FERTILIZATION AND MATURATION

Exercise 2

Abigail A. Garcia, M.Sc.Department of Biological SciencesCollege of Science

FERTILIZATION

Direct interaction and fusion of two germinal cells which results in initiation of cleavage, gastrulation and species-specific development processes that characterizes each organism

A process in sexual reproduction that involves the union of male (sperm) and female (ovum) gametes (each with a single, haploid set of chromosomes) to produce a diploid zygote.

ASCARIS/ ASCARIS UTERUS

Parasitic nematode in intestine

Sperm cells enter the eggs in the genital tract even before final stages of oogenesis is completed

Transparent eggs – possible to study steps in maturation, fertilization and cleavage

2N-4

First polar body

Oogonium (2N)

Primary Oocyte (2N)

Secondary Oocyte (N)

Growth / Maturation

Meiosis I

Meiosis II

Second polar bodies

Ootid (N)Differentiation

ovulation

Arrest at metaphase I until stimulated by hormone

FertilizationNo Fertilization

degeneration MII continues

Arrest at metaphase II

UNFERTILIZED EGG

Absence of extensive membranes observed in fertilized eggs

Vacuolated cytoplasm, inconspicuos nuclei

PRIMARY OOCYTE

MATURATION STAGES

Sperm Penetration Stage

Pronuclear Stage

Fusion Stage

Early Cleavage

SPERM PENETRATION STAGE

Stage of Development: PRIMARY OOCYTE

Characteristics: Presence of small,

dense, and triangular SPERM HEAD

After penetration, become surrounded by a fertilization membrane and thick outer shell (chitinous shell)

Meiosis II continues after this stage

To the left, Stage of Development:

SECONDARY OOCYTE-First polar body-Sperm head -Female chromosomes at MD2

To the right, Stage of Development:

PRIMARY OOCYTE-Sperm head transforming-Female chromosomes at MD1-Presence of fertilization membranes

MATURATION STAGES

Sperm Penetration Stage

Pronuclear Stage

Fusion Stage

Early Cleavage

PRONUCLEAR STAGE

Oocyte has to complete maturation process

Male pronucleus appear as dense body near the center of egg

Presence of perivitelline space between egg and fertilization membrane

Stage of Development: OOTID

MATURATION STAGES

Sperm Penetration Stage

Pronuclear Stage

Fusion Stage

Early Cleavage

FUSION STAGE Male and female

pronuclei fuse following migration towards each other

Presence of two polar bodies; inner 2nd polar body and outer 1st polar body

Fusion of membranes resulting in a diploid zygote nucleus

Stage of Development: OVUM

MATURATION STAGES

Sperm Penetration Stage

Pronuclear Stage

Fusion Stage

Early Cleavage

EARLY CLEAVAGE STAGE

Diploid Zygote Entire cell dividing (differentiate

Telophase from Fusion stage) Observable phases of mitosis

PROPHASE

METAPHASE

ANAPHASE

TELOPHASE

FERTILIZATION AND MATURATION

Exercise 2

Abigail A. Garcia, M.Sc.Department of Biological SciencesCollege of Science