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Biology > Topic 2 & DNA > Flashcards

Topic 2 & DNA Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is a gene?

A

A section of DNA that codes for a specific protein

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2
Q

What are chromosomes made of?

A

DNA

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3
Q

Is DNA a polymer?

A

Yes

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4
Q

What are the monomers of DNA?

A

Nucleotides (DNA is a polymer made from repeating monomers called nucleotides)

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5
Q

What are the components of a nucleotide?

A
  • phosphate group
  • sugar (deoxyribose)
  • base
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6
Q

What are the four bases?

A

Adenine (A)
Cytosine (C)
Guanine (G)
Thymine (T)

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7
Q

How many and what kind of strands are DNA made up of?

A

Two polymer strands

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8
Q

What is the shape of DNA?

A

Double helix

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9
Q

How are the polymer strands made into a double helix?

A

They are twisted

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10
Q

How are bases on one strand linked to those on the other strand?

A

By weak hydrogen bonds

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11
Q

How are the bases linked? (c- b- p-)

A

complementary base pairing

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12
Q

What base pairs with what base?

A

a with t
c with g

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13
Q

How many hydrogen bonds link A and T?

A

2

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14
Q

How many hydrogen bonds link C and G?

A

3

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15
Q

What do the sides of the DNA consist of?

A

A sugar-phosphate backbone

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16
Q

Chromosomes (3 points to make)

A
  • found in nucleus of cells
  • made of dna
  • in human body cells there are 46
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17
Q

allele

A

alternative form of a gene

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18
Q

gamete

A

a sex cell

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19
Q

zygote

A

fertilised egg cell
what is produced when a sperm fuses with an egg

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20
Q

phenotype

A

physical/chemical expression of your genotype

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21
Q

genotype

A

alleles present in the nuclei of your cell

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22
Q

dominant allele

A

if present, is always expressed in phenotype

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23
Q

recessive allele

A

only expressed if dominant allele is absent

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24
Q

homozygous

A

both allleles for a characteristic are the same

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25
Q

heterozygous

A

the two alleles for a characteristic are different

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26
Q

mitosis

A

cell division

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27
Q

cancer

A

uncontrolled cell division
result of dna mutation
can result in tumours forming

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28
Q

benign vs malignant tumour

A

benign: not cancerous, doesn’t invade other tissues or organs
malignant: cancerous, spread by blood to other tissues/organs and invade them to form secondary tumours

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29
Q

cell cycle of healthy vs cancerous cell

A

cell cycle of cancerous cell is quicker

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30
Q

how do secondary tumours occur due to metastatis

A

some of the cancer cells spread to other parts of the body in the blood and invade tissues and organs to form secondary tumours

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31
Q

cell itself normal vs cancerous

A

normal:
large cytoplasm
single nucleus
single nucleolus
fine chromatin

cancerous:
small cytoplasm
multiple nuclei
multiple/large nucleoli
coarse chromatim

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32
Q

what happens in cytokinesis? (1)

A

the cytoplasm and cell membrane divides to formtwo separate diploid cells, each of which has genetically identical chromosomes

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33
Q

what happens in telophase? (1)

A

a nuclear membrane reforms around each new set of chromosomes, separating them

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34
Q

what happens in anaphase (2)

A

1) spindle fibres contract, splitting chromosomes
2) sister chromatids are pulled to opposite ends of the cell

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35
Q

what happens in metaphase (2)

A

1) Chromosomes line up at the centre of the cell
2) Spindle fibres attach to chromosomes at the centromere

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36
Q

What happens in prophase? (3)

A
  1. DNA condenses and chromosomes become visible
  2. The nuclear membrane breaks down
  3. Spindle fibres start to form
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37
Q

What happens in interphase? (3)

A

Dna is replicated
Normal metabolic processes eg respiration continue to occur
New organelles are made

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38
Q

Stages of cell cycle

A

Interphase
mitosis
cytokinesis

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39
Q

stages of mitosis

A

prophase
metaphase
anaphase
telophase

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40
Q

how are proteins made different (a- a-)

A

different proteins have different sequences of the 20 amino acids

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41
Q

how many bases code for one amino acid

A

3 (a triplet) on the dna

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42
Q

how many amino acids

A

20

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43
Q

what are proteins made from

A

amino acids

44
Q

genome

A

entire dna of an organism

45
Q

why is protease sometimes used instead of detergent and salt in step 1 of dna and fruit

A
  • bc this breaks down proteins in cell membrane
  • which breaks down cell membrane
  • therefore releases dna
  • also destroys enzymes that break down dna
46
Q

4 steps of core practical extracting dna from fruit

A

1) grind fruit in detergent and salt (to break open cells by breaking down cell membrane to release dna)
2) filter mixture (to remove debris)
3) pour ice cold ethanol into filtrate (this will precipitate dna as its insoluble in ethanol and so dna can be seen)
4) if desired, remove dna w glass rod

47
Q

haploid chromosomes

A
  • in sex (haploid) cells there is one of each pair of chromosomes
  • so half the number of chromosomes as in a human body cell
48
Q

chromosomes (3)

A
  • in body cells there are pairs of chromosomes
  • cells with two of each pair of chromosomes are said to be diploid
  • in humans there are 23 pairs of 46 chromosomes per cell
49
Q

mitosis vs meiosis 5 points

A

mitosis:
- produces genetically identical cells
- produces diploid cells
- produces 2 cells
- 1 division
- produces body cells

meiosis:
- produces genetically different cells
- produces haploid cells
- produces 4 cells
- 2 division
- produces sex cells

50
Q

meiosis produces (2)

A
  • 4 cells, each with half the number of chromosomes as the original cell and one of each pair of chromosomes (haploid)
  • cells that are genetically different from each other
51
Q

where does meiosis occur in humans

A

women ovaries, men testes

52
Q

haploid cells

A
  • one of each pair of chromosomes
  • so half no of chromosomes
  • in humans these are sex cells
  • in humans sex cells have 23 chromosomes (one of each pair)
53
Q

diploid cells

A
  • two sets of chromosomes (full set) in their nuclei
  • in humans, body cells have 46 chromosomes/23 pairs
54
Q

mitosis produces what kinds of cells (4)

A
  • produces 2 cells
  • produces genetically identical cells
  • produces diploid cells
  • produces body cells
55
Q

importance of mitosis

A

produces genetically identical cells for: growth, repair and asexual reproduction

56
Q

examples of plant specialised cells

A

xylem
phloem

57
Q

plant stem cells (4)

A
  • can produce all cell types throughout plant’s life
  • known as meristem cells
  • found in growing regions (meristems) of plants
  • they divide by mitosis and differentiation to produce plant specialised cells
58
Q

adult stem cells

A
  • found in tissues/organs in adult body
  • can only differentiate to produce a limited number of cell types
  • eg skin cellls in bone marrow can differentiate into different types of blood cell
59
Q

embryonic stem cells

A
  • found in early embryos
  • can differentiate into all cell types
60
Q

stem cells (4 points)

A
  • undifferentiated cells
  • can divide by mitosis and differentiate to produce specialised cells
  • can also divide by mitosis to produce new copies of themselves (self-renew)
  • only stem cells divide by mitosis
61
Q

types of animal stem cells

A

embryonic
adult

62
Q

stem cell risks

A
  • new cells may not function properly
  • if cells are infected w a virus might be transmitted to recipient making them sicker
  • stem cells divide very quickly: if transplanted cells also divide quickly a tumour may develop
  • if stem cells are not from patient the transplanted cells maybe recognised as foreign and trigger immune response to try and destroy them
63
Q

stem cells in medicine benefits

A
  • adult stem cells used to treat some diseases
    (eg leukemia w/ bone marrow transplant as this contains adult stem cells which produce new blood cells)
  • also embryonic stem cells are being tested, could replace damaged tissues by disease or injury
    (eg replace nerve cells of someone w paralysis in spinal cord)”
64
Q

ethical issues with extracting stem cells

A
  • could harm embryos by extracting stem cells
  • embryos used for cells could be destroyed after leading to loss of a potential human life
65
Q

tumour

A

mass of cells
originates from uncontrolled cell division
result of dna mutation

66
Q

synapse

A

gap between neurones

67
Q

synapse passage (5)

A

1) impulse passes along presynaptic neurone
2) at synapse, the impulse triggers the release of a chemical (neurotransmittor)
3) neurotransmittor diffuses across synapse
4) it binds to receptor sites on post-synaptic neurone
5) this triggers an impulse in post-synaptic neurone

68
Q

nervous system passage

A

stimulus
receptor
sensory neurone
impulse
synapse
relay neurone
synapse
motor neurone
effector
response

69
Q

effector

A

produces a response
eg a muscle that contracts or a gland that releases a chemical (likely a hormone)

70
Q

receptor

A

a group of nerve cells that detects a change in the environment ( a stimulus ) eg pain receptors in skin and light receptors in eyes

71
Q

relay neurone (2)

A

found in cns
takes impulse from sensory to motor neurone

72
Q

motor neurone

A

takes impulse from cns to effector

73
Q

sensory neurone

A

takes impulse from receptor to cns

74
Q

myelin sheath

A

fatty substance
acts as an electrical insulator
speeds up movement of electrical impulse

75
Q

axon

A

takes impulse from cell body to axon terminals

76
Q

why don’t relay neurones have a myelin sheath

A
  • unlike sensory and motor neurones, they don’t need to take the nervous impulse a long distance
  • only to other neurones in CNS
  • so passage of impulse can be slower
77
Q

dendron

A

subdivided into dendrites
nervous impulse starts here
dendron takes impulse to cell body

78
Q

cell body

A

contains
nucleus
mitochondria
ribosomes
etc

79
Q

pns meaning

A

peripheral nervous system

80
Q

pns components

A

nerves that lead to and from cns

81
Q

cns

A

central nervous system

82
Q

cns components

A

brain and spinal cord

83
Q

point 1 reflex actions

A

1) stimulus is a change in environment of an organims eg hot flame

84
Q

point 2 reflex actions

A

detected by a receptor eg pain receptors in skin

85
Q

point 3 reflex actions

A

impulses from a receptor pass along a sensory neurone

86
Q

point 4 reflex actions

A

to the spinal cord (co-ordinator)

87
Q

point 5 reflex actions

A

the neurotransmittor (chemical) diffuses across synapse between sensory and relay neurone

88
Q

point 6 reflex actions

A

then a chemical diffuses across synapse between relay and motor neurone

89
Q

point 7 reflex actions

A

motor neurone carries impulse to an effector which is a muscle

90
Q

point 8 reflex actions

A

muscle responds by contracting and finger is moved away

91
Q

reflex arc

A

passage of impulse from receptor to effector

92
Q

reflex action example

A

moving finger away from hot flame

93
Q

growth

A

increase in size/mass

94
Q

what does growth involve in animals?

A

cell division (mitosis)
cell differentiation

95
Q

cell differentiation (2)

A
  • carried out by stem cells
  • cells become specialised eg change shape eg red blood cell changes shape so it can carry oxygen
96
Q

in animals when does growth stop

A

only young animals grow
once adult height has been reached, further growth does not occur

97
Q

what does growth involve in plants (3)

A

cell division (mitosis) (meristem cells)
cell differentiation
cell elongation (by absorbing water)

98
Q

what causes plants to increase in height

A

cell elongation

99
Q

do plants ever stop growing?

A

no
unlike animals they continue to grow throughout their lives

100
Q

where are meristem cells found

A

tips of plants shoots & roots

101
Q

use of percentile growth curves

A

assess child’s growth over time
so overall pattern of development can be seen
so any problems can be highlighted (obesity, dwarfism, malnutrition)

102
Q

what measurements are taken for percentile curves

A

length of baby
mass of baby
baby’s head circumference

103
Q

what does 50th percentile tell us

A

mass that 50% of babies will have at a particular age

104
Q

when will doctors or health professionals investigate in terms of growth percentile curve

A

if baby’s size is above top or below bottom percentile line
if baby’s size increases/decreases by >2 percentile lines over time
if there are inconsistencies eg small baby large head

105
Q

what are reflex actions (4)

A
  • involuntary
  • protect body
  • responses to danger
  • do not involve brain as go via spinal cord which speeds them up

Biology (2 decks)

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