GENEs n Cromosomes

8/11/2019 GENEs n Cromosomes

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GENES

and

CHROMOSOMES

Desi Novaria030 06 059


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GENES

The word pangenesis is made from the Greekwordspan(a prefixmeaning "whole", "encompassing") andgenesis("birth") orgenos("origin").

A geneis a segment of nucleic acidthat contains the information

necessary to produce a functional product, usually aprotein.Genes correspond to units of inheritanceThey contain regulatory regions dictating under what conditions the

product is produced, transcribed regions dictating the structureof the product, andor other functional se!uence regions

Genes consist of a long strand of #A($#Ain some %iruses) thatcontains apromoter, which controls the acti%ity of a gene, and acoding se!uence, which determines what the gene produces.
http://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Inheritancehttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Virushttp://en.wikipedia.org/wiki/Promoterhttp://en.wikipedia.org/wiki/Promoterhttp://en.wikipedia.org/wiki/Virushttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/Inheritancehttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/Greek_language


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the coding se!uence is copied in a process called transcription,producing an $#A copy of the gene&s information. This$#A can then direct the synthesis of proteins %ia the

genetic codeThe genes of eukaryoticorganisms can contain non'codingregions called intronsthat are remo%ed from the messenger$#A in a process known as splicing.

The regions that actually encode the gene product, which can

be much smaller than the introns, are known as exons.
http://en.wikipedia.org/wiki/Transcription_(genetics)http://en.wikipedia.org/wiki/Genetic_codehttp://en.wikipedia.org/wiki/Eukaryotehttp://en.wikipedia.org/wiki/Intronhttp://en.wikipedia.org/wiki/Splicing_(genetics)http://en.wikipedia.org/wiki/Intronhttp://en.wikipedia.org/wiki/Exonhttp://en.wikipedia.org/wiki/Exonhttp://en.wikipedia.org/wiki/Intronhttp://en.wikipedia.org/wiki/Splicing_(genetics)http://en.wikipedia.org/wiki/Intronhttp://en.wikipedia.org/wiki/Eukaryotehttp://en.wikipedia.org/wiki/Genetic_codehttp://en.wikipedia.org/wiki/Transcription_(genetics)


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The total complement of genes in an organism or cell is known asits genome

The genome sieof an organism is loosely dependent on its

complexityprokaryotessuch asbacteriaand archaeaha%egenerally smaller genomes, both in number ofbase pairsandnumber of genes, than e%en single'celled eukaryotes. *owe%er,the largest known genome belongs to the single'celled amoeba

The estimated number of genes in the human genomehas beenrepeatedly re%ised downward since the completion of the*uman Genome +roect current estimates place the humangenome at ust under - billion base pairs and about /,///'0,/// genes.

The gene density of a genome is a measure of the number of genesper million base pairs (called a megabase, 1b) prokaryoticgenomes ha%e much higher gene densities than eukaryotes.
http://en.wikipedia.org/wiki/Genomehttp://en.wikipedia.org/wiki/Genome_sizehttp://en.wikipedia.org/wiki/Prokaryotehttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Archaeahttp://en.wikipedia.org/wiki/Base_pairhttp://en.wikipedia.org/wiki/Eukaryotehttp://en.wikipedia.org/wiki/Amoebahttp://en.wikipedia.org/wiki/Human_genomehttp://en.wikipedia.org/wiki/Human_Genome_Projecthttp://en.wikipedia.org/wiki/Human_Genome_Projecthttp://en.wikipedia.org/wiki/Human_genomehttp://en.wikipedia.org/wiki/Amoebahttp://en.wikipedia.org/wiki/Eukaryotehttp://en.wikipedia.org/wiki/Base_pairhttp://en.wikipedia.org/wiki/Archaeahttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Prokaryotehttp://en.wikipedia.org/wiki/Genome_sizehttp://en.wikipedia.org/wiki/Genome


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2Gene content and genome sie of %arious organisms 3pecies Genome sie (1b) #umber of genes

Mycoplasma genitalium /.04 0//Streptococcus pneumoniae. -//scherichia coli 5.6 55//

Saccharomyces cerevisiae 7 04//rabidopsis thaliana 70 0,0//

Caenorhabditis elegans 89 78,///Sea urchin 475 -,-//

rosophila melanogaster 74/ 7-,9//

us musculus 0// 8,///omo sapiens 8// 9,///Oryza sativa 566 50'00,///
http://en.wikipedia.org/wiki/Mycoplasma_genitaliumhttp://en.wikipedia.org/wiki/Streptococcus_pneumoniaehttp://en.wikipedia.org/wiki/Escherichia_colihttp://en.wikipedia.org/wiki/Saccharomyces_cerevisiaehttp://en.wikipedia.org/wiki/Arabidopsis_thalianahttp://en.wikipedia.org/wiki/Caenorhabditis_eleganshttp://en.wikipedia.org/wiki/Sea_urchinhttp://en.wikipedia.org/wiki/Drosophila_melanogasterhttp://en.wikipedia.org/wiki/Mus_musculushttp://en.wikipedia.org/wiki/Homo_sapienshttp://en.wikipedia.org/wiki/Oryza_sativahttp://en.wikipedia.org/wiki/Oryza_sativahttp://en.wikipedia.org/wiki/Homo_sapienshttp://en.wikipedia.org/wiki/Mus_musculushttp://en.wikipedia.org/wiki/Drosophila_melanogasterhttp://en.wikipedia.org/wiki/Sea_urchinhttp://en.wikipedia.org/wiki/Caenorhabditis_eleganshttp://en.wikipedia.org/wiki/Arabidopsis_thalianahttp://en.wikipedia.org/wiki/Saccharomyces_cerevisiaehttp://en.wikipedia.org/wiki/Escherichia_colihttp://en.wikipedia.org/wiki/Streptococcus_pneumoniaehttp://en.wikipedia.org/wiki/Mycoplasma_genitalium


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ifferent genes for the same trait, which gi%e rise to differentphenotypes, are known as alleles.

Alleles may be dominantor recessi%e dominant alleles gi%e

rise to their corresponding phenotypes when paired withany other allele for the same trait, while recessi%e allelesgi%e rise to their corresponding phenotype only whenpaired with another copy of the same allele.
http://en.wikipedia.org/wiki/Allelehttp://en.wikipedia.org/wiki/Dominant_genehttp://en.wikipedia.org/wiki/Recessive_genehttp://en.wikipedia.org/wiki/Recessive_genehttp://en.wikipedia.org/wiki/Dominant_genehttp://en.wikipedia.org/wiki/Allele


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DNA

The modern study of geneticsat the le%el of #A is known asmolecular geneticsand the synthesis of molecular genetics withtraditional arwiniane%olutionis known as themodern e%olutionary synthesis.

#A consists of a chain made from four types of nucleotide

subunits: adenosine, cytidine, guanosine, and thymidine. ;achnucleotide subunit consists of three components: aphosphategroup, a deoxyribosesugar ring, and a nucleobase

nucleotides in #A or $#A are typically called &bases&conse!uently they are commonly referred to simply by their

purineorpyrimidineoriginal base components adenine,cytosine, guanine, thymine.Adenine and guanine are purines and cytosine and thymine are

pyrimidines.
http://en.wikipedia.org/wiki/Geneticshttp://en.wikipedia.org/wiki/Molecular_geneticshttp://en.wikipedia.org/wiki/Charles_Darwinhttp://en.wikipedia.org/wiki/Evolutionhttp://en.wikipedia.org/wiki/Modern_evolutionary_synthesishttp://en.wikipedia.org/wiki/Nucleotidehttp://en.wikipedia.org/wiki/Adenosinehttp://en.wikipedia.org/wiki/Cytidinehttp://en.wikipedia.org/wiki/Guanosinehttp://en.wikipedia.org/wiki/Thymidinehttp://en.wikipedia.org/wiki/Phosphatehttp://en.wikipedia.org/wiki/Deoxyribosehttp://en.wikipedia.org/wiki/Nucleobasehttp://en.wikipedia.org/wiki/Purinehttp://en.wikipedia.org/wiki/Pyrimidinehttp://en.wikipedia.org/wiki/Pyrimidinehttp://en.wikipedia.org/wiki/Purinehttp://en.wikipedia.org/wiki/Nucleobasehttp://en.wikipedia.org/wiki/Deoxyribosehttp://en.wikipedia.org/wiki/Phosphatehttp://en.wikipedia.org/wiki/Thymidinehttp://en.wikipedia.org/wiki/Guanosinehttp://en.wikipedia.org/wiki/Cytidinehttp://en.wikipedia.org/wiki/Adenosinehttp://en.wikipedia.org/wiki/Nucleotidehttp://en.wikipedia.org/wiki/Modern_evolutionary_synthesishttp://en.wikipedia.org/wiki/Evolutionhttp://en.wikipedia.org/wiki/Charles_Darwinhttp://en.wikipedia.org/wiki/Molecular_geneticshttp://en.wikipedia.org/wiki/Genetics


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The most common form of #A in a cell is in a double helixstructure, in which two indi%idual #A strands twist aroundeach other in a right'handed spiral.


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All nucleic acid synthesis in a cell occurs in the 0&'-& direction,because new monomers are added %ia a dehydrationreaction that uses the exposed -& hydroxyl as a nucleophile.

The expressionof genes encoded in #A begins bytranscribingthe gene into $#A, a second type ofnucleic acidthat is %ery similar to #A, but whosemonomers contain the sugar riboserather than deoxyribose.

The genetic codespecifies the correspondence duringprotein translationbetween codons and amino acids. Thegenetic code is nearly the same for all known organisms.
http://en.wikipedia.org/wiki/Dehydrationhttp://en.wikipedia.org/wiki/Nucleophilehttp://en.wikipedia.org/wiki/Gene_expressionhttp://en.wikipedia.org/wiki/Transcription_(genetics)http://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/Ribosehttp://en.wikipedia.org/wiki/Deoxyribosehttp://en.wikipedia.org/wiki/Genetic_codehttp://en.wikipedia.org/wiki/Translation_(genetics)http://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Translation_(genetics)http://en.wikipedia.org/wiki/Genetic_codehttp://en.wikipedia.org/wiki/Deoxyribosehttp://en.wikipedia.org/wiki/Ribosehttp://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Transcription_(genetics)http://en.wikipedia.org/wiki/Gene_expressionhttp://en.wikipedia.org/wiki/Nucleophilehttp://en.wikipedia.org/wiki/Dehydration


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RNA

$#Ais an intermediate product in the process of manufacturingproteins from genes.

*owe%er, for some gene se!uences, the $#A molecules are theactual functional products.

3ome %irusesstore their entire genomes in the form of $#A, andcontain no #A at all.$#A retro%iruses re!uire the re%erse transcriptionof their genome

from $#A into #A before their proteins can be synthesied.$#A is common as genetic storage material in %iruses, in mammals

in particular $#A inheritance has been obser%ed %ery rarely.
http://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Virushttp://en.wikipedia.org/wiki/Retrovirushttp://en.wikipedia.org/wiki/Reverse_transcriptionhttp://en.wikipedia.org/wiki/Genomehttp://en.wikipedia.org/wiki/Genomehttp://en.wikipedia.org/wiki/Reverse_transcriptionhttp://en.wikipedia.org/wiki/Retrovirushttp://en.wikipedia.org/wiki/Virushttp://en.wikipedia.org/wiki/RNA


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Functional structure of a gene

All genes ha%e regulatory regions in addition to regionsthat explicitly code for a protein or $#A product.

A uni%ersal regulatory region shared by all genes is

known as thepromoter, which pro%ides a position thatis recognied by the transcription machinery when agene is about to be transcribed and expressed.
http://en.wikipedia.org/wiki/Promoterhttp://en.wikipedia.org/wiki/Promoter


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Gene expression

The process of producing a biologically functional molecule ofeither $#A or protein is called gene expression

There are two maor steps separating a protein'coding gene

from its protein:first, the #A on which the gene resides must betranscribedfrom #A to messenger $#A(m$#A)

second, it must be translatedfrom m$#A to protein
http://en.wikipedia.org/wiki/Gene_expressionhttp://en.wikipedia.org/wiki/Transcription_(genetics)http://en.wikipedia.org/wiki/Messenger_RNAhttp://en.wikipedia.org/wiki/Translation_(genetics)http://en.wikipedia.org/wiki/Translation_(genetics)http://en.wikipedia.org/wiki/Messenger_RNAhttp://en.wikipedia.org/wiki/Transcription_(genetics)http://en.wikipedia.org/wiki/Gene_expression


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The earliest level of regulation is at DNA level during transcription


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Chromosomes

>efore cells di%ides, its #A is organie into paired structurescalled chromosomes.

A chromosome consists of a single, %ery long #A helix onwhich thousands of genes are encoded.

*uman #A forms - pairs of chromosomes.;ach chromosomes splits down its length as the #A

duplicates itself.


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Conclusion

A gene is a unit of DNA and RNA.A chromosomes is an assembly of hundreds

of genes.

Every living cell includes a quantity of nucleicacids. One type, DNA (deoyribonucleicacid!, is enclosed in the central nucleus ofthe cell. "he other, RNA (ribonucleic acid!,is more #idely distributed.


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References

$ ab%earson & (')!. *+enetics #hat is a gene-*. Nature441(/'! 0/1234.%56D 4)'304.

^7avalier28mith ". (4/19!. Eu:aryotic gene numbers, non2coding DNA, and genome si;e.6n 7avalier28mith ", ed. The Evolution of Genome Size7hichester


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GENEs n Cromosomes