dna and genome Flashcards
1
Q
Define prokaryotic cell
A
cell with no membrance bound nucleus
2
Q
example of prokaryotic cell
A
bacterium
3
Q
where is dna found in prokaryotic cell
A
cytoplasm
4
Q
in what form is dna found in prokaryotic cell
A
large, single circular chromosome
5
Q
what is a plasmid
A
a small ring of dna
6
Q
are plasmids present in prokaryotic cell?
A
yes
7
Q
where are plasmids in prokaryotes
A
cytoplasm
8
Q
are chromosomes linear or circular in prokaryotic cells
A
circular
9
Q
what is a eukaryotic cell
A
a cell with a membrane bound nucleus
10
Q
are the chromosomes linear or circular in eukaryotes
A
linear
11
Q
what is the chromosome wrapped around in eukaryotic cells
A
histone protein
12
Q
examples of eukaryotic cell
A
yeast, plant, animal
13
Q
where are chromosomes in plant cell
A
mitochondria and chloroplasts
14
Q
where are chromosomes found in animal cells
A
mitochondria
15
Q
what is found in a prokaryote in place of nucleus
A
large circular chromosome
16
Q
are yeast prokaryotic or eukaryotic
A
eukaryotic
17
Q
does yeast have membrane bound nucleus
A
yes
18
Q
are chromosomes linear or circular in yeast
A
circular
19
Q
where are chromosomes in yeast located
A
inside membrane bound nucleus
20
Q
what is the similarity of yeast to prokaryotes
A
they contain some circular DNA plasmids within their cytoplasm
21
Q
do yest have plasmids
A
yes
22
Q
where are plasmids found in yeast
A
cytoplasm
23
Q
what is mitosis
A
cell division
24
Q
what happens initially when copying genetic code in dna replication
A
dna doble helix is unwound by helicase and hydrogen bonds between bases break. both strands unwind steadily to reveal the template strands which will be copied
25
what enxyme replicates dna
dna polymerase
26
what happens after dna is unwound in dna replication
dna polymerase replicates dna
27
what is a primer
a primer is a short strand of nucleotides that bind to 3' end of dna template strand
28
does primer bind to 3' or 5' in dna replication
3'
29
what is required for dna polymerase to start dna replication
primer
30
what does dna polymerase do in replication
adds free nucleotides
31
from what end are free nucleotides added by dna polymerase
3' end of new strand
32
what bonds does dna polymerase form in replication
strong chemical bonds between phosphates and sugars of the new dna strand
33
other than bonds with phosphates and sugars, what other bonds are formed in replication, and where
weak hydrogen bonds are formed between the base pairs of new and template dna strands
34
can dna polymerase add free nucleotides in more than 1 direction
no
35
which strand is replicated continuously
leading strand
36
why is the leading strand replicated continuously
because dna polymerase can only add nucleotides 3' to 5' which is the direction of the leading strand
37
which strand are primers added to in dna replication
lagging strand
38
where are primers added to the lagging strand in dna replication
as it is unwound at the replication fork
39
in what way is the lagging strand replicated
in fragments
40
what joins the fragments of dna in the lagging strand during dna replication
ligase
41
what is ligase
an enzyme
42
what must a nucleus containn for dna replication to occur. 5 things.
1. dna to act as template
2. four types of free dna nucleotides
3. ATP
4.primers
5. enzymes
43
what enzymes are required in dna replication
ligas and dna polymerase
44
what is the structure of dna
antiparallel double helix
45
what does a nucleotide consist of
phosphate group, deoxyribose sugar, base
46
where is carbon atom 1 in nucleotide
on the top right
47
where is carbon atom 2 in nucleotide
bottom right
48
where is carbon atom 3 in nucleotide
lower left
49
where is carbon 4 in nucleotide
top left
50
where is carbon 5 in nucleotide
on the top left between carbon 4 and phosphate group
51
which carbon has the base in nucleotide
carbon 1
52
what is each strand of dna made up of
sugar-phosphate backbone
53
what joins the phosphate group of one nucleotide to the deoxyribose sugar of the next
a strong bond
54
what does th base sequence of the dna molecule form
genetic code
55
what is amplification
when tiny fragments of dna are copied to provide enough for analysis
55
how is amplification done
PCR (polymerase chain reaction)
56
what is are the 3 temperatures applied during pcr thermocycling
1. 92 - 98°C
2. 50 - 65°C
3. 72 - 80°C
57
what are primers in pcr
short strands of nucleotides which are complementary to specific target sequences at the 2 ends of the region of dna which is to be amplified
57
step 1 of pcr
target sequence is mixed with free dna nucleotides in a small tube with heat tolerant dna polymerase
58
step 2 pcr
dna is heated to between 92 and 98°C to seperate the strands
59
step 3 pcr
dna is cooled to between 50 - 65°C to allow complemetary primer to bond to target sequences
60
step 4 pcr
dna is heated to between 70 and 80°C in order to allow the heat tolerant dna polymerase to replicate target sequences
60
step 5 pcr
repeated thermocycling amplifies target sequence
61
steps of pcr in short
1. Combine - dna nucleotides, heat tolerant polymerase and target sequence
2. highest heat - seperate strands
3. Cool - primers bind to target sequence
4. heat - dna polymerase replicates sequence
5. repeat - thermocylcle to amplify
62
how many cycles happen per hour in pcr
30
63
how many copies of the original fragment are made per hour in pcr
30 cycles - 1 million copies
64
how many cylces of pcr to make 1 million copies of target sequence
30
65
what are practical application of pcr
solve crimes, solve paternity suits, diagnose genetic disorders
66
what can restriction endonuclease do after pcr
cut down copies into smaller fragments at specific base sequences
67
what is gel electrophoresis
Gel electrophoresis is a technique used to separate DNA fragments according to their size
68
why does gel electrophoresis work
dna fragments are negativelyu charged so are pulled through gel toward pos electrode
69
what does gel electrophoresis create
dna fingerprint
70
what is dna fingerprint created in gel electrophoresis used for
to compare samples of dna which may or may not coem from the same person
70
what is the phenotype
physical characteristics of an organism determined by the genotpe
70
what determines the phenotype
the proteins produced as a result of gene expression
70
what 2 processes does gene expression involve
trasnscription and translation
70
are all cells in a gene expressed at once
no, only a fraction of cells are expressed
70
what are 2 key differences between rna and dna
rna has the base uracil where dna has thymine
rna has ribose sugar where dna has deoxyribose sugar
70
what is the job of messenger rna (mrna)
carry a copy of dna code from the nucleus to the ribosome.
70
what are each triplet of bases iin the mrna called
codon
70
what is mrna transcribed from and translated into
transcribed from DNA in the nucleus
translated into proteins by ribosomes in the cytoplasm
70
what is the job of tRNA
to carry a specific amino acid to the ribosome
70
what are 2 key things that tRNA has
anticodon, attatchmment site
70
what is an anti codon
exposed triplet of bases
70
what is the attatchment site for in tRNA
specific amino acids
70
what is the job rRNA
forms a ribosome
71
when is primary mRNA formed
when mRNA is transcribed in the nucleus
71
which is the non coding region in primary transcript
introns
71
which is the coding region in primary transcript
exons
71
are exons coding or non coding
coding
71
are wintrons coding or non coding
non coding
71
where does transcription occur
in the nucleus
71
what enxyme is used in transcription
RNA polymerase
71
what does RNA polymerase do in transcription first
moves along the DNA unwinding to double helix and breaking the hydrogen bonds at the bases
72
what does RNA polymerase do in transcription second
synthesises a primary transcript of mRNA from RNA nucleotides through complementary base pairing
73
what happens with the free nucleotides in transcription
attach to the free bases one strand of DNA forming a strand of mRNA
74
what does RNA splicing do
forms a mature mRNA transcript
75
what is the primary mRNA transcript composed of
introns and exons
76
what si removed from the primary transcript in mRNA splicing
introns (the non coding regions)
77
what happens after introns are removed in RNA splicing
the exons which are the coding regions are joined together to form mature transcript
78
what remains the same during splicing
the order of the exons
79
what happens to the mature transcript after splicing
leaves the nucleus through a pore and travels to a ribosome in the cytoplasm
79
what is translation
the part of gene exression where the mature mRNA transcript is used to synthesise a polypeptide chain at the ribosome
80
what does translation synthesise
apolypetide chain
81
what is the frist step of translation
mRNA attaches to the ribosome
82
what is the second step of translation
translation begins at a start codon and ends at a stop codon
83
what is the third step of translation
mRNA codons bond to tRNA anticodons by complementary base pairing
84
what is the fourth step of translation
the genetic code is translated into a sequence of amino acids joined together by peptide bonds
85
what is the fifth step of translation
each tRNA leaves the ribosome as the polypeptide is formed
86
what is the sixth step of translation
the process ends at the last codon on the mRNA called the stop codon
87
what can polypeptides chains be rearranged to form
different proteins such as enzymes, antibodies, hormomes and structural proteins
88
what determines the function of a protein
their shaoe
89
what happens to the polypeptide after gene expression
undergoes a process of folding to form a the 3D shape of a protein
90
why does folding of polypeptides occur
due to hydrogen bonds and other interactions between individual amino acids that link the polpeptide chains together
91
describe the process that results in different mRNA molecules being expressed during gene expression
alternative mRNA splicing
different mature transcripts can be produced from the same primary transcript depending on which exons are retained. so, one gene can code for more than one protein
92
what is cellular differentiation
the process by which a cell expresses certain genes to produce proteins characteristic of that cell type
93
what does celleular differentiation allow the cell to do
carry out specialised functions
94
what are meristems
regions of unspecialised cells in plants
95
what can meristems do
divide (self renew) and/or differentiate
96
what are stem cells
unspecialised cells in animals
97
what can stem cells do
divide (self renew) and/or differentiate
98
what are the 2 types of stem cells in animals
tissue and embryonic
99
what does it mean when we say that tissue stem cells are multipotent
they can differentiate into all of the cell types found in a particular tissue
100
what are tissue cells involved in
the growth, repair and renewal of cells found in a particular tissue.
101
what are embryonic stem cells
stem cells isolated from a human embryo
102
what can embryonic stem cells do
self renew under the correct laboritory conditions
103
what does it mean when we say that embryonic stem cells are pluripotent
they can differentiate 2into all the cell types that make up the organism
104
what are 2 examples of research uses of stem cells in general
1. model cells to study how diseases develop
2. for drug testing in the lab
105
what is an example of therapeutic uses of stem cells in general
1. repair of diseased organs or tissue
106
what are 2 examples of therapeutic uses of tissue stem cells
1. corneal repair, to replace damaged corneal tissue and thus restore sight
2. regenerate burn damaged skin, new skin can be grown in
107
what is the genome
the genome of an organism is its entire hereditary information encoded in DNA
108
what is the genome made up of
the genome is made up of genes and other DNA that do nto code for proteins
109
what are genes
DNA sequences that code for protein
110
what do non coding sequences in eukaryotes do
regulate transcription, or are transcribed into other non-protein molecules
111
what is a mutation
a mutation is an irreversible change in the sequence of nucleotides within a gene or chromosom, resulting in either no protein or an altered protein being synthesised
112
what is referred to as a mutant
a change in the phenotype of an organism due to a mutation of the genotype
113
what is ROLF and what does it relate to
random occurence low frequency
relates to mutation
114
when can mutations occur
during replication or gamete formation
115
what are the 2 main categories of mutation
singl gene and chromosome
116
what is a single gene mutation
the alteration of a DNA nucleotide as a result of substitution, insertion, or deletion
117
what are the the 3 main types of single gene mutation and their sub categories
1. Substitution
- missense
- nonsense
- splice site
2. insertion
- frameshift
3. deletion
- frameshift
118
what is a missense mutation
one base withing a triplet of bases is substituted for another
119
what happens as a result of missense mutations
results in no change to an amino acid or in one amino being changed for another. This may resuwlt in a non functional protein or have little effect on the protein
120
what problems can missense mutations cause
can cause sickle cell disease
121
what is a nonsense mutation
a change in DNA which causes a premature stop codon
122
what happens as a result of nonsense mutations
a shorter protein is produced
123
what problems can nonsense mutations cause
duchenne muscular dystrophy
124
what is a splice site mutation
one base being substituted for antoher at the splice site
125
what happens as a result of splice site mutation
results in some introns being retained/some exons not being included in the mature transcript
126
what problems can splice site mutations cause
Beta thalassemia
127
what is a splice site
the boundary of an exon and an intron
128
what are the 2 framshift single gene mutations
deletion, insertion
129
what happens as a result of the frameshift mutaions (single gene)
all of the codons and amino acids after the mutatiokn are changed having a major effect on the protein produced
130
what is an example of a problem caused by frameshift insertion
Tay-Sachs disease
131
what is an example of a problem caused by frameshift deletion
cystic fibrosis
132
what does SID stand for and what does it relate to
Substitution, Insertion, deletion
single gene mutations
133
what is a chromosome number mutation
a mutation which alters the chromosome number in every cell in the body
134
what can cause chromosome number mutations to occur
they are caused by a gamete containing more or less than 23 chromosomes
135
what is an example of a chromosome number mutation
Down's syndrome can be caused by a sperm or egg containing an extra copy of chromosome 21. The resulting zygote contains 47 instead of 46 chromosomes
136
what is a zygote
fertilized egg cell that results from the union of a female gamete (egg, or ovum) with a male gamete (sperm)
137
What does D-DIT stand for and what does it relate to
Deletion, duplication, inversion, translocation
chromosome mutations
138
Describe deletion in full detail
- a section of chromosome is removed
- occurs when two breaks occur along the length of the chromosome
- middle section of chromosome containing many genes is lost as aresult
- the broken ends of remaining chromosome join
139
Describe Duplication in full detail
- a section of chromosome is added from its homologous partner
- occurs when a broken segment from a similar neighbouring chromosome is inserted
- duplicates a set of genes as a result
140
Descrive inversion in full detail
- a section of chromosome is reversed
- occurs when 2 breaks occur allong the length of chromosome
- segment between breaks rotates 180° and reattaches in this position
- leading to reversed gene sequence
141
describe translocation in full
- a section of chromosome is added to a chromosome, not its homologous partner
- occurs when a segment breaks off of the end of a chromosome and is added to a neighbouring chromosome
- adds additional genes as a result
142
what is a homologous pair
chromosomes are arranged in pairs, the homologoes pair containes one chromosome from each parent of same length and similarly located genes
143
why is gene duplication improtant in evolution
allow potential for beneficial mutations to occur in the duplicated gene. The duplicated gene could undergo mutation producing a protein with my confer a survival advantage
144
3 examples of chromosome structure mutation and causes:
1. Cri du chat syndrome
- caused by deletion of part of
chromosome 5
2. Haemophilia A
- caused by (one cause) an
inversion within the gene
that produces a clotting
factor (factor VIII)
3. Chronic myleoid leukaemia
- caused by a translocation of
chromosome 22 and 9
145
Define evolution
the changes in organisms over generations as a result of genomic variation
146
in what to way can genomic material be inherited
vertical and horsizontal gene trnsfer
147
what is vertical gene transfer
when genes are transferres from parent to offspring in the next generation as a result of sexual or asexual reproduction
148
what is horizontal gene transfer
when genes are transferred between individuals in the sma generation
149
does evolutionary change occur faster in pro or eukaryotes and why
in prokaryotes due to horizontal gene transfer within the same generation
150
what is natural selection
the non-random increase in frequency of DNA sequences that increase survival and the non-random reduction in the frequency of deleterious sequences
151
what is a deleterious DNA sequence
potentially harmful sequences
152
what is Darwin theory of natural selection in 5 main points
1. organisms produce more offspring than the enviromnment can support
2. genetic variations occur within individuals of the population
3. individuals compete for resources e.g food, mates, etc. natural selection occurs when their is selection pressure
4. best adapted individuals in a population survive to reproduce passing on favourable alleles which confer a selctive advantage
5. these alleles increase in frequency within the population
153
what is stabilising selection
occurs within a stable environment and selects for an average phenotype within a population with extremes of the phenotype being selected against.
154
what is directional selection
occurs within a changing environment and one extreme of the phenotype is selected for
155
what is disruptive selection
occurs when 2 different types of environment or resources become available. two or more phenotypes are selected for.
156
define speciation
the generation of a new biological species as a result of isolation, mutation, and selection is called speciation
157
allopatric speciation in short
geographical barriers such as high mountains
158
sympatric speciation in short
behavioral or ecological barriers such as pH of soil
159
what happens as a result of speciation
a population is split into two sub-populations, mutations, natural selection, etc. occur differently in each resulting in both sub-populations becoming so genetically different that they are no longer of the same species and so cannot interbreed
160
what is a species
a species is a group of organsims capable of interbreeding and producing fertile offspring and which does not often breed with othe groups
161
what is genomic sequencing
the analysis of the sequence of bases
162
what is genomics
the study of the entire genome of an individual or a species
163
approximately how many base pairs are in the human genome
3.2 billion
164
what is a model organism
a non-human species tha tis easy to grow and keep in a laboratory and whose biology has been widely studied
165
what are the 3 domains of life
1. bacteria (prokaryotes)
2. archae (prokaryotes living in extreme conditions of heat or salinity)
3. eukaryotes (plants animals, fungi)
166
how can the sequence of events in evolution be determined
fossil evidence and sequence data
167
what can genomic sequencing be used for
comparison of species
168
what does genomic sequencing reveal
many genes are highly conserved across different organisms
169
what is phylogenetics
the study of evolutionary history ans relationships between organisms
170
what is the point of divergence on a phylogenetic tree
where two species shared a common ancestor
171
what does comparison if gene sequences provide
evidence of the 3 domains of life
172
what determines the main sequences of events of evolution
molecular clocks and phylogenteics, the sequence of evvent can be determined using sequence dat a and fossil evidence
173
what can be used to estimate when 2 species diverged from a common ancestor
differences in gene sequences over time and fossil evidence of divergence
174
what do molecular clocks show
they asume a constant mutation rate and show differences in DNA sequence or amino acid sequence due to mutation over time
175
what does bioinformatics involve
bioinformatics combines computer ansd statistical analysis in order to compare sequence data between individuals and/or species
176
why is it useful to know the exact sequence of nucleotide bases in organisms
it allows analysis and comparison of the entire DNA sequence between one organism and another
177
state the property a sequence of DNA must have in order to be used in molecular clock
constant rate of mutation
178
