Chapter 6 - DNA Replication, Repair And Recombinaton Flashcards
1
Q
Parent DNA turns into
A
2 daughter 6
2
Q
DNA replication occurs
A
Before cell division
3
Q
S phase
A
Synthesis phase
4
Q
Hereditary
A
Passed faithfully from one generation to the next
5
Q
Mutations
A
Changes in DNA
6
Q
Mutation produce
A
Variations that underlie the difference between individuals of the same species or overtime they difference between one species and another
7
Q
Crossing over aka
A
Homologous recombination
8
Q
Crossing over
A
Exchange of genetic material (DNA) between homologous chromatids of homologous chromosomes during prophase 1
9
Q
Crossing over occurs when
A
During prophase 1
10
Q
Independent assortment of chromosomes
A
Random alignment of homologous chromosomes pairs tetrads on the metaphase plate during metaphase 1
11
Q
Independent assortment happens when
A
Metaphase 1
12
Q
What are three ways that makes humans different and diverse and not the same
A
Crossing over
Independent assortment
Random fertilization of gametes
13
Q
What acts as a template for its own replication
A
DNA
14
Q
A new strand is aka
A
Daughter strand
15
Q
What are the three models for DNA replication
A
Semiconservative
Dispersive
Conservative
16
Q
DNA replication is what kind of model
A
Semiconservative
17
Q
Semiconservative model
A
Consist of 1 old and 1 new strand
18
Q
Dispersive model
A
Each strand is a mixture of old and new DNA
19
Q
Conservative model
A
2 old DNA strands together and 2 new DNA strands
20
Q
Who confirmed that DNA is semiconservative
A
Confirmed by meselson and stahl
21
Q
Replication origins are recognized by
A
Initiator proteins
22
Q
What is true about eukaryotes and bacteria when it comes to replication forks
A
Eukaryotes have many replication origins, while bacteria have only 1 replication origin`
23
Q
Replication forks
A
Y shaped junctions at which DNA synthesis occurs
24
Q
Replication forks are unidirectional or bidirectional.
A
Bidirectional
25
Replication forks move in what ways
Opposite direction
26
What synthesizes new DNA
DNA polymerase
27
DNA synthesis happens in what direction
5’ to 3’
28
DNA polymerase moves along what strand
Parent strand
29
DNA polymerase moves in which direction
3’ to 5’
30
DNA polymerase adds what? To where?
Deoxyribonucleotide to 3’ end of dna strand
31
Phosphodiester bonds from between what
Free 3’ OH of last nucleotide and free Phosphate of incoming nucleotide
32
What way is the daughter strand made in
In 5’ to 3’ direction
33
DNA replication fork is asymmetrical or symmetrical
Asymmetrical
34
How many DNA polymerase in replication
2
35
DNA polymerase moves continuously, without stopping along what strand
Since this happens what is made continuously
Leading strand
Leading daughter strand
36
DNA polymerase move discontinously along what strand?
What is made? What are the fragments called
Lagging strand
Lagging daughter and Okazaki fragments
37
What proofreads its own work
DNA polymerase
38
In which way does DNA polymerase proofreads
In 3’ to 5’ direction
39
Primase
RNA polymerase that makes RNA primer using DNA as template
40
DNA polymerase can’t work without this first...
Primase, it needs a primer
41
RNA primer
Single stranded sequence of 6-15 ribonucleotides long
42
RNA primer and DNA template are _________ to each other
Antiparallel
43
What is true about RNA primers when it comes to leading daughter strand
Only ONE primer is needed to make leading daughter strand
44
What is true about RNA primers when it comes to lagging daughter strand
Many rna primers are needed
45
RNA Primers are replaced with
Deoxynucleotides
46
Nucleases
Enzymes that removes RNA primers
47
Repair polymerase
DNA polymerase that fills gaps with deoxynucleotides using parent DNA as a template
48
DNA ligase
Joins Okazaki fragments together by catalyzing the formation of phosphodiester bonds
49
How is the DNA polymerase allowed to slide
Protein clamps that are held by leading and lagging strands
50
DNA helicase
Breaks hydrogen bond allow to parent strands to come apart
51
Single strand DNA binding proteins
Bind to each parent strand reforming double helix
52
DNA topoisomerases
Relieve the tension that build up in front of replication fork by producing temporary nicks in the dna
53
Example of dna topoisomerase
DNA gyrase
54
Why do chromosome become shorter?
Repair polymerase is not able to replicate that last section of the lagging strand template due to lack of nucleotide with a free 3’ OH
55
What keeps telomeres long enough
Telomerase
56
Telomerase are found
In tumor, cancer cells, germ line cells, and embryonic and adult stem cells
57
Telomerase adds DNA repeats to what end of the template strand
Why is this important
3’ end
Allows the lagging strand to be completed by DNA polymerase
58
How do we make DNA from RNA
Reverse transcriptase
59
Telomerases carries what
A short piece of RNA whose sequence is complementary to the DNA repeat sequence
60
Why does telomerases uses RNA as a template
To rebuild the telomere by attaching deoxynucleotides to 3’ end of telomere
61
Depurination and deamination are examples of what
Chemical modifications
62
Depurination and deamination only affects what
Nitrogenous bases
63
Depurination
Involves the spontaneous loss of purine base A or G from DNA
64
Deamination
Involves spontaneous loss of amino groups from C in DNA to produce U.
65
What happens when UV radiation damage DNA?
Thymine dimer is formed
66
Thymine dimer
Two adjacent thymine bases become covalently attached to one another
67
What cells are likely to be damaged by UV radiation
Skin cells that are exposed to sunglight
68
Unrepaired thymine dimers leads to
Melanoma
69
Melanoma
Skin cancer that originates in melanocytes and skin cells to produce melanin.
70
Photo reactivating repair mechanism is used by
Plants and bacteria, but not humans
71
Photoreactivation repair mechanism
Repair mech to cleave thymine dimers by plants and bacteria
72
Photoreactivation repair mechanism is catalyzes by
Photolyase
73
Photolyase is activated
Blue light
74
If depurination or deamination is left unrepaired
This results in shorter DNA or an incorrect nucleotide. Will be placed across from the missing base leading to the mutation.
75
What is the basic mechanism of DNA repair
Excision, resynthesis and ligation
76
What repairs deamination, depurination, and thymine dimers in humans
Excision, resynthesis, and ligation
77
Excision
Damage is cut out by the one of series of nucleases, each specialized for type of DNA damage
78
Resynthesis
The original DNA sequences is restored by repair DNA polymerase, which fills in the gap created by the excision event
79
Ligation
DNA ligase seals the nick left in the sugar phosphate backbone of the repaired strand
80
Which way does repair DNA polymerase moves
5’ to 3’
And proofreads in the 3’ to 5t’
81
What are the two types of nucleases
Exonucleases and endonucleases
82
Exonucleases
Cleave nucleotides from 3’ or 5’ ends of DNA/RNA
83
Endonucleases
Cleave nucleotides in the middle of DNA/RNA
84
Mismatch
Mix paired nucleotide
85
What eliminates replication errors
Mismatch repairs
86
Nonhomologous end joining can be caused by
Ionization radiation such as X ray and gamma rays and even products of cell own metabolism
87
Non homologous end joining is a mechanisms that
Repairs double strand breaks in DNA
88
Where can you find nonhomologous end joining
Found in human somatic cels
89
Nonhomologous end joining results in
Short deletions
90
Homologous recombination
Mechanism that repairs double strand breaks with no loss of genetic information
91
Homologous recombination uses
Undamaged DNA as template
92
Branch point
Place where two dna strands, damaged and undamaged, cross.
93
Homologous recombination two main function
Repair breaks in DNA
Creates new combination of DNA sequences
94
During what can homologous recombination allow homologous chromatids of homologous chromosomes to exchange pieces of DNA with each other
Meiosis
95
Sickle cell anemia is caused by
By a single nucleotide change in the b globin gene
96
When there is a single nucleotide change in he b globin gene in sickle cell anemia, what does this create
Abnormal hemoglobin with incorrect sequence of amino acids
97
To develope sickle cell anemia, a person must what
Inherit two copies of the mutant b globin gene
98
What are the three point mutations
Missense
Nonsense
Silent
99
Missense mutations
A new mRNA codon encodes a different amino acid than before
100
Nonsense mutations
Stop codon is generated that doesn’t encode any amino acid
101
Nonsense ultimately does what to proteins
Make it shorter
102
Silent mutation
A new mRNA codon encodes the same amino acid as before
103
Cancer incidence increases dramatically as
Age increases
104
Cancer
Uncontrolled cell proliferation and cell growth
105
What usually happens for cancer to develop
2 or 3 mutations for cancer to develop
