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Biology GCSE AQA > Inheritance, variation and evolution > Flashcards

Inheritance, variation and evolution Flashcards

1
Q

How many chromosomes does a human cell content

A

23 pairs of chromosomes in the nucleus

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2
Q

How many chromosomes does a human sperm and egg cell both contain

A

23 single chromosomes

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3
Q

How can cells divide

A

By mitosis (In mitosis one so is copied into 2 identical daughter cells)

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4
Q

Name 2 gametes

A

Sperm cell and Egg cell

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5
Q

How are gametes made

A

By cell division (Meiosis)

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6
Q

Unlike mitosis what does meiosis produce

A

Non-identical cells (every sperm cell and every egg cell are different)
meiosis takes place in flowering plants (Pollen and egg cells)

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7
Q

What do animals and flowering plants carry out

A

Sexual reproduction

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8
Q

What does sexual reproduction involves

A

Fusion of male and female gametes
Mixing of genetic information (DNA) the offspring receives genetic information from both the male and female parents

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9
Q

What does fusion mean

A

Joining together (Fertilization)

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10
Q

What’s the difference between sexual and asexual reproduction

A

Asexual reproduction involves one parent but sexual involves two people

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11
Q

What does asexual reproduction not involve

A

Gametes this means meiosis will not take place

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12
Q

Asexual reproduction are all genetically identical What do scientists called this

A

Clones (Mitosis=2 identical cells)

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13
Q

Where does meiosis take place

A

In reproductive organs

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14
Q

Cells in the reproductive organs divide by meiosis to form what

A

Gametes

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15
Q

How do gametes join

A

By fertilization to restore the number of chromosomes

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16
Q

Meiosis takes place in the reproductive organs what is this for men and women

A

In men it’s the testes
In females it’s the ovaries

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17
Q

Explain the stages of meiosis

A

In the first stage of meiosis all of the chromosomes are copied (in pairs) then the cell divides into 2 and both of these cells divide one more time forming the gametes (In the gametes the chromosomes are single) 

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18
Q

At the start of meiosis chromosomes are in pairs but at the end of meiosis the chromosomes are gametes that are single what does this mean

A

Meiosis has halved the number of chromosomes

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19
Q

From one original so what does meiosis produce

A

4 gametes and each are genetically different from each other (each gamete has different alleles)

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20
Q

In sexual reproduction gametes from the male and female join together what is this called

A

Fertilization

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21
Q

What happens after fertilization

A

The new cell divide by mitosis (producing a clump of identical cells=Embryo) and the number of cells increase as the embryo as it develops cells differentiate forming different cell types (ex. Mussels)

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22
Q

What does DNA consist of

A

2 strands and each strand is a polymer (each strand is made by joining together lots of smaller molecules)

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23
Q

The DNA is a polymer made up of two strands what does it form

A

A double helix

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24
Q

The DNA is contained instructions what is this called

A

Chromosomes

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25
Q

What is a gene

A

A gene is a small section of DNA on a chromosome

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26
Q

The genetic material in the nucleus of a cell is composed of a chemical what is this called

A

DNA

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27
Q

How are proteins made

A

By joining together amino acids

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28
Q

What does each gene encode for

A

A specific sequence of amino acids to make a specific protein

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29
Q

What is the genome

A

The genome is the entire genetic material of an organism (it makes up humans)

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30
Q

How can scientists use the information about the whole human genome in the future

A

To make medicine

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31
Q

Understanding the human genes will help us to search for genes that are linked to diseases give some examples

A

The risk of developing cancer or Alzheimer’s disease

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32
Q

What does understanding the human genome help us with

A

Understanding and treat inherited disorders example. cystic fibrosis
Research about the risk of developing cancer or Alzheimer’s disease
We can use it to trace human migration patterns from the past (Helping people discover their ancestry)

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33
Q

What are alleles

A

Alleles are versions of a gene

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34
Q

How many pairs of chromosomes control the characteristics of a human

A

22 pairs control characteristics but one of the pairs carries the gene that determines the sex

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35
Q

What does the genotype of a person tell us

A

That alleles are present

36
Q

What is cystic fibrosis

A

A disorder of the cell membranes

37
Q

How is cystic fibrosis controlled

A

By a single gene which has two alleles

38
Q

How can you tell when a person has cystic fibrosis

A

When the person has to have 2 copies of the defective allele (has to have inherited a defective allele from both of the parents)

This means that a person with 1 defective allele and 1 normal allele doesn’t have cystic fibrosis

39
Q

What do you call a person who has 1 defective allele and 1 normal allele

A

They are a carrier of cystic fibrosis allele

40
Q

How is cystic fibrosis caused

A

It’s caused by a recessive allele 

41
Q

How is polydactyly caused

A

By a dominant allele

42
Q

What is polydactyly

A

Having extra fingers or toes

43
Q

Name one solution to discovering inherited disorders

A

Embryo screening

44
Q

what’s the use of embryo screening

A

Embryos are tested to see if they have the alleles of inherited disorder then Embryos which don’t have the defective alleles are then implanted into the woman which can then develop into healthy offspring 

45
Q

What are the issues to embryo screening

A

It is expensive and the money could be spent elsewhere in the health service

A large number of embryos are created by only a small number are implanted this means that some are destroyed and some people think that it’s unethical

46
Q

In the future scientists might be able to correct faulty alleles and use this to treat inherited disorders. What is this called

A

Gene therapy

47
Q

What does a family tree show

A

It only shows phenotypes and NOT genotypes

48
Q

What type of sex chromosomes does a male have

A

XY

49
Q

What type of sex chromosomes does a female have

A

XX

50
Q

What is variation

A

The differences in the characteristics of individuals in a population

51
Q

What are mutations?

A

They are random changes to DNA that take place all the time and most mutations have no effect on the phenotype

52
Q

What are the three main causes of variation

A

The genes they have inherited (genetic causes)
The conditions in which they develop (Environmental causes)
A combination of genes and the environment

53
Q

Give example’s of a genetic variation

A

Hair color and eye color

54
Q

Give some examples of environment variation

A

The color of flowers depends on the pH of soil
language of humans

55
Q

Give some examples of a combination of variations caused by genes and the environment

A

Height in humans (Genetics and enough calcium for bones to develop)

56
Q

How can a new phenotype be beneficial if the environment changes

A

A mutation can help survive and become resistant to viruses causing new phenotypes

57
Q

What is the theory of evolution by natural selection

A

All species of living things have evolved from the simple life forms that developed more than 3 billion years ago (eg. Single cells)

58
Q

What happens if 2 populations of 1 species becomes so different in phenotype

A

They can no longer interbreed to produce fertile offspring meaning they have formed 2 new species

59
Q

Define evolution

A

The change in the inherited characteristics of a population over time through a process of natural selection

60
Q

Explain gene therapy

A

Genetic modification is being explored as a way to treat inherited disorders in humans

61
Q

What are the steps of genetic engineering

A

Identify the gene wanted to transfer (Could be human, plant, or animal genes)
Use enzymes to isolate the gene
Transfer the gene into a small circle of DNA called a plasmid
Plasmids originally came from bacteria and are very useful for transferring DNA from one organism to another in addition you could also use a virus
Then the desired gene is transferred into the cells of the targeted organism and this is always done at the early stages



62
Q

Where did plasmids originally come from 

A

Bacteria

63
Q

What is a vector

A

When the plasmid or virus transfers the DNA from one organism to another

64
Q

What are fossils

A

The remains of organisms from millions of years ago which are found in rocks

65
Q

When does extinction occur

A

When there are no remaining individuals of a species is still alive

66
Q

Name 3 ways how fossils form

A

Fossils can form when parts of organisms have not decayed this happens when the conditions needed for decay are absence (eg. If the temperature is too cold, If there’s not enough oxygen or water).

Fossils can form even if an organism decays; If parts of the organism are slowly replaced by minerals during the decay process.

Fossils can be preserved traces of organisms for example animals can leave foot prints or burrows and plants can leave preserves spaces

67
Q

What do fossils show

A

A huge number of species that have become extinct

68
Q

4 ways how species can become extinct

A

From catastrophic events for example an asteroid colliding with the Earth
Environmental changes
A new disease or a new predator could kill all of the individuals of a species
when there is lack of food or water

69
Q

How can bacteria evolve

A

Bacteria can evolve rapidly because they produce at a fast rate (every 30min)

70
Q

What’s the use of antibiotics

A

To kill bacteria

71
Q

Name one antibiotic

A

Penicillin

72
Q

In what ways are antibiotics used

A

For medicine
For farming to prevent animals from developing bacterial disease

73
Q

Name one common strain of antibiotic resistant bacteria 

A

MRSA

74
Q

Describe how antibiotic resistance happens

A

Mutations of bacterial pathogen’s produce new strains some strains might be resistance to antibiotics and so are not killed.
they survive and reproduce so the population of the resistance strains rises

75
Q

What happens when mutations of bacterial pathogen’s produce new strain

A

The resistant strain will then spread because people are not immune to it and there is no effective treatment

76
Q

How can you reduce the rate of development of antibiotic resistant strains

A

Doctors should not prescribe antibiotics and appropriately (eg. Should not be prescribed to virus)
patients should complete their course of antibiotics so all the bacteria are killed and non-survive to mutate and form resistant strains
restrict the use of antibiotics in farming

77
Q

The development of new antibiotics is expensive and takes a long time and what is it unlikely of

A

As the new antibiotic resistant bacteria emerge all the time it is unlikely to keep up with the new resistant strains 

78
Q

Who was the three domain system developed by

A

Carl woese 

79
Q

In the three domain system what are the organisms divided into

A

Archaea
bacteria
eukaryotes (Protists, Fungi, plants and animals)

80
Q

What is evolutionary trees

A

A method used by scientists to show how they believe organisms are related

81
Q

How did evidence of the internal structures become more developed

A

the improvements in microscopes and the understanding of biochemical processes processed new models of classification were proposed

82
Q

Traditional living things have been classified into groups depending on the structure and characteristics in a system who is the system developed by

A

Carl Linnaeus

83
Q

What did Linneus classify living things into

A

Kingdom
Phylum
Class
Order
Family
Genus
Species

84
Q

How are organisms named

A

By the binomial system of genus and species

85
Q

What do scientists use current classification data for

A

For living organisms and fossil data for extinct organisms

86
Q

What is the binomial name 

A

The genus + species = the name

Biology GCSE AQA (8 decks)

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