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Flashcards in Unit 1 Deck (103):
1

A stem cell is an unspecialised cell that can:

make copies of itself and differentiate (make copies of itself)

2

Differentiation occurs when

when unspecialised cells become specialised

3

A differentiated cell only

Has a few genes switched on

4

the 2 types of stem cells are

embryonic and adult (tissue)

5

embryonic stem cells are

derived from an embryo

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embryonic stem cells have the ability to

differentiate into all cell types

7

Where are adult stem cells found?

in small numbers in the tissue and organs of adults and children, including the brain, bone marrow, skeletal muscle and skin

8

adults stem cells give rise to

a more limited range of cell types.

9

the theraputic uses of stem cells incude:

bone marrow transplants
skin graphs for burns
stem cell graphs for cornea repair

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stem cell research gives us information including:

the study of diseases
drug testing
how the processes of growth, differentiation and gene regulation work

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which type of stem cells has ethical issues surrounding it

embryonic stem cells

12

somatic cells are

the differentiated cells that form the different types of body tissue

13

type of somatic cells are:

epithelial cells (cover the body surface and line body cavities)
connectives tissue ( includes blood, bone and cartilage cells)
muscle cells (form muscle tissue)
nerve cells (form nerve tissue)

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during growth and repair, somatic cells

always divide by mitosis to maintain diploid chromosome number

15

germline cells include

the gametes and the cells that produce gametes (gamete mother cells)

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germline cells can divide by mitosis to

produce more germline cells

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germline cells can also divide by meiosis to

produce haploid gametes

18

if a genetic mutation occurs in a germline cells, it

will be passed on to the offspring during sexual reproduction

19

genetic mutations that occur in somatic cells will

not be passed to the offspring, as these cells are not involved in sexual reproduction

20

Cancer cells continue to

reproduce to produce a mass of abnormal cells called a tumor

21

cancer cells do not

respond to regulatory signals that would instruct them to stop dividing

22

DNA consists of

units called nucleotides

23

Nucleotides are made up of

phosphate
base
deoxyribose sugar

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there are four different types of

nucleotides, depending on the base

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certain bases are complementary to

each other, this is called the base pairing rule

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a pairs with

t

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g pairs with

c

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bases in adjacent strands are

held together by hydrogen bonds

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DNA is held together by a strong chemical bond between

the phosphate of one nucleotide and the carbon 3 of the sugar on another nucleotide

30

the double helix is described as

having two anti-parallel chains of nucleotides because one side goes 5' to 3' and the opposite side goes 3' to 5'

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the base sequence of a DNA determines

the genotype

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DNA is arranged in

tightly coiled nucleotides

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the DNA is packed with

proteins

34

DNA replication occurs in

the nucleus and involves DNA unwinding

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once the DNA has unwound it

unzips to expose its bases

36

the DNA bases are now

used as a template for a new DNA strand to be made

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once the nucleotides are exposed, free floating

nucleotides in the nucleus join on to their complementary bases

38

once the nucleotides are lined back up, they

join to their partner by hydrogen bonds

39

the DNA strand forms a

sugar phosphate backbone

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the DNA strand then

Winds back up to form 2 identical double helix's

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each double helix contains

one original strand and one "new" strand

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DNA polymerase is

an enzyme that controls the sugar phosphate bonding

43

DNA polymerase can also

add nucleotides to the strand but only add nucleotides to a pre-existing chain

44

for DNA polymerase to work a

primer must be present

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what is a primer?

a primer is short sequence of nucleotides at the 3' end

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once the fragments are all in place

the enzyme ligase jooins the fragment together

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when copying a long chromosome

many replication forks operate simultaneously

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for DNA replication to occur, the nucleus must contain:

DNA (template)
Primers
supply of 4 types of nucleotide
enzymes (both ligase and DNA polymerase)
ATP

49

there are 3 types of RNA:

messenger RNA (mRNA)
transfer RNA (mtRNA)
ribosomal RNA (rRNA)

50

RNA is

a nucleic acid with a similar structure to DNA

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the role of RNA is in

Producing proteins

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mRNA is made

in the nucleus

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mRNA carries a copy of

the DNA code from the nucleus to the ribosome

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each tRNA can

carry one specific amino acid from the cytoplasm to the ribosome

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ribosomes are made up of

protein and ribosomal RNA

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RNA is made up of

nucleotides

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nucleotides consists of

phosphate
base
robose sugar

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During protein synthesis

RNA bases pair with their complementary bases

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proteins are made up of

joining together amino acids in a specific sequence

60

the order of amino acids is

dictated by the order of the bases on the DNA

61

two main stages of protein synthesis

Transcription
Translation

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Transcription occurs in

nucleus

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in transcription, a section of DNA is

copied to produce a strand of RNA

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in stage one of transcription,

the section of DNA which codes for the desired protein unwinds and unzips

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in stage two of transcription

Free mRNA nucleotides enter the nucleus and RNA polymerase joins them with their complimentary DNA base starting at 3' end. only one strand of DNA is copied

66

the strand of mRNA produced by transcription is called a

Primary transcription

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Primary transcription contains

regions which code for the production of of the protein called extrons and regions which are non coding which are called introns.

68

the introns must

be removed before translation can occur

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Translation is

the synthesis of a protein in the form of a polypeptide chain

70

the strand of mRNA is

divided into triplet bases called codons

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each codon contains

the code for one amino acid

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tRNA's function is

to pick up a specific amino acid and bring it to the mRNA on the ribosome

73

the structure of tRNA

the anticodon is composed of a triplet of bases which are cfomplementary to an mRNA codon

74

the amino acid binding site can

only pick up one specific amino acid

75

translation occurs in

ribosome

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AUG is the

Start codon. this indicates to the tRNA where to add the first amino acid

77

complementary anticodons pair with

their complementary codon ensuring the amino acids are in the right sequence

78

the amino acids join together by

a peptide bond to form a polypeptide chain

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Stop codons

indicate to the tRNA where to stop adding amino acids

80

Different mRNA molecules are produced from

the same primary transcription depending on which segments are treated as exons and which are treated as introns

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after translation the polypeptide chain can be modified to produce many different proteins

the polypeptide chain can be cut and combined with other polypeptides
a phosphate or carbohydrate group ca n be added to the polypeptide chain

82

types of protein: fibrous

collagen
elastin
keratin

83

types of protein: globular

enzymes
antibodies
hormones

84

types of protein: conjugated

chlorophyll
haemoglobin

85

your phenotypes are determined by

the protein you produce

86

the protein you produce are controlled by

the gene being expressed
only a fraction of the genes in a cell are expressed

87

gene epression can be influenced by

intra-cellular and extra-cellular environmental factors

88

gene expression is controlled by

the regulation of transcription and translation

89

a mutation is

a change to a individuals DNA

90

there are two types of mutation

Gene Mutation
chromosome mutation

91

mutations are

the only source of new variation

92

mutations frequency can be increase

by mutagenic agents

93

examples of mutagenic agents

chemicals (mustard gas)
radiation (UV lights)

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gene mutation involves

a change in the sequence of nucleotides

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this can be by

substitution, deletion or insertion of nucleotides

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a substitution mutation involves

a change In one nucleotide in the DNA sequence of a single gene

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substitution mutation results In

one codon for one amino acid being altered

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substitutions include

missense
nonsense
splice - site mutations

99

missense mutation changes the

codon for an amino acid so that a different acid is inserted

100

an example of a disorder that results from missense mutation

sickle cell anemia

101

nonsense mutation results in

a codon for a specific amino acid being changed to a stop codon

102

nonsense mutation causes

protein synthesis to stop early and results in a shorter protein which is unable to function

103

Splice - site mutation

mutations in the area