Unit 1 - DNA and the Genome Flashcards
(133 cards)
1
Q
The genetic material in the mitochondria of eukaryotic cells is found in…?
A
Circular chromosomes.
2
Q
What is the purpose of the base sequence?
A
Determines the structure of proteins produced by each cell and its function.
Forms the genetic code.
3
Q
What basic sub-unit makes up nucleic acids?
A
Nucleotides.
4
Q
What is the sugar phosphate backbone?
A
A chain of nucleotides joined by strong chemical bonds between the phosphate of a nucleotide and the 3’ carbon in the sugar of another nucleotide.
5
Q
How are strands of DNA joined?
A
Weak hydrogen bonds between complimentary bases to create a double stranded DNA molecule.
6
Q
What are nucleotides comprised of?
A
Deoxyribose sugar, a phosphate and a base.
7
Q
What does the term ‘double stranded antiparallel structure’ refer to?
A
The two stands of DNA run in opposite directions.
One from the 5’ end to the 3’ end and the other from the 3’ end to the 5’ end.
8
Q
What is a eukaryote?
A
Organisms in which cells contain membrane bound organelles. (Nucleus, mitochondria and chloroplast).
9
Q
What is an example of a eukaryote?
A
Humans.
Eukaryote = YOU-karyote
10
Q
What is a prokaryote?
A
Organisms lacking membrane bound organelles.
11
Q
What is an example of a prokaryote?
A
Bacteria.
12
Q
How is DNA organised in prokaryotes?
A
Single circular double stranded chromosome. They also have plasmids (non-essential genes).
13
Q
How is DNA organised in eukaryotes?
A
Linear chromosomes present in the nucleus.
Circular chromosomes in mitochondria and chloroplasts.
14
Q
What is Mitochondrial DNA’s function?
A
Codes for essential enzymes for respiration, tRNA and rRNA needed for making proteins.
15
Q
What do histone proteins do?
A
They are associated proteins that tightly coil and package the DNA double helix.
16
Q
What is special about yeast?
A
Yeast (eukaryote) contains a nucleus, linear chromosomes and plasmids.
It is therefore useful for genetic engineering.
17
Q
What determines the function of a protein?
A
The shape and structure.
18
Q
What does the genetic code determine?
A
The order of amino acids and how a protein is folded.
19
Q
At the ribosome amino acids are linked by (???) bonds to form (???).
A
Peptide
Polypeptides.
20
Q
After translation polypeptide chains become folded and takes on a 3D shape. How is this shape held?
A
Hydrogen bonds.
21
Q
What is RNA?
A
A second type of nucleic acid.
It is made up of nucleotide sub-units and is single stranded.
22
Q
What is the role of tRNA?
A
Collects specific amino acids which it brings to the ribosome in order to build proteins.
23
Q
What does rRNA do?
A
Combines with proteins to form the ribosome.
24
Q
What is differentiation?
A
The process by which a cell developed more specialised functions by expressing the genes characteristic for that type of cells.
25
What function of genes allows for cellular differentiation?
Genes can be switched on or switched off when they are required. This also allows the body to conserve energy.
26
Why does switching off genes not required conserve energy?
Leaving genes for proteins not required on would waste energy by producing protein in cells where they are not needed.
27
What is a human called during the very first stage of development called?
Zygote.
28
What is the difference between adult stem cells and embryonic stem cells?
All embryonic cells are switched on or can be switched on.
29
What term describes a cell that has under gone differentiation and is now perfectly adapted to carrying out a particular function?
The cell has become specialised.
30
Once a cell has become specialised it only expresses genes that…
Code for proteins specific to the role of the cell.
31
What are stem cells?
They are undifferentiated (unspecialised) cells in animals.
32
How is a supply of stem cells maintained for the body?
They can reproduce themselves by repeated mitosis and cell division.
33
What is found in multicellular organisms?
Stem cells.
34
What are the two types of stem cells?
Embryonic stem cells and tissue (adult) stem cells.
35
Where do embryonic stem cells come from?
Early embryos - blastocysts.
36
What does pluripotent mean?
A cell has the potential to differentiate into all the cell types that make up the organism.
37
What is the purpose of tissue stem cells?
They are involved in the growth, repair of cells found in the tissue.
38
What does multipotent mean?
Once a cells becomes differentiated it only expresses the genes that produce proteins characteristic for that type of cells.
(Produced a limited number of cell types).
39
What is stem cell research used for?
Provide information on how cell processes such as cell growing, differentiation and gene regulation work.
40
What are model cells?
Stem cells can be used as model cells to study how diseases develop or for drug testing.
41
Name a Theraputic use of stem cells.
Skin grafts.
42
What do stems cells potentially have to ability to cure?
Diabetes - grow insulin producing cells.
43
What is an ethical issue with stem cell research?
Some feel that embryos are potential humans that are being denied the ability to live.
44
What is a meristem?
A meristem is a group of unspecialised plant cells capable of diving throughout the life of the plant.
Plant growth is restricted to these regions.
45
What are the two types of meristems and their function?
Apical meristem present at the tip of the root and the shoot.
Adds length to the plant.
Lateral meristems allow the stems to thicken.
46
What is a genome?
The entire hereditary information of an organism encoded in DNA.
47
Non-protein-coding regions are made up of DNA sequences that are repeated.
The function of these sequences is unknown.
What are the purposed functions?
1. Protection - some repetitive sequences make up a telomere at the ends of chromosomes. These prevent fraying.
2. Regulation of transcription. RNA polymerase needs transcription factors (activators - start, repressors - prevent) as it cannot initiate transcription itself.
3. Transcription of non-translated RNA - codes for other forms of RNA.
48
What are mutations?
Changes in the DNA that can result in no protein or an altered protein being synthesised.
49
When do mutations occur?
Spontaneously and randomly.
50
Mutagenic agents increase the frequency of mutations. Give 3 example of mutagenic agents.
1. Radiation (UV light, gamma rays).
2. Chemicals (benzene, mustard gas).
3. High temperatures.
51
Name the types of single gene mutations.
Substitution,
Insertion,
Deletion.
D I G(ene mutations) S.
52
What occurs during a substitution single gene mutation?
What type of mutation is this an example of?
One base is substituted for another which codes for a different amino acid.
This is an example of a point mutation as only one amino acid is affected.
May cause a defect (sickle cell anaemia).
53
What occurs during an insertion mutation?
What type of mutation is this?
An additional base is inserted into a triplet of bases.
All amino acids from the point of mutation is affected and is therefor called a frameshift mutation.
Protein will not function or is the wrong one.
54
What occurs during a deletion mutation?
What type of mutation is this?
1+ nucleotides are deleted in a section of DNA.
All amino acids from the point of mutation onwards are affected and is therefor known as a frameshift mutation.
Protein will not function or is the wrong protein.
55
Substitution mutations can be further classified as (?), (?) and (?) mutations.
Missence, nonsense or splice-site.
56
What is a missense mutation?
The altered amino acid makes sense but is different to the original.
May result in a non-functional protein or have little effect on the protein.
DIFFERENT AMINO ACID MADE.
57
What is a nonsense mutation?
Altered amino acid codes for a stop codon.
Protein synthesis is stopped permanently producing a shorter polypeptide.
NO MORE AMINO ACIDS MADE.
58
What is a splice-site mutation?
An intron is included in the mature mRNA resulting in a non-functional protein.
59
Name the four types of chromosome structure mutations.
Duplication, Deletion, Inversion and Translocation.
D I C(romosome mutation) T D.
60
What occurs during a duplication mutation?
Set of genes from one chromosome becomes attached to matching chromosome leading to repeated genes.
61
What is the benefit of gene duplication?
A second copy of a gene which is free from selection pressure.
A potential beneficial mutation can occur whilst the original can still be expressed to produce its protein.
62
What occurs during chromosome structure deletion?
Detached genes are lost completely.
Two breaks occur along the length of a chromosome and the middle segment containing many genes is lost.
63
What occurs during an inversion mutation?
Chromosome breaks in two places and a set of genes rotates through 180 degrees.
64
What occurs during translocation?
Detached genes become attached to a different chromosome in the complement.
65
What is the importance of genetic variation?
To allow a population to evolve over time in response to changing environmental conditions.
66
Define evolution.
The gradual change in organisms over generations as a result of genomic variations.
Such variations involve changes in frequency of alleles of genes and this requires the processes of inheritance, selection, drift and speciation.
67
What is vertical transfer?
Genes are transferred from parents down to their offspring. Either by sexual or asexual reproduction.
68
What is horizontal transfer?
Prokaryotes exchange of genes can be between members of one generation.
69
What are the benefits and drawbacks of horizontal transfer?
Prokaryotes can exchange genetic material horizontally, resulting in faster evolutionary change than vertical transfer.
However, there are no guarantees that the transferred genetic material will give an advantage.
70
Define 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.
71
What is stabilising selection?
An average phenotype is selected for and extremes of the phenotype range are selected against.
Graph becomes narrower.
72
What is directional selection?
Selection favours a version which was initially less common causing a progressive shift in the mean value.
Common during period of environmental change.
Graph moves right/left.
73
What is disruptive selection?
Selection pressure selects extreme versions of a trait at the expense of the intermediate versions.
Can result in the population being split into two distinct groups.
Driving force between sympatric speciation.
Graph has two peaks.
74
Define speciation.
The generation of new biological species by evolution as a result of isolation, mutation and selection.
75
Define species.
A group of organisms capable of interbreeding and producing fertile offspring.
76
When does allopatric speciation occur?
Occurs when gene flow between two(+) populations is prevented by a geographical barrier.
77
What occurs during sympatric speciation?
Two(+) populations live in close proximity to one another int the same environment but still become genetically isolated.
Occurs because gene flow between them is prevented by the presence of a behavioural or ecological barrier.
Promoted by disruptive selection.
78
Define genomics.
The study of genomes.
79
Define genomic sequencing.
The use of DNA sequencing to determine the order of nucleotides in a section of DNA.
Computer and statistical analysis is used to compare sequences.
This information is pieced together to determine the genomic sequence.
80
What is bioinformatics?
The name given to the fusion of molecular biology, statistical analysis and computer technology.
81
What is bioinformatics used for?
Investigation into evolutionary biology, inheritance and personalised medicine.
82
What is phylogenetics?
The study of evolutionary relatedness amongst groups of organisms.
83
By comparing genetic sequences you can discover what about an organism?
Sequences of events in an organism’s evolution.
84
What type of graph shows evolutionary relationships?
Phylogenetic trees.
85
What is a model organism?
Their genome contains genes equivalent to genes in the human genome that are responsible for diseases. They may provide understanding of how these genes work.
86
What do highly conserved genetic sequences indicate?
Relatedness.
| They can be used to establish how close or distant the relationship is.
87
By comparing the genomic sequences of related groups which diverged the degree of change observed is proportional to what?
Is proportional to the length of time that has passed since the groups diverged.
88
Comparing genomic sequences between two related groups which diverged to determine the length of time since diverging is known as what?
A molecular clock.
89
What are the three domains of life?
Bacteria, Archaea, eukaryotes.
90
What, in addition to genomic sequencing, can be used to produce a timeline of evolution?
Fossil dating.
91
What is personal genomics?
A branch of genomics involved in sequencing an individuals genome and analysing it using bioinformatics tools.
92
What possibilities does personal genomics open up?
1. Predictive medicine - look for disease causing mutations or mutations that increase your likelihood of developing a condition.
2. Personalise medicine/pharmacogenetics - customising medical treatment to suit an individuals exact metabolic requirements which would increase drug efficiency whilst reducing side-effects.
93
What are some ethical issues with pharmacogenetics and predictive medicine?
Insurance companies, banks and others may decline services or increase premiums as a result of finding less desirable traits. (genetic discrimination).
94
What is PCR?
Polymerise chain reaction.
| Tiny specific sections of DNA is amplified in vitro.
95
What is amplification?
Tiny fragment of DNA are copied producing many copies.
96
What is thermocycling?
The process taking place during PCR involving three steps carried out at three different temperatures.
97
Name four requirements for PCR.
Primers, supply of nucleotides, DNA sample, DNA polymerase.
98
What are the use of sequence specific primers for PCR?
Used to locate specific DNA target sequence to be copied.
99
What is the first step of PCR?
The DNA fragment to be copied is mixed with a pool of free DNA nucleotides and heat tolerant DNA polymerase.
100
What is the second step of PCR?
Two primers are made in the lab which have matching base pairs to the 3’ ends of the DNA fragment and are added to the mixture.
101
What is the final step of PCR?
DNA is heated to between 92 and 98°C then the DNA is cooled to between 50 and 65°C, then the DNA is heated to between 70 and 80°C. This completes the cycle.
102
What happens during the second temperature change (temperature is lowered to between 50 and 65°)?
Primers are added and bind (anneal) to target sequences.
103
What happens during the first temperature change (temperature raised to 92 to 98°C)?
The two DNA strands separate.
104
What happens during the third temperature change (heated to between 70 and 80°C)?
Heat tolerant DNA polymerase replicates the region of DNA by adding three nucleotides to the 3’ end of the original DNA.
105
The DNA fragment copied goes through 30 cycles per hour making 1 million copies of the original fragment. The number of DNA grows exponentially what type of graph is needed to depict this?
Semi-logarithmic graph paper.
106
Name a use of PCR.
Solving crimes as a tiny quantity of genetic material found at a crime scene can be amplified to provide enough material for various tests such as genetic fingerprinting to identify suspects.
107
What is chromatography?
Chromatography is a technique used to separate the components of a mixture which differ in their degree of solubility.
108
What is gel electrophoresis?
Gel electrophoresis is a laboratory method used to separate mixtures of DNA or proteins according to molecular size and charge.
109
How does gel electrophoresis work?
An electrical current can be passed through the mixture which forces molecules to move through a gel.
Smaller molecules move at a fast rate and are therefore found to have moved further than larger molecules in a given period of time. Banding patterns on the gel can then be compared.
110
Why do cells need to copy their DNA?
DNA is copied during cell division (mitosis) to ensure that new cells have the same number of chromosomes and to ensure that all cells have the same genes.
111
DNA can direct its own replication and reproduce itself.
| How does DNA replicate?
Semi-conservative replication.
112
What is the first step of DNA replication?
The DNA unwinds.
113
What is the second step of DNA replication?
Hydrogen bonds between the bases break causing the strands to separate.
114
What is the third step of DNA replication?
Free nucleotides lineup with complimentary nucleotides.
115
What is the fourth step of DNA replication?
Sugar-phosphate bonds form.
| Two DNA molecules identical to the parent Strand have now formed.
116
What does DNA polymerase do during DNA replication?
Controls the formation of sugar-phosphate bonds when making the new strand.
Adds free DNA nucleotides.
117
What direction does DNA polymerase add nucleotides to the DNA?
3’ to 5’ direction.
118
DNA has an anti parallel structure. What does this mean for DNA replication?
One strand can be built up continuously as the molecule unzips exposing a 3’ nucleotide.
The other stand lags behind until enough of the template strand is exposed to add a primer and then nucleotides to the 3’ end.
119
What is the 3’ to 5’ DNA strand referred to as?
The leading strand as nucleotides can be added by DNA polymerase continuously.
120
What is the 5’ to 3’ DNA strand referred to as?
The lagging strand as DNA polymerase cannot add free nucleotides continuously.
121
What is the first stage of the leading strand’s replication?
After the hydrogen bonds break, the DNA unzips. These template strands become stabilised and expose their bases at y-shaped replication forks.
122
What is the second stage of the replication of the leading strand?
A DNA primer (a short strand of nucleotides which binds to the 3’ end of the template DNA strand) allows polymerase to add DNA nucleotides.
123
What is the third stage of replication of the leading strand?
Once individual nucleotides have become aligned with their complementary partners on the template strand (following the base pair rule) they become joined to the 3’ end of the primer and formation of the complementary strand begins.
124
What is the fourth stage of replication of the leading strand?
DNA polymerase brings about the formation of the sugar-phosphate bond between the primer and the individual nucleotide.
125
Describe the process of the replication of the lagging strand.
Many primers attach along the strand.
These are extended by the DNA polymerase.
The fragments are then joined by the enzyme ligase.
This is a discontinuous process creating the lagging strand.
126
For DNA replication to occur what must be present in the nucleus?
DNA (to act as the template), Primers, a supply of the 4 types of nucleotide, DNA polymerase and ligase enzymes, a supply of ATP (energy)
127
What is translation?
Translation is the synthesis of protein following the code within the mature mRNA transcript.
128
What are the two main features of tRNA?
Each tRNA has an attachment site for a specific amino acid and a triplet of bases known as an anticodon.
129
What does tRNA do?
The tRNA picks up its appropriate amino acid and takes it to the ribosome to be matched with the mRNA.
130
What is the first step of translation?
tRNA molecules become attached to amino acid molecules in the cytoplasm. The tRNA attaches to a specific (complementary) amino acid.
tRNA molecules in the cytoplasm transport amino acids to the ribosome.
131
What is the second step of translation?
The first tRNA molecule moves in by means of base pairing between the anticodon on the tRNA and the complementary codon on the mRNA strand.
This is repeated with more amino acids.
A peptide bond forms between the amino acids.
132
What is the third step of translation?
The first tRNA molecule detaches from the mRNA and is free to collect another amino acid from the cytoplasm.
As translation proceeds the ribosome moves along the mRNA, exposing the next codon, allowing the next tRNA to bring the third amino acid into position.
133
What is alternative RNA splicing?
Alternative segments of RNA may be treated as exons and introns producing a different mature RNA transcript.
