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Master Combined Science - Biology (Foundation) > Combined Biology - 4.6 > Flashcards

Combined Biology - 4.6 Flashcards

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1
Q

What type of cell division leads to identical cells being formed?

A

Mitosis

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2
Q

What type of cell division leads to non-identical cells being formed?

A

Meiosis

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3
Q

What does sexual reproduction, in animals, involve?

A

The joining (fusing) of male and female gametes (sperm and egg)

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4
Q

What does sexual reproduction, in plants, involve?

A

The joining (fusing) of gametes (pollen and egg cells)

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5
Q

What does sexual reproduction lead to and why?

A

Variety in the offspring as there is mixing of genetic information

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6
Q

What is asexual reproduction?

A

One parent (no fusion or mixing of genetic information) leading to genetically identical offspring

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7
Q

What is a clone?

A

Genetically identical offspring (a result of asexual reproduction)

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8
Q

What does meiosis do to the number of chromosomes in the gamete?

A

It halves it (46 to 23)

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9
Q

What happens to the number of chromosomes during fertilisation?

A

It doubles (male and female gametes both have 23 chromosomes, combining to make 46)

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10
Q

What key stages occur when a cell divides to form gametes (meiosis)?

A
  1. Copies of the genetic information are made
  2. The cell divides twice forming four gametes (each with a single set of chromosomes)
  3. All the gametes are genetically different from each other
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11
Q

What is the genetic material in the nucleus of a cell composed of?

A

DNA

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12
Q

What is the structure of DNA?

A

A polymer made up of two strands forming a double helix

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13
Q

What is DNA contained in?

A

Chromosomes

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14
Q

What is a gene?

A

A small section of DNA on a chromosome

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15
Q

What does a gene code for?

A

A particular sequence of amino acids, which make specific proteins

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16
Q

What is the genome of an organism?

A

The entire genetic material of that organism

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17
Q

Why is having the human genome sequence important?

A

It will be of benefit to medicine

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18
Q

Why is understanding the human genome important?

A
  • Genes linked to different types of disease can be searched for
  • Inherited disorders can be understood / treated
  • Migration patterns of the past can be traced
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19
Q

Explain the term: gamete

A

A sex cell (e.g. sperm or egg)

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20
Q

Explain the term: chromosome

A

A long molecule of DNA, found in the nucleus of a cell, which carries genes

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21
Q

Explain the term: gene

A

A short section of DNA, found on a chromosome, carrying the instructions needed to make a protein (and so controls the development of a characteristic)

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22
Q

Explain the term: allele

A

An alternative version of a gene

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23
Q

Explain the term: dominant

A

The allele for the characteristic that’s shown by an organism if two different alleles are present for that characteristic

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24
Q

Explain the term: recessive

A

An allele whose characteristic only appears in an organism if there are two copies present

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25
Q

Explain the term: homozygous

A

Where an organism has two alleles for a particular gene that are the same

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26
Q

Explain the term: heterozygous

A

Where an organism has two alleles for a particular gene that are different

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27
Q

Explain the term: genotype

A

What alleles and organism has, e.g. Tt

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28
Q

Explain the term: phenotype

A

The characteristics an organism has, e.g. tall

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29
Q

Give an example of characteristics controlled by a single gene

A

Fur colour in mice / red-green colour blindness in humans

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30
Q

What controls the phenotype (what is expressed)?

A

Alleles present (or genotype) operating at a molecular level to develop characteristics expressed (as a phenotype)

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31
Q

Which allele is always expressed?

A

The dominant (even if only one copy is present)

32
Q

What are most characteristics a result of?

A

Multiple genes interacting (rather than a single gene)

33
Q

Complete a Punnett square for the % chance of having a boy or girl

A
34
Q

What is polydactyly?

A

An inherited disorder (extra fingers or toes) caused by a dominant allele

35
Q

What is cystic fibrosis?

A

An inherited disorder (cell membrane issues) caused by a recessive allele

36
Q

How many pairs of chromosomes are found in ordinary human body cells?

A

23 pairs

37
Q

22 pairs of chromosomes control characteristic, but what does the 23rd pair control?

A

The gene which determines sex (XX in female and XY in male)

38
Q

How does the phenotype of an organism develop?

A

The interaction between the genome and environment influence development of the phenotype

39
Q

What is variation?

A

Differences in the characteristics of individuals in a population

40
Q

What can cause variation?

A
  • The genes inherited (genetic cause)
  • The conditions in which the organism has developed (environmental cause)
  • A combination of genes and environment
41
Q

Within a population of a species, what usually exists?

A

Extensive genetic variation

42
Q

How do variants in a species arise?

A

Mutations: most have no effect on phenotype, some influence phenotype, and very few determine phenotype

43
Q

If a mutation leads to a new phenotype, suited to an environmental change, what might occur?

A

Relatively rapid change in the species

44
Q

What is evolution?

A

A change in the inherited characteristics of a population over time which may result in the formation of a new species

45
Q

What is the driving force of evolution?

A

Natural selection

46
Q

What is the theory of evolution by natural selection?

A

All species of living things have evolved from simple life forms, that first developed more than three billions years ago

47
Q

Variants that give rise to phenotypes best suited to their environment causes what?

A

Evolution, occurring through natural selection

48
Q

How do new species form?

A

If two populations of one species become so phenotypically different they cannot interbreed (to produce fertile offspring) then they have formed two new species

49
Q

What is selective breeding?

A

Selective breeding is artificial selection – humans breed plants and animals for particular genetic characteristics

50
Q

What does selective breeding involve?

A

Choosing parents with the desired characteristics from a mixed population, which are bred, and offspring with desired characteristics are bred

51
Q

What characteristics might be chosen during selective breeding

A
  • Disease resistance in food crops
  • Animals which produce more milk / meat
  • Domestic dogs of a gentle nature
  • Large / unusual flowers
52
Q

What can selective breeding lead to?

A

Inbreeding – some breeds are prone to diseases or inherited defects

53
Q

What is genetic engineering?

A

A process involving modifying the genome or an organism by introducing a gene from another organism: giving a desired characteristic

54
Q

How have plant crops been genetically engineered?

A

To be resistant to disease / produce bigger and better fruits

55
Q

How have bacterial cells been genetically engineered?

A

To produce useful substances such as human insulin (treating diabetes)

56
Q

How does genetic engineering occur?

A

Genes from chromosomes are ‘cut out’ and transferred to cells of other organisms

57
Q

What are genetically modified (GM) crops?

A

Crops that have had their genes modified: resistance to insect attack / herbicides for example (generally show yield increase)

58
Q

What concerns are there about GM crops?

A

The effect on populations of wild flowers and insects / human health (not being fully explored)

59
Q

How is modern medical research utilising genetic modifications?

A

To overcome some inherited diseases

60
Q

What evidence is there for evolution?

A

Fossils and antibiotic resistance in bacteria

61
Q

What are fossils?

A

The ‘remains’ of an organism from millions of years ago, found in rocks

62
Q

How may fossils be formed?

A
  • From parts of organisms that have not decayed because one or more the conditions for decay was absent
  • Parts of the organism are replaced by minerals as they decay
  • Preserved traces (footprints / burrows etc…)
63
Q

Why are there very few traces of early life forms?

A

They were soft-bodies (fossil record incomplete)

64
Q

What do fossils show?

A

How much / how little different organisms have changed as life developed on Earth

65
Q

What is extinction?

A

When there are no remaining individuals of a species still alive

66
Q

What may cause extinction of a species?

A
  • Environmental changes
  • New predators
  • New diseases
  • Catastrophic events
  • Unable to compete
67
Q

Why can bacteria evolve rapidly?

A

They reproduce at a fast rate

68
Q

How do new strains of bacteria occur?

A

Mutations: some strains may be resistant to antibiotics so are not killed and the resistant strains rises

69
Q

What is MRSA resistant to?

A

Antibiotics

70
Q

How can antibiotic resistance be reduced?

A
  • Reduce prescription of antibiotics, especially when inappropriate (e.g. for a viral infection)
  • Patients should complete course of antibiotics so all bacteria are killed
  • Restriction of agricultural antibiotic use
71
Q

What issues are there with antibiotic development?

A

It is costly and slow – it is unlikely to keep up with the emergence of new resistant strains

72
Q

What did Carl Linnaeus develop?

A

A classification systems, based on structures and characteristics

73
Q

How did Carl Linnaeus characterise living organisms?

A

Kingdom > phylum > class > order > family > genus > species

74
Q

How are organisms named?

A

The binomial system of genus and species

75
Q

What caused new models of classification to be proposed?

A

Evidence of internal structures (microscopes) and biochemical processes were better understood

76
Q

What is the ‘three-domain system’?

A

Carl Woese divided organisms into:

  • Archaea (primitive bacteria)
  • Bacteria (true bacteria)
  • Eukaryota (protists, fungi, plants and animals)
77
Q

How can the relation of organisms be shown?

A

Evolutionary trees – current classification data for living organisms and fossil data for extinct organisms is used

Master Combined Science - Biology (Foundation) (7 decks)

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