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Biology > 7 - DNA, Genes and Chromosomes > Flashcards

7 - DNA, Genes and Chromosomes Flashcards

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1
Q

What does the nucleus contain?

A

Genetic information in the form of chromosomes

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2
Q

What are chromosomes?

A

Long lengths of DNA coiled up

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3
Q

What does diploid mean?

A

There are two copies of each chromosomes arranged in pairs
Human nucleus - 46 chromosomes, 23 pair
Human diploid number - 46

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4
Q

What is DNA?

A
  • A long list of instructions on how to put an organism together and make it work
  • A type of nucleic acid
  • Each separate gene in a DNA molecule is a chemical instruction that codes for a particular protein
  • Each molecule is two strands coiled together to make a double helix
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5
Q

Why are proteins important?

A
  • Control most of the processes in the body

- Determined inherited characteristics

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6
Q

What are genes?

A

Chemical instructions that control proteins

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7
Q

What are alleles?

A

Different versions of the same gene

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8
Q

What are bases?

A 
Chemicals that hold DNA together
A - Adenine
C - Cytosine 
G - Guanine
T - Thymine
Paired complimentarily (A-T and C-G)
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9
Q

What is asexual reproduction?

A

Involves only one parent. The offspring have identical genes to the parent so there is no variation between parent and offspring
Done through Mitosis

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10
Q

What is mitosis?

A

When a cell reproduces itself by splitting to form two cells with identical sets of chromosomes
Used in asexual reproduction and growth and repair

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11
Q

Describe mitosis

A
  • In a cell that is not dividing the DNA is spread out in long strings
  • The cell gets a signal to divide and the duplicates its DNA so there is one copy for the new cells
  • DNA forms x-shaped chromosomes
  • Line up in the middle of the cell and are pulled apart by cell fibres
  • Membranes form around each of the sets of chromosomes and become the new nuclei of the cells
  • The cytoplasm divides
  • There is now two identical cells
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12
Q

Describe mitosis

A
  • In a cell that is not dividing the DNA is spread out in long strings
  • The cell gets a signal to divide and the duplicates its DNA so there is one copy for the new cells
  • DNA forms x-shaped chromosomes
  • Line up in the middle of the cell and are pulled apart by cell fibres
  • Membranes form around each of the sets of chromosomes and become the new nuclei of the cells
  • The cytoplasm divides
  • There is now two identical cells
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13
Q

What is sexual reproduction?

A

The fusion of male and female gametes. Because there are two parents the offspring contain a mixture of their genes

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14
Q

What are gametes?

A

Sperm and egg cells

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15
Q

What does haploid mean?

A

Only half the number of chromosomes

Each gamete has 23 chromosomes - so the haploid number is 23

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16
Q

What is fertilisation?

A

When a male gamete fuses with a female gamete to form a zygote (which has a full set of chromosomes)

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17
Q

What is a zygote?

A

The product of fertilisation which undergoes cell division by mitosis to form an embryo

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18
Q

What is meiosis?

A

Cell division which produces four haploid cells whose chromosomes are not identical

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19
Q

Describe meiosis

A
  • The cell duplicates its DNA and lines up in the centre of the cell
  • The pairs are pulled apart so each new cell has one copy of each chromosome
  • Each new cell will have a mixture of the mother’s and father’s chromosomes which creates variation
  • The cells line up in the centre again and are pulled apart
  • Produces four haploid cells which has a single set of chromosomes and are genetically different
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20
Q

What is the stamen?

A

The male reproductive part of a plant

Consists of the anther and filament

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21
Q

What is the role of the anther?

A

Contains pollen grains which produce the male gametes (sperm)

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22
Q

What is the role of the filament?

A

The stalk that supports the anther

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23
Q

What is the carpel?

A

The female reproductive part of a plant

Consists of the stigma, style and ovary

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24
Q

What is the role of the stigma?

A

The end bit that pollen grains stick to

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25
Q

What is the role of the style?

A

The rod-like section that supports the stigma

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26
Q

What is the role of the ovary?

A

Contains the female gametes (eggs)

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27
Q

What is pollination?

A

The transfer of pollen from the anther to the stigma so the male gametes can fertilise the female gametes in sexual reproduction

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28
Q

What is cross-pollination?

A

A type of sexual reproduction where pollen is transferred from the anther of one plant to the stigma of another
Relies on wind and insects

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29
Q

What are adaptations for insect pollination?

A
  • Bright colours
  • Scented flowers and nectaries
  • Big, sticky pollen grains to stick to insects
  • Sticky stigma so pollen will stick to it
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30
Q

What are nectaries?

A

Glands that secrete nectar

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31
Q

What are nectaries?

A

Glands that secrete nectar

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32
Q

What are adaptations for wind pollination?

A
  • Small, dull petals on the flower
  • No nectaries or strong scents
  • Lots of pollen grains which are small and light to be carried by the wind
  • Long filaments that hang the anthers outside the flower so pollen is blown away by the wind
  • A large, feathery stigma to catch pollen as its carried past by the wind. Hangs out the flower too
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33
Q

Describe fertilisation in plants

A
  • A pollen grain lands on the stigma of a flower
  • A pollen tube grows out the pollen grain and down through the style to the ovary
  • A nucleus from the male gamete moves down the tube to join with a female gamete in the ovary
  • The two nuclei fuse together to make a zygote which becomes an embryo through mitosis
  • Each fertilised female gamete forms a seed
  • the ovary develops into a fruit around the seed
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34
Q

What is germination?

A

When a seed starts to grow

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35
Q

What are the conditions needed for germination?

A

Water - to activate the enzymes that break down the food reserves in the seed
Oxygen - For respiration which provides energy for growth
Temperature - So the enzymes in the seed can work
All the conditions need to be perfect for germination to start

36
Q

How do germinating seeds get energy?

A

From food stores

  • A developed seed contains an embryo and a store of food reserves wrapped in a hard seed coat
  • When a seed starts to germinate it gets glucose for respiration from its own food store which gives it the energy to grow
  • once the plant has grown enough to produce green leaves it can get its own food from photosynthesis
37
Q

How do germinating seeds get energy?

A

From food stores

  • A developed seed contains an embryo and a store of food reserves wrapped in a hard seed coat
  • When a seed starts to germinate it gets glucose for respiration from its own food store which gives it the energy to grow
  • once the plant has grown enough to produce green leaves it can get its own food from photosynthesis
38
Q

Describe the reproduction of strawberry plants

A
  • The parent strawberry plant sends out runners (fast-growing stems that grow out sideways just above the ground)
  • The runners take root at various points (not far away) and new plants start to grow
  • The new plants are clones and has no genetic variation
39
Q

Describe the process of cloning plants

A
  • Gardeners can take cuttings from good parent plants and them plant them to produce identical copies of the parents
  • These plants can be produced quickly and cheaply
40
Q

What is the role of the urethra?

A

MALE
A tube which carries sperm through the penis during ejaculation
Urine also passes through here to exit the body

41
Q

What is the role of the erectile tissue?

A

MALE

Swells when filled with blood to make the penis erect

42
Q

What is the role of the testis?

A

MALE

Where sperm are made

43
Q

What is the role of the gands?

A

MALE

Produce the liquid that’s added to sperm to make semen

44
Q

What is the role of the Vas Deferens (sperm duct)

A

MALE

Muscular tube that carries sperm from the testis towards the urethra

45
Q

What is the role of the scrotal sac?

A

MALE

Hangs behind the penis and contains the testes

46
Q

What is the role of the fallopian tube (oviduct)?

A

FEMALE

A muscular tube that carries the ovum from the ovary to the uterus

47
Q

What is the role of the uterus (womb)?

A

FEMALE

The organ where an embryo grows

48
Q

What is the role of the vagina?

A

FEMALE

Where sperm are deposited

49
Q

What is the role of the cervix?

A

FEMALE

The neck of the uterus

50
Q

What is the role of the endometrium (uterus lining)?

A

FEMALE

Has a good blood supply for implantation of an embryo

51
Q

What is the role of the ovary?

A

FEMALE

The organ that produces ova and sex hormones

52
Q

Describe the female reproductive system

A
  • Ova are female gametes
53
Q

Describe the female reproductive system

A
  • Ova are female gametes which is produced every 28 days from one of two ovaries
  • It passes into the fallopian tube where it might meet sperm and be fertilised
  • If it doesn’t meet sperm it the it will break up and pass out the vagina
  • If it does meet sperm it will start to divide and travel down the fallopian tube to the uterus and attach to the endometrium and develop into an embryo
54
Q

What does oestrogen cause in women?

A
  • Extra hairs on underarms and pubic area
  • Hips widen
  • Development of breasts
  • Ovum release and start of period
55
Q

What does testosterone cause in men?

A
  • Extra hair on face and body
  • Muscles to develop
  • Penis and testicles to enlarge
  • Sperm production
  • Deepening of voice
56
Q

describe the four stages of the menstrual cycle

A

1 - Bleeding starts and the uterus lining breaks down for four days
2 - uterus lining builds up again from day 4 - 14 into a thick spongy layer full of blood vessels ready to receive a fertilised egg
3 - An ovum develops and is released from the ovary at day 14
4 - The wall is maintained until day 28

57
Q

What does oestrogen control?

A
  • Lining of uterus to thicken and grow

- Stimulates the release of an ovum at day 14

58
Q

What does progesterone control?

A
  • Maintains the lining of the uterus
  • When levels fall the uterus lining falls
  • If the woman becomes pregnant the amount will remain high to maintain the uterus lining during pregnancy
59
Q

Describe the role of the placenta in pregnancy

A
  • Develops once the embryo has been planted

- Lets the blood of the embryo and mother get very close to allow exchange of food, oxygen and waste

60
Q

Describe the role of the amniotic fluid in pregnancy

A
  • The amniotic membrane forms which surrounds the embryo and is full of amniotic fluid
  • Amniotic fluid protects the embryo against knocks and bumps
61
Q

What are phenotypes?

A

The characteristics from the parents

62
Q

What are genotypes?

A

The alleles of the parents phenotypes

63
Q

What is a codominant allele?

A

When neither allele is recessive so you show both characteristics from both alleles

64
Q

What is a codominant allele?

A

When neither allele is recessive so you show both characteristics from both alleles

65
Q

What does homozygous mean?

A

When you have two alleles for the same gene

66
Q

What does heterozygous mean?

A

When you have different alleles for that particular gene

67
Q

How can you draw genetic diagrams?

A
  • Punnet squares

- Genetic diagrams

68
Q

What are male chromosomes?

A

XY

69
Q

What are female chromosomes?

A

XX

70
Q

What type of allele is cystic fibrosis?

A

Recessive
In order to inherit the disorder you need two recessive alleles
If you have one recessive allele and one dominant allele you will carry the disease but not suffer from it

71
Q

What is genetic variation?

A

When the offspring is slightly different from their parents due to having a different set of genes

72
Q

What characteristics are inherited?

A
  • Eye colour
  • Height
  • Hair colour
  • Disorder
  • Blood group
73
Q

What characteristics are environmental?

A
  • Health
  • Intelligence
  • Sporting ability
  • Weight
74
Q

What affects variation in plants?

A
  • Sunlight
  • Moisture level
  • Temperature
  • Mineral content of the soil
75
Q

What is the theory of evolution?

A

Life began as simple organisms from which more complex organisms evolved (rather than just existing)

76
Q

Describe natural selection

A
  • Living things show variation
  • Resources to survive are limited meaning individuals must compete to survive so only the ones with the most desirable characteristics will survive
  • The surviving individuals will reproduce together and their offspring are more likely to have desired characteristics
77
Q

Describe natural selection

A
  • Living things show variation
  • Resources to survive are limited meaning individuals must compete to survive so only the ones with the most desirable characteristics will survive
  • The surviving individuals will reproduce together and their offspring are more likely to have desired characteristics
  • This is repeated and happens over a long period of time
  • Individuals who are less suited to the environment are less likely to survive
78
Q

What is a mutation?

A
  • A change to a genetic code
  • Mutations can change the sequence of the DNA bases which could stop the production of a protein or produce a different protein instead
  • This can lead to new characteristics and more variation
  • Mutations can happen randomly when a chromosome doesn’t copy itself properly
79
Q

How are mutations increased?

A
  • Exposure to ionising radiation

- Chemicals called mutagen which are found in tobacco

80
Q

How can mutations be harmful?

A
  • If it occurs in the reproductive cells (offspring may have an abnormality)
  • ## If it occurs in body cells and the mutant cells multiply uncontrollably and invade other parts of the body (e.g. cancer)
81
Q

What is a neutral mutation?

A

When the mutation is neither harmful or beneficial

82
Q

How can mutations be beneficial?

A

By increasing the survival advantage (usually happens through natural selection)

83
Q

What is abiotic-resistance?

A

When a bacteria is mutated and is less affected by antibiotics and survive more

84
Q

What are superbugs?

A

Bacteria that are resistant to most known antibiotics (e.g. MRSA) due to a mutation

85
Q

What Is at the front of a sperm cell?

A

A acrosome which is full of enzymes that can break down the outer layer of the egg cell before fertilisation

Biology (9 decks)

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