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WJEC GCSE flashcards > Biology unit 2 > Flashcards

Biology unit 2 Flashcards

1
Q

what is deoxyribonucleic acid

A

DNA molecules

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2
Q

what are chromosomes

A

strands of DNA, usually arranged in pairs in the nucleus of each cell

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3
Q

what does cytosine pair with

A

guanine

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4
Q

what is an allele

A

the form of a gene

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5
Q

what does double helix mean

A

2 strands of genes in a spiral shape

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6
Q

what does the triplet code determine

A

which amino acid is next linked (by a chemical bond) in the protein chain

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7
Q

DNA has a ladder-like structure, it is made of 2 long chains of alternating _____ and ________ molecules

A

sugar and phosphate

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8
Q

what are the 4 different bases that make up DNA

A

Adenine
Thymine
Cytosine
Guanine

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9
Q

what does adenine pair with

A

thymine

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10
Q

what does thymine pair with

A

adenine

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11
Q

what does guanine pair with

A

cytosine

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12
Q

where does protein synthesis take place

A

in the cytoplasm

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13
Q

who discovered genetic profiling

A

Alec Jeffries in 1984

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14
Q

what are gametes

A

sex cells

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15
Q

what are the gametes of humans called

A

sperm and egg

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16
Q

what is a diploid

A

a full chromosome set (body cell)

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17
Q

what is a haploid

A

gametes containing half chromosome number

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18
Q

give 2 examples where DNA analysis is used

A

paternity testing, identifying suspects in crime cases

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19
Q

what is a genotype

A

set of alleles an individual has that determines a characteristic

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20
Q

who discovered inheritance

A

Gregor Mendel in the 1800’s

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21
Q

what is a gamete

A

sex cells

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22
Q

what are the human gametes

A

sperm and egg

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23
Q

why do gametes only contain half of the genetic information needed to form a new individual

A

so, when fertilisation takes place, they contain the correct number of chromosomes

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24
Q

what is a gene

A

a section of dna that codes to make a particular protein

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25
Q

what is an allele

A

different form/version of the gene

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26
Q

what is a phenotype

A

the appearance of an organism as a result of its genotype/genes

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27
Q

what is heterozygous

A

an individual that has two different alleles for a characteristic

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28
Q

what is dna

A

the chemical that forms genes

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29
Q

what is homozygous

A

an individual that has two of the same alleles for a characteristic

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30
Q

what is a dominant gene

A

only 1 of these alleles is needed for the characteristic to be shown

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31
Q

what is a recessive gene

A

two of these alleles are needed for the characteristic to be shown

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32
Q

what is a chromosome

A

a structure containing genes

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33
Q

describe some ways in which humans may vary

A

eye colour, hair colour, height

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34
Q

what are the two main causes of variation

A

genetic and environmental

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35
Q

what lifestyle choices/factors might be responsible for causing environmental variation between individuals

A

diet, climate, habitat, diseases, culture

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36
Q

what is continuous variation

A

every individual has the characteristic, but it differs for each individual

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37
Q

what is discontinuous variation

A

every individual either has the characteristic or they do not

38
Q

example of continuous variation

A

height, weight

39
Q

example of discontinuous variation

A

tongue rolling, attached ear lobes

40
Q

how is continuous variation shown on a graph

A

bar graph with bars touching and a bell-shaped curve

41
Q

how is discontinuous variation shown on a graph

A

bar graph with bars separated, shown as discrete groups

42
Q

define the word clone

A

genetically identical

43
Q

what is ionising radiation

A

high frequency radiation that damages dna

44
Q

what are liposomes

A

tiny bubbles within a spray used in gene therapy. they act as a vector to transmit the normal genes into the body

45
Q

name 2 advantages of gm plants

A
  • pest/disesease resistant crops so higher yields
  • medicine can be made by gm organisms e.g insulin
46
Q

name 2 disadvantages of gm plants

A
  • superweeds may be created if pollen from gm crops is spread to non gm plants
  • unknown effects of eating new protein produced in gm crops
47
Q

what is mitosis

A

cell division where each division produces 2 daughter cells which have the same number of chromosomes (diploid) and are genetically identical to the mother cell.

48
Q

what does mitosis do

A

allows organisms to grow, replace worn out cells and repair damaged tissues

49
Q

what does meiosis do

A

produces gametes (sex cells)

50
Q

what is meiosis

A

produces 4 daughter cells in every division which have half the number of chromosomes (haploid) and are genetically different to the mother cell

51
Q

what are stem cells

A

undifferentiated cells which have the ability to develop into different types of specialised cell

52
Q

where are stem cells found in plants

A

in the tip of the roots and shoot

53
Q

where are stem cells found in animals

A

bone marrow (adult stem cell)
embryos (embryonic stem cells)

54
Q

name 2 problems of using embryonic stem cells

A

there are ethical issues as to if it is a destruction of life
potential rejection from the body as it is not their own cells

55
Q

name 2-4 advantages of adult stem cells

A

no rejection (if own cells)
no need to find a donor
no destruction of life (not as controversial)
no need for tissue typing

56
Q

give 3 examples of specialised cells

A

muscle cells
nerve cells
blood cells

57
Q

name 3 sources of tissue stem cells

A

adult or foetal tissue e.g bone marrow
umbilical cord blood
aborted foetuses

58
Q

name 2 current stem cell therapies

A

bone marrow transplants
skin grafting

59
Q

what is interspecific competition

A

competition with other species

60
Q

what is intraspecific competition

A

competition between same species

61
Q

what are the physical properties of a gene

A

sequence of bases in the dna

62
Q

what are the functional properties of a gene

A

the protein it makes
the role that the protein has

63
Q

if the sense organ is the eye then what is the stimulus

A

light

64
Q

if the sense organ is the ear then what is the stimuli

A

sound/gravity

65
Q

if the sense organ is the nose then what is the stimulus

A

chemicals

66
Q

if the sense organ is the tongue then what is the stimulus

A

chemicals

67
Q

if the sense organ is the skin then what are the stimuli

A

pressure, temperature, texture

68
Q

if the sense organ is the eye then what is the sense

A

sight

69
Q

if the sense organ is the ear then what is the sense

A

hearing/balance

70
Q

if the sense organ is the nose then what is the sense

A

smell

71
Q

if the sense organ is the tongue then what is the sense

A

taste

72
Q

if the sense organ is the skin then what is the sense

A

touch

73
Q

sense organs are groups of …………… cells

A

receptor

74
Q

sense organs respond to stimuli and relay information as ……………. signals called ………. ………….. to the brain

A

electrical
nerve impluses

75
Q

the central nervous system consists of the ……….. and the …………. ………..

A

brain
spinal cord

76
Q

what is the receptor

A

the change that is detected e.g a ball moving towards you

77
Q

what is the receptor

A

the cells that detect the change e.g light sensitive cells in the retina

78
Q

what neurones transmit information from the receptor to the co-Ordinator

A

sensory neurones

79
Q

what neurones transmit information from the co-Ordinator to the effector

A

motor neurones

80
Q

what is the co-Ordinator

A

this organises the information (brain/spinal cord)

81
Q

what is the effector

A

causes the body to do something (muscle or gland) e.g muscles contract

82
Q

what is the response

A

what the body does e.g catch the ball

83
Q

what is a reflex

A

a fast, automatic reponse to stimulus that protects the body from harm

84
Q

name 2 features of a reflex action

A

very fast
automatic

85
Q

why do we have reflexes

A

to protect the body from harm

86
Q

name a type of reflex

A

withdrawal reflexes e.g touching a hot or sharp object, for protection

87
Q

what is a reflex arc

A

the pathway that messages follow in a reflex

88
Q

what are the 3 neurones involved in the reflex arc

A

sensory
relay
motor

89
Q

what is the synapse

A

a small gap between each neurone which release special chemicals called neurotransmitters to carry messages across the gap

90
Q

what process helps neurotransmitters carry messages across gaps in-between neurones

A

diffusion

WJEC GCSE flashcards (11 decks)

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