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GCSE Biology > Inheritance, Variation and Evolution > Flashcards

Inheritance, Variation and Evolution Flashcards

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1
Q

DNA (Deoxyribonucleic Acid)

A

The genetic material in the nucleus of a cell or in plasmids

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2
Q

Chromosomes

A
  • Long threads of DNA, which are made up of many genes
  • 23 pairs of chromosomes in every cell (46 individual chromosomes)
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3
Q

Why is the 23rd pair of chromosomes in every cell important?

A
  • They are known as the sex chromosomes
  • There is an X and a Y chromosome
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4
Q

Gene

A

A small section of DNA that codes for a protein

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5
Q

Genome

A

Entire set of genetic material in an organism

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6
Q

The Human Genome

A

The complete set of all the different combinations of genes in humans, made by scientists

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7
Q

Why is the human genome useful?

A
  • Allows scientists to identify genes that are linked to genetic diseases
  • Can be used to trace migration of people’s ancestors
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8
Q

Inherited Disease

A

Genes that have been passed down from parents that cause disease

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9
Q

Allele

A

A different version of a gene that controls a characteristic

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10
Q

Homozygous

A

A genotype where the 2 alleles of a characteristic are identical

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11
Q

Heterozygous

A

A genotype where the 2 alleles of a characteristic are different

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12
Q

Dominant Allele

A

An allele that is expressed when it is present

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13
Q

Recessive Allele

A

An allele that is masked when paired with a dominant allele but expressed when paired with itself

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14
Q

Genotype

A

The collection of alleles that determine characteristics

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15
Q

Phenotype

A

Characteristics that are displayed as a result of your genotype

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16
Q

Why is it possible to have different genotypes but the same phenotype?

A

A heterozygous organism and a homozygous dominant organism can both have the same phenotype as they both express dominant allele characteristics

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17
Q

Nucleotide

A

A monomer of DNA made up of a phosphate group, a base and a sugar

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18
Q

What are the 4 different bases found in a nucleotide?

A
  • A (adenine)
  • C (cytosine)
  • G (guanine)
  • T (thymine)
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19
Q

Complementary Base Pairing

A
  • Only complementary bases can pair when joining the double helix
  • A only pairs with T
  • C only pairs with G
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20
Q

Genetic Code

A

A sequence of bases on a strand of DNA

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21
Q

Triplet Code

A

Every 3 bases on a strand of DNA that code for 1 amino acid

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22
Q

How to triplets help make a protein?

A
  • Our cells read the long chain of bases as triplet codes and makes the corresponding amino acid for each code
  • The amino acid are combined into a chain in the same order as the triplet codes
  • The chain folds up to form a protein
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23
Q

Main uses of proteins

A
  • Enzymes
  • Hormones
  • Structural Proteins
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24
Q

Protein Synthesis

A

The process in which cells make proteins

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25
Q

How does protein synthesis work?

A
  • Gene is copied in the nucleus so it’s small enough to leave it. This copy is mRNA
  • mRNA to the ribosome
  • An amino acid chain is made in the ribosome using mRNA
  • The chain detaches from the ribosome and folds to form a protein
  • The ribosomes require energy to make proteins
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26
Q

Polypeptide

A

A chain of amino acids

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27
Q

Mutation

A

A change in the DNA base sequence

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28
Q

What increases risk of mutation?

A
  • Carcinogens
  • Certain types of radiation
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29
Q

How do mutations work?

A
  • If their was a change in the triplet code in a gene this changes what amino acid is being coded for
  • This would change the overall polypeptide
  • This changes the protein that is formed
  • The protein would have a different shape/function
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30
Q

Non-Coding DNA

A
  • DNA that isn’t part of a gene so it doesn’t form any proteins
  • Responsible for gene expression
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31
Q

Gene Expression

A

Whether a present gene is turned on or off and can or can’t produce a certain protein

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32
Q

Types of Mutation

A
  • Substitution
  • Insertion
  • Deletion
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33
Q

Substitution

A

One of the bases is substitutes for another random base

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34
Q

Insertion

A

An extra base is inserted into the sequence

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35
Q

Why is insertion worse than substitution?

A
  • An insertion means all bases are shifted along by one
  • This alters all triplet codes in the gene
  • The amino acid chain would be completely different
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36
Q

Deletion

A

One of the bases is removed from the sequence

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37
Q

Sexual Reproduction

A
  • Relies of fusion of male and female gametes (fertilisation)
  • Offspring have a mix of both parents’ genes
  • Offspring are genetically different from parents
  • This introduces variation through generations
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38
Q

Gametes

A
  • Sperm and egg in animals
  • Pollen and egg in plants
  • Contain only half the genetic material of normal cells
  • Made through meiosis
39
Q

Asexual Reproduction

A
  • Only one parent
  • No gametes needed
  • Offspring are genetically identical so no variation
  • Achieved by mitosis in eukaryotes (animals, plants, fungi)
  • Achieved by binary fission in prokaryotes (bacteria)
40
Q

Asexual Reproduction Advantages

A
  • Only needs one parent
  • Process is fast so a single organism can easily colonise a new area
41
Q

Asexual Reproduction Disadvantages

A
  • All offspring are clones so no genetic variation (more likely to wipe a population with disease)
  • Less chance of adapting to new conditions, e.g. change in climate
42
Q

Sexual Reproduction Advantages

A
  • Lots of genetic variation within a population (less likely to be wiped by disease)
  • Population can adapt to changing conditions (through evolution)
43
Q

Sexual Reproduction Disadvantages

A
  • Requires 2 parents
  • Can take a while to find a mate
  • Resources are used to impress a mate but it doesn’t aid their survival
44
Q

Haploid

A

A cell that contains 1 set of chromosomes

45
Q

Diploid

A

A cell that contains 2 sets of chromosomes

46
Q

Meiosis

A
  • DNA of both chromosomes are replicated (chromosomes form an X shape)
  • Chromosomes line up in pairs along the centre of the cell
  • Chromosome pairs are pulled apart and cell splits in 2
  • Second division - chromosome Xs are pulled apart
  • Makes 4 genetically unique cells called gametes
47
Q

Genetic Diagrams

A

Show all the different combinations of alleles from 2 parents

48
Q

Cystic Fibrosis

A
  • Recessive inherited disorder
  • Lungs and digestive system become clogged with mucus
49
Q

Polydactyly

A
  • Dominant inherited disorder
  • Born with extra fingers and toes
50
Q

Inherited Disorder

A

Group of conditions passed on in alleles that is inherited from a person’s parent’s

51
Q

Embryo Screening

A
  • Embryo cells are taken and screened for genetic disorders
  • Parents and doctors can choose to keep the embryo or discard it and choose a different one
52
Q

Pros of embryo screening

A
  • Reduces overall suffering (fewer people with genetic disorders)
  • Saves money
53
Q

Cons of Embryo screening

A
  • Implies that people with genetic disorders are undesireable and increases prejudice
  • People could start screening for other traits (e.g. eye colour, gender)
54
Q

Mendel’s Pea Plants

A
  • Took a green and a yellow pea plant and bred them
  • All the offspring were yellow
  • Bred the offspring
  • 3/4 were yellow, 1/4 were green
  • Conclusion was that ‘hereditary units’ were passed down generations
  • Tried this with different traits (height, flower colour) and came to the same conclusion
55
Q

History of Genetics after Mendel

A
  • Chromosomes were discovered and observed in the late 1800’s
  • Similarities between chromosomes and hereditary units in early 1900’s
  • Structure of DNA determined in 1953
  • Entire human genome written in 2003
56
Q

Variation

A

Differences between individuals

57
Q

Mutation (genetic variation definition)

A

A change in the DNA code so the protein it codes for is different

58
Q

Natural Selection

A

The process where a species changes over time to respond to changes in the environment, or competition between organisms to survive

59
Q

Process of Natural Selection

A
  • Beneficial mutation occurs in a individual make them more likely to survive and reproduce
  • Gene of beneficial mutation is passed on to offspring
  • Beneficial gene spreads through the population until the species has ‘evolved’
60
Q

Theory of Evolution

A
  • All species of living things evolved from simple life forms that developed around three billion years ago
  • Inheritance of certain characteristics in a population over multiple generations could lead to a change in the species
61
Q

Speciation

A
  • The phenotypes of 2 different populations of a species become so different they can’t interbreed to produce fertile offspring
  • A new species is formed
62
Q

Selective Breeding

A

A process where humans
individuals of a population for particular genetic characteristics

63
Q

Process of Selective Breeding

A
  • Individuals with desired characteristics with a population are selected and bred
  • Offspring with desired characteristic are bred together
  • Process is repeated until the offspring express desired characteristic
64
Q

Drawbacks of Selected Breeding

A
  • Reduces the gene pool of the population
  • Inbreeding meaning offspring are prone to diseases/inherited defects
  • Less variation so agriculture suffers (population can be wiped by disease)
65
Q

Gene Pool

A

All the genes and alleles found in a population

66
Q

Genetic Engineering

A

A process where an organism’s genome is modified by introducing a gene from another organism to give a desired characteristic.

67
Q

Example of Genetic Engineering

A
  • Genetically engineered bacteria to produce insulin to treat type 1 diabetes
  • GM crops that produce more nutrients, are resistant to disease or are bigger and better quality
  • E.g. Golden rice produces lots of beta carotene (vitamin A) which stops blindness
68
Q

Gene Therapy

A
  • Used to treat inherited disorders
  • A person is given the healthy version of a gene
  • Difficult to get it to work as the faulty gene is found in all the cells of the body
  • Solution is to transfer the gene at an early stage of development (egg/embryo stage)
69
Q

Pros of GM crops

A
  • Makes crops with desirable characteristics
  • Makes more food for less money which is beneficial for developing countries
  • Makes sure plants have particular nutrients
70
Q

Cons of GM crops

A
  • Don’t know the impacts of GM crops on health
  • GM crops could reach the wild and outcompete local plants which changes the whole ecosystem
71
Q

Process of Genetic Engineering

A
  • Desired gene is isolated using enzymes and is inserted into a vector (usually a bacterial plasmid or a virus)
  • Vector inserts the gene into the required cells in the organism’s early development
  • This is so that they develop with the desired characteristic
72
Q

Cloning by Transplanting a Cell Nucleus

A
  • Take an egg from a donor female and enucleate it (remove its nucleus)
  • Take an adult body cell from the organism being cloned and enucleate it
  • Put the nucleus of the body cell into the enucleated egg cell
  • Stimulate the with an electric shock so it acts like a zygote and divides by mitosis to form an embryo
  • Implant the embryo into a surrogate mother so it develops and is eventually born
73
Q

Cloning Transgenic Animals

A
  • Scientists place human genes into DNA of other organisms
  • Once an organism has DNA from another species, the organism is transgenic
  • Scientists will clone the transgenic organisms they’ve already made
  • E.g. Cows, sheep and goats are genetically engineered to produce human proteins
74
Q

Cloning by Embryo Transplants

A
  • Pick male and female organisms with desirable traits
  • Take their sex cells and fertilise the egg cell to produce a zygote
  • Let the zygote develop into an embryo
  • Separate the embryo into smaller embryos
  • Place embryos into surrogate mother so they develop into identical clones
75
Q

Advantages of Cloning vs Selective Breeding

A
  • Quicker
  • Genetically identical/No variation
  • No mating needed
76
Q

Cloning plants with cuttings

A
  • Choose plant you want to clone
  • Cut off a small part (ideally shoot or branch)
  • Place the cutting in soil with nutrients and hormones
  • The cutting will grow into a clone of the original plant
77
Q

Advantages of cloning by cuttings

A
  • Quicker
  • Cheaper
78
Q

Micropropagation (Using plant tissues)

A
  • Find a plant with desirable characteristics
  • Take small pieces of plant tissues from the stem and sterilise them
  • Place the plant in agar containing growth hormones and let them grow calluses
  • Transfer calluses into soil with nutrients so they grow into plantlets
  • Transfer plantlets to pots so they grow into adult clones
79
Q

How are plant tissues removed and transferred to the agar?

A
  • Cut the plant with a scalpel
  • Transfer with tweezers
  • Sterilise with sterilising equipment
80
Q

Fossils

A

Preserved remains or traces of a dead organism

81
Q

Gradual Replacement of Minerals

A
  • Body parts decayed slowly
  • As they decayed, they were replaced with minerals and form rock structures in the same shape as the original structures
82
Q

Casts and Impressions

A
  • Casts are formed when an organism is buried in soft material (clay)
  • As the clay hardens it leaves a gap the same shape and size of the organism
  • Impressions are when organisms leave marks in the ground (footprints)
83
Q

Preservations

A
  • No decay occurs due to lack of oxygen and moisture
  • Organisms get stuck in amber or pit tar and remain intact
84
Q

Why are there gaps in the fossil record?

A
  • Many early life forms were soft bodied so would have decayed quickly
  • Some fossils may have bee destroyed
85
Q

Extinction

A

Occurs when there are no remaining individuals of a species alive

86
Q

Reasons for Extinction

A
  • Environment changes quickly (temperature)
  • Arrival of new predators
  • Human hunting
  • Disease
  • New species outcompetes
  • Catastrophic event
87
Q

Species

A

A group of genetically similar organisms that can interbreed and produce fertile offspring.

88
Q

Process of speciation

A
  • Isolation separates 2 populations of the same species
  • The environment is different on either side of the barrier
  • Both populations experience different selection pressures so different traits become favourable for the 2 populations
  • Natural selection occurs and after many generations the populations are so different from each other they can’t interbreed anymore
  • Speciation has occurred
89
Q

How does Antibiotic Resistance occur?

A
  • Mutations of bacterial pathogens produce new strains
  • Some strains are resistant to antibiotics and aren’t killed
    -They survive and replicate so the population of the resistant strain rises
  • The resistant strain spreads as people aren’t
    immune to it and there isn’t an effective treatment.
90
Q

Why is Antibiotic resistance a problem?

A
  • Doctors give out antibiotics where they won’t help
  • Farmers put antibiotics in the food of healthy animals
91
Q

Linnean System

A
  • Grouped species based on characteristics and bone structure
  • Kingdom, Phylum, Class, Order, Family, Genus, Species
  • Binomial Naming System:
  • Species named after their Genus and Species
  • Genus is in capital letter only and name is written in italics
92
Q

3 Domain System - Carl Woese

A
  • 3 Domains that go above kingdoms
  • Archaea (primitive bacteria living in extreme environments)
  • Bacteria (true bacteria)
  • Eukaryota (all eukaryotes)
93
Q

Pneumonic to Remember classification

A

Dear Kate, Please Come Over For Great Spaghetti

GCSE Biology (6 decks)

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