Chromosome:

 CHROMOSOME:

Chromosome

Definition:

A chromosome is a thread-like structure in the nucleus of the cell.

Nucleus:

The nucleus contains DNA and carries the genetic material of the cell.

History:

They were discovered by Waldeyer in 1876.

 

Word History:

A chromosome is the name given to these structures as they readily absorb dyes and become colored (Chromo=Colour and Soma= Body)

• Prokaryotic cells' chromosomes consist entirely of DNA and are not enclosed in a nuclear membrane.
• In Eukaryotic cells the chromosomes are found within the nucleus and are composed of chromatin material chemical DNA and protein.

Scientists have labeled them  nucleatide A, C, T, and G.

Code of gene:

Usually, a protein or a group of proteins though there are a few exceptions. In multi-celled creatures like ourselves Proteins, which are coded for by genes, interact with other proteins and molecules to make up living cells. Cells make up tissues, tissues make up organs, and organs ultimately make up entire living creatures.

 Individuals have different traits, in this case, differences in beak shape mainly because of differences, or mutations, in their genetic code. These differences can either cause changes in a specific protein shape (and therefore its function) or mutations can cause when or how much of a particular protein will be reproduced.

Structure of Chromosome:

You may have seen images showing DNA trapped inside a chromosome sort of like this. This is NOT how chromosomes hold their DNA. If you were to unravel a chromosome you would see that it’s made of a thread sort of like a spool of yarn. You see that that fiber is a collection of protein orbs called histones which are wrapped with a string-like structure. You find that this is the chain of DNA. It is extremely long - millions of nucleotides long and often contains hundreds of genes along its length. In this image, we're looking at a chromosome in its condensed yarn-like form but chromosomes are only packaged tightly like this when a cell reproduces. This structure helps with durability as the cell is splitting in 2. For most of a cell's life, however, chromosomes exist in a loose, noodle-like structure, along with other chromosomes safe inside the nucleus (or centerpiece) of a cell. In this image see an entire set of human chromosomes taken from a cell right as it was getting ready to reproduce. Your genome, the entire collection of genes that help make you who you are, is written across 23 pairs of chromosomes. That's 46 altogether. With very few exceptions, each cell in your body contains its own full copy of your chromosomes your entire genetic code.

Types of Chromosome:

Telomeres:

The terminal ends of chromosomes are called telomeres. which prevent two chromosomes from attaching to each other from their end.

Metacentric:

On the basis of the position of the centromere along the length, a chromosome may be called a metacentric (centromere located in the center).

Submetacentric:

Centromere is located slightly away from the center.

Acrocentric:

Centromere is located near the end.

Telocentric:

Centromere is located at an end.

Chromosome Organization:

Appropriately said as a metaphysic chromosome  that simply means chromosome looks very different in different stages of cell cycle like an interface they have appearance like these generally beads on string in prophase Things become more complicated and chromosome is now more densely packed whereas in metaphase the chromosome looks like that characteristic x-shaped structure so a different time point in the cell cycle chromosome would look very different so overall the appearance of chromosome is highly Dynamic just like you don't look similar when you are a teenager versus a young person or even a mature person chromosome doesn't look the same always so let's look at the level of chromosome organization at the simplest level we can see nucleosomes nucleosomes are combination of DNA and histone proteins and histone is wrapped around the histones are actually wrapped by the DNA histones are basic proteins which has lysine and Arginine like basic amino acids and they are found in the nucleus are canonical histones such as h3h4 h2a h2b they combine with each other forming dimers eventually that dimers associate forms tetramer and ultimately uh histone octamar is generated so each of these histones are repeated twice in an histone octoma so overall the octomar look like a ball and the DNA is wrapping around it so this is known as the nucleosomal DNA there are interaction between the histone and the DNA the DNA is negatively charged due to the presence of phosphate group and the histone is positively charged due to the presence of basic amino acids such as lysine and arginine so around 200 base pairs of DNA is wrapped around 1.6 left-handed super helical turns around these histone octomas this is called nucleosome or the basic unit of chromosome at the simplest organization the chromosome shows a beads on string appearance and majorly these beads on string structures are predominant in the interphase there are also other structures such as the 30 nanometer fiber the 13 nanometer fibers are bit more complicated and they are a bit more organized there are H1 histones which helps formation of these kind of 30 nanometer structure the most common model of 30 nanometer structure is the solenoid model and this is characterized by interaction between consecutive nucleosome here in this model any nucleosome n interacts with n plus one number of nucleosome there are also zigzag model it implies the interaction between alternate nucleosome that means in and N plus 2 and it doesn't interact with nplus 1 in this particular model.

Examples:

One member of each pair of your chromosomes came from your mother, and the other came from your father If you were to examine the 2 individuals of a pair you'd find that for the most part both contain the exact same genes in the exact same locations.  however, you would find slight sequence variations between them. These are the results of mutations. Most of these mutations happened long ago and have been passed down from parent to child for many generations. Others, however, are completely unique to you. These mutations occurred either in the sperm or egg which fused to make you or they occurred early on in your development making it into all or many of your cells as you matured. These unique mutations represent brand new genetic information - sequences of DNA that may have never been seen before in the history of the cosmos.

• .Human has 46 chromosomes in each somatic cell.
• .Potato has 48 chromosomes.
• .Fruit fly Drosophila has 8 chromosomes.