Ch. 17-18 Flashcards
Gene Expression, Mitosis and Meiosis (203 cards)
1
Q
gene expression
A
the process by which information encoded in DNA directs the synthesis of proteins, or RNAs that are not translated into proteins and instead function as RNAs
2
Q
transcription
A
-the synthesis of RNA using a DNA template
-DNA is transcribed into RNA (same language)
-it starts and stops at specific sequences
3
Q
translation
A
-the synthesis of a polypeptide using the genetic information encoded in an mRNA molecule
-RNA is translated into protein (different language; change of language from nucleotides to amino acids)
4
Q
what bases does DNA use?
A
A, G, C, and T
5
Q
what bases does RNA use?
A
A, G, C and U
(an RNA ‘U’ pairs with DNA ‘A’ during transcription)
6
Q
what is the function of DNA in protein coding genes?
A
for protein coding genes, DNA serves as a template to produce a single strand messenger RNA (mRNA)
7
Q
what does mRNA carry, and where to?
A
mRNA carries the genetic information to the ribosome
8
Q
what occurs in the ribosome after mRNA carries the genetic information there?
A
the information is translated into proteins
9
Q
how is transcription and translation different in bacteria?
A
in bacteria, transcription and translation are not separated into separate compartments, and they can occur simultaneously
10
Q
where do eukaryotes export mRNA to and from, for translation?
A
eukaryotes must export the mRNA from the nucleus to cytoplasm for translation
11
Q
pre-mRNA
A
-before the mRNA leaves the nucleus it starts out as pre-mRNA
-the pre-mRNA has certain regions removed, a cap is added to the 5’ end and additional ‘A’ nucleotides added to the 3’ end before it leaves the nucleus as a mature mRNA
12
Q
primary transcript
A
the initial RNA transcript from any gene before it is processed; also applies to RNAs that are not translated into protein
13
Q
template strand of DNA
A
-used to generate the mRNA
-during transcription the two strands of DNA separate, and only one of the two strands is used as the template for the mRNA
-for any gene, the same strand always serves as the template strand
-different genes on the same chromosome can use opposite strands of DNA as the template strand
-the mRNA is synthesized in the 5’ to 3’ direction, and it is antiparallel to the template strand
14
Q
coding strand
A
-aka the nontemplate strand
-the nontemplate strand has the same nucleotide sequence as the mRNA, except that T is substituted for U
15
Q
The Genetic Code
A
-there are only 4 bases in DNA and multiple nucleotides must be combined together to specify the different amino acids
16
Q
triplet code
A
a genetic information system in which a set of three-nucleotide-long words specify the amino acids for polypeptide chains
17
Q
codons
A
the mRNA nucleotide triplets
18
Q
how was the genetic code determined?
A
by making synthetic mRNAs and combining them with ribosomes, amino acids, and other components in a test tube
-ex: an RNA molecule with only U (UUUUUUUUUUUU) would produce a polypeptide with only phenylalanine (PhePhePhePhe)
19
Q
characteristics of the genetic code
A
-the genetic code is REDUNDANT, more than one codon is used for most amino acids
-the genetic code is NOT AMBIGUOUS, one codon codes for only one amino acid
20
Q
AUG codon
A
-codes for methionine
-the start signal for translation
21
Q
UAA, UAG, and UGA codons
A
-do not code for an amino acid
-they are the stop signals for translation
22
Q
reading frame
A
-each mRNA will have three possible frames that can be translated into amino acids
-only one strand is used, called the reading frame
-generally begins from the first AUG in the mRNA sequence
23
Q
the genetic code is universal
A
-the genetic code applies to all organisms
-same code used in bacteria, plants, and people
-implies that all life on earth had a common ancestor
-a useful feature for molecular biologists
24
Q
RNA polymerase
A
-the enzyme that links ribonucleotides into a growing RNA chain during transcription, based on complementary binding to nucleotides on a DNA template strand
-does not need a primer, unlike DNA polymerase
-works in a 5’ to 3’ direction
-unwinds the DNA as it goes to expose the template strand
25
promoter
the site where RNA polymerase attaches and begins transcription
26
terminator
a specific sequence in bacteria that signals the end of transcription (termination is different in eukaryotes)
27
transcription unit
the stretch of DNA that is transcribed into RNA
28
the 3 phases of producing an RNA:
1. initiation
2. elongation
3. termination
29
downstream
the direction of transcription (the termination sequence is downstream from the promoter)
30
upstream
the opposite direction of transcription
31
initiation of transcription
-in bacteria, RNA polymerase binds to a specific sequence in the promoter
32
transcription factors
-other proteins in eukaryotes that bind that bind to the DNA first
-typically have a DNA binding domain and a protein interaction domain
33
general transcription factors
-a protein that binds to DNA to initiate the transcription of genetic information into messenger RNA, for eukaryotes
-poly A signal sequence
34
sigma factor
-a protein in bacteria/prokaryotes that is necessary for the start of transcription
-GC rich terminator sequence
35
transcription initiation complex
when RNA polymerase forms a complex with the transcription factors
36
RNA polymerase II
used to transcribe mRNA (eukaryotes have three RNA polymerases)
37
TATA box
-the many promoters in eukaryotes that contain a specific sequence TATAAAA, to which transcription factors bind in order to establish the transcription initiation complex
38
Pribnow box
-a six-nucleotide sequence of TATAAT that is a vital part of the promoter site on DNA for transcription to occur in bacteria/prokaryotes
39
start point
-the site where transcription actually begins
-the promoter consists of DNA sequences dozens of nucleotides upstream from the start point
40
elongation of transcription
-RNA polymerase untwists the DNA, exposing about 10-20 nucleotides at a time
-RNA nucleotides that are complementary to the DNA template are added to the 3' end of the growing RNA molecule
41
termination of transcription in bacteria
-the terminator sequence in the DNA is transcribed into RNA, and the newly formed RNA forms a structure that causes the polymerase to fall off the DNA
-the mRNA in bacteria doesn't need to be processed and translation can begin
42
termination of transcription in eukaryotes
-the RNA polymerase passes through a specific sequence in the DNA that creates a polyadenylation signal (AAUAAA) in the pre-mRNA molecule
- 10-31 nucleotides downstream of the polyadenylation signal proteins that associate with the newly formed pre-mRNA cut it free from the RNA polymerase
43
extensive processing of pre-mRNA in eukaryotes
-before the pre-mRNA can leave the nucleus it undergoes extensive processing that alters both ends of the RNA and cuts sequences out of the middle
-the 5’ end of the pre-mRNA receives a 5’ cap, which is a modified guanine nucleotide
-a special enzyme adds 50 – 250 adenine nucleotides to the 3’ end. This long stretch of As is called a poly-A tail
-the 5’ cap and poly-A tail protect the mRNA from degradation, are used to export the mRNA form the nucleus, and help to attach ribosomes to the 5’ end of the RNA
44
Untranslated Regions (UTRs)
the regions of RNA that are not translated (not all of the RNA nucleotides will be translated into amino acids)
45
RNA splicing
-most eukaryotic genes and the RNA transcripts produced from them have long stretches of nucleotides that are not translated into protein
-the sequence of DNA nucleotides that codes for a polypeptide are not contiguous, but are split into regions
-the 5’ UTR and 3’ UTR are included in exons, even though they are not translated into proteins
46
introns
-the noncoding regions of nucleotides that lie between coding regions
-aka intervening sequences
47
exons
the regions of nucleotides that are expressed (usually translated into protein)
48
splicing
the process in which intervening sequences (introns) are cut out of the pre-mRNA (primary transcript)
49
splicesosome
-a large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron, releasing the intron, and joining the two adjacent exons
-contains several small nuclear ribonucleoproteins (snRNPs)
50
ribonucleoproteins (snRNPs)
each snRNP contains a small nuclear RNA (snRNA) that can act as a catalyst in the splicing process
51
ribozymes
-are RNA molecules that function as catalysts (therefore not all biological catalysts are made of protein)
-some organisms only use snRNAs to catalyze splicing without using any proteins
52
why can RNAs operate as enzymes?
-because they can adopt specific three dimensional shapes, and the bases contain functional groups that can interact with other molecules
53
what gives RNA a high degree of specificity?
the ability to form complementary bonds with other nucleic acids gives RNAs a high degree of specificity
54
alternative RNA splicing
-a process that creates different mRNA molecules from the same primary transcript, depending on which RNA segments are treated as exons and which as introns
-multiple proteins can be produced from the same gene (with alternative splicing different, but related proteins can be made from the same gene)
55
domains
-discrete structural and functional regions that proteins can have (ex: a DNA binding domain, or an active site for an enzyme, or a kinase domain)
-different exons can code for different domains
56
how can alternative splicing produce proteins with different functions?
by adding or removing specific domains
57
Prokaryotes versus Eukaryotes
-cellular location: cytoplasm (prok) vs nucleus (euk)
-AT rich promoter: Pribnow box (prok) vs TAT box (euk)
-proteins aid in RNA polymerase binding: sigma factor (prok) vs general transcription factors (euk)
-no mRNA modification, translation immediately occurs after mRNA synthesis (prok) vs extensive mRNA modifcation occurs prior to transport out of nucleus (euk)
58
what does translation bring together in order to make a protein?
mRNA, rRNA, and tRNA
59
mRNA
carries the genetic information from the DNA
60
rRNA molecules
are ribozymes that are integral parts of ribosomes where translation occurs
61
tRNA
converts the codons in the mRNA to the proper amino acid in the polypeptide
62
tRNA molecule
-a tRNA molecule is a short, single strand of RNA that adopts a specific shape, containing three loop domains
-one of the loops contains a triplet anticodon that is complementary to the codon in mRNA
-each tRNA molecule with a specific anticodon carries a specific amino acid
63
anticodon
complementary to the codon in mRNA
64
aminoacyl-tRNA synthetases
-link the correct amino acid to the correct tRNA
-there are 20 different aminoacyl-tRNA synthetases, one for each amino acid
65
active site of the aminoacyl-tRNA synthetase
-fits only a specific combination of amino acid and tRNA
-this molecular recognition ensures that the correct amino acid is associated with the correct tRNA
66
what are ribosomes made of?
-rRNA and protein
-each ribosome is made of two subunits, a large subunit and a small subunit
-each subunit contains one or more rRNA molecules
-the rRNA molecules are ribozymes and carry out the main functions of the ribosomes
-the proteins support the function of the ribozymes
67
ribosomes
-are essentially large ribozymes
-because there are so many ribosomes in a cell, rRNA is the most abundant type of RNA in the cell
-also have entry sites for the mRNA and exit tunnels for the polypeptide
68
P site, A site, and E site
the 3 locations that ribosomes contain for tRNAs to bind to an mRNA
69
P site
holds the tRNA that is attached to the growing polypeptide
70
A site
holds the tRNA attached to the next amino acid to be added to the polypeptide
71
E site
the exit site for the prior tRNA that has incorporated its amino acid already
72
3 phases of translation
1. initiation
2. elongation
3. termination
(like transcription)
73
what 3 things are brought together during translation initiation?
a small ribsomal subunit, an mRNA, and an initiator tRNA carrying Met
74
translation initiation in bacteria vs eukaryotes
-in bacteria, the small ribosomal subunit can bind the mRNA and tRNA in any order
-in eukaryotes, the small ribosomal subunit binds the 5' cap of the mRNA and then scans along the mRNA until it finds the start codon (AUG). then the initiator tRNA hydrogen bonds to the start codon
75
translation initiation complex
-once the mRNA and tRNA are in place on the small ribosomal subunit, the large ribosomal subunit binds to create the translation initiation complex
-this step requires an input of energy, which comes from the hydrolysis of GTP (very similar to ATP)
-initiation factors help to assemble the complex
-the initiator tRNA sits in the P site of the ribosome
76
initiation factors
other proteins that help to assemble the translation initiation complex
77
elongation factors
other proteins necessary for elongation and helps elongation to occur
78
translation elongation
-the codon in the A site of the ribosome base pairs with the appropriate tRNA (this step requires an energy input, GTP hydrolysis, which ensures the accuracy and efficiency of codon recognition)
-the energy input (GTP hydrolysis) moves the mRNA through the ribosome
-a peptide bond forms between the carboxyl group on one amino acid (in the P site) and the amino group on the next amino acid (in the A site)
-the tRNA in the A site moves to the P site moves to the E site and is released
-empty A site to receive next tRNA
79
peptide bond
-a covalent bond that forms between the two adjacent amino acids and the growing polypeptide is attached to the tRNA in the A site
-rRNA molecules in the ribosome catalyze the peptide bond
80
N-terminus and C-terminus
-the Met amino acid is at the N-terminus of the polypeptide
-the last amino acid added to the polypeptide chain is at the C-terminus
-polypeptides are always listed in order from the N-terminus to the C-terminus
-the codons for the amino acids at the N-terminus of a polypeptide are found at the 5' end of a molecule
81
release factor
-binds to the codon when a stop codon enters the A site of the ribosome
-is a protein, shaped like a tRNA
-promotes the hydrolysis of the covalent bond between the amino acid and the tRNA sitting in the P site of the ribosome, freeing the polypeptide
82
translation termination
-stop codon on mRNA in A site
-release factor into A site
-release polypeptide chain
-release mRNA
-release ribosomal subunits
-release uncharged tRNAs
[hydrolysis of two additional GTP molecules breaks apart the ribosomal complex; parts are recycled to be used again]
83
polyribosome
the whole complex of many ribosomes found on one mRNA molecule
84
post-translational modifications
-the polypeptide begins to fold into its secondary and tertiary shapes as it is being synthesized
-after synthesis, a polypeptide may undergo modification: (add sugars, lipids, or phosphate groups to specific amino acids; enzymes can remove one or more amino acids, particularly from the N-terminus; enzymes may cleave the polypeptide into multiple pieces)
85
chaperonin
a protein that assists with protein folding
86
signal peptide
a sequence of about 20 amino acids at or near the N-terminus of a polypeptide that targets it to the endoplasmic reticulum or other organelles in a eukaryotic cell
(other kinds of signal peptides for other organelles in the cell are recognized after the polypeptide has completed synthesis from a free ribosome in the cytoplasm)
87
signal recognition particle (SRP)
binds to the signal peptide and carries the ribosome to the ER so that the polypeptide is inserted into the ER lumen
88
mutations
are changes to the nucleotide sequence of DNA
89
point mutation
-a change in a single nucleotide pair in a gene
-can result in three difference classes of mutations
90
the 3 different classes of mutations
1. silent mutations
2. missense mutations
3. nonsense mutations
91
silent mutations
-occur when a nucleotide-pair substitution results in a codon that codes for the same amino acid in the polypeptide
-there is no functional change in the polypeptide
92
missense mutations
-occur when a nucleotide-pair substitution results in a codon that codes for a different amino acid in the polypeptide
-sometimes doesn't affect the protein function very much
sometimes changing one amino acid significantly impairs the function of the protein
-sometimes results in a protein with improved function because the new amino acid improves upon the previous amino acid
93
when would a missense mutation not affect the protein function much?
-if the location of the amino acid in the protein is not in a critical spot
-or if the new amino acid may have properties very similar to the old amino acid and can function in its place (ex: changing Lys for Arg, which are both positively charged)
94
when would a missense mutation significantly impair the function of the protein?
-if the change occurs in a critical location, such as the active site of a protein
-if the new amino acid is very different from the old amino acid (ex: changing Lys for Phe, a hydrophilic to a hydrophobic change)
95
nonsense mutations
-occur when a nucleotide-pair substitution creates a stop codon and terminates a polypeptide prematurely
-almost always produce nonfunctional proteins
96
insertions
a type of mutation when there are additions of nucleotide pairs in a gene (can be single or many nucleotide pairs)
97
deletions
a type of mutation when there are losses of nucleotide pairs in a gene (can be single or many nucleotide pairs)
98
frameshift mutation
-when inserting or deleting nucleotide pairs alter the reading frame, which subsequently alters all of the amino acids that follow the insertion or deletion (lots of missense mutations)
99
mutagens
-are physical and chemical agents that interact with DNA in ways that cause mutations (ex: x-rays, UV light, chemicals that mimic nucleotides, chemicals that insert into DNA and distort the DNA structure)
-are usually carcinogenic
100
carcinogens
-cancer causing chemicals
-usually mutagenic
101
the central dogma
genetic information flows in one direction only, from DNA to RNA to protein, meaning that the information encoded in DNA is transcribed into RNA, which is then translated into a protein
DNA--->RNA--->protein
102
functional RNAs
rRNA, tRNA, and miRNA
103
when are genes turned "on"?
when they are transcribed and the mRNA is translated into protein
104
when are genes turned "off"?
when they are not transcribed
105
how does regulation of gene expression enable cells to respond to environmental conditions?
-all organisms must regulate which genes are expressed at any given time
-genes are turned on and off in response to signals from their external and internal environments
-enables cells to maintain internal conditions within a narrow range (homeostasis)
106
homeostasis
maintaining internal conditions within a narrow range
107
constitutively expressed
-some genes are always "on"
-the presence of the protein or RNA is essential for the function of the cell (ex: rRNA, tRNA, actin, tubulin, enzymes for glycolysis and cellular respiration, etc.)
-the amount of the RNA or protein stays at a fairly constant level in the cell
108
how does regulation of gene expression allow cells to efficiently control cellular resources?
-bacterial cells don't waste energy making tryptophan, if it is available in the environment (no need to go through transcription and translation to produce enzymes necessary to make tryptophan)
-in multicellular organisms, cells have specific jobs, requiring specific proteins (each cell type has the same DNA content, but uses different sets of genes to generate cell specific proteins)
109
tryptophan
an essential amino acid that the body needs to function properly but cannot produce on its own
110
bacterial operons
a cluster of functionally related genes can be coordinately controlled by a single "on-off" switch
111
operator
-the "switch", or segment of DNA usually positioned within the promoter
-sequences of nucleotides between the promoter and the transcriptional start where active repressors can bind
112
operon
the entire stretch of DNA that includes the operator, the promoter, and the genes that they control
113
repressors
proteins that can inhibit transcription
114
trp operon
-a group of genes in bacteria that are transcribed together to produce enzymes that synthesize the amino acid tryptophan
-anabolic metabolism
-repressible operon
-is ON when tryptophan is absent
-is OFF when tryptophan is present
115
repressible operon
-is one that is usually on
-binding of a repressor to the operator shuts off transcription
-ex: trp operon
116
inducible operon
-is one that is usually off
-a molecule called an inducer inactivates the repressor and turns on transcription
-ex: lac operon
117
lac operon
-is inducible
-contains genes that codes for enzymes used in the hydrolysis and metabolism of lactose (when lactose is present a bacteria will turn on these genes in order to digest the lactose)
-catabolic metabolism (break apart lactose)
-is OFF when lactose is absent
-is ON when lactose is present
118
lac repressor
-by itself, the lac repressor is active and switches the lac operon off
-the presence of lactose inactivates the repressor, turning the lac operon on
119
beta-galactosidase
enzyme that binds to lactose and breaks it down into glucose and galactose (encoded by lacZ gene)
120
permease
a transmembrane transporter protein that allows lactose to permeate/flood into the cell (encoded by lacY gene)
121
cyclic AMP (cAMP)
-a small, hydrophilic molecule that acts as a second messenger, or cellular signal, in many biological processes
-high cAMP means low glucose or low energy
122
abundant lac mRNA synthesized (high operon expression) occurs with:
low glucose, high lactose
123
little lac mRNA synthesized ("leaky" gene expression) occurs with:
high glucose, high lactose
124
operon "off" with:
-low/absent glucose, low/absent lactose
-or high glucose, low/absent lactose
125
heterochromatin
highly packed, genes within this structure are usually not expressed
126
euchromatin
loosely packed, genes within this structure are more active
127
histone acetylation
-acetyl groups are attached to an amino acid in histone tails
-opens up chromatin structure and promotes transcription
128
DNA methylation
-the addition of methyl groups to certain bases in DNA
-can condense chromatin and reduce expression (ex: methyl cytosine in eukaryotes, methyl adenine and cytosine in prokaryotes)
-can cause long-term inactivation of genes in cellular differentiation
129
eukaryotic transcriptional regulation
-RNA requires the assistance of transcription factors to initiate transcription
-general transcription factors are essential for the transcription of all protein-coding genes
-a few bind to the TATA box within the promoter
-many bind to proteins , including other transcription factors and RNA polymerase II
130
control elements
-segments of noncoding DNA that serve as binding sites for transcription factors, which help regulate transcription
-eukaryotic genes generally have multiple
-can be located near the promoter (proximal) or at a distance (distal) from the promoter
131
enhancers
-for genes that are not expressed all the time, high levels of transcription depend on the presence of additional, specific transcription factors
-some of these transcription factors bind to enhancers, specific sequences of DNA, which can be distantly located from the promoter
-can be located upstream, downstream, or within an intron
-the DNA is bent, allowing the transcription factors bound to the enhancers to interact with the transcription initiation complex and RNA polymerase
132
activators
activate transcription
133
differential gene expression
the expression of different genes by cells with the same genome
134
post transcriptional regulation
after an mRNA is produced a cell has additional mechanisms to control the amount of protein produced
135
microRNAs (miRNAs)
-are short RNA molecules that can bind to 3' UTR of other mRNAs
-can inhibit protein translation by causing the degradation of the mRNA or preventing translation at the ribosome
136
differentiation
-the process by which a cell or group of cells becomes specialized in structure and function
-during development signals between cells activate specific transcription factors that begin the differentiation process
137
Myoblasts
are cells determined to form muscle cells and produce large amounts of muscle-specific proteins
138
MyoD
a “master regulatory gene” that encodes a transcription factor that commits the cell to becoming skeletal muscle
139
polycistronic mRNA
-a molecule that encodes multiple proteins, typically two or more, on a single strand
-bacterial mRNAs
140
plasticity of cells
"flexibility" of turning genes on/off and responding to conditions of environment
141
the cell cycle
-is an ordered sequence of events in the life of a cell, from its origin in the division of a parent cell until its own division into two
-during the cell cycle, all of the DNA must be copied and split into two separate cells
142
cell division
-is the reproduction of cells
-one cell divides into two daughter cells, each containing an identical copy of the genetic material (DNA)
-occurs during M phase of cell cycle
-ensures that both daughter cells receive exact copies of the genetic material
143
mitosis
is the division of the genetic material in the nucleus
144
cytokinesis
-is the division of the cytoplasm, which usually follows immediately after mitosis
-there are exceptions: sometimes mitosis occurs without cytokinesis
145
phases of the cell cycle
-M phase
-Interphase
146
M phase (mitotic phase)
-includes both mitosis and cytokinesis
-very short, only about 10% of the cell cycle time is spent in M phase
147
interphase
-is much longer than M phase (about 90% of the cell cycle)
-characterized by cell growth and replication of genetic material
148
3 parts of interphase
-cells that are actively cycling through the cell cycle have 3 different parts of interphase:
1. G1 or the first gap phase
2. S or the DNA synthesis phase
3. G2 or the second gap phase
-cells that are not actively cycling are in a non-dividing state called G0 phase
149
genome
-is a cell's complete complement of DNA
-it includes both the coding and non-coding regions of DNA
150
coding regions
are those regions that encode the genetic information for protein or RNA
151
non-coding regions
do not encode for protein or RNA
152
chromosome
a very long DNA molecule and its associated proteins
153
chromatin
is the complex of DNA and proteins that makes up chromosomes
154
what is the genomic organization in prokaryotes?
prokaryotes have one chromosome that is arranged in a circle
-can have plasmids
155
plasmids
smaller circles of DNA that carry certain genes
156
what is the genomic organization in eukaryotes?
-have multiple chromosomes that are linear in structure
-each eukaryotic species has a characteristic number of chromosomes (humans have 46)
157
how does the degree of chromosome packaging within the nucleus change during the cell cycle?
-during G1, S, and G2 the chromosomes are not packed as tightly (allows proteins to access the DNA for transcription and replication)
-during M phase the chromosomes condense, they become more tightly packed, before they separate into daughter cells (the image we typically see of chromosomes is when they are condensed during this phase)
158
S phase
each chromosome is replicated (copied) during the S phase and then held together
159
sister chromatids
after the S phase there are two copies of each chromosome that are joined together called sister chromatids
160
cohesins
proteins that hold sister chromatids together
161
sister chromatid cohesion
the process by which sister chromatids are held together by cohesin proteins
162
centromere
each chromosome contains a centromere, a region containing specific DNA sequences where the 2 chromatids are the most closely attached
163
arm of chromatid
the part of the chromatid on each side of the centromere is referred to as the arm of the chromatid
164
sister chromatid separation
during mitosis the 2 sister chromatids are separated into the 2 daughter cells
165
mitosis
depends on the function of the mitotic spindle
166
mitotic spindle
-an assemblage of microtubules and associated proteins that is involved in the movement of chromosomes during mitosis
-dynamic (changes during mitosis)
-starts at the centrosome which is located adjacent to the nuclear envelope in the cytoplasm
-during mitosis the two centrosomes move away from each other
-each centrosome forms one pole of the mitotic spindle
-spindle microtubules grow out from centrosome towards the opposite centrosome
-some spindle microtubules do not attach to the kinetochores of the chromosomes
167
centrosome
microtubule organizing center
168
centrioles
-animals have a pair of centrioles in the centrosome, but are not required for mitosis
-plants don't have them
169
interphase
the centrosome duplicates, including the centrioles, and both centrosomes stay near the nucleus
170
aster
-are radial arrays of short microtubules
-forms at each centrosome
171
kinetochore
-a structure of proteins associated with specific sections of chromosomal DNA at the centromere
-each sister chromatid has a kinetochore
-the two on each chromosome face away from each other
172
kinetochore microtubules
when spindle microtubules attach to the kinetochores of each chromosome
173
polar microtubules
unattached microtubules from each spindle pole can overlap each other
174
five phases of mitosis
-Interphase
-Prophase
-Prometaphase
-Metaphase
-Anaphase
-Telophase
175
G2 of interphase
-centrosomes duplicate
-chromosomes duplicated during S phase (can't see them because they haven't condensed yet)
-nucleolus and nuclear envelop are present
-growth phase for the cell
176
prophase
-beginning of mitosis
-chromosomes start to condense
-nucleolus disappears
-mitotic spindle starts to form (centrosomes move away from each other, asters form)
-nuclear envelop is still intact
177
prometaphase
-nuclear envelope breaks down
-chromosomes are even more condensed
-kinetochores form
-spindle microtubules enter the nuclear area (can attach to kinetochores; chromosomes attached to microtubules begin to move back and forth; some microtubules do not attach to kinetochores and form polar microtubules; both kinetochores on each chromosome may not be attached to microtubules yet)
178
metaphase
-centrosomes are at opposite poles
-the chromosomes align at the metaphase plate
-the kinetochores of each chromosome are attached to kinetochore microtubules coming from opposite poles
179
metaphase plate
is an imaginary structure located at a plan midway between the two poles on which the centromeres of all the duplicated chromosomes are located
180
anaphase
-begins when the cohesin proteins holding the sister chromatids together are cleaved, releasing the two chromatids from each other (each chromatid is now a chromosome)
-liberated chromosomes move away from each other toward the two spindle poles
-the cell elongates as the polar microtubules lengthen
-each spindle pole has a complete set of chromosomes
181
telophase
-a nuclear envelope forms around each collection of chromosomes
-spindle microtubules depolymerize
-chromosomes become less condensed
-nucleolus reforms
-mitosis is complete: two identical nuclei have formed
-need cytokinesis to divide the cytoplasm
182
cytokinesis
division of the cytoplasm
183
cleavage
animal cells use actin microfilaments and myosin during this process
184
cleavage furrow
a shallow groove that appears on the cell surface that aligns with the metaphase plate
185
myosin motor proteins
cause the microfilament ring to contract to form the cleavage furrow, during cytokinesis
186
cytokinesis in animal cells
-microfilaments form a ring just beneath the plasma membrane
-this ring contracts to form the cleavage furrow
-continued contraction of the microfilament ring deepens the cleavage furrow until the cell pinches in two
187
cytokinesis in plant cells
-different process than animal cells
-vesicles from the Golgi move along microtubules to the metaphase plate
-vesicles coalesce and produce the cell plate
-vesicles carry cell wall material
-cell plate grows until it connects with the plasma membrane
188
how do the chromosomes move?
-motor proteins at the kinetochore pull the chromosomes along the microtubules
-motor proteins at the spindle poles pull the microtubules toward the poles
-microtubules also shrink
189
motor proteins function
-they move the poles apart
-motor proteins between the overlapping polar microtubules cause the microtubules to slide past each other pushing the poles apart
-motor proteins on the astral microtubules also help to pull the poles apart
190
binary fission
-"division in half"
-asexual reproduction of single cell eukaryotes (yeast, amoebas, etc.), still use the process of mitosis
-also refers to asexual reproduction in bacteria (bacteria are small and hard to visualize, don't know as much about how they divide, do not use mitosis)
191
cell cycle rate
-some cells divide very quickly (cells of developing embryo, yeast, rapidly dividing human cells like intestinal cells, etc.)
-some rarely divide (liver, kidney, lung cells: only divide in response to damage to replace the lost cells)
- and some do not divide (neurons and muscle cells)
192
cell cycle control system
a cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle
193
checkpoint
a control point where stop and go-ahead signals can regulate the cell cycle
194
G1 checkpoint
-is a restriction point
-once past the G1 checkpoint the cell will progress all the way through the cell cycle
195
anchorage dependence
is the requirement that most animal cells must be attached to a substratum in order to initiate cell division
196
density-dependent inhibition
the phenomenon observed in normal animal cells that causes them to stop dividing when they come into contact with one another
197
cancer cells
-are cells that have escaped the normal signals that regulate the cell cycle
-no density-dependent inhibition or anchorage dependence
-when grown in culture they don't need growth factors
-divide indefinitely (as long as they have nutrients, they are "immortal")
198
tranformation
a process that converts a normal cell to a cancer cell
199
benign tumor
a mass of abnormal cells with specific genetic and cellular changes such that the cells are not capable of surviving at a new site and remain at the site of the tumor's origin
200
malignant tumors
-are cancerous tumors containing cells that have significant genetic and cellular changes and are capable of invading and surviving in new sites
-can impair the functions of one or more organs
201
metastasis
the spread of cancer cells to locations distant from their original site
202
treating cancer
-cut it out with surgery
-damage the DNA with radiation (cancer cells can't repair their DNA as well as normal cells)
-chemotherapy uses drugs that prevent proliferative cells from dividing (doesn't only hit cancer cells)
-immunotherapy uses a person's own immune system to fight cancer
203
epigenetic phenomena
-DNA methylation and histone acetylation are examples
-refers to changes in gene expression that occur without altering the underlying DNA sequence
