Cornell Notes Intro to Genetics

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Cornell Notes: Hard Core Introduction to Genetics

Genetics is all about DNA (deoxyribonucleic acid)

DNA is found on your CHROMOSOMES. Everyone’s DNA is slightly different.
(that’s why it can be used in shows like CSI to find identities)

GENES are “lists” of DNA that act as a code for a specific PROTEIN.
Proteins control chemical reactions in your body
Those chemical reactions are responsible for the expression of TRAITS.

PHYSICAL TRAITS = what an organism looks like

       Physical Traits of Hamster #1:

       Physical Traits of a ____________:

You get your CHROMOSOMES (DNA) from your parents. Human “body” cells have
46 chromosomes. You got 23 CHROMOSOMES from each of your parents. (23 from
one sperm cell and 23 from one egg cell). Sperm cells and egg cells are GAMETES that
have half the number of chromosomes as body cells do.

Each TRAIT is controlled by two GENES
One GENE comes from a CHROMOSOME from the mother
One GENE comes from a CHROMOSOME from the father


Some GENES are DOMINANT while others are RECESSIVE.
Dominant genes “overpower” recessive genes. If you have one or two DOMINANT
GENES for a TRAIT, you’ll see that TRAIT. You must have two RECESSIVE
GENES in order for that trait to be expressed (visible)

ALLELES = different forms of the same gene
Example: If the GENE codes for hamster eye color, ALLELES are for red, black, etc.

GENOTYPE = genetic combination (two alleles) that makes a trait (TT Tt tt)
Capital letters = DOMINANT ALLELES
Lowercase letters = RECESSIVE ALLELES
PHENOTYPE = physical appearance

HOMOZYGOUS = two of the same ALLELES for a trait (TT or tt)
HETEROZYGOUS = one of each allele (Tt)

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