segregation of homologous chromosomes

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13
Q

when do homologous chromosomes separate during meiosis?

A

anaphase 1

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14
Q

when do sister chromatids separate during meiosis?

A

anaphase 2

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15
Q

how many chromosomes do daughter cells have after the second meiotic division?

A

23

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16
Q

name the 3 things which increase genetic variation in offspring?

A
  • independent segregation
  • crossing over
  • random fertilisation of haploid gametes
17
Q

describe crossing over

A
  1. homologous pairs twist around each other
  2. sister chromatids break + recombine to non-sister chromatid
  3. broken portions exchanged between homologous chromosomes
  4. new combinations of maternal/paternal alleles
18
Q

describe independent segregation

A

arrangement/combination of homologous pairs random in daughter cells (for both meiotic divisions)

19
Q

what is the formula to find the no. of possible combinations of chromosomes of maternal and paternal origin in its daughter cells as a result of MEIOSIS?

A

2^n (where n = no. of pairs of homologous chromosomes)

20
Q

what is the formula to find the no. of possible combinations of chromosomes in offspring after random FERTILISATION?

A

(2^n)^2 (where n = no. of pairs of homologous chromosomes)

21
Q

define genetic diversity

A

the no. of different alleles of genes in a population

22
Q

Genetic diversity is a factor enabling _______ ______ to occur

A

natural selection

23
Q

define natural selection

A

species better adapted to suit environment thru process of selection via environmental pressures

24
Q

The principles of natural selection in the evolution of populations.

  1. Random mutation can result in new _____ of a gene.
  2. Many mutations are harmful but, in certain environments, the new ____ of a gene might be beneficial = increased __________success.
  3. The advantageous ____ is inherited by members of the next ________.
  4. As a result, over many generations, the new ____ increases in ______ in the population.
A
  1. allele
  2. allele, reproductive
  3. allele, generation
  4. allele, frequency
25
Q

what are the 2 major factors in evolution + contribute to diversity of organisms?

A

adaptation and selection

26
Q

where does genetic diversity come from?

A
  • change in quantity/structure of DNA (mutations)

- recombining DNA of 2 individuals after meiosis + binary fission

27
Q

Natural selection results in species that are…..

A

better adapted to their environment

28
Q

Adaptations may be….. (3 things)

A

anatomical, physiological or behavioural

29
Q

definition of polygenes

A

characteristics that are influenced by more than one gene

30
Q

effect of environment on _______ produces individuals within pop. that vary about the _____.

A

polygenes, mean

31
Q

what is directional selection?

A
  • changes characteristics of pop.
  • favours/selections phenotypes at one extreme of pop.
  • distribution curve the same BUT mean shifts left or right
  • occurs when conditions aren’t stable
32
Q

what is stabilising selection?

A
  • preserves characteristics of pop.
  • favours/selects phenotypes around the mean
  • distribution curve becomes narrower/higher mean doesn’t change
  • when environmental conditions are stable
33
Q

what happens to the distribution curve and mean of directional selection?

A 
curve = remains same shape 
mean = shifts left or right
34
Q

what happens to the distribution curve and mean of stabilising selection?

A 
curve = becomes narrower and higher
mean = does not change
35
Q

is antibiotic resistance directional or stabilising selection?

A

directional

36
Q

how do antibiotics work?

A
  1. H2O potential lower in bacteria cells = H2O enters via osmosis
  2. meurin walls can’t withstand pressure
  3. osmotic lysis = zone of inhibition
37
Q

describe how there is penicillin resistant bacteria:

A
  1. new allele of resistance
  2. allele codes for penicillinase (active site complementary to antibiotic) = breaks down antibiotic
  3. susceptible bacteria die, mutant bacteria are selected for
  4. binary fission = pass on allele for resistance
  5. frequency of that allele increases
  6. distribution curve shifted in direction of pop. having greater resistance
38
Q

an example of stabilising selection

A

human birth weights

  • mortality rate are greater at 2 extremes (being selected against)
  • those around the mean less likely to die (selected for)

Biology (25 decks)

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