deck_691868 Flashcards
regulate passage through the cell cycle
cyclin-CDK complexes - G1: cyclin D -> pass restriction point- S-Phase: Cyclin E -> initiates DNA replication- M-phase (mitotic): Cyclin B -> promotes mitosis
Activation of CDK’s
cycling binding -> cyclin-CDK activation -> cyclin is degredated -> continuation of cell cycle
Interphase
Increases cell size, chromosomes and centrosomes replicate- G1 (longest phase) 2N, 2C- S (DNA Synthesis) 2N, 4C- G2 - 2N, 4CG1 and G2 are gaps between DNA replication and Mitosis
Mitosis/M-Phase
lasts a couple hours Prophase - Prometaphase - Metaphase - Anaphase A Anaphase B Telophase
Static cells
no longer dividing, post mitotic, long lived - in G0 ex. CNS cells, skeletal or cardiac muscle cells
Stable Cells
divide episodically to maintain tissue/organ structure ex. Periosteal/perichondreal cells, smooth muscle cells, endothelial cells, fibroblasts
Renewing Cells
display regular mitotic activity, daughter cells will either differentiate of remain as stem cells- Differentiating cells may be lost from the body- Slowly renewing cells (may increase in size) – smooth mm of hollow organs, fibroblasts in uterine wall, lens epithelial cells, slow growing tumor cells- Rapidly renewing cells – blood cells, epithelial cells of skin, mucosal lining of GI tract, tumor cells
Prophase
replicated chromosome condense due to phosphorylation of histones; spindles begin to assemble
Prometaphase
abrupt break down of nuclear envelope (phosphorylation of nuclear lamins
Metaphase
- chromosomes line up and kinetochore microtubules on each chromosome attach to spindle
Anaphase A -
kinetochore microtubules depolymerize/get shorter pulling chromatids apart
Anaphase B
- spindle poles push apart pulling chromatids apart
Telophase -
new nuclear envelopes form and contractile ring forms
classes of microtubules in a mitotic spindle
1) Astral (unattached) radiate from MTOC to cortical cytoskeleton – acts as anchor (probably actin)2) Polar from centrioles to equator3) Kinetochore from centrioles to kinetochores of condensed chromosomes
Mitosis and meiosis differences
Diploid Cells -> 2 diploid Daughter CellsDiploid cell -> 4 haploid cells-1 cell division-2 cell divisions-Both have 1 S phase-No pairing of homologous chrom.’s in prophase-synapsis of homologous chromosomes in prophase-Non recombinant in prophase-Recombination b/w sister chromatids-Sister chromatids separated in metaphase-Sister chromatids remain together during metaphase 1 and seperate in metaphase 2-Centromeres divide at anaphase-centromeres divide at anaphase 2 not 1-Conservative process (daughter cells identical to parent)-promotes variation
Meiosis in males
even distribution of cytoplasm among cells
Meiosis in females
uneven distribution of cytoplasm b/w ovum and polar bodiesbegins as fetus then arrests (in prophase1)begins again in pubertyarrests again at menopause
First meiotic division
DNA content 4C -> 2C and chromosome # is 46 (2N) -> 23 (1N)Prophase I • Leptotene – condensation, assembly of lateral elements of SC• Zygotene – assembly of central elements of SC• Pachytene – homologous recombination• Diplotene/diakinesis – female – decondensation, transcription especially of rRNA: translation especially of egg specific proteins
Second meiotic division
DNA content 2C -> 1C; chromosome # 23 -> 23 (1N)Just like mitosis
Mechanisms to mix genes
- Independent assortment of maternal and paternal homologos - meiotic div. I- Crossing over - meiotic prophase I
bivalent
tetrad or four chromatids the way chromosomes line up during metaphase 1 of meiosis
