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Biology Paper 2 > B6 - Inheritance, variation and evolution > Flashcards

B6 - Inheritance, variation and evolution Flashcards

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1
Q

What is a gene?

A

Genes are the instructions to make proteins.
They are small sections of DNA that code for specific sequences of amino acids which undergo polymerisation to form a protein.

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2
Q

What is DNA?

A

The molecule/chemical that makes up your genetic material.

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3
Q

What is a genome?

A

The entire genetic material of an organism.

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4
Q

What is a gamete?

A

A sex cell (sperm and ova/eggs)

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5
Q

What is a chromosome?

A

The structures that carry genes.
Each chromosome carries thousands of genes.

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6
Q

How many chromosomes are found in a normal body cell?

A

46 or 23 pairs.

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7
Q

How many chromosomes are found in a gamete?

A

23

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8
Q

What is the nucleus?

A

Organelle found in eukaryotic cells that controls the activities of the cells and contains genetic material.

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9
Q

What does DNA stand for?

A

Deoxyribonucleic acid.

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10
Q

Is DNA a polymer or monomer?

A

Polymer.

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11
Q

What is the DNA of a cell split into?

A

46 chromosomes.

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12
Q

How many different types of chromosomes do we have in each cell?

A

23 types - because we have 2 of each type, one from each parent.

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13
Q

What sex chromosomes do women have?

A

Two X chromosomes.

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14
Q

What sex chromosomes do men have?

A

One X chromosome and one Y chromosome.

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15
Q

What is a mutation?

A

A change to an organism’s DNA/genes.

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16
Q

When do mutations occur?

A

Randomly when a chromosome isn’t replicated correctly.

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17
Q

What increases the chance of a mutation?

A

Ionising radiation.
Substances called mutagens.

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18
Q

What are alleles?

A

Different versions of the same genes.
Caused by mutations. Affect things like eye colour.

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19
Q

In what circumstance will a gene mutation have little effect?

A

Characteristics, such as eye colour, are controlled by several genes, so a mutation in one of these genes will not lead to a big change.

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20
Q

What can be the drastic effects of mutations?

A

It can change the function of the protein it codes for or the protein won’t be made at all.

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21
Q

What is an insertion?

A

A new base is added into the DNA sequence when it shouldn’t be.

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22
Q

What is a deletion?

A

A random base is removed from the DNA sequence.

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23
Q

What is a substitution?

A

A random base is changed to a different base.

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24
Q

How many types of mutations are there?

A

3

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25
Q

What is the effect of an insertion or deletion on a triplet code?

A

Known as “frame shift mutation”. Has a knock on effect on more that one triplet code and therefore more than one amino acid.

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26
Q

How many bases code for one amino acid?

A

3 ( a base triplet)

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27
Q

What is the effect of substitution on a triplet code?

A

There is a different triplet code, meaning a different amino acid is used when it is “read” to make a protein.

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28
Q

Describe the 5 steps of mitosis.

A
  1. Genetic material duplicated.
  2. Chromosomes are pulled apart by fibers.
  3. Chromosomes are separated.
  4. Membrane forms around each set of chromosomes.
  5. Cytoplasm and membrane divide producing 2 daughter cells.
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29
Q

How does mitosis lead to cancer?

A

If one cell is damaged, it creates lots of cells that are damaged leading to tumours.

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30
Q

Do cells divide forever?

A

No, they will eventually die.

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31
Q

What is meiosis?

A

Form of cell division involved in the formation of gametes.

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32
Q

What stage must occur prior to meiosis?

A

Interphase - copies of genetic information made.

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33
Q

What happens during the first stage of meiosis?

A

Chromosome pairs line up along cell equator.
Pairs of chromosomes are separated and moved to opposite ends of the cell.
Chromosome number halved.

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34
Q

What happens during the second stage of meiosis?

A

Chromosomes line up along cell equator.
Chromatids are separated and moved to opposite ends of the cell.
4 unique haploid gametes are produced.

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35
Q

What is an immature sex cell/parent cell?

A

Has a full set of 46 chromosomes.

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36
Q

What happens during the first stage of meiosis that causes variation in the cells produced?

A

When the pairs line up the chromosomes pulled to the left and the chromosomes pulled to the right are completely random.
Allowing each cell to have a different combination of maternal and paternal chromosomes.

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37
Q

What is a haploid cell?

A

Contains half the genetic material of a normal cell.

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38
Q

What happens when 2 gametes combine?

A

They form a normal cell that can grow into a new organism.

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39
Q

What are the 2 types of reproduction?

A

Sexual and asexual.

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40
Q

Why is reproduction important?

A

It gives rise to more members of a species which is important for the survival of the species.

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41
Q

How many organisms are needed for sexual reproduction?

A

2

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42
Q

How many organisms are needed for asexual reproduction?

A

1

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43
Q

What cell division process is involved in making sexual reproduction?

A

Meiosis.

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44
Q

What cell division process is involved in making asexual reproduction?

A

Mitosis. Binary fission in bacterial cells.

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45
Q

Why type of reproduction produces organisms that are identical to each other and the parent(s)?

A

Asexual.

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46
Q

What organisms reproduce asexually?

A

Some plants, bacteria and an animal called Hydra.

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47
Q

What is an advantage of sexual reproduction?

A

Variation in genetics, meaning the chance of extinction is reduced.

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48
Q

What are some disadvantages of sexual reproduction?

A

Takes time.
Two parents are needed.

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49
Q

What are some advantages of asexual reproduction?

A

It’s fast.
Only one parent is needed.

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50
Q

What is a disadvantage of asexual reproduction?

A

No variation increases the chance of extinction as they are less likely to be able to adapt to conditions.

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51
Q

Give examples of organisms that use both methods of reproduction.

A

The parasite that causes malaria.
Fungi.
Some plants.

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52
Q

Why does the parasite that causes malaria reproduce both sexually and asexually?

A

Reproduces sexually in the mosquito but reproduces asexually in humans.

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53
Q

What is a zygote?

A

A fertilised egg cell.

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54
Q

What type of chromosomes does a normal body cell have?

A

22 pairs of autosomes.
1 pair of sex chromosomes.

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55
Q

What is an autosome?

A

Chromosomes that contain genes that don’t determine sex.

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56
Q

What type of chromosomes does a gamete have?

A

22 single autosomes.
1 sex chromosomes.

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57
Q

What is a genotype?

A

The alleles a person had inherited.

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58
Q

What is a phenotype?

A

The visible characteristics.

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59
Q

For how many weeks is our development determined purely by X chromosomes?

A

5-6 weeks.

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60
Q

What is the sex determining gene on the Y chromosome called?

A

SRY

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61
Q

What does the SRY cause?

A

Gonads to develop into testes. The testes produce a hormone called androgen which causes the embryo to develop into a male.

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62
Q

What is an allele?

A

Different version of the same gene.

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63
Q

What is the dominant allele?

A

Only 1 copy of the allele is needed to have a characteristic.

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64
Q

What is the recessive allele?

A

Two copies of the allele are needed to inherit a characteristic.

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65
Q

What is the male gamete in flowering plants?

A

Pollen.

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66
Q

What are 2 ways a person can reduce the chance of developing type 2 diabetes?

A
  1. Eat less carbohydrates
  2. Exercise more
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67
Q

How can a diagram showing the inheritance of a disease through a family show the disease to be recessive?

A

Parents without the disease have a child with the disease.

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68
Q

Give 2 examples of structural proteins in a living organism.

A

Keratin - makes nail, hair and horns in animals
Collagen - cartilage, tendons, teeth and skin.

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69
Q

Give 3 examples of chemical proteins in a living organism.

A

Enzymes
Hormones
Haemoglobin

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70
Q

What is the dominant allele?

A

Only 1 copy of the allele is needed to have a characteristic.

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71
Q

What is the recessive allele?

A

2 copies of the allele are needed to inherit a characteristic.

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72
Q

What is the age of onset for Cystic Fibrosis (CF) ?

A

Birth

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73
Q

What are the symptoms of CF?

A

Thick sticky mucus in lungs and digestive system.

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74
Q

Is there a cure for CF?

A

No

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75
Q

What is the effect on life expectancy for CF?

A

Shortened life expectancy.

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76
Q

How many faulty alleles are needed to inherit CF?

A

2

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77
Q

Is CF caused by the dominant or recessive gene?

A

Recessive

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78
Q

What is the age of onset for Polydactyly (Poly)?

A

Birth

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79
Q

What are the symptoms of poly?

A

Additional fingers or toes.

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80
Q

What is the cure for poly?

A

Extra fingers/toes removed by small surgical procedure or clamping.

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81
Q

What is the affect of poly on life expectancy?

A

No affect.

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82
Q

What is the number of faulty alleles you need to inherit poly?

A

1

83
Q

Is poly caused by the dominant or recessive gene?

A

Dominant.

84
Q

What is the age of onset of Huntington’s disorder?

A

30-50

85
Q

What are the symptoms of Huntington’s?

A

Brain condition that affects movement and causes personality and emotional changes.

86
Q

Is there a cure to Huntington’s?

A

No

87
Q

How is life expectancy affected by Huntinton’s?

A

15-20 years after onset.

88
Q

What is the number of faulty alleles needed to inherit Huntington’s?

A

1

89
Q

Is Huntington’s caused by the dominant or recessive gene?

A

Dominant

90
Q

What is evolution?

A

A change in the inherited characteristics of a population over time through natural selection.

91
Q

What is speciation?

A

Formation of a new species as a product of evolution.

92
Q

What is the theory of evolution?

A

That all species of life have evolved from simple life forms more than 3 billion years ago.

93
Q

Explain natural selection.

A

There are small variations in living things of the same species.
Some organisms are more likely to survive and reproduce.
Passing on their characteristics onto their offspring.

94
Q

What are the variations within a species caused by?

A

Mutations

95
Q

What did Lamarak believe?

A

All members of the same species have identical characteristics.
The individual is capable of changing within it’s life time and passing on these changes to their offspring.

96
Q

What did Darwin believe?

A

Variation is common among animals of the same species.
Individual is unchanging.
Population is capable of changing when parents pass on features to their offspring.

97
Q

What is a species?

A

A group of living things that can be bred together to produce offspring, and the offspring is capable of reproduction.

98
Q

When does speciation happen?

A

When a population of the same species become so different they can no longer breed together to produce fertile offspring.

99
Q

3 steps of specieation.

A

Isolation
Mutation
Natural selection
Speciation

100
Q

Give 4 pieces of evidence for evolution.

A

Fossils
Knowledge of genes
Rapid changes observed
Antibiotic resistant bacteria

101
Q

Give 4 examples of fossils.

A

Hard parts that don’t decay e.g. teeth and bones.
Whole organisms preserved in ice.
Hard parts of an organism get replaced by minerals (most common)
Traces of plants and animals get left behind in soft material that hardens over time.

102
Q

Explain the peppered moth case study.

A

White moths started off as dominant.
Environment changed - Industrial Revolution
Black moths became dominant.

103
Q

Disadvantages of fossils.

A

Many animals were soft-bodied.
Geological activity destroyed some fossils.
Only formed under right conditions.

104
Q

What does the domain consist of?

A

Eukaryota
Archaea
Bacteria

105
Q

What are the 6 kingdoms of life?

A

Plants
Animals
Fungi
Protists
Archaebacteria
Eubacteria

106
Q

What are the 4 kingdoms of life in Eukarya?

A

Plants
Animals
Fungi
Protists

107
Q

Anagram to remember the classification pyramid.

A

Domain
Kids, Prefer, Candy, Over, Fried, Green, Spinach

108
Q

What is selective breeding?

A

People taking charge of selection to produce new varieties of various species.

109
Q

How are dog breeds like the Corgi selectively bred?

A

From the grey wolf.

110
Q

How was wild mustard plant selectively bred?

A

To form broccoli, cauliflower, cabbage and kale.

111
Q

How is natural selection different to selective breeding?

A

Because it is not a natural process, humans intervene.

112
Q

What is genetic engineering?

A

Involves changing the genetic material of an organism.

113
Q

What is an organism that has been genetically engineered called?

A

A genetically modified organism.

114
Q

Give 4 examples of genetically modified organisms.

A

Potatoes that contain more starch are more resistant to pests.
Crops that are resistant to viruses
Flood resistant rice
Bacterial cells that produce human insulin for diabetics.

115
Q

What are the advantages of GM crops? (5)

A

Produce a greater yield.
Resistant to insect attacks.
Produce bigger and better fruits.
Resistant to herbicides allowing farmers to spray them without harming the crops.
Food security

116
Q

What are the disadvantages of GM crops?

A

Dangerous to eat
Lack of biodiversity
Allergies

117
Q

Explain the process of GM bacteria.

A

DNA containing gene removed from cell.
Enzymes isolate gene.
Plasmid removed from bacteria.
Enzymes insert gene into plasmid.
Bacteria reproduce.

118
Q

What is a clone?

A

An organism that is genetically identical to another.

119
Q

State 1 ways plants can be cloned.

A

Plant cuttings - taking cuttings from plants with desirable characteristics and planting them.

120
Q

State 2 ways plants can be cloned.

A

Plant cuttings
Tissue culture

121
Q

What do plant cuttings involve?

A

Taking cuttings from plants with desirable characteristics and planting them.

122
Q

What does tissue culture involve?

A

A few plants are put into a growth medium with hormones and grow into complete new plants.

123
Q

Why is tissue culture useful?

A

Can preserve rare species.
Can produce lots of stock quickly.

124
Q

Why are plant cuttings good?

A

Cheap, quick and simple.

125
Q

How can farmers clone cattle from a bull and a cow?

A

Sperm taken from bull. Egg taken from cow.
Sperm artificially fertilises egg.
Embryo that develops is then split to form clones.
Clones are then implanted into cows to grow into calfs.

126
Q

Describe process of adult cell cloning.

A

Nucleus taken out of egg cell.
Nucleus from adult cell is put into egg cell.
Egg cell develops into an embryo.
Stem cells taken from embryo.
Stem cells can be used to treat disease and repair damaged tissue.

127
Q

Describe the process of cloning sheep (Dolly the sheep).

A

A body cell is taken from the animal that is “ideal”.
Put into an enucleated egg cell.
Egg cell forms embryo.
Embryo put into a third sheep.
Grows into a mature sheep.

128
Q

What are the pros of cloning? (2)

A

Lots of ideal offspring.
Help preserve endangered species.

129
Q

What are the cons of cloning?

A

Reduces gene pool.
Cloned animals not as healthy.
May result in severely disabled children if humans cloned.

130
Q

What is a gene pool?

A

The variety of genes in a species - large gene pool - more capable to cope with environmental challenges.

131
Q

What is an enucleated cell?

A

Cell which it’s nucleus has been removed.

132
Q

What is screening for genetic disorders?

A

Testing for genetic disorders or the presence of a genetic abnormality or allele.

133
Q

When does screening take place?

A

Before being born.
After being born - newborn.
PGD.

134
Q

What is PGD?

A

Preimplantation genetic disorders - testing a cell from an embryo before implantation.

135
Q

What 2 inherited disorders do we screen for in the UK?

A

Sickle cell disorder.
Cystic Fibrosis

136
Q

What are 3 inherited disorders?

A

Cystic fibrosis
Huntington’s disorder
Polydactyly.

137
Q

What does IVF stand for?

A

In Vitro Fertilisation

138
Q

Describe the process of IVF.

A

Female takes fertility hormones that release several eggs.
Small operation to remove eggs.
Males sperm is collected and eggs are fertilised in a petri dish.
Once embryo is formed - it is placed in the female’s uterus.

139
Q

Describe PDG.

A

Once embryos are at the 8 cell stage once cel is removed from each embryo.
Cells tested for allele that causes disease.
Only embryos that are without the disease are implanted into the mother.

140
Q

Give 2 methods used to harvest cells from an embryo for testing.

A

Amniocentesis.
Chronic villus

141
Q

What stage of pregnancy is amniocentesis carried out?

A

15-16 weeks of pregnancy.

142
Q

What does amniocentesis involve?

A

Taking some of the fluid from around the developing fetus. Fetal cells can be used for screening.

143
Q

What stage of pregnancy is chronic villus carried out?

A

10-12 weeks of pregnancy.

144
Q

What does chronic villus invlove?

A

Take a small sample of tissue from the developing placenta. Provides fetal cells to screen.

145
Q

What is the structure of DNA?

A

A polymer in the shape of a double helix made up of 4 nucleotides (monomers).

146
Q

What are the 4 bases that make up DNA?

A

A C T G

147
Q

How do the 4 bases pair up?

A

A and T pair up.
C and G pair up.

148
Q

What is the function of DNA?

A

Contains genetic code which then code for proteins.

149
Q

Where in a cell are proteins made?

A

Ribosomes - cytoplasm

150
Q

What are the monomers of proteins?

A

Amino acids

151
Q

What happens when the 4 bases don’t pair up correctly?

A

Mutation occurs.

152
Q

What 3 parts make up a nucleotide?

A

Phosphate
Sugar
Base

153
Q

What 2 parts of a nucleotide are always present?

A

Phosphate
Sugar

154
Q

What part of a nucleotide changes?

A

The base

155
Q

What is the A base?

A

Adenine

156
Q

What is the T base?

A

Thymine

157
Q

What is the C base?

A

Cytosine

158
Q

What is the G base?

A

Guanine

159
Q

What is the purpose of the sugar and phosphate “backbone”?

A

Forms protective casing around bases.

160
Q

What is the genetic code?

A

The sequence of bases.

161
Q

What is a triplet code?

A

Made up of 3 bases.
Codes for an amino acid.

162
Q

How are proteins different from one another?

A

Each protein type is made up of a different sequence of amino acids.
Each type therefore has a unique shape, therefore, function.

163
Q

What are the 3 uses of proteins by our body?

A

Enzymes
Hormones
Structural proteins

164
Q

What is the function of structural proteins?

A

Add strength to cells and tissues.

165
Q

What is the function of hormones?

A

Send messages around the body.

166
Q

Give 3 steps to summarise transcription.

A

In the nucleus, DNA unwinds.
A strand of mRNA is made which has a complementary sequence to DNA.
mRNA moves out of nucleus

167
Q

What does it mean when an organism is heterozygous?

A

When they have two different alleles (one dominant and one recessive)

168
Q

What does it mean when an organism is homozygous?

A

When an organism has two copies of the same allele.

169
Q

What are the monomers of DNA?

A

Nucleotides.

170
Q

How do nucleotides interact to form a DNA molecule?

A

Sugar and phosphate backbone is formed.
Base connect to sugar.
Complementary base pairs.
Joined together by weak hydrogen bonds.

171
Q

How does a gene code for a protein?

A

A sequence of 3 bases in a gene codes for an amino acid.
The order of amino acids determines the structure and function of the protein.

172
Q

Why is the folding of amino acids important in proteins such as enzymes?

A

The folding of amino acids determines the shape of the active site, which must be highly specific to the shape of the substrate.

173
Q

What are the 2 stages of protein synthesis?

A

Transcription
Translation

174
Q

What does transcription involve?

A

The formation of mRNA from a DNA template.

175
Q

What does translation involve?

A

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

176
Q

Give 3 steps to summarise translation.

A

mRNA moves into cytoplasm and binds to ribosome
Ribosome moves along mRNA and reads the genetic code so carrier molecules can attach the amino acids in the correct order.
The ribosome releases the chain of amino acids - protein is made.

177
Q

What is RNA?

A

Ribonucleic acid.

178
Q

How does RNA differ from DNA?

A

RNA is single stranded and has exposed bases.
Has a sugar called ribose (DNA has a sugar called deoxyribose).
RNA has the base uracil, DNA has base thymine.

179
Q

What are 2 types of RNA?

A

mRNA
tRNA

180
Q

What is mRNA?

A

Messenger RNA - carries a copy of the DNA base sequence of a specific gene to the cytoplasm.

181
Q

What is tRNA?

A

Transfer RNA - transport specific amino acids to the ribosome

182
Q

What would happen if there was a mutation in DNA?

A

Mutation in mRNA - wrong amino acid being made and used in protein.

183
Q

Similarities between mRNA and DNA?

A

Both have helix structure.
Both have phosphate-sugar backbone with bases attached.

184
Q

What is gene expression?

A

The process by which specific genes are activated to produce a required protein.

185
Q

Why are only a small fraction of the genes in any cell expressed?

A

Each cell is specialised to carry out a certain task and will only need to express certain genes.

186
Q

What does every cell in a multicellular organism have?

A

A full set of chromosomes with every gene needed to make every protein that that organism will ever make.

187
Q

What is an inherited disorder?

A

A disorder caused by the inheritance of certain alleles.

188
Q

What are the ethical issues with embryonic screening?

A

Idea of designer babies - for the parents convenience rather than child’s well being
Destruction of embryos - seen as murder.

189
Q

What is gene therapy?

A

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

190
Q

Ethical issue concerning gene therapy.

A

Some people believe it is playing god.

191
Q

What is a sex-linked characteristic?

A

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

192
Q

Why are the majority of genes found on the X chromosome rather than the Y?

A

X is bigger than Y so more genes can be carried on it.

193
Q

Why are men more likely to show the phenotype for a recessive sex linked trait than women?

A

Males have only one X chromosome. A single recessive gene on that X chromosome will cause the disease.

194
Q

What is variation?

A

Differences of the characteristics of individuals in a population.

195
Q

What are 2 causes of variation?

A

Environment
Genetics

196
Q

What is genetic variation?

A

Differences in the genotypes of organisms in the same species. Creates differences in phenotypes.

197
Q

What creates genetic variation within a species?

A

Spontaneous mutations
Sexual reproduction

198
Q

What is the sue of genetically modified bacterial cells?

A

To produce human insulin to treat diabetes.

199
Q

What is tissue culture?

A

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

200
Q

How are plants grown using tissue culture?

A

Select a plant that shows desired characteristics.
Cut samples from meristem.
Grow in a meristem containing a growth medium.
Transfer to compost for future growth.

201
Q

What must be ensured when growing tissue cultures?

A

Aseptic conditions to prevent contamination from micoorganisms.

202
Q

What does the growth medium in tissue culture contain?

A

Nutrients and growth hormones.

203
Q

Advantages of tissue culture.

A

Saves endangered species.
Fast and simple
Enables growth of plants with desirable characteristics.
Little space needed.

204
Q

2 disadvantages of tissue culture.

A

Reduction in gene pool
Often have low life span

Biology Paper 2 (3 decks)

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