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Yr 12 Biology > Topcic 4- Genetic Imformation & Variation > Flashcards

Topcic 4- Genetic Imformation & Variation Flashcards

1
Q

Contrast eukaryotic and prokaryotic DNA?

A

Eukaryotic:

-longer
-linear
-associated with histones

Prokaryotic:

-shorter
-circular
-not associated with proteins

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2
Q

What are the similarities between prokaryotic and eukaryotic DNA?

A

-both made of DNA nucleotides containing deoxyribose, a phosphate group and nitrogenous base

  • nucleotides are joined together by phosphodieters bond to make polymer chains
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3
Q

What does a DNA molecule form when combined with its associated protein?

A

A chromosome

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4
Q

Why do the mitochondria and chloroplasts of eukaryotic cells contain DNA?

A

So they can transcribe, translate and transfer to the enzymes they need for protein synthesis and respiration

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5
Q

What is a gene?

A

A base sequence of DNA that codes for:

  1. The amino acid sequence of a polypeptide
  2. A functional RNA
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6
Q

What is a locus?

A

The exact position that one particular gene is found on a chromosome

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7
Q

What are the 3 features a genetic code has?

A
  1. Degenerate
  2. Universal
  3. Non-overlapping
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8
Q

What does is mean when a genetic sequence is degenerate?

A

More than one triplet of bases code for the same amino acid

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9
Q

What does it mean when the genetic code is universal?

A

The same triplet of bases code for the same amino acid in all organisms

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10
Q

What does is mean when a genetic code is non-overlapping?

A

Each base is only involved in one triplet

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11
Q

What’s an advantage of a genetic code being non-overlapping?

A

because if a point mutation occurs it will only affect one codon and therefore one amino acid

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12
Q

What are introns?

A

Sections of DNA that do not code for polypeptides, only found in eukaryotic DNA not prokaryotic

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13
Q

What are exons?

A

The sequence of DNA that do code for amino acids

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14
Q

What is a genome?

A

An organism complete set of genes in a cell

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15
Q

What is a proteome?

A

Full range of proteins that a cell is able to produce

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16
Q

Why does the genome never change but the proteome is constantly changing?

A

The proteome is constantly changing depending on the protein which is currently needed

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17
Q

What is messenger RNA?

A

Short single stranded molecules found in the cytoplasm and nucleus

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18
Q

Why is mRNA complementary to DNA?

A

As it’s made during transcription, where is copied from DNA

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19
Q

What is the name of the sequence of bases which the tRNA has?

A

-Anticodon, which are complementary to codons on the mRNA molecule

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20
Q

What is tRNA?

A

A single stranded polynucleotide strand that is folded into a clover shape

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21
Q

How are the base pairs on the tRNA molecules held together?

A

By hydrogen bonds

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22
Q

What is transcription?

A

Where one gene on the DNA is coped into the mRNA

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23
Q

What is translation?

A

Where mRNA joins with a ribosome and corresponding tRNA molecules brings the specific amino acid the codon codes for

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24
Q

Describe transcription?

A
  1. DNA helix unwinds to expose the bases to act as a template
  2. Only one chain of the DNA acts as a template
  3. The unwinding and unzipping is catalysed by DNA helicase
  4. DNA helicase breaks the hydrogen bonds between bases
  5. Free mRNA nucleotides in the nucleus align opposite exposed complementary DNA bases
  6. The enzyme RNA polymerase joins together the RNA nucleotides to create a new RNA polymer chain. One entire gene is copied
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25
Q

Once the mRNA is copied form the DNA what happens to it?

A

It’s modified then leaves the nucleus via the nuclear pores

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26
Q

Describe translation?

A
  1. Once the modified mRNA has left the nucleus is attached to a ribosome in the cytoplasm
  2. The ribosome attaches at the start codon
  3. The tRNA molecules with the complementary anticodon to the start codon aligns opposite the mRNA, held in place by the ribosome
  4. The ribosome will move along one codon on the mRNA molecule to the enable another complementary tRNA to attach to the next codon on the mRNA
  5. The two amino acids that have been delivered by the tRNA molecule are joined by a peptide bond, this is catalysed by an enzyme and requires ATP
  6. This continues until the ribosome reaches the stop codon at the end of the mRNA molecule. The stop codon does not code for an amino acid, therefore the ribosome detaches and translation ends
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27
Q

What happens to the polypeptide chain after translation?

A

It enters the Golgi body for folding and modification

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28
Q

What is a gene mutation?

A

A change in the base sequence of the DNA. Gene mutations randomly occur during DNA replication

29
Q

What can a gene mutation result in?

A

-base being deleted

  • substituted for a different one
30
Q

Why may a base substitution have no Impact?

A

Because the new codon may still code may still code for the same amino acid, as the code is degenerate

31
Q

What do base deletions result in?

A

Results in a frame shifts due to the removal of one base changes all of the subsequent codons

32
Q

Why are base deletions more harmful than base substitutions?

A

-Because it results in the removal of base, which changes all of the subsequent codons

  • which is more harmful as multiple amino acids will be incorrectly coded for
33
Q

What are the chromosomes mutations?

A

Change in the number of chromosomes which can arise spontaneously by chromosome non-disjunction during meiosis

34
Q

What is non-disjunction?

A

When the chromatids don’t split equally during anaphase

35
Q

What are the 2 forms of chromosome mutation?

A
  1. Changes in the whole sets of chromosomes (polyploidy)
  2. Changes in the number of individual chromosomes (aneuploidy)
36
Q

Describe polyploidy?

A

Changes in the whole sets of chromosomes occur when organisms have three or more sets of chromosomes rather than the usual two, mainly occurs in plants

37
Q

Describe aneuploidy?

A

-this is changes in the number of individual chromosomes

38
Q

What is the cause aneuploidy?

A
  • due to individual homologous pairs of chromosomes fails to separate during meiosis

Results in a gamete having one or more or fewer chromosomes, this causes downsyndrome

39
Q

What are the different types of natural selection?

A
  • directional selection
  • stabilising selection
40
Q

What is genetic diversity?

A

The number of alleles of genes in a population

41
Q

When does natural selection take place?

A

When there is genetic diversity within a population

42
Q

What does natural selection lead to?

A

Leads to evolution in populations

43
Q

What is evolution?

A

The change in allele frequency over many generations in a population

44
Q

What is the effect on the species, after natural selection takes place?

A

They are better adapted to their environment

45
Q

What are different types of adaptations?

A

Anatomical-structural features

physiological- different reactions in the body (amount of chemicals)

-behavioural- how the organism behaves

46
Q

Describe the process of natural selection?

A
  1. New alleles for a gene are created by random mutations
  2. If the new alleles increases the chances of the individual to survive in that environment, they are more likely to survive and reproduce
  3. This reproduction passes on the advantageous alleles to the next generation
  4. As a result over many generations the new alleles increases in frequency in the population
47
Q

Describe directional selection?

A

-when the environmental conditions change and the phenotypes best suited to the new conditions are more likely to survive

-as a result these individuals will breed and produce offspring

  • over time the mean of the population will move towards these individuals.
48
Q

Describe stabilising selection?

A
  • phenotypes with successful characteristics are preserved and those of greater diversity are reduced
  • this selection isn’t caused by a change in environment
  • if the environment stays the same then the individuals closest to the mean are favoured because they have the alleles that have given them the survival advantage

-the furthest form the mean are selected against

49
Q

What is the niche of a species?

A

It’s role within the environment

50
Q

What do species of the same niche do?

A

Compete with each other and a better adapted species survive via natural selection

51
Q

What is the generic name?

A

To which organism an individual belongs to

52
Q

What is the specific name?

A

The species which the organism belongs

53
Q

What is courtship behaviour used for?

A

For members of the same species to recognises one another during mating

54
Q

What may be similar in courtship behaviour of two organism of the same species?

A

May share similar physical, biochemical and behavioural characteristics

55
Q

What does courtship behaviour enable before mating?

A

-recognise members of their own species

  • form a pair bond
  • synchronise mating period

-become able to breed

56
Q

What is classification?

A

Process of naming and organising organisms into groups based on their characteristics

57
Q

What is the order of classification?

A

-Phylum
- class
-order
-family
-genus
-species

58
Q

What is biodiversity?

A

The variety of living organisms

59
Q

How can biodiversity be measured?

A
  • species diversity- number of different species and the number of different individuals in a community- can be measured by random sampling
  • genetic diversity- measure of the genetic variation found in a particular species

-ecosystem diversity- range of different habitats

60
Q

What is the equation for index of diversity?

A

N(N -1)
——————-
D= § n (n -1)

D= diversity index
N= total number of organisms
n= total number of organisms of each species
§ = sum of

61
Q

How does agriculture effect biodiversity ?

A

-agriculture ecosystems reduce the biodiversity and the number of species present because humans select for a particular characteristic, this therefore:

-reduces the number of alleles
-then genetic diversity of the population

-farmland is typically used for only a single species and therefore means that fewer individuals of other species can survive there

62
Q

What techniques are used to maintain biodiversity?

A
  • using hedgerows instead of fences
  • growing different crops in the same area, known as intercropping
    -reducing the use of herbicides and pesticides
  • preserving waste lands instead of draining these for farmland use
63
Q

How can the genetic diversity within or between a species be determined?

A

By comparing the:

  • base sequence of DNA

-the base sequence of mRNA

-amino acid sequence of the proteins encoded by DNA and mRNA

64
Q

What are the limitations of scientist using the shape or size to classify species?

A

-characteristics could be coded by more than one gene
-the same characteristics could have arisen separately
The characteristics could be influenced by the environment and not the genes

65
Q

What is gene technology used for?

A

To read the base sequence of organisms

66
Q

Why might random sampling not be representative of a population?

A

Due to chance and sampling bias

67
Q

How is sampling bias eliminated?

A

-By using a quadrat or transect

  • these can be used by placing these on randomly generated coordinates in the sample area
68
Q

How is the reliability of results from sampling increased?

A

Larger sample size is needed

Yr 12 Biology (8 decks)

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