CBG 222 Flashcards
Cell cycle is divided into
Interphase
Nuclear divisison
Cytokinesis
Interphase consist of:
G1, S, G2 & G0
G1 - protein synthesis & growth, cellular content except chr. duplicates, preparation of dna repl. ( 10hrs)
S - DNA replication, chromosome replicated by cell (9 hrs)
G2 - Space for organelles & protein for mitosis to be made. The cell doubles check the duplicated chromosome for error. (4 hrs)
G0 - Resting phase ( nerve cells)
Mitosis is the
production of 2 diploid daughter cells with the same DNA by copying their chromosomes.
Stages in Mitosis
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
How many type of cell division and are:
Two
Mitosis & Meiosis
Cell cycle is a
reg pattern of events a dividing cell undergoes
2 succ div in Meiosis are:
Meiosis 1 (Reduction)
Meiosis 2 ( Division)
Meiosis 1 contains
I P M A 1
Prophase 1 has 5 phases:
Leptotene
Zygotene
Pachytene
Diplotene
Diakinensis
Prophase 1 phases
Leptotene - chromosome condenses
Zygotene -synapsis occurs to form bivalent which consist of tetrads
Pachytene - crossing over occurs to form chiasma
Diplotene - h. chromosome start to seperate but remain attached at chiasma
Diakinensis - h. Chrm continue to seperate but chiasma moves to end of the chromosome
Metaphase 1 and Anaphase 1
Met 1 - h. Chrms line up on d equatorial plate
Met 2 - h. chrms move to opp poles of the cell.
Spermatogenesis is divided into 3 phases:
Spermatogonial ( mitosis)
Spermatocyte ( meiosis)
Spermatid ( spermiogenesis/sperm maturation)
Spermiogenesis phase:
Golgi
Cap
Acrosome
Maturation
Life cycle of sperm
Spermatogonia to
P. spermatocyte ( At d end of mitotic division, spermatogonial phase) to
S. Spermatocyte ( After the end of the Ist meiotic division, as they enter prophase of meiosis 2). to
2 spermatids (At the end of meiosis 2). to
Sperm
Life cycle of ova
Oogonia to
P. oocyte ( Become At prophase 1 of meiosis 1). to
S. oocyte & polar body ( Begin meiosis 2 but stop at metaphase 2) to
Fertilized egg and polar body
Microsporogenesis is the
formation of 4 haploid microspores by meiosis on angiosperm; the formation of pollen and male gametophyte.
Importance of meiosis
Prod. of gametes
Red. in Chrm no.
Maint. of chrm no in somatic cells
Prod. of variation
Spermatogenesis takes about how many days & how many are produced
Takes about 74 days
300M cells are produced every day
Hormones involved in Oogenesis
FSH
LH
Estrogen
Progesterone
Eggs can be into 2 categories:
1) prop. of yolk to cytoplasm of d ovum
2) distribution of yolk granules/platelets in d cyt. of d ova/egg.
Egg type according to prop. of yolk to cytoplasm
• Microlecithal eggs : alecithal / oligolecithal / miolecithal
E.g eggs of amphioxus, marsupials & eutherian mammals
2) Mesolecithal eggs : medialecithal eggs.
E.g eggs of many amphibians, ganoid fishes, sharks, diploid
3) Macrolecithal / Polylecithal eggs.
E.g eggs of teleost fishes, gymnophiona, reptiles, birds, monotremes
Egg types according to distr. of yolk
Homolecithal / Isolecithall eg Amphioxus, many invertebrates & mammalians eggs
Centrolecithal e.g many insect $ arthropods eggs
Teleolecithal eg birds, reptiles, amphibians, fishes & monotreme eggs
Forms of fertilization
Isogamy
Anisogamy/ Heterogamy
Cortical reaction is
a process initiated during fertilization by d release of cortical granules from d egg to prevent polyspermy
