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Ellie Owen > Biology Topic 6 - Inheritance, Variation And Evolution > Flashcards

Biology Topic 6 - Inheritance, Variation And Evolution Flashcards

1
Q

What is sexual reproduction?

A

-type of reproduction
-involves production of gametes by mitosis
-a gamete from each parent fuses to form a zygote
-genetic information from each gamete is mixed

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2
Q

What are gametes?

A

-Sex cells
-haploid(half the number of chromosomes)

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3
Q

What is meiosis?

A

-form of cell division involved in formation of gametes in reproductive organs
-chromosomes number is halved
-involves two divisions

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4
Q

What must occur prior to meiosis?

A

Interphase-copies of genetic information are made during this process

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5
Q

What happens during the first stage of meiosis?

A

-chromosome pairs line up along the cell equator
-the pair of chromosomes are separated and move to opposite poles of the cell
-chromosome number is halved

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6
Q

What happens during the second stage of meiosis?

A

-chromosomes line up along cell equator
-chromatids are separated and move to opposite poles of the cell
-four unique haploid gametes are produced

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7
Q

Why is meiosis important for sexual reproduction?

A

-it increases genetic variation
-it ensures that the zygote formed at fertilisation is diploid

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8
Q

What is the advantage of sexual reproduction?

A

-Creates genetic variation in offspring, increasing probability of a species adapting to and surviving environmental changes
-natural selection can be made quicker in selective breeding to increase food production

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9
Q

Describe the disadvantages of sexual reproduction?

A

-two parents are required. This makes reproduction difficult in endangered populations or in species which exhibit solitary lifestyles
-more time and energy is required so fewer offspring are produced

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10
Q

What is asexual reproduction?

A

-type of reproduction
-involves mitosis only
-produces genetically identical offspring known as daughter cells

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11
Q

Describe the advantages asexual reproduction
?

A

-only one parent is required
-lots of offspring can be produced in short period of time
-requires less energy and time as do not need a mate

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12
Q

What is the disadvantage of asexual reproduction?

A

No genetic variation reducing the probability of a species being able to adapt to environmental change

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13
Q

What is DNA?

A

-a double stranded polymer of nucleotides, wound to form a double helix
-the genetic material of the cell found in its nucleus

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14
Q

Define genome?

A

Entire genetic material of an organism

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15
Q

What is a chromosome?

A

A long, coiled molecules of DNA that carries genetic information in the form of genes

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16
Q

How many chromosomes do human body cells have?

A

46 chromosomes (23 pairs)

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17
Q

Define gene?

A

A small section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein

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18
Q

Explain how a gene codes for a protein?

A
  • a sequence of three bases in a gene forms a triplet
    -each triplet codes for an amino acids
    -order of amino acids determines the structure and function of protein formed
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19
Q

What is protein synthesis?

A

Formation of a protein from a gene

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20
Q

What are the two stages of protein synthesis?

A

1-transcription
2-translation

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21
Q

What does transcription involve?

A

The formation of mRNA from a DNA template

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22
Q

Outline transcription

A

1-DNA double helix unwinds
2-RNA polymerase binds to a specific base sequence of non-coding DNA in front of a gene and moves along the DNA strand
3-RNA polymerase joins free RNA nucleotides ton complementary bases on the coding DNA strand
4-mRNA formation complete. mRNA detaches and leaves the nucleus

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23
Q

What does translation involve?

A

A ribosome joins amino acids in a specific order dictated by mRNA to form a protein

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24
Q

What is mutation?

A

A random change in the base sequence of DNA which results mostly in no change to the protein coded for, or genetic variations of the protein
Mutations occur continuously

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25
Q

What is non-coding DNA?

A

DNA which does not code for a protein but instead controls gene expression

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26
Q

Describe the effect of a gene mutation in non-coding DNA

A

Gene expression may be altered, affecting protein production and the resulting phenotype

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27
Q

What are alleles?

A

Different versions of the same gene

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28
Q

What is a dominant allele?

A

A version of a gene where only one copy is needed for it to be expressed

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29
Q

What is a recessive allele?

A

A version of a gene where two copies are needed for it to be expressed

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30
Q

What is meant when an organism is homozygous?

A

When an organism has two copies of the same allele

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31
Q

What is meant when an organism is heterozygous?

A

When an organism has two different versions of the same gene

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32
Q

What is the genotype?

A

The genes present for a trait

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33
Q

What is the phenotype?

A

The visible characteristics

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34
Q

What is three problem with single gene crosses?

A

Most characteristics are controlled by multiple alleles rather than just one

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35
Q

What is an inherited disorder?

A

A disorder caused by the inheritance of certain alleles

36
Q

How are embryos screened for inherited disorders?

A

During IVF, one cell is removed and tested for disorder-causing alleles

37
Q

What is gene therapy?

A

The insertion of a normal allele into the cells of a person with an inherited disorder to functionally replace the faulty allele

38
Q

What are sex chromosomes?

A

A pair of chromosomes that determine sex:
-males=X + Y
-females = two X chromosomes

39
Q

What is a sex-linked characteristic?

A

A characteristic that is coded for by an allele found on a sex chromosome

40
Q

What is variation?

A

Differences in the characteristics of individuals in a population is called variation

41
Q

What are the two causes of variation within a species?

A

-genetics
-environment
-a mixture of both

42
Q

What is genetic variation?

A

-variation in the genotypes of organisms of the same species due to the prescience of different alleles
-creates differences in phenotypes

43
Q

What creates genetic variation in a species?

A

-spontaneous mutations
-sexual reproduction

44
Q

What is a mutation?

A

A random change to the base sequence in DNA which results in genetic variants
They occur continuously

45
Q

What is the consequence of a new phenotype caused by a mutation being suited to an environmental change?

A

There will be a rapid change in the species

46
Q

What is evolution?

A

-A gradual change in the inherited traits within a population over time
-occurs due to natural selection which may result in the formation of a new species

47
Q

How do two populations become different species?

A

When their phenotypes become different to the extent that they can no longer interbreed to produce fertile offspring

48
Q

What is selective breeding?

A

The process by which humans artificially select organisms with desirable characteristics and breed to produce offspring with similar phenotypes

49
Q

What is the main advantage of selective breeding?

A

Creates organisms with desirable features

50
Q

Other than in agriculture, where else is selective breeding useful?

A

-in medical research
-in sports e.g. horse racing

51
Q

What is genetic engineering?

A

-the modification of the genome of an organism by the insertion of a desired gene from another organism
-enables the formation of an organism with beneficial characteristics

52
Q

What is a use for genetically modified bacteria cells?

A

To produce human insulin to treat diabetes mellitus

53
Q

What is the name for crops that have their genes modified?

A

Genetically modified crops

54
Q

How is genetic engineering used to protect crops against insects?

A

-the gene for toxin production in Bt can be isolated and inserted into the DNA of crops
-Bt crops now secrete the toxin which kills any insect larvae that feed on it

55
Q

What is a vector?

A

A structure that delivers the desired gene into the recipient cell

56
Q

How can plants be cloned?

A

-taking plant cuttings
-tissue culture

57
Q

What is tissue culture?

A

Using small groups of cells from part of a plant to grow identical new plants

58
Q

What must be ensured when preparing tissue cultures?

A

Ensure aseptic conditions to prevent contamination by microorganisms

59
Q

What does the growth medium contain?

A

Nutrients and growth hormones

60
Q

Describe the plant cuttings method of plant cloning

A

Older but simpler method than tissue culture

Gardeners use this method to produce many identical new plants from a parent plant

61
Q

What does embryo transplanting involve?

A

-pre-specialised cells from a developing animal embryo are split apart
-the resulting separate but identical embryos are transplanted into host mothers

62
Q

Outline the theory of evolution by natural selection?

A

-individuals of a species show a wide range of variation for a characteristic
-those with the characteristic most suited to the environment will survive breed most successfully
-the desirable characteristic that has enabled the individuals to survive are passed onto their offspring

63
Q

Why was Darwin’s theory of evolution not accepted initially?

A

-most people believed in creationism
-insufficient evidence to prove the theory
-the mechanism of variation and inheritance was not known at the time

64
Q

What was jean-baptistery lamarck’s theory of inheritance?

A

That changes during the lifetime of an organism can be inherited

65
Q

What is speciation?

A

The formation of a new species, when two populations become so varied that they cannot interbreed to produce fertile offspring

66
Q

What is the definition of a species?

A

A group of organisms with similar characteristics which are able to interbreed to produce fertile offspring

67
Q

Why is genetic variation so important in speciation?

A

Genetic variation produces phenotypic variation, some of which are better suited to the environment and are selected

68
Q

How did Mendel study inheritance?

A

Through carry breeding experiments on plant animals analysing the ratio of characteristics in offspring

69
Q

Why was Mendel’s work not recognised until after his death?

A

-he could not explain the mechanism of inheritance, as chromosomes were only discovered after his death

70
Q

State two kinds of evidence used to show evolution

A

-fossils
-casting

71
Q

How are fossils formed?

A

-parts of organisms that have not decayed due to conditions needed for decay being absent
-parts of organisms that have been replaced by minerals as they decayed
-traces of organisms are preserved, covered in sediment and becoming rock

72
Q

Why are there few traces of early life-forms left behind?

A

They are mostly soft-bodied

73
Q

How do fossils act as evidence for evolution?

A

Scientists can identify the ages of the fossils and use them to show how organisms change over time

74
Q

What do branches in evolutionary trees indicate?

A

Where speciation has occurred

75
Q

What is extinctions?

A

Where there are no individuals of a species still alive

76
Q

State the factors that may lead to extinction?

A

-new disease
-predation
-competition
-changes to the environment
-catastrophic events

77
Q

State the factors that may lead to extinction?

A

-new disease
-predation
-competition
-changes to the environment
-catastrophic events

78
Q

What enables bacteria to evolve quickly?

A

Fast rate of reproduction

79
Q

Why are resistant strains of bacteria dangerous?

A

People have no immunity to them and there is no effective treatment

80
Q

Why is it difficult to keep up with emerging resistance strains?

A

Developing antibiotics have a high cost and take a long time to develop

81
Q

What features are living creatures traditionally classified by?

A

By their structure and characteristics

82
Q

Why were new classification models proposed?

A

-developments in microscopy allowed better examination of internal structures
-improvement in understanding of biochemical processes

83
Q

Which organisms belong in the domain archaea?

A

Bacteria, usually living in extreme environments

84
Q

Which organisms belong in the domain bacteria?

A

Bacteria

85
Q

How are evolutionary trees created?

A

By examining the DNA of different species and analysing how similar the sequences are

Ellie Owen (27 decks)

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