condensation – chromatids become evident (remember that each chromatid is
actually a chromosome even though we refer to the pair of chromatids as a
microtubules and kinetochore microtubules form
arrive on metaphase plate
are lined up on the metaphase plate
chromatids bound to kinetochore microtubule on opposite spindles
of the centrosome (and centrioles in some cases).
Ingredient for metaphase mitiotic spindles
1) Keep the chromatids paired until it is time to segregate.
2) Have unstable kinetochore microtubules that can sample the cytoplasm and only stabilize upon being captured by a kinetochore.
3) Give each chromatid a kinetochore with a geometry such that two kinetochore microtubules from the same spindle can't capture both chromatids of a chromosome.
4) Have a checkpoint at metaphase that senses when all the chromatids have been captured and only then allow the chromatids to separate.
How does cytokinesis happen in animals
actin and myosin, and it constricts and divides the cell
How does cytokenesis happen in plants
In plants – vesicles fuse to make cell membrane and cell plate, which eventually becomes the new cell wall.
• DNA begins to compact
• Synapsis: pairing of homologous chromosomes
• Chiasmata form, crossing over.
• Nuclear envelope breakdown
• Spindle fiber forms
• Microtubules attach to kinetochores (one per homolog not per chromatid)
• Chromosomes line up at metaphase plate held together by chiasmata.
• Separation of homologous chromosomes into separate cells.Note: each cell now has two copies (two chromatids) of each homologous chromosome - these chromatids are not identical because of crossing over.
Is telphase optional in meiosis?
Basically just like mitosis except that you have half the number of homologs.
When the pairs of chromsome dont seperate properly and you end up with less or more
When an egg with the extra chromosome joins with a normal sperm to make an embryo, the embryo will have three copies of chromosome 21.
What matters, the number or chromosomes or the ration?
Its the ratio of chromosomes that matter
If genes are linked; Dominant alleles are cis (alleles on same homologous chromosome)
trans (alleles on different homologous chromosomes)
Types of alleles
wild type: the predominant allele (>99% in a population)
Mutant allele: a change from the wild type of allele, typically the result of a recent mutation. Also can refer to alleles that cause disease.
Polymorphic: present >1% of population
*complex gene interactions
- interation between albino (Aa) locus and (Bb) locus
-1st locus determines something
- 2nd locus determines something else
*often results from genes involved in different steps of the same process/pathway
Gene: unit of heredity
Allele: Different gene flavour
Homozygous: Having two of the same allele
Hemizygous: gene missing from 1 chromosome
Heterozygous: Having two diferent alleles
Genotype: the set of alleles an organism
phenotype: the set of traits organism display
Linkage of alleles with crossing over
How is a gene defined?
By its location on the chromosomes
Measure of distance
-occurs at random parts of the chromosome
-depends on how far apart genes are on the chromosome
-measured of physical distance along the chromosome (Thomas Hunt Morgan)
* The more recombination the farther apart the genes are
Are genes on the same chromosome
Polygenetic or multigetic traits
Multiple genes contribute to a trait
ex: heart attack risk
-6 genes affect
-If each gene has a semidominatn alleles, 12 genetic risk level
Enviromental contributions to phenotype
Penetrance: % of individuals of a given genotype that show the phenotype at all
Expressitivity: The degree to which a phenotype is expressed (ex. shades at pink in a flower)
-Absence of O2
Generates NAD+glycolysis going
-lactic acid by product (or alcohol)
-never occurs in brain cells
Note: Gluconeogenesis: process by which intermediates of glycolysis/ citnic acid cylce ae used to form glucose.
-Intermediates can also--> COH fatty acids
---> amino acids/ purines- pyrimidines
Electron Transport Chain
1.NADH oxidized e-given to NADH-Q reductase - proton pumped
2.FADH oxided e- given to succinate dydrogenase - proton not pumped
3. e- go to ubiquinone--> cytochrome C reductase
4. e- go to cytochrome C---> cytochrome C oxidase - proton pumped -O2 e- acceptor- H2o +2H+
Purpose: set up "electochemical gradient"
*oxidation of enzymes--> conformation change-->trans H+
*Chlorophyll a- action center
*Chlorophyll b (max absorption blue 420nm/red 680nm
*ring attached to tail (inside thylakoid membrane)
Absorption spectrum- where pigment absorbs most light
Action spectrum- corresponds roughly to combined spectra of chlorophyll/ cartenoid
1. Pyruvate oxidized to a 2C acetyl group and CO2 released
2. Reduction of NAD+---> NADH+H+
3. CoA is attached
look at diagram
1. ATP invested, phosphate added
2. isomerization, ATP invested, phosphaleadded
3. Symmetry- split into 2 C3 atoms (63p)
4. 2x-63P oxidized 2 molecules NADH+H+ formed
5. P group transferred to ADP--> ATP (2x)
6. Isomenzation, loss of H2O (2x)
7. Transfer other phosphate to ADP--> ATP (2x) **substrate level phosphorylation
2ATP invested---4ATP made 2Pi invested
2(NADH+H+) 2(H2O) evolved * last step has LARGE delta G
Reduction: gain of electron
Oxidation: loss of electron
Oxidation of organic molecules decreased the number of C-H bonds
Tendency to gai/lose electrons is called redox potential
ex. NAD+ 2H--- +H+ (2H+ +2e-)
1. 6O2 combines with acceptor RUBp forming 6(3PG) (rubisco)
2. 6(36P) is reduced to 63P is 2 step rxn requiring 12ATP and 12 NADDH+12+
3. About 1/6 63P (2) used to make sugars- output
4. Remaining 63P (1) precessed to make RUMP
5. RUMP--RuBp with the use of ATP
3Stages: carbon fixation (1). Reduction and sugar production (2)(3)Regenration RuBp (4)(5)
*photorespiration: O2 instead od CO2--releases CO2 reduces net c fixed
Kinase: inhibits by high ATP
-Citnic Acid Ccle: 1st dehydrogenase: high NAD+ activates high NADH+H+ inhibits
-regulated by H+ gradient
Citric Acid Cycle
1. 2C acetlyl and 4C oxaloacetate combine-- 6C
2. Iso citrate oxidized, CO2 released NAD+ reduced
3. alpha-ketoglurate oxidized, NAD+ reduced, CO2 released