(a)+Chromosomes

All About **C h r o m o s o m e s **

**__Chromosomes__**

Chromosomes are coiled up strands of DNA. They are thread-like structures, freely floating inside the nucleus of a cell. Chromosomes also contain proteins, which help the coiling up of DNA, and help control the chromosomes’ functions. Trivia: The name "Chromosome" literally means "coloured bodies" because they are made up of tightly coiled DNA which scientists consider as colorful dyes used in research. Chromosomes (Chromo= Colour; Soma=body). Chromosomes are marked with basic dyes to identify which two original chromosomes participated in the translocation. The positions of the color boundaries on the chromosomes identify the breakpoints.The length of each chromosome varies between 10 000 to 1 000 000 nucleotides.”

Nucleotides: Nucleotides are molecules, that when combined, form the structural units of DNA and RNA (Nucleotide).

A nucleotide is the basic building block of nucleic acids. RNA and DNA are polymers are created by long chains of nucleotides. A nucleotide contains a sugar molecule that is attached to a phosphate group and a nitrogen-containing base. The bases used in DNA are adenine (A), cytosine (C), guanine (G), and thymine (T). Nucleotides carry the code for protein and enzymes as well as determine the genetic structure of life. They also transport and transform cellular energy and regulate enzymes. We would not have genetic codes if there were no nucleotides. Breakpoints: The location on a chromosome where a portion has broken off or is missing (Genetics).

In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.

Not all living things have the same chromosomes. Chromosomes can be either linear or circular depending on which organism they belong to. Prokaryotic cells in organisms such as bacteria, do not contain nuclei and have small, circular structures of chromosomes. On the other hand, Eukaryotic cells in humans, along with other animals and plants, contain linear chromosomes that are arranged in pairs.

All cells contain a nucleus that has a membrane around it. Inside the nucleus are chromosomes which are made from a molecule called deoxyribonucleic acid. This is commonly known as DNA. DNA is a very long molecule, and when it uncoils, it can be from 1.7 to 8.5 cm long ( Molecular Biology of the Cell, NCBI). However, these DNA strands are highly coiled to make it much shorter, and it also divided into lengths called chromosomes.

media type="youtube" key="DBI7IJWqv3g" height="390" width="640" In human nucleus, there are 23 pairs of chromosomes. There are 2 types of chromosomes: - Sex Chromosomes : chromosomes that contain specific traits in a human being which will determine one's sex. There are 1 pair of sex chromosomes in human nucleus. - Autosomes : any chromosomes other than sex chromosomes that contain all other hereditary information. There are 22 pair of autosomes in human nucleus 

**Chromosomes,cells and DNA**A

media type="file" key="Chromosomes Video for Website" width="360" height="270" Understanding the Structure of a Chromosome



**__<span style="font-family: 'Calibri','sans-serif'; font-size: 11pt;">Karyotype Definition: __**

<span style="color: #000000; font-family: 'Calibri','sans-serif'; font-size: 11pt; margin: 0in 0in 0pt;">A karyotype is a picture of human chromosomes arranged systematically in pairs. The individual cells are stained with a particular dye and photographed under a microscope. There are normally 23 pairs of chromosomes, which gives the total number of 46 chromosomes, and the 23rd pair is the Sex Chromosomes. Karyotypes are used to find any chromosomal problems, which can be found if the chromosones are different, missing or there are extra chromosones.

A karyotype is an observed characteristics (number, type, shape etc) of the chromosomes of an individual or species (karyotype). Chromosomes are analyzed by organizing them into a KARYOTYPE.
 * Another definition of a Karyotype:**

For example, Karyotypes of males and females are not the same. -Females have two large X chromosomes -Males have one large X and a small Y chromosome. (These are called sex chromosomes and are placed at the end of the Karyotype" Usual growths (such as birth defects) can be also partially associated with chromosome abnormalities.  For example, people, who have Down Syndrome have 21 pairs of chromosomes.  __**What can karyotypes determine:**__
 * <span style="direction: ltr; font-family: Calibri; font-size: 11pt; margin-bottom: 0px; margin-top: 0in; unicode-bidi: embed; vertical-align: middle;">Whether chromosomal problems have passed on from parents to there children
 * <span style="direction: ltr; font-family: Calibri; font-size: 11pt; margin-bottom: 0px; margin-top: 0in; unicode-bidi: embed; vertical-align: middle;">Whether chromosomal problem are causing a woman to miscarriage or keeping her from becoming pregnant
 * <span style="direction: ltr; font-family: Calibri; font-size: 11pt; margin-bottom: 0px; margin-top: 0in; unicode-bidi: embed; vertical-align: middle;">Whether chromosomal problems made a fetus stillborn
 * <span style="direction: ltr; font-family: Calibri; font-size: 11pt; margin-bottom: 0px; margin-top: 0in; unicode-bidi: embed; vertical-align: middle;">Whether chromosomes are the reason for a baby's birth defects or disabilities
 * <span style="direction: ltr; font-family: Calibri; font-size: 11pt; margin-bottom: 0px; margin-top: 0in; unicode-bidi: embed; vertical-align: middle;">If there is a suitable cure for a person's cancer
 * <span style="direction: ltr; font-family: Calibri; font-size: 11pt; margin-bottom: 0px; margin-top: 0in; unicode-bidi: embed; vertical-align: middle;">Whether an unborn baby is male or female (Male if there is a Y chromosone, female if there isn't)

__<span style="direction: ltr; font-family: Calibri; font-size: 11pt; margin-bottom: 0px; margin-top: 0in; unicode-bidi: embed; vertical-align: middle;">Uses of karyotypes __ <span style="direction: ltr; font-family: Calibri; font-size: 11pt; margin-bottom: 0px; margin-top: 0in; unicode-bidi: embed; vertical-align: middle;">- To study chromosomal aberrations <span style="direction: ltr; font-family: Calibri; font-size: 11pt; margin-bottom: 0px; margin-top: 0in; unicode-bidi: embed; vertical-align: middle;">- To study cellular function <span style="direction: ltr; font-family: Calibri; font-size: 11pt; margin-bottom: 0px; margin-top: 0in; unicode-bidi: embed; vertical-align: middle;">- To study taxonomic relationships <span style="direction: ltr; font-family: Calibri; font-size: 11pt; margin-bottom: 0px; margin-top: 0in; unicode-bidi: embed; vertical-align: middle;">- to gather information about past evolutionarty events

__**<span style="direction: ltr; font-family: Calibri; font-size: 11pt; margin-bottom: 0px; margin-top: 0in; unicode-bidi: embed; vertical-align: middle;">Sources: **__

Karyotype. Digital image. //Biology Activities//. Web. 26 Apr. 2011. [].

"Karyotype - Definition from Biology-Online.org." //Life Science Reference - Biology Online//. Web. 26 Apr. 2011. [].

"Karyotype Test." //WebMD - Better Information. Better Health.// Web. 25 Apr. 2011. [].

Pickering, W. R. "11.1 Variation and Inheritance." //Complete Biology//. Oxford: Oxford UP, 2000. 188-89. Print.

"What Is a Chromosome? - Genetics Home Reference." //Genetics Home Reference - Your Guide to Understanding Genetic Conditions//. Web. 25 Apr. 2011. [].

"Nucleotide - Definition from Biology-Online.org." //Life Science Reference - Biology Online//. Web. 28 Apr. 2011. <[]>. "Genetics Glossary." //Human Genetics Association of New Jersey (HGANJ)//. Web. 28 Apr. 2011. <[]>.

"Karyotype - Wiktionary." Wiktionary, the Free Dictionary. Web. 27 Apr. 2011. <[]>.