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The total DNA(genetic information)contained in an organism or a cell is

regarded as the genome. Thus, thegenome is the storehouse of biologicalinformation.

It is includes and the DNA inmitochondria ,and chloroplasts.

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A chromosome is an organized structureof DNA and protein that is found in cells.

It is a single piece of coiled DNAcontaining many genes, regulatoryelements and othernucleotidesequences. Chromosomes also contain

DNA-bound proteins, which serve topackage the DNA and control itsfunctions.

http://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Genehttp://en.wikipedia.org/wiki/Regulatory_sequencehttp://en.wikipedia.org/wiki/Regulatory_sequencehttp://en.wikipedia.org/wiki/Genetic_sequencehttp://en.wikipedia.org/wiki/Genetic_sequencehttp://en.wikipedia.org/wiki/Genetic_sequencehttp://en.wikipedia.org/wiki/Genetic_sequencehttp://en.wikipedia.org/wiki/Regulatory_sequencehttp://en.wikipedia.org/wiki/Regulatory_sequencehttp://en.wikipedia.org/wiki/Genehttp://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/DNA

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In eukaryotes, nuclear chromosomes arepackaged by proteins into a condensed

structure called chromatin. This allowsthe very long DNA molecules to fit intothe cell nucleus. The structure ofchromosomes and chromatin varies

through the cell cycle.

http://en.wikipedia.org/wiki/Chromatinhttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Cell_cyclehttp://en.wikipedia.org/wiki/Cell_cyclehttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Chromatin

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In the nucleus of each cell, the DNAmolecule is packaged into thread-likestructures called chromosomes.

Each chromosome is made up of DNAtightly coiled many times around proteinscalled histones that support its structure.

Each chromosome has a constrictionpoint called the centromere, whichdivides the chromosome into twosections, or arms.

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The short arm of the chromosome is labeledthe p arm. The long arm of thechromosome is labeled the q arm.

The location of the centromere on eachchromosome gives its characteristic shape,and can be used to help describe thelocation of specific genes.

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There are four types of chromosomes basedupon the position of the centromere.

Metacentric : In this type of chromosomethe centromere occurs in the centre and allthe four chromatids are of equal length.

Submetacentric : In this type ofchromosome the centromere is a littleaway from the centre and thereforechromatids of one side are slightly longerthan the other

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Acrocentric : In this type of chromosome thecentromere is located closer to one end ofchromatid therefore the chromatids on

opposite side are very long.

Telocentric : In this type of chromosome thecentromere is placed at one end of the

chromatid and hence only one arm. Suchtelocentric chromosomes are not seen inhuman cells.

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Mutation: Any change or random error in

a DNA sequence

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-Mutations can also occur in body cells,and while its not

passed on to the offspring, can impairthe functioning of thecell and can cause problems for theindividual (example:

cancer)

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1.Point Mutation: a change in a single

base pair in DNA -A change in a single nitrogen base can

change the entire

structure of a protein because a changein a single amino acidcan affect the shape of the protein.

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Frameshift Mutation: a type of mutation inwhich a single base is added or deletedfrom DNA

-This new sequence would then betranscribed into mRNA. But the mRNAwould be out of position by one base. As aresult,every codon after the deleted base would

be different. This mutation would causenearly every amino acid in the proteinafter the deletion or addition to bechanged

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Deletion: A large section of achromosome can be deleted resulting inthe loss of a number of genes.

Duplication: In this mutation, some genesare duplicated and displayed twice onthe same chromosome.

Inversion: chromosome becomesorientated in the reverse of its usualdirection

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Translocation: part of

the chromosome breaks off and attaches

to another

- Few chromosome mutations are passed

on to the next generation because the

zygote usually dies. In cases where thezygote survives, it is often sterile and thus

incapable of producing offspring.

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-Any agent that can cause a

change in DNA is called amutagen.Mutagens include high energyradiation, chemicals, and even hightemperatures.

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