This document discusses embryology and cell division. It begins by defining embryology as the study of developmental processes from a single cell to established organ structures. This occurs through embryogenesis in the first 8 weeks and fetal development from 9 weeks to birth. The document also discusses meiosis, which reduces cells from diploid to haploid and alters germ cell shape, allowing for fertilization and zygote formation. Meiosis is significant because it produces haploid cells, reduces DNA amounts, and generates genetic variability through crossovers during chiasma formation.

2. 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.

3. 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

4. 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

5. CELL DIVISION
Interphase – Between
 G1;1 to several hrs
 Respond to growth factors
 S; 6-8 hrs
 DNA replication
 G2; 2-4 hrs
 Preparing for division

6. Mitosis: (1 – 2hrs)
 Prophase – Before
 Metaphase – After
 Anaphase – So much
 Telophase – End of relationship.

8. 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 1
Meiosis-2 (HOMOTYPICAL)

10. SIGNIFICANCE OF MEIOSIS
1. Haploid number of chromosomes
2. Half the amount of DNA
3. Genetic Variability
1. Cross overs
2. Random distribution

11.  Crossovers
 Chiasma formation

12. THANK YOU