Genetics

• There are approximately 23,000 genes in the human genome.
• Genes are the units of instruction that the cells of the human body use to carry out their functions.
• There are over 200 different types of cells in the human body (for example, muscle cells, liver cells, and nerve cells).
• A genome is the complete collection of hereditary information for an individual organism. In cellular life forms, the hereditary information exists as DNA.
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• A chromosome, by definition, is a threadlike strand of DNA in a cell nucleus that carries genes.
• Human cells have 23 pairs of nuclear chromosomes. A chromosome is made up of a DNA molecule that contains genes.
• There are 24 distinct human chromosomes out of which 22 are autosomal chromosomes and the remaining two are sex-determining chromosomes.
•  Every individual has two sets of the 22 chromosomes, X chromosome from the mother and an X or a Y chromosome from the father.
• Chromosomes are in the nucleus.

• Living organisms are a product of genes that they inherit and enviromental factors that have acted on them.
• A gene is a section of DNA.
• The DNA molecule is made up of base pairs. Genes are sections of these.
• A human gene may be 3,000 base pairs long of a chromosome.
• Each gene is a code specifying a particulat combination of amino acids, that will make a specific protein.
• Different versions of a gene is called an allele.
• If yu have a brown eyes allele from one parent and a blue eye allele from the ther parent. The blue allele will not show.
• It takes 8 hours for 1 of your cells to completely copy it's DNA.

• Humans have 23 pairs of chromosmes.
• Your gender is controlled by pair 23 called the sex chromosome.
• They are represented by X AND Y.
• ** represents girl.
• XY represents boy.
• The possible genders for parents would be XY or **.
• Punnett square:

                           Mother

     F                     X             X       

     A

     T             X     **          **

     H   

     E             Y    YX           YX

     R

50% chance of a boy

50% chance of a girl

• A different version of a gene is called an allele.
• One allele is always dominent
• One allele is always recessive
• If you inherit a dominent allele you will have his characteristic
• If you inherit a recessive allele it will only show affect if both parents have it.
• Dominent alleles with a capital letter
• Recessive alleles with a lower letter.