Genetics Part II

MITOSIS – four phase process of cellular division (Prophase, Metaphase, Anaphase and Telophase) by which identical daughter cells are produced, this type of cellular division reproduces identical genetic material for the growth of vital organs and tissues.

MEIOSIS – is a multiphase process that is divided into two main parts, a reduction division by which haploid (n) daughter cells are created from diploid cells (2n), and an equalization division similar to mitosis. When gametes unite in fertilization a zygote is formed with combined and duplicated genetic material, if a canary sex cell has approximately +- 20 chromosome pairs it would have +-40 chromosome pairs after fertilization, meiosis reestablishes the (n) count to the new daughter cells produced to completes the life cycle. .

PROPHASE I

SYNAPSIS

The centrioles have migrated towards opposing poles and the duplicated chromosomes Are made visible and begin to align into homologous pairs.

MATERNAL CHROMOSOMES

CENTRIOLES

PATERNAL CHROMOSOMES

PROPHASE

“Crossover takes place”

Bivalents are formed and exchange of genetic material, which is responsible for genetic variability,

occurs.

METAPHASE I

The nuclear membrane disintegrates,

the bivalents separate and begin

to migrate towards the poles.

TELOPHASE I

The chromatid segment duplicates and the cell starts to divide and nuclear membranes for both cells begin to form.

TELOPHASE I

After the cellular membranes are formed two daughter cells have evolved with similar chromosome content, due to crossover it is not identical.

METAPHASE II

In this second phase the nuclear membrane once again dissolves and the microtubules activate. The tetrads align on the equatorial plate.

ANAPHASE II

The microtubules begin to contract and pull, the chromatids separate and

begin to migrate to opposing poles.

TEOPHASE II

The nuclear membranes are reformed and four daughter cells are formed each with haploid (n) number of

chromosomes..

GENOME

CHROMOSOMIC DNA

NUCLEAR MEMBRANE

Canaries have + - 40 pairs of chromosomes, 9 pairs of macro chromosomes including the 2 sex chromosomes WW&WZ , and the rest are micro chromosomes, aprox. 31 pairs

ANAPHASE I

The microtubules begin to pull the chromosomes by their centromeres and the bivalents are separated into

opposing poles, two diploid (2n)cells are formed.