Trait : example (tall, short, dimples, freckles, hair color, skin color, eye lash length, shape of your
nose, if your ear lobes touch your head or hang)
Gregor Mendel: Father of Genetics
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Priest
Scientist
Discovered genes by studying peas
Genes are segments (parts) of DNA. They carry instructions for the traits of an organism. When
organisms reproduce, genetic information from each parent is passed to the next generation. This
passing of traits from parent to offspring is called heredity.
BB = purebred (purebred of a dominate trait)
bb = purebred (purebred of a recessive trait)
purebreds have nothing mixed with them, they are pure!
Hybrid: an organism that has two different allele of the same gene. (There is a mix: Bb)
Factors: are the same as genes
Allele: Bb the B is an allele and the b is an allele
Punnett Square: are used to predict each possible combination of alleles that may occur in the
offspring of a cross.
(what are the possibilities with two parents)
Parent one TT
Parent two tt
T= tall
t = short
Parent one is written across the top of the Punnett square, with one letter above each box.
Parent two is written top to bottom on the left side of the Punnett Square, with one letter next to
each box.
T= tall
t = short
In each box you will have two letters
The letter above the box and the letter to the left of the box.
Ex. The upper left hand box will have a Tt
The dominant (capital letter is always written first)
Co-dominance: when two alleles are both expressed.
Ex. Father chicken has black feathers
Mother chicken has white feathers
Offspring has black and white feathers
(both show up and both are seen)
Incomplete dominance: when a dominant allele is only partly expressed.
Ex. Father chicken has black feathers
Mother chicken has white feathers
Offspring has grey feathers
(a mixture of the two is expressed)
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Genes occur in pairs. X
Each gene in a pair is called an allele
Genes are located in chromosomes, and chromosomes are what cells pass on to offspring.
Chromosomes are found in the nucleus of a cell
Genes contain DNA
DNA is the genetic material of all living things
DNA is the building blocks of life
DNA contains a code that can be copied
No one has the exact same DNA as you (unless you are an identical twin)
Identical twins have the same DNA but different finger prints.
DNA stands for deoxyribonucleic acid
Humans have 46 chromosomes
They occur in 23 pairs
 Humans have 2 sex
chromosomes
 Males have XY
 Females have XX