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Biology > 9.Genetic diversity and adaptation > Flashcards

9.Genetic diversity and adaptation Flashcards

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1
Q

Define a gene mutation

A

Any change to one or more nucleotide bases or sequence of bases in DNA

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2
Q

Name 3 consequences of gene substitution

A
  • One of the 3 stop codons are formed which prematurely stops the production of the polypeptide chain. This results in a significantly different protein that wouldn’t be able to function properly
  • Another codon is formed, which codes for a different amino acid. This change in the polypeptide chain may cause a change in the proteins tertiary structure meaning the protein produce will be dysfunctional.
  • The formation of different codon but codes for the same amino acid. This is because the genetic code is degenerate. It will have no effect on the overall protein shape/function
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3
Q

What is substitution

A

A type of gene mutation in which a nucleotide in a DNA molecule is replaced by another nucleotide

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4
Q

What is deletion

A

A gene mutation arises when a nucleotide is lost from the normal DNA sequence

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5
Q

What is the consequence of a deletion mutation

A

The deletion of a base causes a frameshift for every codon downstream of the mutation. This alters most triplets downstream meaning the amino acids coded for are different, significantly altering the proteins tertiary structure and therefore its dysfunction.

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6
Q

What is a chromosomes mutation

A

A change in the structure or number of whole chromosomes

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7
Q

Describe and explain the two forms chromosome mutations can take

A
  • changes in whole sets of chromosomes (polyploid)

- changes in the number of individual chromosomes (non-disjunction)

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8
Q

What is polyploid

A

Occurs when organisms have 3 or more sets or chromosomes rather than the usual two.

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9
Q

What is non-disjunction

A

Sometimes individual homologous pairs fail to separate during meiosis. This results in a gamete having one more or one fewer chromosome. This produces an offspring with more or fewer chromosomes in their body cells

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10
Q

Name two ways cell division occurs

A
  • mitosis

- meiosis

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11
Q

Why is meiosis important

A

The number of chromosomes must be lowered from diploid to haploid to maintain a constant number of chromosomes. This occurs during meiosis

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12
Q

How many nuclear divisions occur in meiosis

A

2

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13
Q

What occurs in the first division (meiosis I)

A
  • homologous chromosomes pair up and their chromatids wrap around each other
  • equivalent portions of these chromatids may be exchanged in the process (crossing over)
  • the homologous pairs separate with one chromosome from each pair going into one of the two daughter cells
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14
Q

What is crossing over

A

The process whereby a chromatid breaks during meiosis and re-joins to the chromatid of its homologous chromosome so that their alleles are exchanged

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15
Q

What occurs in the second division (meiosis II)

A
  • the chromatids separate and go into separate daughter cells
  • this means there are 4 daughter cells at the end of this process
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16
Q

In what two ways does meiosis bring about genetic variation

A
  • independent segregation of homologous chromosomes

- crossing over

17
Q

What is independent segregation of homologous chromosomes

A

When homologous pairs line up, they do so randomly. This means the combination of chromosomes of maternal and paternal origin are up to chance

18
Q

How does independent segregation of homologous chromosomes bring out about genetic variation

A

Each member of a homologous pair of chromosomes have exactly the same genes and determine the same characteristics. However the genes of these alleles may be different therefore it produces new genetic combinations

19
Q

What is the calculation for the possible combinations of chromosomes for each daughter cell

A

2^n (where n is the number of homologous chromosomes)

20
Q

What is the calculation for the possible combinations of chromosomes of a zygote (after fertilisation)

A

(2^n)^2

21
Q

What is genetic diversity

A

The number of different alleles of genes in a population

22
Q

What is a population

A

A group of individuals of the same species that live in the same place and can interbreed

23
Q

Why are alleles of a population not equally likely to be passed on to the next generation

A

Only certain individuals are reproductively successful to pass on their alleles

24
Q

What is allele frequency

A

The number of times an allele occurs within the gene pool

25
Q

What is a gene pool

A

The total number of alleles in a particular population at a specific time

26
Q

How does differences of the reproductive success of individuals affect allele frequency

A
  • within any population there is a gene pool
  • random mutation of alleles within this gene pool may result in a new allele of a gene (most cases is harmful)
  • in some environments this mutation has a selective advantage so more likely to survive/ live longer so have a better chance of successful breeding
  • only individuals that reproduce successfully pass on their alleles
  • offspring now have advantageous allele and are more likely to survive and reproduce successfully
  • over time this causes the frequency of the newer advantageous allele to increase
27
Q

Name the three types of selection and the individuals they favour

A
  • directional (favour one extreme individuals)
  • stabilising (favour the average)
  • disruptive (doesn’t favour the average)
28
Q

Using the example of the resistance of penicillin, explain directional selection

A
  • spontaneous mutation occurred in the allele of a gene in a bacterium that enabled it to make a new protein that broke down the antibiotic for penicillin (penicillinase)
  • this happened in an individual being treated with penicillin
  • due to its advantageous mutation the bacterium survived and was able to reproduce
  • this increased the population of bacterium of the penicillin resistant bacteria
  • this shifts the normal distribution curve in one direction (towards the direction of a population of having a greater resistance)
29
Q

Using the example of human birth weights, explain stabilising selection

A
  • most babies are born with average mass
  • babies that aren’t (caused by its genes are less likely to survive
  • this means that these babies have an increased chance of successful reproduction and to pass on the gene for this baby weight
  • this means the average is favoured causing the normal distribution curve to steepen
30
Q

Name the 3 types of adaptations are there

A
  • anatomical
  • physiological
  • behavioural

Biology (23 decks)

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