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Heredity Notes
Heredity- the passing of traits from parent to offspring
Genetics- the scientific study of heredity
Mendel- is the father of heredity, scientist who discovered the principles of heredity
Gene- the set of instructions for inherited traits. Basic unit of heredity
Trait- genetically determined characteristics
Genotype
* Definition- the entire genetic make up of an organism
* Two letters put together (one allele from mom and one allele from dad)
* There are three types of genotypes
 Heterozygous- Rr
 Homozygous Dominant- RR
 Homozygous Recessive- rr
Phenotype
* Definition- organism’s appearance
* Sounds like photo- it is what I see if you are in a photograph
* Examples- hair color, height, eye color
Allele
* Definition- one of the alternate forms of a gene
* One letter (you get one allele from mom OR one allele from dad)
* There are two types of alleles
 dominant (D)
 recessive (d)
Heterozygous Genotype
* In a hybrid, (Rr) the organism will take the DOMINANT trait.
Sexual Reproduction
* Definition- male and female reproductive cells combine to form an offspring
with genetic material from both.
* An offspring made from sexual reproduction can NEVER be identical to their
parents, because it has genetic material from both mom and dad
Asexual Reproduction
* Definition- produces one or more organisms that are IDENTICAL to itself.
Example- amoeba
Dominant vs. Recessive Traits
Punnett Squares- The chart used to show all of the ways traits can be
passed
* In a Punnett Square the parents are located on the top and the other on the
side.
Rr- 2:4 or 50%
rr- 1:4 or 25%
RR- 1:4 or 25%
red- 3:4 or 75%
white- 1:4 or 25%
R= Red
r= white
Biggest to smallest- Cell
Chromosomes
Gene
DNA
Pedigree- A chart that shows the presence or absence of a trait according to the
relationships within a family across several generations