Cell Bio

Maddie Hempel p.3

Fertilization & Develpoment


During the process of fertilization the Acrosome enzymes dissolve the eggs protective covering and allows entrance to the nucleus, then the gametes join creating the diploid. which restores the # of chromosomes and forms a membrane around the egg & sperm. The zygote is a fertilized egg with a diploid set of chromosomes. An embryo is a fetus early developing organism.

Internal vs. External Fertillization

External is the process of gametes fusing outside the body of a female. This can happen to water breeding fish, amphibians,frogs etc. Internal prevents scattering of gametes outside environmental exposure, the gametes are short lived.
The Morula is a solid ball of cells, Blastula is a fluid filled hollow sphere and gastrulation is several 100 cells growing before mitotic divison.

Different kinds of phases

Prophase 1- are chromosomes lined up at tetrads that pair bonds to non sister chromatids that exchange genetic info though crossing over at any location. Humans have 2-3 crossovers per chromosomal pair when spindle fibers form.
Metaphase1- Is the centromere attaches to spindle fibers and pulled to center, tetrads line up side by side.
Anaphase 1-Homologous chromosomes separate and move to opposite ends of cell. They will only receive 1 chromosome per homologous pair.
Telophase 1- The spindle is broken down the chromosomes uncoils and plasma divide. Each cell has only 1 pair.
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Meiosis is cell divisions that produce gametes eggs and sperm. They contain half the # of parent chromosomes. It involves cell division in 2 parts from prophase to telophase 1 and prophase to telophase 2. Meiosis phase 2 is similar to mitosis it separates sister chromatids into identical cells. 4 haploid cells are produced each with 1 chromosome from the pair.Meiosis also makes mistakes such as karyotype, nondisjunction, trisomy, monosomy and polyploidy.


At puberty the male hormones stimulate the release of Luteinizing hormone (LH) and Follicle stimulating hormone (FSH). LH produces testosterone it stimulates sperm production in the testes. Testosterone also produces secondary male characteristics such as sex organs, sperm, body hair, muscle mass, lower voice and growth of arms and legs. At puberty the female has FSH & LH hormones. FSH stimulates follicle surrounding the egg and the hormone estrogen. Estrogen cause secondary characteristics like organ growth, body hair, bone growth, broading hips, development of breast, buttocks, thighs and menstrual cycle.
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