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Biology > Genetic Diversity > Flashcards

Genetic Diversity Flashcards

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1
Q

What is a genetic mutation?

A

Any change to the quality or sequence of DNA

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2
Q

What is a germline mutation?

A

Change in the DNA base sequence of gametes

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3
Q

Who is affected by a germline mutation?

A

The offspring only

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4
Q

What is a somatic mutation?

A

Change in the DNA sequence in cell other than gametes

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5
Q

When do gene mutation occur?

A

During DNA replication randomly and spontaneously

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6
Q

Why do gene mutations occur during DNA replication?

A

Vulnerable to damage as DNA helicase has broken hydrogen bonds between the strands

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7
Q

What are the 2 types of gene mutation?

A

Base substitution and base deletion

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8
Q

What is base substitution?

A

DNA molecule is replaced by a different DNA molecule with a different base

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9
Q

What is the significance of base substitution?

A
  • depends on role of amino acid
  • can alter tertiary structure of a protein or could be part of an intron
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10
Q

How can base substitution lead to a non-functional protein/enzyme?

A
  • base in DNA molecule has been replaced with a different base
  • sequence of amino acids altered
  • alters tertiary shape of protein/enzyme as different hydrogen bonds form
  • active sit is no longer complementary to the substrate so no E- complex formed
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11
Q

What is base deletion?

A

A nucleotide is lost from the sequence so all bases shift to left so triplets are read wrong (frameshift)

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12
Q

How does a base deletion result in a non-functional protein/enzyme?

A
  • DNA base has been lost from the sequence so all
  • all bases shift left (frameshift)
  • DNA bases read wrong
  • change in amino acids altered sequence
  • alters bonds in tertiary structure which alters shape
  • enzyme no longer complementary to the substrate so no E-S complexes formed
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13
Q

What are the 2 types of chromosome mutations?

A
  • changes to whole sets of chromosomes
  • changes to individual chromosomes
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14
Q

How does a change to a whole sets of chromosomes occur and what is it called?

A

3 or more sets of chromosomes rather than the normal 2 (polyploidy)

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15
Q

How does changes to individual chromosomes occur?

A
  • non-disjunction in meiosis as the individual chromosomes have failed to split
  • gametes have either one more to one fewer chromosome
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16
Q

What does meiosis produce?

A

4 genetically different daughter cells each with half the number of chromosomes than the parent cell

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17
Q

What is a chromosome?

A

Thread like structure made up of protein and DNA that passes on hereditary material

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18
Q

What is a chromatid?

A

One of the 2 strands of a chromosome that are joined by a centromere

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19
Q

What is a centromere?

A

Joins pair of sister chromatids together

20
Q

What is a diploid cell and how may copies of each chromosome does it have?

A
  • normal body cell
  • 2 copies
21
Q

What is a haploid cell and how many copies of the chromosomes does it have?

A
  • gamete
  • 1 copy
22
Q

What happens before meiosis 1?

A
  • chromosomes replicate (2 copies of the chromatids)
  • DNA condenses to form double armed chromosomes (2 sister chromatids joined by centromeres)
23
Q

What happens in meiosis 1?

A
  • chromosomes arrange into homologous pairs and wrap around eachother crossing over
  • homologous pairs are separated into different daughter cells (half the number of chromosomes)
24
Q

What happens in meiosis 2?

A
  • 2nd division and chromosomes are separated with each sister chromatids going into different directions
  • creating 4 haploid cells
25
Q

What are the 2 ways meiosis creates genetic variation?

A
  • independent segregation of homologous chromosomes
  • genetic recombination by crossing over
26
Q

What is independent segregation of homologous chromosomes?

A
  • maternal and paternal chromosomes are randomly mixed
  • as the homologous pairs that line up in meiosis 1 are split into different daughter cells with any possible combination of other homologous pairs are
27
Q

How does genetic recombination by crossing over cause genetic diversity?

A
  • in meiosis 1 chromatids twist around eachother creating tension breaking off portions of chromatids
  • the broken off chromatids can join of its homologous pair
  • giving the chromatids the same genes but different combinations of maternal and paternal alleles
28
Q

What is an allele?

A

A version of a gene

29
Q

What causes new alleles to arise?

A

Genetic mutations

30
Q

What is the gene pool?

A

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

31
Q

What is genetic diversity?

A
  • the number of different alleles of a gene in a population
  • the greater the number of different alleles the greater the genetic diversity
32
Q

Why is a large genetic diversity good?

A

More likely individuals can survive an environmental change

33
Q

What are the 2 factors that can cause variation in a species?

A

Genes and the environment

34
Q

What does genetic diversity enable and why?

A

Natural selection because some alleles will be more advantageous than others so they are more likely to survive and reproduce

35
Q

How dos natural selection occur?

A
  • there is a gene pool with a variety of alleles in a population at
  • random mutation of alleles result in a new allele
  • the new allele is advantageous other alleles in the population
  • individual with the new allele has a higher chance of surviving and reproducing
  • the new allele is passed to the next generation
  • increasing frequency of the new allele in the population
36
Q

What are the 2 types of selection?

A

Directional and stabilising

37
Q

What is directional selection?

A

When selection favours individuals that vary in one direction from the mean population changing the phenotype of the population

38
Q

How does directional selection occur?

A
  • environmental change occurs
  • a phenotype that varies from the mean is best suited to the environment
  • those individuals are more likely to survive and reproduce
  • pass the advantageous allele to next generation
  • mean moves in direction of these individuals as the alleles become more frequent in the population
39
Q

How did directional selection lead to penicillin resistant bacteria?

A
  • random mutation occurred in allele of a gene of a bacterium
  • that allele produced an enzyme called penicillinase that broke down penicillin
  • the bacteria was able to break down penicillin when exposed to it by penicillinase so it survived
  • it reproduced by binary fission passing the allele onto the next generation
  • population of penicillin-resistant bacteria increase increasing the frequency of the allele
  • populations normal distribution curve shifted in direction of resistance
40
Q

What happens to the characteristics n a population in directional selection?

A

Changes characteristics of the population

41
Q

What phenotype is favoured in directional selection?

A

Phenotypes away from the mean

42
Q

What environmental conditions causes directional selection?

A

Changing environmental conditions

43
Q

What happens to normal distribution curve in directional selection?

A

Curve remains same shape but shifts to left or right

44
Q

What is stabilising selection?

A

Selection that favours average individuals and preserves characteristics of a population

45
Q

How does stabilising selection occur?

A
  • environmental conditions remain stable
  • individuals with phenotypes closest to mean are favoured
  • more likely to survive and reproduce
  • pass on allele to next generation
  • eliminating extreme phenotypes
46
Q

What are the 3 different adaptations that are caused by natural selection?

A
  • anatomical (e.g. thick fur)
  • physiological (e.g. oxidising fat for additional after in dry environment)
  • behavioural (e.g. bird migration)

Biology (11 decks)

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