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GCSE Biology Paper 2 > Inheritance, Variation and Evolution > Flashcards

Inheritance, Variation and Evolution Flashcards

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1
Q

Why is it important for us to understand the human genome?

A
  • allows us to identify genes linked to different types of diseases which can help develop treatments for them
  • to trace migration of people around the world by looking at slight differences in genomes
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2
Q

What is DNA made up of?

A

Polymers of repeating units of nucleotides. Each one has an alternating sugar-phosphate backbone.

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3
Q

What are the four different bases that join to each sugar in a DNA strand? What are their pairs? What is this called?

A

A, T, C and G. A always pair up with T. C always pair up with G. This is called complementary base pairing.

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4
Q

How does a gene code for specific amino acids?

A

The order of the bases decides the order of amino acids in a protein. Each one is coded for by a sequence of three bases.

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5
Q

How do ribosomes get the DNA from the nucleus to make proteins?

A

A molecule called mRNA is made by copying the DNA. It acts as a messenger between the DNA and the ribosome, carrying over the code, bringing the correct amino acids in the right order.

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6
Q

What are some examples of proteins with specific tasks?

A
  • Enzymes
  • Hormones
  • Structural proteins - physically strong E.g. collagen
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7
Q

How do mutations work?

A

They change the sequence of the DNA bases in a gene, which produces a genetic variant.

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8
Q

What is an example of a mutation seriously affecting a protein, changing its shape and/or its ability to function?

A
  • change of the shape of an enzyme’s active site
  • structural proteins like collagen could lose their strength, making them pretty useless
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9
Q

What is an insertion and what does it do?

A

Where a new base is inserted into the DNA base sequence. They change the way the groups of three bases are read which changes the amino acid they code for.

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10
Q

What are deletions and what do they do?

A

When a random base is deleted from the DNA base sequence. They change the way the groups of three bases are read which changes the amino acid they code for.

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11
Q

What are substitutions and what do they do?

A

When a random base in the DNA base sequence is changes to a different base. change the way the groups of three bases are read which changes the amino acid they code for.

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12
Q

What is the process of asexual reproduction called and what does it produce?

A

Mitosis. It produces clones that are genetically identical to the parent, with the exact same genetic information. This is because all of the chromosomes come form the same place

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13
Q

What are gametes? How are they made?

A

Sexual reproduction cells (sperm and egg in humans) with 23 chromosomes each. They fuse to form a cell with the cull number of chromosomes. They are made through meiosis.

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14
Q

What is the process of meiosis?

A
  • cell duplicates its genetic information forming two-armed chromosomes
  • the chromosomes arrange themselves into pairs
  • the pairs line up in the middle of the cell
  • the pairs are pulled apart so each new cell has one copy of each chromosome
  • they all line up in the centre again
  • the arms are pulled apart
  • results in four gametes, each with a single set of chromosomes, all genetically different because the chromosomes all get shuffled up
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15
Q

What happens after two gamete cells fuse together in fertilisation?

A

The resulting cell divides by mitosis to replicate itself and then does this loads of times to form an embryo. As the embryo develops the cells start to differentiate.

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16
Q

What are some of the advantages of sexual reproduction?

A
  • produces variation in the offspring
  • increases the chance of a species surviving a change in the environment
  • leads to adaptation which gives species a better chance of survival
  • allows for selective breeding
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17
Q

What are some of the advantages of asexual reproduction?

A
  • only needs one parent
  • uses less energy
  • faster
  • many identical offspring can be produced in favourable conditions
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18
Q

What are some examples of organisms being able to use both sexual and asexual reproduction?

A
  • The malaria parasite reproduces sexually when in the mosquito and asexually when in the human
  • Strawberry plants produce ‘runners’ which are stems that grow horizontally on the surface of the soil with new, identical strawberry plants growing out of it
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19
Q

What decides a person’s sex?

A

In every human body cell there is one pair of chromosomes either labelled XX or XY. Males have XY and females have XX.

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20
Q

Why is there a 50% of each gender.

A

Because the X and Y chromosomes are split apart in the first meiosis division.

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21
Q

What are the two types of genetic diagrams?

A

The Punnett Square and the Genetic Cross Diagram

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22
Q

What are alleles?

A

Different versions of genes. You have two alleles for every gene in your body, one on each chromosome pair.

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23
Q

What do homozygous and heterozygous mean?

A
  • Homozygous - having the same two alleles for a gene
  • Heterozygous - having two different alleles for a gene
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24
Q

What is the difference between a genotype and a phenotype?

A

A genotype is the combination of alleles you have. A phenotype is the characteristic displayed by your alleles.

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25
Q

What is cystic fibrosis and what causes it?

A

A genetic disorder of the cell membranes which makes the body produce thick sticky mucus in the air passages and pancreas. It’s cause by a recessive allele.

26
Q

What is polydactyly and what causes it?

A

A genetic disorder where a person is born with extra fingers or toes, it’s not life threatening. It is caused by a dominant gene.

27
Q

What is embryonic screening?

A

When cells are removed from an embryo to analyse its genes, looking for genetic disorders

28
Q

What are the arguments against embryonic screening?

A
  • implies that people with genetic disorders are undesireable
  • could lead to everyone wanting to do this so that they can choose the physical characteristics of their children
  • it’s expensive
29
Q

What are the arguments in favour of embryonic screening?

A
  • helps prevent suffering
  • treating disorders costs the government money, so they should be prevented
  • there are laws to regulate it
30
Q

How do genetics cause variation?

A

Because most organisms inherit some of their genes from their mother and some from their father, no two of the same species are genetically identical, except twins. This means that there are variations in each generation.

31
Q

How does environment cause variation? Give an example.

A

The conditions that organisms live and grow in can cause variations. E.g. plants with more sunlight are luscious and green but growing the same plant in the darkness will give it yellow leaves.

32
Q

What are some examples of characteristics that are determined by a mixture of genetic and environmental factors?

A

athletic or academic prowess, weight, height, skin colour, condition of your teeth.

33
Q

What is Darwin’s theory of evolution?

A

All of today’s species have evolved from simple life forms that first started to develop three billion years ago.

34
Q

What is the idea of the survival of the fittest?

A

Variation and adaptation leads to different phenotypes —> The individuals with phenotype most fitted to the environment is the most likely to survive —> this means that they reproduce, passing on the mutated gene —>less well adapted organisms gradually go extinct

35
Q

What is speciation?

A

When the phenotype of an organism changes so much over multiple generation that a whole different species is created.

36
Q

What are some of the things that cause extinction?

A
  • environmental changes too quickly
  • new predator kills them all
  • new disease
  • can’t compete with another new species
  • a catastrophic event
37
Q

Why was Darwin’s theory of evolution controversial at the time?

A
  • it went against religious beliefs
  • back then he couldn’t explain how these changes came about
  • he didn’t have enough evidence to convince other scientists
38
Q

What is selective breeding?

A

When humans artificially select the plants or animals that posses a desired characteristic and breed them so that the gene carries through to the next generations. E.g. disease resistance, more meat or milk etc.

39
Q

What is the process of selective breeding?

A
  • select the organisms with desired characteristic
  • breed them together
  • select the best offspring
  • breed them together
  • continue over several generations
40
Q

What are the problems with selective breeding?

A
  • reduces number of different alleles (gene pool)
  • inbreeding can cause health problems like harmful genetic defects
  • new diseases appear
41
Q

What is the process of genetic engineering?

A
  • useful gene cut from one organism’s genome using enzymes and is inserted into a vector
  • vector is usually a virus or bacterial plasmid
  • vector is introduced to the target organism and the useful gene is inserted into its cells
42
Q

What are some of the uses of genetic engineering?

A
  • bacteria to produce insulin for diabetics
  • GM crops to improve the quality and/or size of their crops
  • sheep to produce drugs in their milk
43
Q

What are the cons of GM crops?

A
  • decreases number of wild flowers and biodiversity
  • some say they aren’t safe to eat
  • transplanted genes might get out into the natural environment
44
Q

What are the pros of GM crops?

A
  • increase the yield, making more food
  • could put it missing nutrients, increasing nutritional value
45
Q

What is tissue culture?

A

When a few plant cells are put in a growth medium with hormones and they grow into new plants. Used to preserve rare plants.

46
Q

What are cuttings?

A

Cut off good parent plants and planted to to produce genetically identical clones. This can be done quickly and cheaply.

47
Q

What is the process of embryo transplants?

A

sperm cells taken —> used to artificially fertilise an egg cell —> embryo split to form clones —> clone embryos implanted into other organisms

48
Q

What is the process of adult cloning?

A

nuclei taken from an egg cell and an adult body cell —> adult nucleus put into egg cell —> egg stimulated to divide by electric shock —> embryo implanted into womb to grow into clone of the adult body cell

49
Q

What are some of the arguments against cloning?

A
  • reduced gene pool, could lead to inbreeding
  • cloned animals may not be as healthy
  • could be tried on humans in the future
50
Q

What are some of the arguments in favour of cloning?

A
  • better understanding of ageing
  • help preserve endangered species
51
Q

What are the three ways that fossils can be formed?

A
  • gradual replacement by minerals
  • casts and impressions
  • preservation in amber or ice
52
Q

What are some of the theories about where the first living thing came from?

A
  • primordial swamp
  • simple organic molecules brought to earth of comets and then evolved
53
Q

What is isolation and how does it lead to speciation?

A

When populations of a species are separated and half to adapt to the conditions of their different environments. Eventually they will adapt so much that they won’t be able to breed together to produce fertile offspring.

54
Q

Who was Alfred Russel Wallace and how did he contribute to the theory of evolution by natural selection?

A

A scientist who worked with Charles Darwin. He came up with the idea of natural selection on his own and then travelled the world collecting evidence for it. E.g. butterflies using warning colours to deter predators.

55
Q

How does bacteria become antibiotic-resistant? Give an example

A

They develop mutations in their DNA which can lead to antibiotic-resistant strains. They reproduce rapidly so they evolve quickly. E.g. MRSA is antibiotic resistant . It’s spreads quickly, is hard to treat and can be fatal if it enters the bloodstream.

56
Q

What causes antibiotic resistance?

A
  • antibiotics being taken when not actually needed
  • people not taking their full course of antibiotics
  • antibiotics being given to animals to prevent illness
57
Q

What was Linnaeus’ original system of classification?

A

Kingdom
Phylum
Class
Order
Family
Genus
Species

58
Q

How and why did knowledge of classification increase through the years? What method did Carl Woese use?

A

As knowledge of the biology of animals increased and microscopes improved, scientists got a better understanding of it. Woese used RNA analysis.

59
Q

What is Woese’s three domain system?

A
  • ARCHAEA - certain types of prokaryotic cells
  • BACTERIA - true bacteria E.g. E-coli
  • EUKARYOTA - plants, animals, fungi, protists
60
Q

What are evolutionary trees used to show?

A

The common ancestors and relationships between species, showing how closely related they are and how many characteristics they are likely to share.

GCSE Biology Paper 2 (3 decks)

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