DNA & The Genome Flashcards
1
Q
What is the name for the basic units which make up strands of DNA?
A
Nucleotides.
2
Q
What are the DNA base pairing rules?
A
Adenine to Thymine, Cytosine to Guanine are the DNA base pairing rules.
3
Q
The two strands of DNA are held together by which kind of bonds?
A
Weak hydrogen bonds hold together two strands of DNA.
4
Q
What are DNA nucleotides made up of?
A
DNA nucleotides are made up of: a deoxyribose sugar, phosphate and base.
5
Q
DNA is found as linear chromosomes, tightly coiled and packaged with associated proteins, called histones, in which type of organism?
A
DNA is packaged like this in eukaryotes.
6
Q
what are prokaryotes?
A
organisms that lack true membrane-bound nucleus.
7
Q
where is the DNA found in prokaryotes?
A
Cytoplasm.
8
Q
example of prokaryote
A
Bacteria is a type of prokaryote.
9
Q
what are eukaryotes?
A
Organisms that have a membrane-bound nucleus that stores their genetic information.
10
Q
example of eukaryotes
A
fungi, animals, and plants are examples of eukaryotes.
11
Q
organisation of chromosomal DNA in prokaryotes?
A
Prokaryotes have circular DNA organisation.
12
Q
plasmids are found in one type of eukaryote
A
Yeast cells are the only type of eukaryote that contains plasmids.
13
Q
DNA is wrapped around _ _ _ _ _ _ _ _
A
DNA is wrapped around histones.
14
Q
what does DNA polymerase need to be present before it can start replicating DNA?
A
primer.
15
Q
True or False: The lagging strands are replicated continuously?
A
False- The lagging strands are replicated continously.
16
Q
Fragments on lagging strands are joined then together using the enzyme DNA _ _ _ _ _ _ _
A
Fragments on lagging strands are joined then together using the enzyme DNA ligase.
17
Q
DNA unwinding occurs at multiple locations along a DNA molecule at _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
A
DNA unwinding occurs at multiple locations along a DNA molecule at Replication Forks.
18
Q
Which enzymes are required for DNA replication?
A
Ligase, DNA Polymerase
19
Q
Why can both strands of DNA not be replicated continuously?
A
DNA nucleotides can only be added continuously in a 5’ to 3’ direction.
20
Q
what is the name for the repeating units that make up a strand of DNA?
A
Nucleotides
21
Q
What is a nucleotide made from?
A
Deoxyribose sugar, phosphate, base
22
Q
Which end of the DNA strand is called the 3’ end?
A
End with the deoxyribose sugar
23
Q
Which end of the DNA strand is called the 5’ end?
A
End with the phosphate
24
Q
What shape is a DNA molecule?
A
Double helix
25
What is the complementary base pairing rule?
Adenine and Thymine always pair, Guanine and Cytosine always pair
26
What bonds hold the complementary base pairs together?
Weak hydrogen bonds
27
Which bonds hold the deoxyribose sugar of one nucleotide to the phosphate of another?
Strong chemical bonds
28
Why are DNA strands described as anti-parallel?
One strand runs from the 3’-5’ direction and the other runs in the 5’-3’ direction
29
Where do you find DNA in a eukaryote?
In the nucleus, in the mitochondria, in the chloroplast
30
How is DNA stored in prokaryotes?
As a large single, circular chromosome and in plasmids
31
what is a plasmid?
A small ring of DNA or small circular DNA
32
How is DNA stored in eukaryotes?
Linear chromosomes in the nucleus, small circular chromosomes in the mitochondria and chloroplast. Yeast has plasmids
33
How is DNA packaged within the nucleus of eukaryotes?
Tightly coiled and packaged with associated proteins called histones
34
What enzyme is responsible for DNA replication?
DNA polymerase
35
What is the function of a primer?
To provide a start point for DNA polymerase
36
Why is DNA replication required?
Before mitosis to ensure that both daughter cells get an identical copy of the genetic info from the parent cell
37
What is required in order for DNA replication to take place?
```
DNA polymerase
Ligase enzymes
DNA nucleotides
Primers
Template DNA
ATP
```
38
Which enzyme joins the fragments of DNA on the lagging strand?
Ligase
39
Which bonds are broken to separate the two strands of DNA?
Hydrogen bonds
40
What is mean by discontinuous synthesis of the lagging strand?
Strand is replicated in fragments
41
What is a primer?
A short strand of nucleotides which binds to the 3’ end of the template strand allowing DNA polymerase to add nucleotides.
42
What is the function of PCR?
To amplify a sequence of DNA
43
What are the requirements for PCR?
```
Template DNA
heat tolerant
DNA polymerase
Primers
Free DNA nucleotides
```
44
When is PCR used?
Crime scene analysis
Paternity tests
Diagnosing genetic disorders
45
Why are there multiple replication forks on one strand of DNA?
To allow speedy replication
46
Why is DNA heated in the first stage of PCR?
To break hydrogen bonds between bases and separate the two strands
47
Why is DNA cooled during the second stage of PCR?
To allow primers to bind to target sequences
48
Why is heat-tolerant DNA polymerase used in PCR?
It doesn’t denature during the hearing cycles.
49
Why is DNA heated back up for the third stage of PCR?
To allow heat tolerant DNA polymerase to replicate the region of DNA
50
What are the primers used in PCR?
Short strands of nucleotides which are complementary to specific target sequences at the two ends of the region of the DNA to be amplified
51
What temperature does the first stage of PCR occur at?
95^C
52
What temperature does the second stage of PCR occur at?
58^C
53
What temperature does the third stage of PCR occur at?
75^C
54
Why is there a leading and lagging strand in DNA replication?
Parent strands are anti-parallel but DNA polymerase can only add DNA nucleotides to the 3’ end of the new DNA strand which is forming
55
What is the difference between DNA polymerase and heat-tolerant polymerase?
DNA polymerase denatures at lower temperatures than heat-tolerant polymerase
56
Which bonds are synthesised by DNA / heat-tolerant DNA polymerase?
Strong chemical bonds / covalent bonds between sugar and phosphates of adjacent nucleotides.
57
Which rule allows the molecules of DNA to be copied?
Complementary base pairing rule
58
Which strand in DNA replication requires the use of many primers?
Lagging strand
59
Which enzyme is responsible for transcription?
RNA polymerase
60
Which process produces a primary mRNA transcript?
Transcription
61
Which process takes place to turn a primary mRNA transcript into a mature mRNA molecule?
RNA splicing
62
Which process is when the mature mRNA is used to direct the synthesis of a protein?
Translation
63
Gene expression involves which two processes?
transcription and translation
64
Where does transcription take place?
In the nucleus
65
Where does translation take place?
At the ribosome
66
Which molecule carries specific amino acids to the ribosome?
tRNA
67
What is the ribosome composed of?
rRNA and protein
68
What is the function of RNA polymerase?
Unwinds the double helix and breaks the hydrogen bonds between the bases. It synthesises a primary transcript of mRNA from RNA nucleotides by complementary base pairing.
69
Describe the complementary base pairing used to build a molecule of RNA.
Adenine—Uracil, Cytosine—Guanine
70
Which bonds hold amino acids together to form a polypeptide?
Peptide bond
71
What happens during RNA splicing?
Introns are removed and exons are joined together to form the mature transcript.
72
Which codons begin and end translation?
START and STOP codons.
73
What is the function of tRNA?
Carries a specific amino acid to the ribosome and has an anticodon which is complementary to a codon.
74
What is the function of mRNA?
It carries a complimentary copy of the DNA code from the nucleus to a ribosome in the cytoplasm.
75
What is determined by the proteins produced during gene expression?
the phenotype of the organism
76
What is alternative RNA splicing?
When introns are treated as exons or exons are treated as introns leading to different exons retained in the mature mRNA.
77
How can one gene lead to the production of many proteins?
RNA alternative splicing
78
Proteins have a 3D what interactions are involved in this?
Hydrogen bonds between amino acids and other interactions between individual amino acids.
79
What is an intron?
A non-coding region of mRNA.
80
What is an exon?
Coding region of mRNA.
81
Describe the structure of a tRNA?
It folds due to complementary base pairing and has an amino acid attachment site at one end and an anti-codon at the other end.
82
What is the three types of RNA involved in gene expression?
mRNA, tRNA and rRNA.
83
What is an anti-codon?
an exposed triplet of bases on the tRNA.
84
What happens during translation at the ribosome?
tRNA with complementary anticodons bond with codons on the mRNA by complimentary base pairing, translating the code into a sequence of amino acids. Peptide bonds form between amino acids.
85
What are the differences between RNA and DNA nucleotides?
RNA contains RIBOSE SUGAR and URACIL and is SINGLE stranded, DNA contains DEOXYRIBOSE SUGAR and THYMINE and is DOUBLE stranded.
86
What is a codon?
A sequence of three bases on mRNA which codes for one specific amino acid.
87
What is meant by cellular differentiation?
Process by which a cell expresses certain genes to produce proteins characteristic for that type of cell.
88
What is a meristem?
Region of unspecialised cells in plants capable of cell division and/or differentiation.
89
What is a stem cell?
Unspecialised cells in animals which can divide (self-renew) and/or differentiate to form specialised cells.
90
What is the difference between tissue (adult) stem cells and embryonic stem cells?
Tissue (adult) stem cells can only differentiate into all types of cell found in a particular tissue (multipotent) but embryonic stem cells can become all the cell types needed by the organism (pluripotent)
91
What does pluripotent mean?
Can differentiate into all the cell types that make up the organism.
92
What does multipotent mean?
Can differentiate into a limited range of cells/ all types of cell found in a particular tissue.
93
Why do organisms have tissue (adult) stem cells?
To grow, repair and replenish/renew differentiated cells that are found in tissues.
94
Why do people have ethical concerns with the use of embryonic stem cells?
Embryos get destroyed which some people think is the same as murder/ killing a potential life.
95
What are the two therapeutic uses of stem cells?
Corneal repair and growing skin grafts for regeneration of damaged skin.
96
What are some of the ways that stem cells can be used in research?
Used as model cells to test drugs, used to study cell processes like cell growth, differentiation and gene regulation and to study how diseases develop.
97
Give an example of a tissue adult stem cell?
Blood stem cells in bone marrow which go on to differentiate into all the cells of the blood.
98
How can stem cells found in the embryo differentiate into all cell types?
All the genes in embryonic stem cells can be switched on.
99
What type of stem cells are pluripotent?
Embryonic stem cells.
100
What type of stem cells are multipotent?
Tissue stem cells.
101
What is meant by the genome?
An organisms entire hereditary information encoded within its DNA.
102
What is meant by a coding region of the genome?
A region of DNA that is translated.
103
What is meant by a non-coding region of the genome?
It does not code for protein.
104
What are the known functions of the non-coding regions?
Regulate transcription or are transcribed but not translated.
105
What are most of eukaryotes genomes consisted of?
Non-coding sequences.
106
What is an example of non-translated forms of RNA?
tRNA and rRNA.
107
What is meant by transcription?
Sequence of DNA is copied to make RNA molecule.
108
What is meant by translation?
Sequence of mRNA used to create protein.
109
What is the function of rRNA?
Combines with protein to form the ribosome.
110
What is the function of tRNA?
Carries a specific amino acid and has an anticodon which is complementary to a codon on mRNA.
111
Is all of the genome found in the nucleus of eukaryotes?
No, also in mitochondria or chloroplasts
112
What is a mutation?
A random change in the DNA that can result in no protein or an altered protein being synthesised.
113
Name the three types of single-gene mutations?
Substitution, Insertion, Deletion
114
Name the four types of chromosomes mutations?
Translocation, Inversion, Deletion, Duplication
115
What happens in a substitution mutation?
One base is replaced by another
116
What happens during deletion point mutations?
One base is removed
117
What happens during insertion point mutations?
One base is added
118
What is meant by a missense mutation?
When one amino acid has been substituted and this results in a non-functional protein or may have little effect on the protein.
119
What is meant by a nonsense mutation?
When a premature stop codon has been inserted and results in a shorter protein.
120
What is the result of a splice-site mutation?
In some introns being retained in the mature mRNA and/or some exons not being included in the mature transcript.
121
Which mutations are frameshift mutations?
Insertion and deletion
122
What is meant by a frameshift mutation?
Causes all of the codons and all of the amino acids after the mutation to be changed. This has a major effect on the protein produced.
123
What is meant by a chromosome mutation?
A change to the sequence of genes on a chromosome.
124
What happens in a translocation mutation?
A section of a chromosome is added to another chromosome, not a homologous partner.
125
What happens in an inversion mutation?
Where a section of a chromosome is reversed.
126
What happens in a deletion chromosome mutation?
A section of a chromosome is removed.
127
What happens in a duplication mutation?
A section of a chromosome is added from its homologous partner.
128
What is a mutagenic agent?
Something which increases the frequency of mutations.
129
Give an example of a mutagenic agent?
Mustard gas, U.V. Radiation, X-Rays
130
Why is duplication important in evolution?
duplication allows potential beneficial mutations to occur in a duplicated gene whilst the original gene can still be expressed to produce its protein.
131
Which type of point mutation can lead to an expansion of a nucleotide sequence?
Insertion
132
Explain how a mutation can lead to the same amino acid being produced?
Many amino acids have more than one codon.
133
What is evolution?
The changes in organisms over generations as a result of genomic variation.
134
What is meant by vertical gene transfer?
where genes are transferred from parents to offspring by sexual or asexual reproduction.
135
What is meant by horizontal gene transfer?
Where genes are transferred between individuals in the same generation.
136
Which type of gene transfer leads to rapid evolutionary change?
Horizontal Gene Transfer
137
Which organisms only transfer genetic material by vertical gene transfer?
Eukaryotes
138
Which organisms can transfer genetic information by both vertical and horizontal gene transfer?
Prokaryotes
139
What is speciation?
The generation of new species by evolution as a result of isolation, mutation, and selection.
140
What is Natural Selection?
The non-random increase in the frequency of DNA sequences increases survival and non-random reduction in the frequency of deleterious sequences.
141
What is the definition of a species?
A group of organisms that can interbreed to produce fertile offspring.
142
What is meant by ‘stabilising selection’?
An average phenotype is selected for and extremes of the phenotype range are selected against.
143
What is meant by ‘disruptive selection’?
Two or more phenotypes are slected for.
144
What is meant by ‘directional selection’?
One extreme of the phenotype range is selected for.
145
Summarise natural selection.
Organisms who are better adapted to their environment are more likely to survive to pass on their genes.
146
What is the importance of isolation barriers?
They prevent gene flow between sub-populations during speciation.
147
What is meant by sympatric speciation?
Speciation brought about by a behavioural or ecological barrier e.g. different breeding seasons, different mating rituals
148
How do you know if organisms have undergone speciation?
They can no longer interbreed to produce fertile offspring.
149
What is meant by allopatric speciation?
Speciation brought about by geographical barriers e.g. river, sea, mountain range.
150
What is genomics?
The study of genomes
151
What is genomic sequencing?
Determines the sequence of nucleotide bases for individual genes or entire genomes.
152
What is bioinformatics?
The use of computers and statistical analysis to compare sequence data.
153
What are three types of organisms which have had their genome sequences?
Pest species, disease-causing organisms and model organisms.
154
What is phylogenetics?
The study of evolutionary history and relationships.
155
What was the order of evolution of life on earth?
Last universal ancestor, prokaryotes, photosynthesis, eukaryotes, multicellular organisms, animals, vertebrates, land plants
156
How can we work out the sequence of evolution of life on Earth?
Using sequence data and fossil evidence.
157
How is a molecular clock constructed?
They assume a constant mutation rate and show differences in DNA sequences or amino acid sequences. The difference in sequences indicates the time of divergence from a common ancestor.
158
How could differences in DNA sequences tell you how distantly related two organisms are?
The more differences in the DNA sequences the more distantly related.
159
What is pharmacogenetics?
The use of genome information in the choice of drugs.
160
What are the three domains of life?
Archaea, bacteria, eukaryotes
161
What is personalised medicine?
An individual’s genome sequence can be used to select the most effective drugs and dosage to treat their disease.
162
Comparison of genomes has revealed?
That many genes are highly conserved across different organisms.
163
What is used to identify base sequences?
Computer programs, by looking for sequences similar to known genes.
