(a)	+Chromosomes+(Q+1-3)

media type="youtube" key="9kQpYdCnU14" height="315" width="560" //__**The structure of a chromosome : **__//

Chromosomes are built from many genes that are combinations of DNA molecules. They are found inside the nucleus in any living things. In Humans for example, there are 23 chromosomes that have the codes to creating a unique human being. Chromosomes are bonded into pairs because they got it from two parents. One chromosome is made from genes which made from DNA. Genes are bonded together to create a long strand that carries coded information that are the characteristic needed to grow a living thing. ("Chromatid")

**What do chromosomes do?**
The unique structure of chromosomes helps to tightly pack the DNA molecules together. Without such packaging the DNA molecules would be too long to fit into a cell. The total distance of all DNA molecules in a human cell, unwounded, is 6 ft., or 1.8m. Another function of the chromosomes is that it helps to maintain accurately the DNA information and structure inside cells during the process of cell division, a process essential for development and growth of organisms, when DNA is copied and distributed in the cell divisions.

**How are chromosomes inherited?**
In humans, each reproductive cell contains a copy of one chromosome. When two gametes (sperm and the egg) are joined, a chromosome from each gamete is also joined into one cell (that has got two chromosomes, one from each gamete). That cell then duplicates itself many times two create a human offspring with 23 sets of chromosomes in every cell. The process of meiosis cell division is vital in order for sexual reproduction in eukaryotic organisms. In this process, a parent cell will divide two times; the first division is meiosis 1 and the second is meiosis 2. There are a total of 10 phases, which are listed below:

Meiosis 1: prophase 1, metaphase 1, anaphase 1, and telophase 1 Meiosis 2: prophase 2, metaphase 2, anaphase 2, and telophase 2

In the first kind of division in meiosis, the number of cells is doubled but the number of chromosomes is not. This results in 1/2 as many chromosomes per cell.

The second kind of division is similar to the process of mitosis - where two daughter cells are produced which are identical to the parent cell. This type of cell division allows multicellular organisms to grow and repair damaged tissue, while meiosis on the other hand, is for sexual reproduction. In the second kind of division the number of chromosomes does not get reduced. The whole process of meiosis can be show in the diagrams below:





In addition, here is a video demonstrating the process of meiosis: media type="youtube" key="kVMb4Js99tA" width="425" height="350"

**Does every species have the same type of chromosomes?**
Chromosomes vary in shapes and numbers in different species. Humans along with some other animals and plants have chromosomes arranged in pairs (karyotypes) and exist within the nucleus of the cells. Most bacteria have one or two circular chromosomes.

A summative video on chromosomes:
media type="youtube" key="zf7tbymrv9o" height="315" width="420"

__// Karyotypes: //__ A Karyotype is the organization of a person’s chromosomes, usually in pairs, in descending order of size. A karyotype is valuable because someone can use it to detect chromosome abnormalities which in turn helps to pick up on diseases or malformations such as Down syndrome.



There are 46 chromosomes in total and two chromosomes paired up so there are 23 pairs of chromosomes. The number is assigned to the each pair of chromosome based on their sizes. //Autosomes come before sex chromosomes. Autosomes are normal since it determines your hair colors, eye colors, allergies. Sex chromosomes determine you’re sexuality either as X or Y. Healthy Human would have 44 autosomes and 2 sex chromosomes. //

Moreover each chromosome has different banding pattern. And near the center of the chromosome there is a constricted region which has a constriction, called a centromere. It divides the chromosomes in two parts; shorter arm is called the 'p arm' and the longer arm is called the 'q arm'.

**Gender of the individual:**

 * The individual is male if there are an X chromosome and a Y chromosome.
 * The individual is female if there are two X chromosomes.

Punnet squares:

**Species name:**

 * The number of chromosomes determines which species the organism belongs to.

Common examples: ( "Chromosome Numbers")

**Infected disorders or disease**

 * Disorders are identified if there is an unusual number of chromosomes in the individual.
 * Human karyotyping is mostly used to examine abnormalities or genetic disorders.

//It so // //It some cases, it can be unreliable as doesn’t show some of the following concepts: // //me cases, it can be unreliable as doesn’t show some of the following concepts: //
 * //Presence and Location of tiny mutations //
 * //The number of genes in a chromosomes //
 * //Individual DNA genes //

Citations:
 * //Presence and Location of tiny mutations //
 * //The number of genes in a chromosomes //
 * //Individual DNA genes //

"Chromatid." // Simple English Wikipedia //. Wikimedia Foundation. Web. 01 June 2012. . "Chromosome Numbers in Different Species." // General and Medical Genetics //. Colorado State University. Web. 01 June 2012. ."Telomere - What Are Telomeres?" // News Medical //. Web. 01 June 2012. <http://www.news-medical.net/health/Telomere-What-are-Telomeres.aspx>. "Telomere Biology and the Risk of Cancer." // National Cancer Institute //. Web. 01 June 2012. [].

Karyotype. N.p., n.d. Web. 29 May 2012. <http://www.genome.gov/glossary/?id=114>.

// Biology : Meiosis - Cell Division. Dir. Zammsblog. YouTube. YouTube, 03 Aug. 2009. Web. 01 June 2012. []. //

// "Inheriting Chromosomes." Inheriting Chromosomes. Web. 01 June 2012. []. //

// "Mitosis and Meiosis." Http: //faculty.clintoncc.suny.edu. Web. 1 June 2012. [].//