Separate Biology - 4.6 Flashcards
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 is a clone?
A
Genetically identical offspring (a result of asexual reproduction)
8
Q
What does meiosis do to the number of chromosomes in the gamete?
A
It halves it (46 to 23)
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)
10
Q
What key stages occur when a cell divides to form gametes (meiosis)?
A
- Copies of the genetic information are made
- The cell divides twice forming four gametes (each with a single set of chromosomes)
- All the gametes are genetically different from each other
11
Q
Separate Q. What are the advantages of sexual reproduction?
A
- Produces variation
- If the environment changes, variation gives a survival advantage by natural selection (taken advantage of by human selective breeding)
12
Q
Separate Q. What are the advantages of asexual reproduction?
A
- Only one parent needed
- More time and energy efficient (no mate to find)
- Faster than sexual reproduction
- Many identical offspring can be produced when conditions are favourable
13
Q
Separate Q. How do malarial parasites reproduce?
A
Asexually in the human host but sexually in the mosquito
14
Q
Separate Q. How do (many) fungi reproduce?
A
Asexually by spores but also sexually to allow for variation
15
Q
Separate Q. How do (many) plants reproduce?
A
Sexual reproduction: Via seed dispersal
Asexual reproduction: Via runners (e.g. strawberry plants) or bulb division (e.g. Daffodil or potato plants).
16
Q
What is the genetic material in the nucleus of a cell composed of?
A
DNA
17
Q
What is the structure of DNA?
A
A polymer made up of two strands forming a double helix
18
Q
What is DNA contained in?
A
Chromosomes
19
Q
What is a gene?
A
A small section of DNA on a chromosome
20
Q
What does a gene code for?
A
A particular sequence of amino acids, which make specific proteins
21
Q
What is the genome of an organism?
A
The entire genetic material of that organism
22
Q
Why is having the human genome sequence important?
A
It will be of benefit to medicine
23
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
24
Q
Separate Q. DNA as a polymer is made from how many nucleotides (and what are these)?
A
4x different nucleotides – each consists of a common sugar and phosphate group with one of four different bases attached to the sugar
25
Separate Q. What are the four bases DNA contains?
A, T, C and G
26
Separate Q. How does a particular amino acid get coded?
A sequence of three bases is the code – the order of bases controls the order in which amino acids are assembled to produce a particular protein
27
Separate Q. What do long strands of DNA consist of?
Alternating sugar and phosphate sections (attached to each sugar is one of four bases)
28
Separate Q. What is the DNA polymer made up of?
Repeating nucleotide units
29
Separate Higher Q. How may genetic variants influence the phenotype in coding DNA?
The activity of a protein might be altered
30
Separate Higher Q. How may genetic variants influence the phenotype in non-coding DNA?
How the genes are expressed may be altered
31
Separate Higher Q. Where are proteins synthesised?
On ribosomes (according to a template)
32
Separate Higher Q. How are proteins synthesised?
Carrier molecules bring specific amino acids to add to the growing protein chain (in the correct order))
33
Separate Higher Q. What does the unique shape of a folded protein chain allow for?
The unique shape enables proteins to do their job as enzymes, hormones or forming structures (such as collagen)
34
Separate Higher Q. What are proteins used for?
* Enzymes
* Hormones
* Forming structures (e.g. collagen)
35
Separate Higher Q. Mutations occur continuously – what is the outcome for most of these?
Most do not alter the protein (or only alter it slightly so that the appearance / function is not changed)
36
Separate Higher Q. What might happen if a mutation codes for an altered protein (with a different shape)?
An enzyme may no longer fit the substrate binding site / a structural protein may lose its strength
37
Separate Higher Q. What do non-coding parts of DNA do?
Not all parts of DNA code for proteins – non-coding parts can switch genes on/off
38
Separate Higher Q. What can variations in non-coding parts of DNA lead to?
How genes are expressed may be affected (as non-coding parts of DNA can switch genes on/off)
39
Explain the term: gamete
A sex cell (e.g. sperm or egg)
40
Explain the term: chromosome
A long molecule of DNA, found in the nucleus of a cell, which carries genes
41
Explain the term: gene
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)
42
Explain the term: allele
An alternative version of a gene
43
Explain the term: dominant
The allele for the characteristic that’s shown by an organism if two different alleles are present for that characteristic
44
Explain the term: recessive
An allele whose characteristic only appears in an organism if there are two copies present
45
Explain the term: homozygous
Where an organism has two alleles for a particular gene that are the same
46
Explain the term: heterozygous
Where an organism has two alleles for a particular gene that are different
47
Explain the term: genotype
What alleles and organism has, e.g. Tt
48
Explain the term: phenotype
The characteristics an organism has, e.g. tall
49
Give an example of characteristics controlled by a single gene
Fur colour in mice / red-green colour blindness in humans
50
What controls the phenotype (what is expressed)?
Alleles present (or genotype) operating at a molecular level to develop characteristics expressed (as a phenotype)
51
Which allele is always expressed?
The dominant (even if only one copy is present)
52
What are most characteristics a result of?
Multiple genes interacting (rather than a single gene)
53
Complete a Punnett square for the % chance of having a boy or girl
54
What is polydactyly?
An inherited disorder (extra fingers or toes) caused by a dominant allele
55
What is cystic fibrosis?
An inherited disorder (cell membrane issues) caused by a recessive allele
56
How many pairs of chromosomes are found in ordinary human body cells?
23 pairs
57
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)
58
How does the phenotype of an organism develop?
The interaction between the genome and environment influence development of the phenotype
59
What is variation?
Differences in the characteristics of individuals in a population
60
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
61
Within a population of a species, what usually exists?
Extensive genetic variation
62
How do variants in a species arise?
Mutations: most have no effect on phenotype, some influence phenotype, and very few determine phenotype
63
If a mutation leads to a new phenotype, suited to an environmental change, what might occur?
Relatively rapid change in the species
64
What is evolution?
A change in the inherited characteristics of a population over time which may result in the formation of a new species
65
What is the driving force of evolution?
Natural selection
66
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
67
Variants that give rise to phenotypes best suited to their environment causes what?
Evolution, occurring through natural selection
68
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
69
What is selective breeding?
Selective breeding is artificial selection – humans breed plants and animals for particular genetic characteristics
70
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
71
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
72
What can selective breeding lead to?
Inbreeding – some breeds are prone to diseases or inherited defects
73
What is genetic engineering?
A process involving modifying the genome or an organism by introducing a gene from another organism: giving a desired characteristic
74
How have plant crops been genetically engineered?
To be resistant to disease / produce bigger and better fruits
75
How have bacterial cells been genetically engineered?
To produce useful substances such as human insulin (treating diabetes)
76
How does genetic engineering occur?
Genes from chromosomes are ‘cut out’ and transferred to cells of other organisms
77
What are genetically modified (GM) crops?
Crops that have had their genes modified: resistance to insect attack / herbicides for example (generally show yield increase)
78
What concerns are there about GM crops?
The effect on populations of wild flowers and insects / human health (not being fully explored)
79
How is modern medical research utilising genetic modifications?
To overcome some inherited diseases
80
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)
81
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)
82
Higher Q. How are genes transferred during genetic engineering?
The bacterial plasmid / virus vector inserts the gene into the required cells
83
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
84
Separate Q. What is tissue culture?
Small groups of cells from part of a plant grow to form identical new plants
85
Separate Q. Why is tissue culture important?
It can preserve rare plant species or be used commercially in nurseries
86
Separate Q. What is a cutting?
A small part of a plant that is taken from a parent plant to produce many identical new plants.
87
Separate Q. What is embryo transplant?
Splitting apart cells from a developing embryo before they become specialised and transplanting these identical embryos into host mothers
88
Separate Q. What is adult cell cloning?
The nucleus is removed from an unfertilised egg and replaced with a nucleus from an adult body cell – electrical shock stimulates the egg cell to divide, forming an embryo
89
Separate Q. In adult cell cloning, what do the embryo cells contain?
The same genetic information as the adult body cell from where the nucleus came from.
90
Separate Q. In adult cell cloning, where does the embryo which has developed into a ball of cells go?
It is inserted into the womb of an adult female to continue its development.
91
Separate Q. Who proposed the theory of evolution by natural selection?
Charles Darwin
92
Separate Q. What are the key principles of the theory of evolution by natural selection?
1. Individual organisms with a particular species show a wide range of variation for a characteristic
2. Individuals with characteristic most suited to the environment are more likely to survive and breed
3. Characteristics are then passed to the next generation
93
Separate Q. Where did Charles Darwin publish his ideas about evolution?
In the book On the Origin of Species (1859) which was greeted with much controversy.
94
Separate Q. Why was the theory of evolution by natural selection only gradually accepted?
* The theory challenged the idea that God made all the animals and plants
* There was insufficient evidence at the time
* The mechanisms of inheritance and variation was not known until 50 years after the publication
95
Separate Q. What did Jean-Baptiste Lamarck theorise?
Changes occur in an organism during its lifetime which can then be inherited
96
Separate Q. What did Alfred Russel Wallace propose?
He independently proposed the theory of evolution by natural selection along with Darwin
97
Separate Q. What was Wallace best known for?
He worked worldwide gathering evidence for evolutionary theory – best known for his work on warning colourations and his theory of speciation
98
Separate Q. What did Gregor Mendel discover?
Inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged
99
Separate Q. When was the behaviour of chromosomes during cell division observed?
The late 19th Century
100
Separate Q. When were Mendel’s ‘units’ and chromosomes linked?
In the early 20th Century: chromosomes and the ‘units’ behaved in similar ways leading to the ‘units’, now known as genes, being located on the chromosomes
101
Separate Q. When was the structure of DNA and the mechanism of gene function determined?
The mid-20th Century
102
What evidence is there for evolution?
Fossils and antibiotic resistance in bacteria
103
What are fossils?
The ‘remains’ of an organism from millions of years ago, found in rocks
104
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…)
105
Why are there very few traces of early life forms?
They were soft-bodies (fossil record incomplete)
106
What do fossils show?
How much / how little different organisms have changed as life developed on Earth
107
What is extinction?
When there are no remaining individuals of a species still alive
108
What may cause extinction of a species?
* Environmental changes
* New predators
* New diseases
* Catastrophic events
* Unable to compete
109
Why can bacteria evolve rapidly?
They reproduce at a fast rate
110
How do new strains of bacteria occur?
Mutations: some strains may be resistant to antibiotics so are not killed and the resistant strains rises
111
What is MRSA resistant to?
Antibiotics
112
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
113
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
114
What did Carl Linnaeus develop?
A classification systems, based on structures and characteristics
115
How did Carl Linnaeus characterise living organisms?
Kingdom \> phylum \> class \> order \> family \> genus \> species
116
How are organisms named?
The binomial system of genus and species
117
What caused new models of classification to be proposed?
Evidence of internal structures (microscopes) and biochemical processes were better understood
118
What is the ‘three-domain system’?
Carl Woese divided organisms into:
* Archaea (primitive bacteria)
* Bacteria (true bacteria)
* Eukaryota (protists, fungi, plants and animals)
119
How can the relation of organisms be shown?
Evolutionary trees – current classification data for living organisms and fossil data for extinct organisms is used
