Genetics mode of inheritance

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Genetics mode of inheritance
::Gene::
It is a part of DNA that has promoter and coding sequence that can be transcribed into RNA.

::Allele::
Alleles are alternative forms of gene located at one site on a chromosome; alleles determine the traits of individuals, refer to the possible variations of a gene.
Wild- type (normal) allele: the gene sequence that codes for a normally functioning product.
Mutant (disease) alleles: sequences that code of defective proteins.
Most genes have multiple alleles.

::Locus::
Locus refers to the address of a gene.
For example the gene associated with cystic fibrosis is located on chromosome 7

Basic concepts of formal genetics:
Mendel generated two genetic laws
:: Law of Segregation::
Applies to diploid organisms reproducing sexually
:: Alternate alleles account for inherited variation in traits.
:: Sexually reproducing organisms posses genes that occur in pairs and that only one member of this pair is transmitted to the offspring.
:: An organisms inherits 2 alleles, 1 from each parent.
:: If the 2 differ the dominant allele is responsible fro the trait. The recessive allele is expressed only if there are 2 such alleles.
The 2 alleles segregate during gamete formation, so that each gamete gets one, they rejoin in the zygote.

:: Law of Independent Assortment::

: Alleles of different genes segregate independently.


:: Genotype versus Phenotype::
::Genotype::
Refers to the genes of an individual which can be represented by two latteres or by a short descriptive phrase ((meaning individual genetic constitution at a locus))
Homozygous
Means that both alleles are the same
Heterozygous
Means that the members of the allelic pair are different

:: Phenotype::
Refers to physical or observable characteristic of the individual.
It is the result of interaction of genotype and environmental factors.

To be continued

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وهذا تعريف لـ phenotype صغته بطريقه اخرى
This is the "outward, physical manifestation" of the organism. These are the physical parts, the sum of the atoms, molecules, macromolecules, cells, structures, metabolism, energy utilization, tissues, organs, reflexes and behaviors; anything that is part of the observable structure, function or behavior of a living organism.

وتعريف لـ genotype
This is the "internally coded, inheritable information" carried by all living organisms. This stored information is used as a "blueprint" or set of instructions for building and maintaining a living creature. These instructions are found within almost all cells (the "internal" part), they are written in a coded language (the genetic code), they are copied at the time of cell division or reproduction and are passed from one generation to the next ("inheritable"). These instructions are intimately involved with all aspects of the life of a cell or an organism. They control everything from the formation of protein macromolecules, to the regulation of metabolism and synthesis.

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