Gregor Mendel was an Austrian monk in the 1800s who is considered the father of modern genetics. He studied inheritance of traits in pea plants by cross-breeding them. Peas were useful for his experiments because they have a short life cycle, are self-pollinating, and have simple traits that occur in only two variations. Through his experiments, Mendel discovered that traits are passed from parents to offspring through discrete units called alleles located on chromosomes. He established that some alleles are dominant and others recessive through his Law of Dominance. Mendel also discovered the principle of segregation, where each gamete receives one of the two alleles for each trait from the parental generation.

2. Who was Gregor Mendel?
•1800’s
•“Father” of modern genetics
•Cross-bred pea plants to study
inheritance of traits
•Why peas?
•Have a quick reproductive cycle
•They are self-pollinating
•He studied simple traits-traits that occurred in
only one of two possible variations.

4. Pea plants can be self-fertilized or cross-fertilized

5. Homozygous (purebred)- 2 identical alleles for a trait
Heterozygous (hybrid) – 2 different alleles for a trait
HYBRIDS
GeneticsVocabulary

6. GENOTYPE - what
genes, letters, the
organism has (TT, Tt, tt)
PHENOTYPE- (physical
char.) what it looks like
(tall or short)
* Genotype determines
phenotype
TT x tt
Tt x Tt
TT Tt Tt tt

7. •P generation– the
parental generation =
beginning of genetic
study
•F1 generation– 1st
offspring generation
•F2 generation– 2nd
offspring generation
originating from the F1

8. Mendel discovered that each trait is controlled by 2
factors called
alleles- different forms
of a gene
Genes- piece of a chromosome
that codes for a protein,
determining a trait
Genes are located on
chromosomes

10. Dominant Allele:
•Expresses its effect even in
presence of another allele
for the trait
Recessive Allele:
• Allele is not expressed if it is
in presence of a dominant
allele
• Will only be expressed in
the homozygous condition
Mendel’s Law of
Dominance

11. Mendel’s Principle of Segregation
•Chromosome
pairs separate
during meiosis so
that each gamete
receives just 1
allele for each trait

12. Check for understanding
1. The passing of traits from parents to offspring is known as _____
2. Who was the father of genetics? _________
3. Genes are located on _______________
4. Every gene is made of two
a. genotypes b. alleles c. cells
5. The organism’s outward appearance, such as wrinkled seeds are
referred to as the
a) phenotype b) genotype
* Turn in WB p. 160-164 if you did not yesterday & pick up a Punnett
square sheet from the other tray.
* Please write the answers to these questions on the back of the
chromosome-DNA labelling worksheet that we did Tuesday.

13. 6. The letters (ex. RR) that represent the traits are referred to as the
a) phenotype b) genotype
7. An organism that has two different alleles, or letters, such as Rr is:
a) homozygous b) heterozygous
8. An organism that has two of the same alleles, or letters, such as RR
is:
a) homozygous b) heterozygous
9. Which of the following sets would represent Mendel’s Parent (P)
generation?
a) RR x RR b) Rr x Rr c) RR x rr
10. When two different alleles occur together, such as R r, the one that
is expressed is a) dominant b) recessive

14. 11. a. What is the diagram shown below called?
b. What do these
letters actually
represent?
c. What do these
letters actually
represent?

15. Check for understanding
1. A one-eyed purple people eater is crossed with a two
eyed purple people eater. All of their offspring have two
eyes. Which trait is dominant?

16. 2. If you use the letter E for this gene. What
is the genotype of the offspring, if the parents
were EE x ee?
Are these offspring the F1 or F2 generation?
3. If you crossed the offspring with each
other? How many of the new offspring would
you expect to have two eyes?
EE = two eyes
Ee = two eyes
ee = one eye

17. Mendel’s Principle of Independent Assortment
•Alleles for one trait segregate independently from
alleles for another trait in metaphase 1 of meiosis.
•Each chromosome in the homologous pair line up
randomly.

19. Let's review what you know about genetics......