Saturday, December 15, 2012

Basic Genetics

http://www.dummies.com/how-to/content/genetics-for-dummies-cheat-sheet.html


Alleles: Alternative forms of a gene.
Autosomal chromosome: A nonsex chromosome.
Chromosome: A linear or circular strand composed of DNA that contains genes.
Diploid: An organism with two copies of each chromosome.
DNA: Deoxyribonucleic acid; the molecule that carries genetic information.
Dominant: A phenotype or allele that completely masks the presence of the other, recessive allele in the heterozygote.
Gene: The fundamental unit of heredity; a specific section of DNA within a chromosome.
Genotype: The genetic makeup of an individual; the allele(s) possessed at a given locus.
Heterozygote: An individual with two different alleles of a given gene or locus.
Homozygote: An individual with two identical alleles of a given gene or locus.
Locus: A specific location of a chromosome.
Phenotype: The physical characteristics of an individual.
Recessive: A phenotype or allele exhibited only when homozygous.



Laws of Inheritance
Segregation: In diploid organisms, chromosome pairs (and their alleles) are separated into individual gametes (eggs or sperm) to transmit genetic information to offspring. 

Dominance: A dominant allele completely masks the effects of a recessive allele. A dominant allele produces the same phenotype in heterozygotes and in homozygotes.

Independent Assortment: Alleles on different chromosomes are distributed randomly to individual gametes.


Adenine
Guanine
Cytosine
Thymine

Punnett Square (A= dominant trait) (a=recessive trait)


Example: (Heterozygous & Heterozygous)
Dominant= 75%  Recessive=25%



Example: (Homozygous & Homozygous)

Recessive=100%

This is homozygous recessive, if it was dominant (AA & AA) 100% of the offspring would have dominant traits.



Example: (Homozygous & Heterozygous)
Dominant=100%

Dominant=50% Recessive=50%



Aa=Dominant
AA=Dominant
aa=Recessive



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