Module 11 (DNA Replication and Cell Division) Flashcards
1
Q
Why does cell division occur?
A
Cell growth
Cell replacement
Cell healing
Cell reproduction
2
Q
How can a cell make more cells?
A
Using the process known as cell division
3
Q
Requirements of cell division
A
- The parent cell must be big enough to divide (so the daughter cells get enough cytoplasmic components)
- The two daughter cells must each receive all of the genetic material from the parent cell
4
Q
How do prokaryotic cells divide?
A
Using binary fission
5
Q
Steps of Binary Fission
A
Protein bind circular DNA to inner membrane
DNA replication travels bidirectionally
The new circular DNA is also attached to the inner membrane
Cell elongates, and starts to pinch at middle of cell
New cell membrane and cell wall separates the daughter cells
6
Q
Genome
A
Genetic material of an organism
7
Q
Mitochondrial genome
A
Maternally inherited
8
Q
Is there a correlation between genome size and organismal complexity?
A
No! There is no correlation. An amoeba has 670000kb, but a human has 3100kb
9
Q
Nucleoid
A
Loops of circular DNA, coiled around itself, bound together by proteins
10
Q
Chromatin
A
Nucleosomes packaged together, forms a strand (about 30nm in diameter)
11
Q
Nucleosomes
A
DNA is wrapped around histone proteins twice (10nm in diameter)
12
Q
Coiled chromatin fiber
A
Chromatin fiber is further coiled (300nm)
13
Q
Coiled coil
A
The coiled chromatin fiber is coiled further (700nm)
14
Q
Chromatid
A
Only visible in cells that are about to divide, made from coiled coils (1400nm)
15
Q
Stem cells
A
Undifferentiated cell that can undergo unlimited amounts of cell division and differentiate into any of the specialized cells (found in bone marrow when talking about blood cells)
16
Q
Somatic cells
A
Nonrepoductive cell, most common type of cell (normal)
17
Q
Germ cells
A
Reproductive cells that produce gametes (eggs or sperm)
18
Q
The time when the parent cell divides into two daughter cells
A
M phase
19
Q
How does cell division occur in eukaryotes?
A
Through the cell cycle
20
Q
The time between two successive M phases is known as…
A
Interphase
21
Q
Cytokinesis
A
The division of the cytoplasm into two daughter cells
22
Q
Mitosis
A
Separation of replicated chromosomes
23
Q
How long does interphase usually last between two M phases?
A
Around 10-14 hours
24
Q
Cell’s preparations before division
A
DNA replication in nucleus
Increasing the size of the cell
25
G1 phase
First stage in interphase
- increase cell size and protein content
- 1st gap phase
- Synthesis and activation of regulatory proteins
26
S phase
"Synthesis" phase, second phase in interphase
- DNA replication
27
G2 phase
Third phase of interphase
- Second "gap" phase
- Preparation for M phase
28
G0 phase
Separate from G1, no active preparation for cell division
- cells that do not divide (liver cells- hepatocytes)
29
What does it mean by "DNA replication is semiconservative"?
Each strand of parental DNA acts as a template strand for the synthesis of a daughter strand
30
One strand of DNA is ________, one strand is _________
One strand is old parental, one strand is newly synthesized
31
Replication Fork
The place where the two strands of DNA split from each other during replication
32
Helicase
Unwinds parental DNA at replication fork
33
Single-strand binding protein
Holds the single stranded regions of the parental strands to prevent them from coming back together.
34
Topoisomerase
Relieves the stress of unwinding the DNA, works upstream the replication fork
35
DNA Polymerase
Adds bases to nucleotide strand, requires four deoxyribonucleotides (dATP, dGTP, dCTP, dTTP)
- Only synthesize DNA in 5'-3'
- Can usually correct mistakes as it goes
- Needs an RNA primer
- Also removes RNA primers and replaces with DNA bases
36
RNA primase
Creates the RNA primer with the 3' OH group that allows the DNA polymerase to start to synthesize the DNA
37
What is the purpose of the 3'OH group on the RNA primer?
It attacks the phosphate bond of the incoming nucleotide to initiate the synthesis
38
Leading strand
The strand that grows continuously toward the replication fork
39
Lagging strand
The strand that grows away from the replication fork, synthesized in segments
40
Okazaki fragments
The synthesized pieces of the lagging strand that are disconnected from each other
41
DNA ligase
Okazaki fragments are joined together after RNA primers have been replaced with DNA nucleotides
42
Trombone Model
As the DNA is being unwound, one strand is looped
43
How are DNA replication errors caught?
- DNA polymerase can detect mispairing of hydrogen bonding
- Removes incorrect nucleotide, and inserts correct one
44
Replication of circular DNA
Happens in most bacteria
- Single origin of replication, replication goes in both directions until they meet on the opposite side and fuse
45
Leading and lagging in circular DNA
Each replication fork has a leading strand and a lagging strand (two replication forks)
46
Linear DNA origins of replication
Eukaryotes have multiple origins of replication, multiple replication forks, and proceeds bidirectionally, when two replication bubbles meet, DNA ligase seals the gap in fragments
47
At the end of Linear DNA...
On the lagging strand, the primer is removed and leaves a section of template of DNA unreplicated, every time DNA is replicated one strand is shortened
48
Telomeres
End of chromosomes with repeated sequence, repeats thousands and thousands of times
49
Telomerase
Extends the ends of the chromosome by replacing missing nucleotides
- Ribonucleoprotein -> protein RNA complex
- Carries its own primer (template RNA)
- Reverse transcriptase activity
50
What types of cells is telomerase active
Stem cells
Germ cells (sex cells)
51
Hayflick limit
The maximum number of times that a cell can replicate before the telomeres become too short
About 50 times
52
Haploid
A cell with one copy of each chromosome
53
Diploid
A cell with two copies of each chromosome
54
Sister chromatids
Identical copies of chromosomes after DNA replication, held together at the centromere
55
Karyotype
A visual representation of one's chromosomes
56
Mitosis
For somatic cells to duplicate
57
Stages of Mitosis
Prophase, Prometaphase, Metaphase, Anaphase, Telophase
58
Prophase
Chromosomes condense, cell assembles mitotic spindle, centrosomes duplicate and migrate to opposite poles
59
Prometaphase
Nuclear membrane breaks down, microtubules of grow and shrink looking for chromosomes (attach to them)
60
Kinetochores
Two protein complexes that a centromere is associated with, one on each side of centromere, site of attachment for microtubule
61
Metaphase
Mitotic spindle lengthens and shortens pushing chromosomes toward center of the cell
62
Metaphase plate
The plane approximately half way between the two poles of the spindle where the chromosomes line up
63
Mitotic spindle
Made of microtubules, pull chromosomes apart
64
Anaphase
Centromere divides and kinetochore microtubules shorten, pulls chromatids apart, one to each pole
65
Telophase
Complete set of chromosomes arrives at spindle pole, microtubules of mitotic spindle break down, nuclear envelopes form around each chromosome set, chromosomes decondense
66
Cytokinesis in animal cells
The division of the parent cell into two daughter cells
- Ring of actin filaments form around inner face of cell membrane, which contracts and pinches the cytoplasm, divides it
67
Contractile ring
Forms at the equator of the cell, ring of actin filaments, contracts to pinch the cytoplasm of the cell
68
Cytokinesis in plant cells
Forms phragmoplast in middle of cell during telophase, guide vesicles with cell-wall components to middle of the cell, vesicles fuse to form a new cell wall in the middle (late Anaphase and Telophase), which then fuses with original cell wall
69
Phragmoplast
Overlapping microtubules that guide vesicles containing cell-wall components to the middle of the cell in plant cells
70
Cell plate
The new cell wall formed by fused vesicles in the middle of the parent plant cell
71
Meiosis
Produce daughter cells with half as many chromosomes as the parental cell, source of variability, one round of DNA synthesis, two rounds of cell division
72
By the end of meiosis I
The homologous chromosomes separate
73
By the end of meiosis II
The sister chromatids separate
74
Meiosis I, Prophase I
Homologous chromosomes pair with each other, chiasma occurs
75
Synapsis
When homologous chromosomes pair with each other
76
Bivalent
Two pairs of sister chromatids (tetrad)
77
Chiasma
Crossing over of DNA segments, exchanging genetic information, random, also helps hold bivalents together
78
Meiosis I, Prometaphase I
Spindles attach to kinetochores on chromosomes
79
Meiosis I
Results in homologous chromosomes separated, haploid cells, reductional division (# of chromosomes are halved)
80
Meiosis II
Sister chromatids separate, results in gametes, equational division, Cells in meiosis II have the same # of chromosomes at the beginning and the end
81
Mitosis vs. Meiosis
Suggests that meiosis evolved from mitosis, common ancestor of eukaryotes
82
Cytoplasmic division in female gametes
One cell with most of the cytoplasm, three polar bodies with only small amounts of cytoplasm, only the large one is yielded
83
Oocyte
Female egg
84
Cytoplasmic division in male gametes
Equal cytoplasmic division, most of cytolasm is eliminated
85
Sperm meeting egg
Restores diploid state and increases genetic diversity
86
Initiation of DNA repliaction
G1/S transition
87
Initiation of mitosis
G2/M transition
88
How are is the cell cycle controlled?
Cyclic activity of proteins and kinase
89
What are the proteins and kinases that control the cell cycle?
Cyclins and cyclin-dependent kinases (CDK)
90
Cyclins
Regulatory protein subunits of specific protein kinases
91
CDKs
Kinases that phosphorylate other proteins whose actions are necessary for the cell cycle to progress (protein is active), only active when bound to cyclin
- Different types that act at different steps of the cell cycle
92
Cyclin D and Cyclin E
Levels increase in G1 phase, activates transcription factors that lead to expression of DNA polymerase
93
Cyclin A
Activates CDKs that initiate DNA synthesis during S phase
94
Cyclin B
Increases during G2 phase, activate CDKs that initiate the breakdown of nuclear envelope, formation of mitotic spindle
95
DNA damage checkpoint
Checks for damaged DNA before the S phase (for example, breaks in DNA strand)
96
DNA replication checkpoint
Checks for unreplicated DNA at the end of G2
97
Spindle assembly checkpoint
Checks that all chromosomes are attached to the spindle before the cell continues with mitosis
98
If DNA is damaged by radiation
Activates a protein kinase that phosphorylates the p53 protein, which activates the transcription of some genes, one blocks the activity of the G1/S cyclin-CDK complex, freezes the cell at the G1/S transition, cell is able to repair damage
99
p53 is often called...
The guardian of the genome
100
Phosphorylated p53 also...
Stimulates the production of bax protein, represses transcription of Bcl-2 protein, shift the overall concentrations of of them, creating Bax-bax dimers, creating apoptosis
101
Apoptosis
Increase of Bax-bax dimers causes programmed cell death
102
Apoptosis in embryotic development
Hands initially look like a paddle until cells are killed, creating digits
103
Uses of apoptosis
Maintenance of tissue size, elimiation of specific cells, elimination of genetically damaged cells
104
Cancerous cells
Unable to undergo apoptosis, uncontrolled cell division
105
Oncogenes
Cancer-causing genes first discovered in viruses
106
Proto-oncogenes
Normal genes important in cell division that have the potential to mutate into oncogenes
107
Tumour suppressor gene
Opposite of oncogenes, inhibit cell division, p53 protein is an example
108
Metastasis
When cancer cells invade tissues
109
Angiogenesis
The blood vessel formation caused by cancer cells
