Combined Biology - 4.6 Flashcards Preview

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Flashcards in Combined Biology - 4.6 Deck (74)
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1
Q

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

A

Mitosis

2
Q

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

A

Meiosis

3
Q

What does sexual reproduction, in animals, involve?

A

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

4
Q

What does sexual reproduction, in plants, involve?

A

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

5
Q

What does sexual reproduction lead to and why?

A

Variety in the offspring as there is mixing of genetic information

6
Q

What is asexual reproduction?

A

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

7
Q

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

A

It halves it (46 to 23)

8
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)

9
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
10
Q

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

A

DNA

11
Q

What is the structure of DNA?

A

A polymer made up of two strands forming a double helix

12
Q

What is DNA contained in?

A

Chromosomes

13
Q

What is a gene?

A

A small section of DNA on a chromosome

14
Q

What does a gene code for?

A

A particular sequence of amino acids, which make specific proteins

15
Q

What is the genome of an organism?

A

The entire genetic material of that organism

16
Q

Why is having the human genome sequence important?

A

It will be of benefit to medicine

17
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
18
Q

Explain the term: gamete

A

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

19
Q

Explain the term: chromosome

A

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

20
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)

21
Q

Explain the term: allele

A

An alternative version of a gene

22
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

23
Q

Explain the term: recessive

A

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

24
Q

Explain the term: homozygous

A

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

25
Q

Explain the term: heterozygous

A

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

26
Q

Explain the term: genotype

A

the combination of alleles

27
Q

Explain the term: phenotype

A

The characteristics an organism has, e.g. tall

28
Q

Give an example of characteristics controlled by a single gene

A

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

29
Q

Which allele is always expressed?

A

The dominant (even if only one copy is present)

30
Q

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

A
31
Q

What is polydactyly?

A

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

32
Q

What is cystic fibrosis?

A

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

33
Q

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

A

23 pairs

34
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)

35
Q

What is variation?

A

Differences in the characteristics of individuals in a population

36
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
37
Q

How do variants in a species arise?

A

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

38
Q

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

A

Relatively rapid change in the species

39
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

40
Q

What is the driving force of evolution?

A

Natural selection

41
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

42
Q

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

A

Evolution, occurring through natural selection

43
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

44
Q

What is selective breeding?

A

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

45
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

46
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
47
Q

What can selective breeding lead to?

A

Inbreeding – some breeds are prone to diseases or inherited defects

48
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

49
Q

How have plant crops been genetically engineered?

A

To be resistant to disease / produce bigger and better fruits

50
Q

How have bacterial cells been genetically engineered?

A

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

51
Q

How does genetic engineering occur?

A

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

52
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)

53
Q

What concerns are there about GM crops?

A

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

54
Q

Higher Q. How are vectors used in genetic engineering?

A

Enzymes isolate the required gene, which is inserted into a vector (usually a bacterial plasmid / virus)

55
Q

Higher Q. How are genes transferred during genetic engineering?

A

The bacterial plasmid / virus vector inserts the gene into the required cells

56
Q

Higher Q. Why are genes transferred at an early stage of the organism’s development during genetic engineering?

A

So they develop with the desired characteristic

57
Q

What evidence is there for evolution?

A

Fossils and antibiotic resistance in bacteria

58
Q

What are fossils?

A

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

59
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…)
60
Q

Why are there very few traces of early life forms?

A

They were soft-bodies (fossil record incomplete)

61
Q

What do fossils show?

A

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

62
Q

What is extinction?

A

When there are no remaining individuals of a species still alive

63
Q

What may cause extinction of a species?

A
  • Environmental changes
  • New predators
  • New diseases
  • Catastrophic events
  • Unable to compete
64
Q

Why can bacteria evolve rapidly?

A

They reproduce at a fast rate

65
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

66
Q

What is MRSA resistant to?

A

Antibiotics

67
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
68
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

69
Q

What did Carl Linnaeus develop?

A

A classification systems, based on structures and characteristics

70
Q

How did Carl Linnaeus characterise living organisms?

A

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

71
Q

How are organisms named?

A

The binomial system of genus and species

72
Q

What caused new models of classification to be proposed?

A

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

73
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)
74
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