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GCSE Biology > Topic 6 - Inheritance, Variation and Evolution > Flashcards

Topic 6 - Inheritance, Variation and Evolution Flashcards

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1
Q

Describe sexual reproduction

A
  • fusion of gametes
  • requires 2 parents (egg and sperm cell)
  • offspring contain a mixture of their parents’ genes (unique individuals made)
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2
Q

Describe asexual reproduction

A
  • no fusion of gametes
  • only one parent required
  • offspring are identical to parents (clones)
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3
Q

Pros and cons of sexual reproduction

A

+ allows genetic variation
+ allows selective breeding
- slow
- needs to find a mate

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4
Q

Pros and cons of asexual reproduction

A

+ less energy
+ fast
- faulty genetic material may be passed on
- bad if environment changes

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5
Q

What are some organisms that use both types of reproduction?

A
  • parasite that causes malaria - sexual in mosquito and asexual in human
  • fungi spores
  • plant seeds
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6
Q

Describe the process of meiosis

A
  • chromosomes copy themselves (giving double the amount)
  • the copied chromosomes arrange themselves as pairs
  • the pairs line up in the centre of the cell
  • the pairs are pulled apart by protein fibres (some of the fathers and mothers chromosomes go into each cell)
  • the chromosomes line up again and are pulled apart
  • the chromosomes now separate, giving 4 cells with half the amount of original chromosomes
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7
Q

Describe meiosis in 3 words

A

copy divide divide

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8
Q

Where does meiosis occur?

A

gametes (sex cells)

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9
Q

What does meiosis produce?

A

4 different haploid cells

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10
Q

Define the genome

A

All of the genetic material in an organism

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11
Q

Why is understanding the human genome really important for science and medicine?

A
  • allows scientists to link genes to different types of diseases
  • knowing which genes are linked to inherited diseases helps scientists understand them better and develop treatments
  • scientists can use DNA sequencing to trace human migration patterns from the past
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12
Q

Define a gene

A

A short section of a chromosome.

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13
Q

What is DNA made of?

A

DNA is a polymer made of two strands in a double helix structure.

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14
Q

What are some issues with people knowing your genome?

A
  • can be sold to 3rd parties
  • who does the DNA belong to?
  • can lead to being targeted by drug companies
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15
Q

What are positives of knowing peoples genomes?

A
  • can identify criminals
  • can discover family
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16
Q

What are nucleotides made up of?

A
  • a sugar
  • a phosphate
  • one base
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17
Q

How many bases is DNA made up of?

A

4

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18
Q

How many bases code for 1 amino acid?

A

3

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19
Q

What does a gene code for?

A

a particular sequence of amino acids to make a protein

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20
Q

Which bases pair with which?

A

A - T
C - G

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21
Q

What do the non-coding parts of DNA do?

A

they switch genes on and off - they control whether or not a gene is expressed

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22
Q

How does DNA cause a protein to be synthesised? (6 marks)

A
  • DNA is the code for making proteins
  • the code consists of base pairs (A-T and C-G)
  • DNA is too big to leave the nucleus so it makes a single strand copy of itself (mRNA)
  • the messenger RNA goes into the ribosomes and is translated (the bases are read)
  • 3 bases code for one amino acid
  • the tRNA brings amino acids to the ribosomes and the the correct order
  • amino acids join up to make proteins
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23
Q

Define a mutation

A

a change in the DNA code - they occur continously

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24
Q

Describe the 3 types of mutations

A
  • insertions - new base is inserted in the DNA base sequence where it shouldn’t be
  • deletions - a random base is deleted from the sequence
  • substitutions - a random base in the DNA base sequence is changed
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25
Q

Which are the least and most damaging types of mutations?

A
  • insertion and deletion are the most damaging - they change the code for every amino acid after the mutation point
  • substitution only affects 1 amino acid
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26
Q

Explain how a change in the base pair sequence of DNA can lead to a non-functioning enzyme. (6 marks)

A
  • mutations change the sequence of base pairs
  • if the sequence changes, the amino acids will change so the protein will have a different shape
  • enzymes are proteins
  • if the shape changes, the substrate won’t fit in the active site and it can’t bind
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27
Q

Define homozygous

A

two alleles are the same

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28
Q

Define heterozygous

A

one of each allele

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29
Q

Describe how to answer a punnett square question

A
  • write the parents alleles genotype
  • draw a punnett square
  • write the outcomes (probability in %)
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30
Q

Define a dominant allele

A

only one copy is needed to have feature (stronger)

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31
Q

Define a recessive allele

A

both copies are needed to have feature

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32
Q

Define an allele

A

different versions of the same gene

33
Q

Define a genotype

A

the pair of alleles someone has

34
Q

Define a phenotype

A

the feature someone has

35
Q

Describe polydactyly

A
  • extra digits (fingers or toes)
  • caused by a dominant allele
36
Q

Describe cystic fibrosis

A
  • causes a build up of mucus
  • caused by a recessive allele
37
Q

What is selective breeding?

A

when humans breed plants and animals for desired characteristics

38
Q

What are some examples of desired characteristics?

A
  • animals that produce more meat or milk
  • crops with disease resistance
  • dogs with a gentle nature
  • plants with big/unique flowers
39
Q

Describe the process of selective breeding

A
  • select the animals which have the characteristics you’re after
  • breed them
  • select the best of the offspring and breed them together
  • continue this process over several generations
40
Q

What are drawbacks of selective breeding?

A
  • reduces the gene pool (the number of different alleles) in a population - leads to inbreeding
  • more chance of inheriting harmful genetic defects
  • a new disease would be more dangerous because of the lack of variation - less chance of any resistant alleles being present
41
Q

What is the theory of evolution?

A

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

42
Q

Define evolution

A

organisms changing over time through natural selection to best adapt to their environment

43
Q

Describe natural selection

A
  • in any population, there is variation
  • mutations may cause increased variations
  • organisms compete for resources
  • some organisms are better adapted
  • these organisms will survive and breed, passing on genes for beneficial phenotypes to their offspring
44
Q

What are the 7 words you need to describe natural selection?

A
  • variation
  • mutation
  • adaption
  • survive
  • breed
  • genes
  • offspring
45
Q

Why wasn’t Darwin believed?

A
  • it went against religious theories
  • DNA wasn’t discovered yet - so he couldn’t explain why traits were passed on
  • there wasn’t much evidence
46
Q

Who came up with the theory of evolution?

A

Charles Darwin

47
Q

What was Jean-Baptiste Lamarck’s theory?

A

he argued that the organism will change over its lifetime - he thought that if a characteristic was used a lot by an organism, it would become more developed during its lifetime

48
Q

Define genetic engineering

A

Genetic engineering means altering the genome of one organism by adding genes from another organism

49
Q

Describe the process of genetic engineering

A
  • a useful gene is cut from one organism’s genome using enzymes and is inserted into a vector (bacterial plasmid)
  • the vector is introducted into the targetorganism and the useful gene is insterted into its cell
50
Q

Describe some uses of genetic engineering

A
  • bacteria have been genetically modified to produce human insulin (used to treat diabetes)
  • GM crops have improved features - e.g bigger fruit, disease resistant
  • sheep have been genetically engineered to produce substances in their milk that can treat human diseases
51
Q

Pros of genetic engineering

A
  • can protect plants from being eaten
  • produces useful human substances e.g insulin
  • engineer plants to increase yield
  • can treat genetic diseases through gene therapy
52
Q

Cons of genetic engineering

A
  • leads to less variation - reduces biodiversity
  • transplanted genes may transfer to wild plants
  • long term effects aren’t known
  • hard to control
53
Q

Name the 4 types of cloning

A
  • tissue culture
  • cuttings
  • cloning embryos
  • adult cell cloning
54
Q

Describe tissue culture (cloning)

A

a tissue sample is taken and combined with hormones to grow large amounts of clones of the parent plant

55
Q

Give some pros and cons of tissue culture (cloning)

A

+ can produce thousands of offspring
+ helps scientists preserve rare plant species
- more expensive than taking cuttings
- requires equipment

56
Q

Describe taking cuttings (cloning) and give some pros and cons

A

cut some leaves off the plant and replant them with rooting powder
+ cheap and easy
- not very reliable

57
Q

Describe cloning embryos (for cows)

A
  • give fertility hormones to a top-quality cow, collect her eggs and fertilise them to produce embryos
  • divide each embryo into cells, and each cell will grow into an identical embryo
  • transfer embryos to host mothers and identical calves will be born
58
Q

Give some pros and cons of cloning embryos

A

+ can produce more calves
- skilled and expensive work

59
Q

Describe the process of adult cell cloning

A
  • nucleus is removed from an unfertilised egg cell
  • nucleus is taken from an adult body cell
  • the nucleus from the adult cell is inserted in the empty egg cell
  • new egg cell gets an electric shock to stimulate it to start dividing
  • inserted into surrogate mother
60
Q

Give some pros and cons of adult cell cloning

A

+ we can make copies with desired characteristics
+ endangered species can be repopulated
- low success rate
- cloned animals have short life spans
- regarded as immoral

61
Q

Define species

A

A group of similar organisms that can reproduce to give fertile offspring

62
Q

Define speciation

A

the formation of new species - occurs when populations of the same species become so different that they can no longer breed to produce fertile offspring

63
Q

What are the key terms for a speciation question?

A

SIGNS
Speciation:
Isolation
Genetic variation
Natural selection
Species

64
Q

Describe speciation

A
  • 2 groups of the same species become isolated
  • the animals start adapting to their environment though natural selection
  • natural selection works differently on the different populations
  • after generations of adaptation and natural selection, the 2 populations are so different, they can no longer produce fertile offspring
  • speciation has occured
65
Q

Which scientist was a pioneer of the system of speciation?

A

Alfred Russel Wallace

66
Q

What did Gregor Mendel do?

A
  • he carried out breeding experiments on pea plants
  • he found that the inheritance of each characteristic is determined by ‘units’ that are passed on to offspring
67
Q

What 3 conclusions did Mendel reach?

A
  • characteristics in plants are determined by “hereditary units”
  • hereditary units are passed on to offspring unchanged from both parents - one unit from each parent
  • hereditary units can be dominant or recessive
68
Q

Define fossils

A

Fossils are the remains of organisms which existed thousands/millions of years ago

69
Q

Describe the 4 types of fossils

A
  • trace - not the actual organism, but the impression it left behind e.g footprints
  • permineralisation - harder parts of the animal/plant are replaced by minerals as they decay and become part of the rock
  • hard part preservation - when the hard parts of an animal can’t decay
  • whole organism preservation - whole animal is preserved
70
Q

Why is the fossil record incomplete?

A
  • lots are destroyed by the movement of the Earth
  • lots of organisms don’t fossillise
  • not all fossils have been discovered
71
Q

Define extinction

A

when all members of a species have died out and none remain

72
Q

What are some causes of extinction?

A
  • new predators
  • new diseases
  • new competitors
  • catastrophic event
    etc.
73
Q

Define antibiotic resistance

A

when a bacteria that used to be killed by an antibiotic isn’t affected by it anymore

74
Q

How do we prevent antibiotic resistance?

A
  • good hygiene
  • doctors should not prescribe antibiotics inappropriately
  • patients should complete their course of antibiotics
  • the agricultural use of antibiotics should be restricted
75
Q

What 2 things did Carl Linnaeus create?

A
  • binomial naming system
  • system of classification
76
Q

What are the 7 groups Linneaus organised living things into?

A
  • kingdom
  • phylum
  • class
  • order
  • family
  • genus
  • species
77
Q

Describe Linnaues’ binomial naming system

A

Organisms are given a two part Latin name
- first part is the genus
- second part is the species

78
Q

How did Woese change the classification system?

A

introduced the 3 domain system - splits organisms into 3 large groups called domains:
- archaea - thought to be primitive bacteria, live in extreme places
- bacteria - true bacteria
- eukaryota - everything else, including plants, animals, fungi etc.
domains are the boradest level of classification

GCSE Biology (7 decks)

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