DNA and The Genome Flashcards
1
Q
Describe a nucleotide and a long chain of nucleotides.
A
Made of a deoxyribose sugar, phosphate and base. Long chain of nucleotides joined together by sugar phosphate backbone and is called polynucleotides.
2
Q
What is the base pairing rule?
A
Adenine pairs with Thymine
Cytosine pairs with Guanine
3
Q
What kind of structure does DNA have?
A
Hydrogen bonds. Double stranded anti parallel structure with the deoxyribose sugar at the 3’ end and the phosphate at the 5’ end. Forms a double helix.
4
Q
What is a prokaryote?
A
- doesn’t have a nucleus
- single double stranded circular chromosomes in the cytoplasm
- plasmid (carries non-essential genes)
5
Q
What is a eukaryote?
A
- has a nucleus
- several linear chromosomes in nucleus
- mitochondrial and chloroplast DNA (extra DNA out with the nucleus)
6
Q
Is yeast a eukaryote or a prokaryote?
A
Eukaryote even though it has a circular plasmid.
7
Q
What is mitochondrial DNA?
A
- circular double stranded DNA
8
Q
What is chloroplast DNA?
A
- circular double stranded DNA
9
Q
How is DNA organised?
A
DNA in the linear chromosomes of the nucleus of eukaryotes is tightly coiled and packaged with proteins.
10
Q
What model does DNA replicate by?
A
Semi conservative model
11
Q
What are the requirements for DNA replication?
A
Original DNA template, supply of DNA nucleotides, primers, enzymes (DNA polymerase, helicase, ligase), supply of ATP
12
Q
What does DNA helicase do?
A
unzips the double-stranded DNA molecule
13
Q
What does DNA polymerase do?
A
controls formation of sugar-phosphate bond and attaches free nucleotides to the DNA strand
14
Q
What does DNA ligase do?
A
seals any gaps between nucleotides
15
Q
Rule for Replication
A
DNA polymerase can only join nucleotides to the 3’ end of a growing strand
16
Q
What is the leading and lagging strand?
A
One strand will be replicated continuously (leading) and the other in fragments (lagging) because of replication rule
17
Q
Replication of Leading Strand
A
- Hydrogen bonds break and DNA unzips
- DNA primer attaches
- DNA polymerase attaches free nucleotides to 3’ end
- Continuous process until strand is copied
18
Q
Replication of Lagging Strand
A
- Hydrogen bonds break and DNA unzips
- Many DNA primers attach along strand
- Discontinuous process so fragments joined by ligase
19
Q
What does PCR stand for and what is it used for?
A
Polymerase Chain Reaction
amplifies specific sections of DNA
20
Q
Temperatures and Process of PCR
A
95 degrees- DNA strands separate
50-60- primers bind
72- heat tolerant DNA polymerase replicates
Repeat many times- amplify region of DNA
21
Q
Nucleotides shapes
A
Circle= phosphate Pentagon= deoxyribose sugar Rectangle= base
22
Q
polypeptides=
A
another word for protein
23
Q
codon=
A
3 bases
24
Q
genome=
A
all the DNA an organism has
25
Differences between RNA and DNA
```
RNA= single-stranded, DNA= double stranded
R= ribose sugar, D= deoxyribose sugar
R= uracil, D= thymine
```
26
What is transcription?
Synthesis of mRNA from section of DNA (gene), starting from part of DNA called the promoter (start codon). mRNA then carries genetic code from DNA in nucleus to ribosomes (where proteins made).
27
Process of Transcription
1. DNA untwists + unzips as hydrogen bonds btwn bases break
2. RNA polymerase add nucleotides onto 3' end of sense strand following base pairing rules
3. RNA polymerase join ribose sugars to phosphate group using strong chemical bonds
4. Formation of molecule stops when stop codon reached. Molecule produced= primary transcript
5. RNA splicing occurs where sections not needed for final protein removed from primary transcript
28
What is gene expression controlled by?
regulation of transcription and translation
29
exons=
coding regions
30
introns=
non-coding regions
31
What occurs in RNA splicing? Where does mature transcript go afterwards?
Introns are removed and exons are spliced together to form a continuous sequence= mature transcript → leaves nucleus to travel to ribosomes in cytoplasm (translation)
32
What is translation?
mRNA is turned into a polypeptide by tRNA at the ribosome
33
Process of Translation
1. mRNA molecule attaches to a ribosome
2. tRNA molecules transport specific amino acids to ribosome
3. each mRNA codon codes for specific amino acid
4. triplet codon mRNA + anticodons translate gentic code into sequence of amino acids
5. peptide bonds form btwn adjacent amino acids= polypetide
6. used tRNA molecules exit ribosome + collect another specific amino acid
7. start + stop codons signal start + end of translation
34
What can occur in post-translational modification of a protein?
cutting and combing polypeptide chains or by adding phosphate or carbohydrate groups to the protein
35
How is a phenotype determined?
It is determined by the proteins produced as the result of gene expression, influenced by intra- and extra- cellular environmental factors.
36
What is the benefit of RNA splicing?
one gene can produce many different proteins depending on which segments are treated as introns and exons
37
Protein shape
3d- peptide bonds, folded polypeptide chains, hydrogen bonds
38
mutations=
changes in the genome which are random, spontaneous and very rare
39
mutant=
an organism whose phenotype has been altered by a mutation
40
What are the types of mutations?
point mutations, chromosome structure mutatuons, polyploidy
41
What are the 3 main types of point mutations?
- deletion- one base pair has been removed
- insertion- an extra base has been added
- substitution- one base has been swapped for another
42
What are the types of substitution?
- silent- same amino acid coded for
- nonsense- stop codon coded for (protein synthesis halted)
- neutral- similar amino acid coded for (little- no effect on protein)
- missense- different amino acid coded for ( synthesised protein function altered)
- splice site mutation
43
What is a point mutation?
involves change in order of the base pair of a gene
44
What is a splice site mutation?
RNA splicing removes introns + joins exons together, mutations at start/end → one or more introns not being removed from mRNA → translation of protein that does not function properly
45
What are the types of chromosome structural mutations?
Deletion- drastic effect as genes are lost
Inversion- reverses normal sequence of genes → formation of nonviable gametes
Translocation- transfer of genes from another chromosome which is not its matching partner → problems during pairing of chromosomes to nonviable gametes
46
What is the importance of gene duplication in evolution?
Duplication of genes produces second copy of gene that is free from natural selection, additional gene can be altered (mutation) without affecting OG genes function → confer advantage by increasing fitness + chance of survival
47
What is a polyploidy mutation?
the duplication of all the chromosomes → extra sets of chromosomes
48
Importance of polyploidy in food crops=
polyploidy crops= larger and increased seed and fruit size (economic importance)
49
Importance of polyploidy in evolution=
polyploidy= increase in genetic diversity
50
What is evolution?
the gradual change in the characteristics of the population of organisms over successive generations as a result of variation in the population's genes
51
What are the two types of gene transfer?
1. Vertical transfer of genetic material- from parent to offspring as a result of sexual/asexual reproduction
2. Horizontal gene transfer- genetic material passed from one cell to another (occurs mostly in prokaryotes and viruses)
52
What is natural selection?
the non random increase in frequency of DNA sequences that increase survival
53
genetic drift=
the random increase or decrease in frequency of genetic sequences
54
stabilising selection=
mean is unchanged but selection favours middle value
55
directional selction=
selection favours either low or high value which changes mean value
56
disruptive selection=
selection favours both extreme high and low so 2 means arise
57
What is sexual selection?
the non-random increase in the frequency of DNA sequences that increase reproduction
58
How does sexual selection operate?
1. male to male competition
| 2. female choice
59
Why does genetic drift occur?
1. sampling error
2. neutral mutations
3. founder effect
60
founder effect=
if a population becomes isolated and is not large enough to contain the entire gene pool, gene frequencies will be different in that one
61
What is speciation?
the formation of new biological species
62
What are the two types of speciation?
allopatric and sympatric
63
allopatric speciation=
when gene flow between two or more populations is prevented by a geographical barrier
64
sympatric speciation=
when two or more populations live in close proximity in same environment but become genetically isolated because of behavioural or ecological barrier or polyploidy
65
What is a hybrid zone?
an environment may contain several subpopulations of a species that can't all interbreed- only breed with neighbour
66
What does the comparison of genomes show?
many genes are highly conserved (similar) across different organisms
67
What is required to compare sequence data?
computer and bioinformatics
68
Main events in evolution
last universal ancestor, prokaryotes, prokaryotes able to photosynthesise, eukaryotes, multicellular organisms
69
How can the main events in evolution be determined?
sequence data and fossil evidence
70
In pharmacogenetics, what can you do after getting your genome?
predict which medicines and which dosages will be most effective
71
What is cellular differentiation?
the process by which a cell develops more specialised functions by expressing the genes characteristic for that type of cell
72
omnipotent stem cells=
adult stem cells
73
pluripotent stem cells=
embryonic stem cells
74
Roles of proteins
1. Structural- muscle
2. Signalling- hormones and recptors
3. Catalytic- enzymes
4. Immunological- antibodies
75
Fibrous proteins
keratin, silk, collagen
76
Globular proteins
structural proteins, enzymes, hormones
77
stem cell research
gain information about how cell processes occur (cell growth, gene expression/regulation)
78
Stem cells can be used as _ to study _
model cells
| how diseases develop and drug testing
