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

Combined Biology - 4.6 Flashcards

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
Explain the term: homozygous
Where an organism has two alleles for a particular gene that are the same
26
Explain the term: heterozygous
Where an organism has two alleles for a particular gene that are different
27
Explain the term: genotype
What alleles and organism has, e.g. Tt
28
Explain the term: phenotype
The characteristics an organism has, e.g. tall
29
Give an example of characteristics controlled by a single gene
Fur colour in mice / red-green colour blindness in humans
30
What controls the phenotype (what is expressed)?
Alleles present (or genotype) operating at a molecular level to develop characteristics expressed (as a phenotype)
31
Which allele is always expressed?
The dominant (even if only one copy is present)
32
What are most characteristics a result of?
Multiple genes interacting (rather than a single gene)
33
Complete a Punnett square for the % chance of having a boy or girl
34
What is polydactyly?
An inherited disorder (extra fingers or toes) caused by a dominant allele
35
What is cystic fibrosis?
An inherited disorder (cell membrane issues) caused by a recessive allele
36
How many pairs of chromosomes are found in ordinary human body cells?
23 pairs
37
22 pairs of chromosomes control characteristic, but what does the 23rd pair control?
The gene which determines sex (XX in female and XY in male)
38
How does the phenotype of an organism develop?
The interaction between the genome and environment influence development of the phenotype
39
What is variation?
Differences in the characteristics of individuals in a population
40
What can cause variation?
* The genes inherited (genetic cause) * The conditions in which the organism has developed (environmental cause) * A combination of genes and environment
41
Within a population of a species, what usually exists?
Extensive genetic variation
42
How do variants in a species arise?
Mutations: most have no effect on phenotype, some influence phenotype, and very few determine phenotype
43
If a mutation leads to a new phenotype, suited to an environmental change, what might occur?
Relatively rapid change in the species
44
What is evolution?
A change in the inherited characteristics of a population over time which may result in the formation of a new species
45
What is the driving force of evolution?
Natural selection
46
What is the theory of evolution by natural selection?
All species of living things have evolved from simple life forms, that first developed more than three billions years ago
47
Variants that give rise to phenotypes best suited to their environment causes what?
Evolution, occurring through natural selection
48
How do new species form?
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
What is selective breeding?
Selective breeding is artificial selection – humans breed plants and animals for particular genetic characteristics
50
What does selective breeding involve?
Choosing parents with the desired characteristics from a mixed population, which are bred, and offspring with desired characteristics are bred
51
What characteristics might be chosen during selective breeding
* Disease resistance in food crops * Animals which produce more milk / meat * Domestic dogs of a gentle nature * Large / unusual flowers
52
What can selective breeding lead to?
Inbreeding – some breeds are prone to diseases or inherited defects
53
What is genetic engineering?
A process involving modifying the genome or an organism by introducing a gene from another organism: giving a desired characteristic
54
How have plant crops been genetically engineered?
To be resistant to disease / produce bigger and better fruits
55
How have bacterial cells been genetically engineered?
To produce useful substances such as human insulin (treating diabetes)
56
How does genetic engineering occur?
Genes from chromosomes are ‘cut out’ and transferred to cells of other organisms
57
What are genetically modified (GM) crops?
Crops that have had their genes modified: resistance to insect attack / herbicides for example (generally show yield increase)
58
What concerns are there about GM crops?
The effect on populations of wild flowers and insects / human health (not being fully explored)
59
How is modern medical research utilising genetic modifications?
To overcome some inherited diseases
60
Higher Q. How are enzymes used in genetic engineering?
Enzymes isolate the required gene, which is inserted into a vector (usually a bacterial plasmid / virus)
61
Higher Q. How are vectors used in genetic engineering?
Enzymes isolate the required gene, which is inserted into a vector (usually a bacterial plasmid / virus)
62
Higher Q. How are genes transferred during genetic engineering?
The bacterial plasmid / virus vector inserts the gene into the required cells
63
Higher Q. Why are genes transferred at an early stage of the organism’s development during genetic engineering?
So they develop with the desired characteristic
64
What evidence is there for evolution?
Fossils and antibiotic resistance in bacteria
65
What are fossils?
The ‘remains’ of an organism from millions of years ago, found in rocks
66
How may fossils be formed?
* 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…)
67
Why are there very few traces of early life forms?
They were soft-bodies (fossil record incomplete)
68
What do fossils show?
How much / how little different organisms have changed as life developed on Earth
69
What is extinction?
When there are no remaining individuals of a species still alive
70
What may cause extinction of a species?
* Environmental changes * New predators * New diseases * Catastrophic events * Unable to compete
71
Why can bacteria evolve rapidly?
They reproduce at a fast rate
72
How do new strains of bacteria occur?
Mutations: some strains may be resistant to antibiotics so are not killed and the resistant strains rises
73
What is MRSA resistant to?
Antibiotics
74
How can antibiotic resistance be reduced?
* 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
75
What issues are there with antibiotic development?
It is costly and slow – it is unlikely to keep up with the emergence of new resistant strains
76
What did Carl Linnaeus develop?
A classification systems, based on structures and characteristics
77
How did Carl Linnaeus characterise living organisms?
Kingdom \> phylum \> class \> order \> family \> genus \> species
78
How are organisms named?
The binomial system of genus and species
79
What caused new models of classification to be proposed?
Evidence of internal structures (microscopes) and biochemical processes were better understood
80
What is the ‘three-domain system’?
Carl Woese divided organisms into: * Archaea (primitive bacteria) * Bacteria (true bacteria) * Eukaryota (protists, fungi, plants and animals)
81
How can the relation of organisms be shown?
Evolutionary trees – current classification data for living organisms and fossil data for extinct organisms is used

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

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