Cell Cycle Division Flashcards
Cell Cycle Def.
Process by which cells divide passing their DNA onto genetically identical daughter cells
Consequences of faults in DNA replictation
Chromosome Anomalies (mutation), inherited disease and cancer
G0 in cell cycle
Optional non-replication phase. Differentiated cells tend to remain in this phase
G1 Cell Cycle (10 hrs)
A period of cell growth in preparation for cell division. All cell components excluding chromosomes are duplicated
S (synthesis-phase) Cell Cycle (5 hrs)
DNA (chromosome) replication occurs. A second double helix is formed
G2 Cell Cycle (3-4 hrs)
Resting phase before cell division. Checks chromosomes for replication error and repairs are made
Mitosos (2hrs)
Dividing of cell into identical daughter cells. Daughter cells recieve 1 of each chromosome
Cytokenisis
Daughter cells form and split from eachother
Mitosis Stages
Prophase, ProMetaphase, Metaphase, Anaphase + Telophase and cytokinesis
Prophase Outline
Chromosome containing 2 sister double helixes condenses and becomes visible. Bipolar spindles develop
Prometaphase
Nuclear envelope dissolves. Chromosomes migrate to equatorial plate (metaphase plate)
Metaphase
Fully condensed chromosomes exist at metaphase plate. Kinetochore microtubule of aster poles are attached to centromeres
Anaphase
Centromere splits and chromosome pairs are pulled to opposite sides
Telophase
Chromosomes at poles recondense, nuclear membrane reforms and cytoplasm begins to split
Cytokenisis Outline
Cytoplasm fully splits into 2 identical daughter cells
Centrosome Def.
Form cell poles, microtubule organisation centre. Polar fibres grow out
Kinetochore Def.
Protein structure at centromere attaches chromatids to spndle fibres via kinetochore microtubules
Centromere Def.
DNA sequence necessary for cell segregation during division. Chromatids without centromeres won’t be separated by spindle fibres pulling them apart (as they couldn’t attach), thus won’t be passed onto daughter cells
Meiosis Def.
Produces haploid cells (gametes)
How many times does a cell divide by meiosis
2
Stages of Meiosis (I and II)
Prophase I, Metaphase I, Anaphase I, Telophase & cytokinesis I. Prophase II, Metaphase II, Anaphase II and Telophase & Cytokinesis II
Differences at metaphase mitosis and meiosis
In meiosis parental and maternal homologs associate and stand at metaphase plate in bivalent formation. In mitosis parental and maternal homologs don’t associate and stand signally at metaphase plate
Number of rounds of DNA synthesis in both mitosis and meiosis
1
Differences in mitosis and meiosis
cell divides once in mitosis and twice in meiosis, parental & maternal homologs associate in meiosis and don’t in mitosis, recombination is abnormal in mitosis but frequent in meiosis, daughter cells differ (haploid) in meoisis and are identical (diploid) in mitosis
2 Ways Diversity Is Created in Meiosis
Recombination and Independent Assortment
Recombination Def.
Breakage of the DNA duplex in 1 maternal and 1 paternal chromatid + joined at ends. DNA is transferred (none lost or gained)
Non-Disjunction
When recombination accidentally happens in mitosis and DNA sequences are lost
Independent Assortment Def
Spindle fibres pulls 2 chromatids towards pole. With each chromatid having an equal chance to be pulled a specific pole
Chiasmata DEf.
Same function as centromere acts as a crossing over point between homologs. Holds homologs together until Anaphase I. Lach of chiasmata may result in incorrect chromosome number in cells
Where in meiosis to oocytes stop before puberty
Prophase 1
Name of cell gametes form from in females
Ooginium to
primary oocyte
Name of cell gametes form from in males
Spermatotangium and primary spermocyte
Polar body function in gamete formation
Get rid of spare set of chromosome
Gamete cell in females
Ovum
Gamete cell in males
Spermatoza
Allele Def.
Copy of a gene. Vary by their DNA base sequence
Polymorphism
In populations genes have many alleles
GTA and GTB genes
Stimulates glycotransferes which glycosates proteins in proteins and lipids on cell membrane. Forming A and B antigens
What would result in heterozygous GTA and GTB
Co. Dominance AB blood type
GTA transfers
N-acetylgalactosamine
GTB Tranfers
Galactose
GTO genes
Doesn’t activate an enzyme
Human Inherited Disease
Genetic (DNA) defects. Genotype effects Phenotype
Monogenic Defects Def.
Disease carried by dominant/recessive gene. Follows simple Mendelian pattern
Polygenic Defects
Several gene interactions cause disease. Non-Mendelian
Euchromatic Def.
Mainly C-G pairs + more transcriptionally active
Heterochromatin
Mainly A-T pairs and less transcriptionally active
