M2 Lecture 15,18, part of 20 Flashcards
- What are some functions/roles of actively dividing cells?
o Increasing population of single-celled organism
o Growth of multicellular tissue
o Asexual reproduction + replacement of cells lost to wear and tear
7.2 The Cell Cycle in Prokaryotic Organisms
In the 3-period cycle newly formed prok. Cell must:
Increase in size
Replicate circular chromosome
Move each of two daughter chromosomes into progeny cell during cell division
7.2 The Cell Cycle in Prokaryotic Organisms
What is binary fission?
: division into two parts
7.2 The Cell Cycle in Prokaryotic Organisms
Exlapin the 3 periods of the 3 period cell cycle:
o B period:
Daughter cells are formed, they grow during B period, initiate DNA synthesis
When nutrients = abundant, prokaryotic cells = no need for B period (b/c can grow quickly enough for it to divide cytoplasm as soon as DNA replication is complete + chromosomes are separated
o C period:
Once chromosomes = replicated, they separate to opposite ends of cell (poles)
o D period:
Membrane pinches together between them and 2 daughter cells are formed via binary fission
- 2 a Replication occupies most of the cell cycle in rapidly dividing prokaryotic cells
- Bacteria + Archaea: use DNA as what?
… as hereditary info then packaged into circular chromosome
7.2 a Replication occupies most of the cell cycle in rapidly dividing prokaryotic cells
Where are chromosomes located, what are they?
o Compacted in central region called nucleoid
- A chromosome is a long DNA molecule with part or all of the genetic material of an organism.
- 2 b Replicated chromosomes are distributed actively to the daughter cells in binary fission
- Bacterial chromosomes separate ____ to membrane dynamics and is linked to DNA replication
independantly
7.2 b Replicated chromosomes are distributed actively to the daughter cells in binary fission
What is the Origin of replication (ori)?
o specific region in middle of cell where replication of bacterial chromosomes begins @ specific region of DNA sequence
7.2 b Replicated chromosomes are distributed actively to the daughter cells in binary fission
Where is Ori located?
o Ori = located where enzymes for DNA replicated are located
7.2 b Replicated chromosomes are distributed actively to the daughter cells in binary fission
o Completion of ori duplication results in what happening?
two new origins migrate towards opposite poles while replication continues for rest of chromosome
7.2 b Replicated chromosomes are distributed actively to the daughter cells in binary fission
o Division of cytoplasm is accomplished by what?
Inward constriction of ring of cytoskeleton proteins
7.2 c Mitosis has evolved from an early form of binary fission
Is Prokaryotic mechanism of cell division effective? If so, why?
o b/c most prokaryotic organisms have single chromosome
Means: daughter cell receiving minimum one copy of chromosome= genetic information = complete
7.2 c Mitosis has evolved from an early form of binary fission
Is Eukaryotic mechanism of cell division effective? Why or why not?
o b/c genetic info = divided amongst linear chromosomes, each chromosome has much greater length of DNA
o Daughter cell fails to receive a copy of chromosomes = lethal
o Most of cell cycle eukaryotic chromosomes = contained within nuclear membrane
7.2 c Mitosis has evolved from an early form of binary fission
o Bacteria + archaea have (an or no?) internal membrane around nucleoid
What does this mean for the organisms?
require different cellular and chromosomal machinery for distributing chromosomes to daughter cells (mitosis)
7.2 c Mitosis has evolved from an early form of binary fission
What is the evolutionary advancement of binary fission?
How does this benefit the cell?
• Evolutionary advancement: ability to hold two newly created molecules of double-stranded DNA (chromatids) following DNA synthesis
o Enables cells to keep track of chromosomes and orient them relative to cytoskeleton and ensure distribution to daughter cells
7.2 c Mitosis has evolved from an early form of binary fission
• Main components of cytoskeleton (are/aren’t?) present in ancestral prokaryotic cells, there (is/isn’t?) evolution
are, is
7.2 c Mitosis has evolved from an early form of binary fission
in higher eukaryotes what happens to the nuclear membrane at time when chromosomes are distributed
it disintegrates and reforms around daughter cells
7.2 c Mitosis has evolved from an early form of binary fission
What does variation in miotic apparatus result in?
What is a miotic apparatus?
evolution
a temporary structure in a dividing cell that enables the chromosomes to move to the poles of the cell
- 3 Mitosis and the eukaryotic cell cycle
- Eukaryotes require what to be genetic copies of parent
daughter cells
- 3 Mitosis and the eukaryotic cell cycle
- What are the 3 interrelated systems to eukaryotic mitosis?
o 1. Master program = orderly + timely progression through cell cycle
o 2. Process of DNA synthesis replicates each DNA chromosome into near perfect copies
o 3. Structural + mechanical web of interwoven cables + motors of cytoskeleton separates daughter cells
- 3 a Chromosmes are genetic units divided by mitosis
- The hereditary information of eukaryote chromosomes is distributed where? What does this enable?
= distributed among DNA molecules
= o DNA combines with proteins for stability
o Assist in packaging during cell division + expression of genes
7.3 a Chromosmes are genetic units divided by mitosis
Differnce between haploid, diploid, and ploidy?
Haploid:
- Haploid= n chromosomes not in pairs (singular)
o Yeast can be both haploid and diploid
Haploid organisms/cells have only one set of chromosomes, abbreviated as n.
Diploid:
- 2 copies of each chromosome 2n
Ploidy:
- # of chromosome sets = ploidy
- 3 a Chromosmes are genetic units divided by mitosis
- Waht occurs Before cell divides in mitosis?
replication of DNA provides in given chromosomes produces 2 identical copies of DNA = chromatids
- 3 a Chromosomes are genetic units divided by mitosis
- Eukaryotes contain copies of each chromosome in where?
Are humans haploid of diploid?
nucleus
diploid
- 3 a Chromosmes are genetic units divided by mitosis
- What are chromatids?
= held together by proteins called cohesins
7.3 a Chromosomes are genetic units divided by mitosis
o During mitosis what happens to the sister chromatids?
o Each daughter nucleus receives what from parent?
= separated
= same genetic info as parent
7.3 a Chromosomes are genetic units divided by mitosis
What is chromosome segregation?
Equal division from cell division into daughter cells =
7.3 a Chromosomes are genetic units divided by mitosis
Precision + replication + segregation in cell cycle creates what?
Mutations during replication create what?
= group of cells known as clones
= cells of clone genetically similar but not identical
7.3 a Chromosomes are genetic units divided by mitosis
Single cell (zygote) is what?
parent cell
- 3 b Interface extends from one end of mitosis to the beginning of nest mitosis
- Information of new daughter cell marks the beginning of what?
- What is the first and longest stage
= (beginning of mitotic cell cycle)
= interphase
7.3 b Interface extends from one end of mitosis to the beginning of nest mitosis
Interphase compromises of 3 phases of cell cycle, what are they?
1 G1 phase
• Cell carries out function and grows
• Only phase of cell cycle that varies in length (others are uniform)
• Pace of division depends on G1
• Stage where cell types stop dividing (shunt from G1 known as G0 phase)
2 S phase
• DNA replication and chromosome duplication
G2 phase
• Brief gap in cell cycle where cell growth continues, and cell prepares for mitosis and cytokinesis
- 3 b Interface extends from one end of mitosis to the beginning of nest mitosis
- During all stages of interphase what happens to chromosomes?
= are organized and loosely packaged within nucleus
- 3 b Interface extends from one end of mitosis to the beginning of nest mitosis
- Internal regularory controls what?
o Internal controls are vulnerable to what?
= each phase of cell cycle (successful completion before next) also regulates # of cycles
= cells, viruses, and signal molecules (hormone)
- 3 b Interface extends from one end of mitosis to the beginning of nest mitosis
- In interphase the appropriate suite of genes are expressed for what?
What happens to DNA during interphase?
= cell maintenance and metabolism
= DNA is replicated
7.3c After interphase, mitosis proceeds in 5 stages
Mitosis involves what sort of events? What happens during these events?
= Mitosis involves nuclear + cytoplasmic events
Nuclear:
In nucleus: normal gene expression decreases, DNA condenses and kinetochores = built up
Cytoplasmic:
- In cytoplasm = cytoskeleton prepares for partitioning of chromosomes
- 3c After interphase, mitosis proceeds in 5 stages
1. Prophase (before)?
a. Extended chromosomes replicated in interphase = condensed
b. Condensation packs long DNA molecules for division in mitosis
c. DNA compacted by winding double helix around small + charged protein to form nucleosome
d. Proteins = histones make up nuclear core
e. Short segment of DNA extends between one nucleosome and the next = linker
f. Solenoid = coiled structure of nucleosomes
g. During condensation = nucleus becomes smaller and disappears (shut down of RNA synthesis)
h. In cytoplasm, miotic spindle forms between two centrosomes during their migration to poles
i. Spindle = bundle of microtubules
- 3c After interphase, mitosis proceeds in 5 stages
2. Prometaphase (in-between)
a. End of prophase, nuclear envelope breaks down
b. Bundles of spindles of microtubules, grow from centrosomes @ opposing poles towards centre
i. Attach @ Centro mirror of chromosomes
c. Two sister chromatins held together by cohesin proteins
d. Complex of proteins (kinetochore) has formed on each chromatid @ Centro mirror
e. Microtubules bind to kinetochores = connection determine outcomes of mitosis b/c they attach sister chromatids of each chromosome to microtubules leading to opposite poles one big web
i. Microtubules that don’t attach to chores, overall, those from opposite poles
- 3c After interphase, mitosis proceeds in 5 stages
3. Metaphase
a. Spindle reaches final form; chromosomes move onto spindle alignment = metaphase plate
b. Chromosomes complete condensation, X shape (based on location of centromirror and length and thickness of chromatin arms)
c. When arms are assembled @ midpoint with two sister chromatids, metaphase leads to actual separation of chromatids
d. Only chromosomes with Centro mirror towards mirror have X shape
e. Chromosomes take on visible shape only when highly condensed
f. Karyotype = fully arranged condensed chromosomes
i. Very distinctive
- 3c After interphase, mitosis proceeds in 5 stages
4. Anaphase (back) (segregation of whores to opposing poles brothel style)
a. Sister chromatids separate and move to opposing spindle poles
b. Kinetochores move towards opposite poles = first sign of movement
c. Movement continues until chromatids (known as daughter chromosomes) reach two poles = segregation
- 3c After interphase, mitosis proceeds in 5 stages
5. Telophase (end) (pimp phase)
a. Spindle disassembles and chromosomes at each pole de-condense + return to extended state of interphase
b. Condensation proceeds= reapportion of nucleolus
c. RNA transcription resume + reformation of nuclear envelope around chromosomes @ each pole = two daughter nuclei
d. Cytoskeleton resumes normal responsibilities (not managing whores)
e. nuclear division is complete, cell has two nuclei
- chromosomes = composed of pair of nucleic acid backbones making up DNA double helix
- DNA molecules may attach to each other as sister chromatids
- B/C sister chromatids remain attached to each other following DNA synthesis, referred to as one chromosome
- Before replication, one chromosome is composed of one DNA double helix, after composed of two double helixes
o DNA replication increases amount of DNA in nucleus but not number of chromosomes
o During cell division, each of daughter cells receives one of sister chromatids
- 3 d cytokinesis completes cell division by dividing cell division of daughter cell
- What is Cytokinesis? What does it follow? What does it produce? During what phases does it occur?
= division of cytoplasm
= o Follows nuclear division stage of mitosis, produces two daughter cells containing one of daughter nuclei
o Begins during telophase or anaphase
7.3 d cytokinesis completes cell division by dividing cell division of daughter cell
o Completion of cytokinesis means what?
- Does this occur via same or different pathways?
= (2 new cells that have progressed to interphase)
= o Proceeds by different pathways
7.3 d cytokinesis completes cell division by dividing cell division of daughter cell
Animals + Fungi vs Plants in cytoplasmic division?
What determines cytoplasmic division?
Animals and fungi: cytoplasm cut into two parts
Plants: new cell wall (cell plate) forms between daughter nuclei and grows until it divides cytoplasm
= o Cytoplasmic division: determined by layer of microtubules @ formal spindle mid-point
= Furrowing: layer of microtubules @ formal spindle midpoint expands laterally until stretches between dividing cells
7.3 d cytokinesis completes cell division by dividing cell division of daughter cell
During furrowing, what does the developing layer consist of + what does this create?
How is furrowing powered? Results in what?
= • Developing layer = band of microfilament inside plasma membrane develops = creates belt in between layers
= • Powered by motor proteins = microfilament is constricted to help cell divide (belt tightens for division)
• Constriction = groove in plasma membrane (furrow) resulting in separation of daughter cells
7.3 d cytokinesis completes cell division by dividing cell division of daughter cell
• What is cytoplasmic division? Function?
= isolation of daughter nuclei in daughter cells + distributes organelles and other structures equally between daughter cells
7.3 d cytokinesis completes cell division by dividing cell division of daughter cell
o What is Cell plate formation?
• Vesicles contain components of what?
= Plant cells are walled: plane of cell division = important
Plate cell formation, layer of microtubules @ spindle mid point = organixing site by vesicles produced by ER and golgi complex
= cell wall
7.3 d cytokinesis completes cell division by dividing cell division of daughter cell
the fusion of vesicle walls results in what forming?
= formation of cell plate (stretching across former spindle mid point)
7.3 d cytokinesis completes cell division by dividing cell division of daughter cell
Vesicle membrane fuses with what to create what?
fuses with plate to form cell wall
7.4 Formation and Action of the mitotic spindle
What is the Mitotic spindle central to?
Made up of?
What does mitotic activity depend on?
= central to mitosis and cytokinesis
= Made up of microtubules and proteins
= Activity depends on changing patterns of organization during cell cycle
7.4 Formation and Action of the mitotic spindle
Microtubules are a major part of what phase?
When mitosis approaches what do the microtubules do?
= interphase cytoskeleton of euk. Cells
= Mitosis approaches = microtubules disassemble from interphase arrangements and reorganize into spindle (which grows until fills near entire cell)
7.4 Formation and Action of the mitotic spindle
• Reorganization of microtubules follows one of 2 paths. Describe.
follows one of 2 paths (depends on presence/absence of centrosome in interphase)
o One organized spindle formation = same with or w/o presence of centrosome
7.4 a Animals and Plants form spindles in different ways
Do Animal and protists have chromosomes? What extends from this cite? Describe this site.
o Have centrosomes: site near nucleus where microtubules go outward in all directions
Main microtubule organizing centre of cell, anchoring microtubule cytoskeleton during interphase and positioning cytoplasmic organelles
Contains pair of centrioles
• Important to mitotic spindle
• Function: generate microtubules needed for flagella/cilia (aka cell motility)
7.4 a Animals and Plants form spindles in different ways
- DNA replication in S phase?
- Prophase in M phase?
- Late prophase:
= centrioles in chromosome duplicate producing 2 pairs of centrioles
= : centrosomes separate into 2 parts
o Duplicated chromosomes (with centrioles inside continue to separate until they reach opposite poles)
o Movement of centrosomes = microtubules between lengthen and increase
= centrosomes = fully separated,
o microtubules extend between = large mass – early spindle
o when nucelar envelope breaks down @ end of prophase = spindle moves into region once occupied by nucleus and grows until it fits cytoplasm
o microtubules grow in length
o Asters = centrosomes at the spindle tip (from pole ends)
Separation = spindles ensure daughter cells receive pair of chromosomes
• No centrioles or centrosome present in flowering plants
7.4 a Animals and Plants form spindles in different way
Asters?
= centrosomes at the spindle tip (from pole ends)
7.4 b Mitotic Spindles can move chromosomes by a combination of two mechanisms
- Fully formed spindles @ metaphase = contain what?
o 1. Kinetochore microtubules?
Chromosome move toward poles via what?
o 2. non-kinetochore microtubules?
The Separation of chromosomes @ anaphase are a combo of what 2 groups?
= many microtubules (2 groups)
= Connect chromosomes to spindle poles
Chromosomes climb to poles via microtubules using motor proteins in kinetochores
Tubulin subunits of kinetochore microtubules disassemble when kinetochore climbs (microtubules shorten as a result)
Kinetochore microtubules do not move with respect to poles during anaphase
= motor proteins @ spindle poles pull kinetochore microtubules poleward (disassembly of microtubules into tubulin)
= Extend between spindle poles w/o connecting to chromosomes (form microtubule overlap)
Elongation of spindles = cell elongation in metaphase and anaphase
Pushing movement = produced by microtubules sliding over one another (overlap) powered by microtubule motors (ex of dynein movement)
= kineto and non-kinetochores
- 5 b Cell-Cycle checkpoints ensure accurate cell division
- Cell has control points aka what?
- 3 key checkpoints
What do they do?
Describe each?
= control proteins = cyclins
= (prevent next phase from occurring until current phase is carried out effectively)
- G/S1 Checkpoint:
a. Main point in cell cycle
b. Cell cycle arrest = cell stops proceeding through cell cycle if DNA is damaged
c. Primary checkpoint for extracellular reading for cell growth and division (hormone or growth factor absent = potential arrest) - G2/M checkpoint
a. Junction b/w G2 and M phases
b. Arrests occur if = DNA not replicated fully in S, DNA is damaged - Mitotic spindle checkpoint
a. Within M phase before metaphase
b. Assesses whether chromosomes are attached properly to mitotic spindle for proper metaphase plate alignment
c. Essential for production of daughter cells
d. One cell begins anaphase = irreversibly committed to completing M
- 5 c Cyclins and cyclin-dependant kinases are the internal controls that directly regulate cell division
- Regulation of cell = internal control system of protein cyclins and enzymes called
Activity of CDK =
Concentration of cyclins change in cell cycle (b/c of what?
Regulation of cyclin-CDK complexes activity are coupled with what ?
= cyclin-dependant kinases
o CDK = protein kinase that phosphorylates + regulates activity of target proteins
= DNA replication, mitosis, cytokinesis
Cyclin dependant b/c their activity depends on if they are bound to cyclin molecule
= synthesis and degradation), concentration of CDK = constant
= cell-cycle checkpoints
- 5 d External controls coordinate the mitotic cell cycle of individual cells with the overall activities of the organism
- Internal controls regulating cell-cycle = respond to what?
o Animals signal molecules?
o Plant signal molecules?
- External factors bind to what? what does this trigger?
o Effects what?
o Cell surface receptors in animals = recognize contact with molecules of extracellular matrix – results in what?
= signal molecules (from outside of dividing cell)
= peptide hormones, and growth or death factors
= growth hormones
= bind to receptors on cell surface, response = triggering of reactions inside of cell (often include adding phosphate to cyclin-CDK complexes – affects function)
= speed, slow, stop progress of cell division
= in inhibit division of cell (contact inhibition)
- 5 e Stem cells exhibit asymmetric cell division
- What is Asymmetric cell division
= producing twin daughter cells
7.5 f Most cells in multicellular body cannot divide indefinitely
- what is Cellular senescence?
- What are the 2 contributing factors?
= loss of constant division ability over time
= 1. DNA damage
- Telomere shortening
a. Telomere: repetitive DNA sequences added to end of chromosomes
b. Once telomere diminish to minimum length = cell division stops
- 5 g Cell-cycle controls are lost in cancer
- What are Cancer cells? What do they do to the CDK cyclin-system?
= mutations in variety of genes, many encode cyclin-CDK system- when mutated = oncogenes
o System breaks down = no more checkpoints, unlimited division
7.5h Some cells are programmed to die
- What is Apoptosis
o Initiation of cell death results from what?
o Can healthy cells undergo apoptosis? Why?
= programmed cell death
o Ancient mechanism common in mult. Euk.
= internal or external signals
= for specific functions (fingers result of web skin cell apoptosis)
8.1 Mechanism of Genetic Recombination
- Genetic variability in population allows populations to what?
o What is the source of variability in populations?:
o Diversity is amplified by what? What is this process called?
= evolve
= mutation in DNA sequence
= = amplified via shuffling of existing mutations in different combos: Genetic recombination
Genetic recombination = origin of sexual aspect
Without genetic recombination = asexual reproduction (clones)
- 1 Mechanism of Genetic Recombination
- Recombination requires what?
What is DNA?
DNA Recombination occurs between what regions?
What does Homology allow?
= o 2 DNA double helix
o Mechanism for bringing DNA into proximity + collection of enzymes for “cut, exchange, paste” DNA
= - DNA:
o Double helix
o Sugar phosphate backbones (winds)
Held together by strong covalent bonds
o Paired bases (ribs)
Pairs with partners via weak hydrogen bonds
• H bonds can be broken = separates DNA molecule = forms template for cell division replication
= regions of similar DNA base sequences
o Regions = homologous
= allows diff. DNA molecules to position and combine
o Homologous regions of DNA:
o Paired with enzymes that separate H bonds of one double helix + allows reassociation of bases with complimentary bases homologous (non-sister) chromatid
Involves cutting sugar-phosphate group and linking to non-sister chromatids
8.1 Mechanism of Genetic Recombination
What is one recombination event?
Cutting and pasting 4 DNA backbones
What is Sexual Reproduction?
What is an Evolutionary advantage to sexual reproduction?
= Produces offspring by male/female union (gametes)
o Meiosis produces gametes with half chromosome number
= : genetic shuffling of sex = unique offspring
