 Genes
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Made up of DNA
Located on the Chromosomes
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During Meiosis pairs of genes separate and each new
cell gets one form of a gene for a specific trait.
Genes may have different forms and we call these
Alleles.
Always come in pairs (two genes for each trait.)
 An
organism recieves two genes for each
trait, one from each parent.
 One of these genes may be stronger or more
Dominant , so it overpowers the other and
shows up in the offspring. The gene not
expressed is called the recessive gene.
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Two forms of a gene(alleles) that are the same
produce a homozygous organism.
Two forms of a gene (alleles) that are different
produce a heterozygous organism.
 Organisms
that receive 2 of the same gene
type – both dominant or both recessive will
have pure traits
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Ex. A cow has two genes for black color, which is
dominant in some breeds. Any offspring of that
animal will be black. This animal is considered
homozygous with a pure dominant trait for color.
A cow that has genes for a red color is also
considered pure, however because red is a
recessive trait they would be considered
homozygous pure with a pure recessive trait for
color.
 Organisms
with two unlike genes for a
certain trait are called Hybrid.
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A cow with a dominant gene for black color and
recessive gene for red color is considered a
hybrid for that trait.
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The offspring from a pure black bull bred to a pure red
cow would be what?
 An
organism may be Dominant in certain
traits and recessive in others.
 Dominant traits in one organism may be
recessive traits in another organism.