Gregor Mendel, known as the father of genetics, discovered key principles of inheritance through experiments with garden pea plants, including the laws of segregation, independent assortment, and dominance. These laws explain how traits are passed from parents to offspring, introducing concepts such as homozygous and heterozygous alleles, as well as genotype and phenotype. The Punnett square serves as a tool to predict the genetic outcomes of crosses between organisms by illustrating possible allele combinations.

1. MENDELIAN INHERITANCE

2. Who is Gregor Mendel?
Gregor Mendel is an Austrian
monk, scientist and teacher
who is considered as the
father of genetics.
He was the first one to set the
primary tenets relating to the
transmission of traits from
parents to offspring thru his
experiment using garden pea
plant.

3. FUNDAMENTAL LAWS OF INHERITANCE
1.LAW OF SEGREGATION
- during gamete formation, the
allele for each gene segregates or
separates from each other such that
each gamete formed carries only one
allele.

4. FUNDAMENTAL LAWS OF INHERITANCE
2. LAW OF INDEPENDENT ASSORTMENT
- genes for different traits assort
independent of each other during
genetic formation;
- a trait does not affect the
inheritance of another trait.

5. FUNDAMENTAL LAWS OF INHERITANCE
3. LAW OF DOMINANCE
- the presence of a dominant allele
conceals, masks or prevents the
expression of the recessive allele.
Dominant – trait that is always expressed;
represented by capital letter.
Recessive – trait always masked by the
dominant trait; represented by small letter.

6. HOMOZYGOUS AND HETEROZYGOUS
Homozygous – term used to refer to
organism that has two identical alleles
for a particular trait.
1. Homozygous dominant
2. Homozygous recessive
Heterozygous – term used for
organism that has two different alleles
for the same gene.

7. GENOTYPE AND PHENOTYPE
Genotype – the genetic make up of
an organism; description of the genes
present in an organism.
Phenotype – the physical
characteristics that an organism
manifests/show.

8. PUNNETT SQUARE
- Grid that enables one to predict the outcome
of simple genetic crosses;
- Simulates two organisms reproducing sexually,
examining just one of the many genes that get
passed on.
- - the completed square shows every possible
way the offspring could inherit this gene, and
what the chances are for each result.

9. STEPS IN PERFORMING PUNNET SQUARE:
1. Name the alleles involved. Choose a letter to represent
the alleles. Write the dominant allele with any capital
letter, and the recessive allele with the same letter in
lowercase.
SAMPLE PROBLEM: In guinea pigs, short hair is dominant
over long hair. What type of offspring do you expect if
you crossed a homozygous short haired guinea pig to a
homozygous long haired one?

10. STEPS IN PERFORMING PUNNET SQUARE:
2. Check each parent’s genotype for the trait.
3. Draw a 2x2 square. Leave room above the box and to
its left.
4. Label the rows with one parent’s genotype and the
columns with the other parent’s genotype. Separate the
alleles of the parents in each row or column.
5. Complete the Punnet Square by having each box
combine the letters from its rows and column. If there is a
dominant allele, write it first before the recessive one.

11. STEPS IN PERFORMING PUNNET SQUARE:
6. Interpret the Punnett Square by determining the
genotype and phenotype.
What if we cross bred 2 heterozygous shorthaired guinea
pigs, what will be the resulting offspring?