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Biology 9-1 iGCSE Oxford AQA > Inheritance > Flashcards

Inheritance Flashcards

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1
Q

Where are chromosomes found?

A

In the nucleus of a cell

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2
Q

What are chromosomes?

A

Thread-like structures that carry genetic info, each carry large number of genes

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3
Q

What do different genes control?

A

Development of different characterises

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4
Q

What do each body cells have? (chromosome wise)

A

2 copies of each chromosome (1 from mother and 1 from father)

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5
Q

How many chromosomes do human cells have?

A

46

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6
Q

What is the cell cycle?

A

Series of stages where cells divide to produce new cells

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7
Q

What is the name of the stage of the cell cycle when a cell divides?

A

Mitosis

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8
Q

What is mitosis used for?

A

To grow or replace cells that are damaged

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9
Q

What do you get at the end of a cell cycle?

A

2 new cells identical to original cell (with same number of chromosomes)

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10
Q

Where does mitosis occur?

A

In normal body cells

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11
Q

What does mitosis result in? (mention chromosomes)

A

Results in 2 diploid cells produced + with 2n chromosomes in daughter cell

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12
Q

Explain how mitosis works

A
  1. Copies of genetic material are made
  2. The cell then divides once to form two genetically identical body cells
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13
Q

How can you represent normal body cells?

A

2n

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14
Q

How can you represent gametes?

A

n

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15
Q

What can you call normal body cells?

A

Diploid

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16
Q

What can you call gametes?

A

Haploid

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17
Q

What is an allele?

A

Different version of a same gene

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18
Q

Humans have ___ versions of every gene

A

2 (1 from dad and 1 from mum)

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19
Q

What can alleles be?

A

Recessive or dominant

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20
Q

How do you represent a dominant allele?

A

With a capital letter e.g. A

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21
Q

How do you represent a recessive allele?

A

Lower case letter - a

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22
Q

What is a genotype?

A

Combination of alleles

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23
Q

What is a phenotype?

A

Characteristic

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24
Q

What does Aa represent?

A

Heterozygous

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25
Q

What does AA represent?

A

Homozygous Dominant

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26
Q

What does aa represent?

A

Homozygous Recessive

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27
Q

What is sexual reproduction?

A

Involves the fusion of male and female gametes. Because there are TWO parents, the offspring contain a mixture of their parents’ genes.

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28
Q

What is asexual reproduction?

A

When there’s one parent. No fusion of gametes, no mixing of chromosomes and no genetic variation between parent and offspring. Offspring are genetically identical to parent - clones.

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29
Q

Why is there variation in offspring for sexual reproduction?

A
  1. Egg and sperm fuse together (fertilisation) to form cell with full number of chromosomes 2. Mixture of genetic info produces variation in offspring
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30
Q

In humans, how many chromosomes do each gamete contain?

A

23 chromosomes (half number of chromosomes in normal cell)

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31
Q

How asexual reproduction happen?

A

By mitosis

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32
Q

Give an example of a plant that reproduces asexually?

A

E.g. strawberry plants produce ‘runners’

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33
Q

What are chromosomes essentially (i.e. what are they made out of)?

A

Long molecules of DNA

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34
Q

What is DNA (composition wise)?

A

A polymer

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35
Q

What is DNA made up of?

A

2 strands coiled together in shape of double helix

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36
Q

What is DNA?

A
  1. A chemical that all genetic material in a cell is made up from
  2. Contains coded information that determines inherited characteristics
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37
Q

Describe how genes produce proteins (4 marks)

A
  1. Gene = sequence of bases
  2. 3 bases code for 1 amino acid
  3. Order of bases controls order of amino acids
  4. Amino acids are assembled to make (specific) protein
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38
Q

What is a gene?

A

Small section of DNA found on a chromosome

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39
Q

How many amino acids are used to make proteins?

A

20

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40
Q

What do the strands in DNA contain?

A

Four different compounds called bases

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41
Q

_ ___ code for 1 amino acid

A

3 bases

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42
Q

How many types of DNA bases are there?

A

4

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43
Q

What does the order in amino acids control?

A

The order in which amino acids are assembled to produce a particular protein

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44
Q

Name 3 examples of types of proteins

A
  1. Hormones
  2. Enzymes
  3. Structural Proteins (e.g. collagen - very strong)
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45
Q

Not all genes are switched __

A

on

46
Q

What switches on certain genes?

A

Stem cells

47
Q

What do cells in reproductive organs divide to form?

A

Gametes

48
Q

How are gametes produced?

A

By Meiosis

49
Q

How many cells are produced in meiosis? (mention no. of chromosomes)

A

4 cells (with n number of chromosomes in daughter cells)

50
Q

Explain how meiosis works

A
  1. Copies of genetic information are made
  2. Cells then divides twice to form 4 gametes, each with a single set of chromosomes
51
Q

How does an (human) organism form (after fertilisation)?

A
  1. After 2 gametes fuse, new cell divides by mitosis to make copy of itself
  2. Mitosis repeats many times = produce lots of new cells in embryo
  3. As it develops, cells differentiate & become specialised to make up whole organism
52
Q

What is variation?

A

Differences within a specie

53
Q

What causes variation?

A
  1. Genes
  2. Environment
54
Q

What causes genetic variation?

A

Combining of genes (from mum and dad)

55
Q

What are most characteristics due to?

A

Genes AND the Environment

56
Q

Give an example of genetic and environmental characteristic and explain it

A

Height:

  1. Maximum height of animal is determined by genes
  2. Whether it grows that tall depends on its environment
57
Q

What else introduces variation?

A

Mutations

58
Q

What are mutations?

A

Changes to sequence of bases in DNA

59
Q

What pair of chromosomes determine your sex?

A

23rd pair

60
Q

In females, are sex chromosomes the same or different?

A

Same (XX)

61
Q

In males, are sex chromosomes the same or different?

A

Different (XY)

62
Q

What is meant by homozygous?

A

Both chromosomes in a pair contain the same allele of a gene

63
Q

What is meant by heterozygous?

A

Chromsomes in a pair contain different alleles of a gene

64
Q

What is meant by recessive?

A

Not expressed if dominant allele present

65
Q

What 3 conclusions did Mendel reach?

A
  1. Characteristics in plants = determined by “hereditary units”
  2. Hereditary units = passed onto offspring unchanged from both parents, unit from each
  3. Hereditary units can be recessive or dominant - if individual has both, dominant will be expressed
66
Q

Give 3 examples of genetic disorders

A
  1. Polydactyly
  2. Cystic Fibrosis
  3. Sickle Cell Anaemia
67
Q

What does polydactyly cause?

A

Organism to have extra fingers/toes

68
Q

What allele causes polydactyly?

A

Dominant allele

69
Q

What are symptoms of cystic fibrosis?

A

Lots of mucus in air passages and pancreas = Problems with breathing, digestion and infertility

70
Q

Cystic fibrosis is a genetic disorder of…

A

cell membranes

71
Q

What allele causes cystic fibrosis?

A

Recessive allele

72
Q

What does sickle cell anaemia cause?

A

Causes red blood cells to become ‘sickled’ in shape = can’t carry oxygen as well + cells can become damaged

73
Q

What allele sickle cell anaemia is carried on?

A

Co-dominant allele

74
Q

Sickle cell anaemia in carried on a co-dominant allele, what does this mean for their red blood cells?

A

Some will be sickled and some will be normal

75
Q

How is Down’s syndrome caused?

A

By the presence of an extra chromosome

76
Q

How can embryos can be screened for genetic disorders?

A
  1. During IVF, embryos are fertilised in lab
  2. DNA isolated from embryo
  3. Probe mixed with embryo DNA
  4. Probe binds with embryo DNA
  5. Show alleles/genes for disorder +ive = discarded OR -ive = implanted into uterus
77
Q

Name 3 reasons for embryo screening

A
  1. Treating disorders costs government (& taxpayers) lot of money
  2. Stop people suffering
  3. Laws to stop it from going too far
78
Q

Name 3 reasons against embryo screening

A
  1. Increase prejudice: implies people with genetic problems are ‘undesirable’
  2. Screening is expensive
  3. May come a point where people want to screen embryos so they can pick most ‘desirable’ one
79
Q

What is selective breeding?

A

When humans artificially select plants or animals that they’re going to breed

80
Q

Why is selective breeding done?

A

So genes for desired characteristic remain in population e.g. Crops with disease resistance

81
Q

Describe the process of selective breeding

A
  1. From existing stock, select ones with desired characteristics
  2. Breed them with each other
  3. Select best of offspring & breed them together
  4. Continue process over several generations - desirable trait gets stronger and stronger
  5. Eventually, all offspring will have characteristic
82
Q

Name the drawback of selective breeding

A

Reduces gene pool i.e. no. of different alleles in population decreases (DUE to inbreeding)

83
Q

Why does inbreeding causes health problems?

A

More chance of organisms inheriting harmful genetic deflects when gene pool is limited

84
Q

If new disease appears, how might it affect an inbreed population and why?

A

Reduced gene pool = less chance of resistant alleles present in population = little variation ∴ most of population may die (all stock are closely related)

85
Q

What is genetic engineering?

A

Transferring desired gene to other organism so it has desired characteristics

86
Q

Describe the process of genetic engineering

A
  1. Useful gene is isolated (cut) from organism’s cell using enzymes into vector (usually virus or bacterial plasmid)
  2. Vector is introduced to target organism, useful gene is inserted into its cell(s)
87
Q

How can we make organisms develop with desired characteristics?

A

Transfer of gene is carried out when organism receiving gene is at early stage of development (e.g. egg/embryo)

88
Q

Name 4 uses of genetic engineering

A
  1. GM crops
  2. Treat diabetes
  3. Gene therapy
  4. Treating human diseases
89
Q

Explain how genetic engineering can be used to treat diabetes

A

Bacteria - genetically modified to produce human insulin

90
Q

Explain how genetic engineering can be used to treat human diseases - use an example

A

Sheep - genetically engineered to produce substances, like drugs, in their milk

91
Q

What is gene therapy?

A

Researching genetic modification treatments for inherited diseases (e.g. by inserting working genes)

92
Q

Describe how bacteria can be engineered to produce human insulin

A
  1. Remove insulting gene out of a human cell using a special enzyme
  2. Remove plasmid from a bacterial cell
  3. Break plasmid open using special enzyme
  4. Add insulin gene into plasmid, using a different specialised enzyme
  5. Allow genetically modified plasmid to be taken up by a bacterial cell
  6. Bacteria multiply serval times
  7. Insulting gene is “switched on” and bacteria begin to produce insulin
  8. Culture bacteria and process insulin
93
Q

Name 2 pros of GM crops

A
  1. Increases crop yields
  2. Some crops can be modified to provide more nutritional value
94
Q

How can using GM crops increase crop yields

A
  1. GM crops can be produced to be resistant pests (insects and herbicides) 2. Can be genetically modified to grow better in drought conditions
95
Q

Name 3 cons of GM crops

A
  1. Don’t fully understand effects of eating them on human health
  2. Reduces farmland biodiversity
  3. Transplanted genes may get into natural environment
96
Q

How might GM crops reduces farmland biodiversity?

A

GM crops will affect number of wild flowers (and population of insects)

97
Q

What is bad thing about GM crops transplanting genes into the natural environment?

A

E.g. herbicides resistance gene may be picked up by weeds - ‘superweed’

98
Q

Name 2 ways plants can be cloned

A

Via:

  1. Tissue Culture
  2. Cuttings
99
Q

Describe cutting

A
  1. Small piece of plant removed - stem of leaf
  2. Stem treated with rooting hormones
  3. Replanted in soil, with moist, warm conditions perfect for growth
100
Q

Explain how tissue culture works

A

Few plant cells put in growth medium with hormones and grow into new plants = clones of parent plant

101
Q

What are advantages of taking a cutting? (name 3)

A
  • Simple (older method used by gardeners)
  • Plants produced quickly and cheaply
102
Q

What are advantages of using a tissue culture? (name 3)

A

Plants can be made:

  • very quickly
  • in very little space
  • & grown all year
103
Q

Who uses tissue cultures? (name 2 groups)

A
  1. Scientists to preserve rare plants that are hard to reproduce naturally
  2. Plant nurseries to produce lots of stock quickly
104
Q

Explain how animals can be cloned using embryo transplants

A
  1. Sperm cells taken from prize male and egg cells taken from prize female
  2. Sperm used to artificially fertilise egg cell to produce embryo
  3. Embryo is divided into number of individual cells
  4. Each cell divides into a identical embryo
  5. Cloned embryos implanted into uterus of host mothers and identical offspring are born
105
Q

Describe how adult cell cloning works

A
  1. Haploid nucleus is removed from unfertilised egg cell (enucleated)
  2. Diploid nucleus is removed from adult body cell (e.g. skin cell) and inserted into ‘empty’ egg cell
  3. Egg cell is stimulated by electric shock - makes it divide like normal embryo
  4. When embryo is ball of cells, it’s implanted into womb of adult female
  5. Grows into genetically identical copy (clone) of original adult body cell - has same genetic info
106
Q

Name 3 pros of cloning

A
  • Study of animal clones = lead to greater understanding of…
    • Development of embryo
    • Ageing and age-related disorders
  • Help preserve endangered species
  • Gets lots of ideal offspring
107
Q

Name 3 cons of cloning

A
  • ‘Reduced gene pool’ - fewer alleles in population
  • Worry - humans may be cloned in future
  • Cloned animals may not be as healthy as normal ones
108
Q

What is the disadvantage of a ‘reduced gene pool’?

A

If population is closely related and new disease comes = could be wiped out

Bc no allele in population giving resistance

109
Q

What is the issue with cloning humans?

A

Any success may follow many unsuccessful attempts e.g. there may be children born severely disabled

110
Q

Every cell has ____ genes and chromosomes but…

A

Every cell has SAME genes and chromosomes but NOT ALL are switched on

111
Q

How are GM crops made?

A

Infect plant embryos with bacteria = so genes get incorporated into plant genes

Biology 9-1 iGCSE Oxford AQA (11 decks)

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