EMBRYOLOGY Study of developmental process amazing integration of increasingly complex

phenomenon EMBRYOGENESIS (Organogenesis)

period of first eight (08) weeks from a single cell to establishing organ primodia.

FOETAL PERIOD from 9th week to birth in which differentiation

continues while foetus grows and gains weight.

REPRODUCTION OF CELLS

Meiosis and cyto differentiation Reduce number;diploid (46 ) to haploid (23) Alteration in shape of germ cells

Fertilization of spermatozoa and oocyte Zygote formation

Somatic cell: 23 pair or diploid chromosome

22 pair of matching chromosome “autosome”

One pair of “sex chromosome” XX--genetically female XY-- genetically male

Pairs not in proximity closer in meiotic division

CELL DIVISIONInterphase – Between

G1;1 to several hrs Respond to growth factors

S; 6-8 hrs DNA replication

G2; 2-4 hrs Preparing for division

Mitosis: (1 – 2hrs)

Prophase – Before Metaphase – After Anaphase – So much Telophase – End of relationship.

MEIOSIS (DECREASE IN NUMBER)Meiosis-1 (HETEROTYPICAL) Prophase

Leptotene Stage (RIBBON) Zygotene Stage (YOLKED TOGETHER) Pachytene Stage (THICKNESS) Diplotene Stage ( DOUBLE) Diakinesis Stage

Metaphase 1 Anaphase 1 Telophase 1Meiosis-2 (HOMOTYPICAL)

SIGNIFICANCE OF MEIOSIS

1. Haploid number of chromosomes2. Half the amount of DNA3. Genetic Variability

1. Cross overs2. Random distribution

Crossovers Chiasma formation

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