1. Performance Objectives:
What are the basic principals of heredity & why is Gregor Mendel known as the “Father of Genetics”? L.8.2B.2
Performance Objectives:
Use various scientific resources to research and support the historical findings of Gregor Mendel to explain the basic principles of heredity
This objective will be developed further in L.8.2.C.1 The purpose here

2. Genetics & Heredity
Heredity is the passing of traits from parent to offspring
Traits: physical characteristics of an organism
Example: eye color, hair color, & height
Genetics is the study of how traits are passed from parent to offspring by looking at genes

3. Who is the “Father of Genetics”?

4. Gregor Mendel
Basic laws of heredity were first formed during the mid- 1800’s by an Austrian botanist monk named Gregor Mendel.
His work laid the foundation to the study of heredity, Mendel is referred to as “The Father of Genetics.”

5. The work of Gregor Mendel
worked with pea plants…
…he called them his children!
Why pea plants???
There was a long-standing tradition of breeding pea plants at the monastery where Mendel lived and worked

6. Mendel’ Pea Plants
So…they were readily available and they come in lots of varieties!
Mendel observed differences in multiple traits over many generations because pea plants reproduce rapidly and have many visible traits.
He performed monohybrid crosses in a breeding experiment where organisms differed in a single given trait.
Yellow
Plant Height
Tall
Short
Pod color
Seed Shape
Pod Shape
Seed Color
Green
Round
Wrinkled
Smooth
Pinched

7. And best of all…
Pea plants flowers can reproduce by themselves (self-pollinate)
This allowed Mendel to see if strains were true breeding and to produce hybrids

8. Mendel’s garden

9. Mendel’s Experiments
Mendel noticed that some plants always produced offspring that expressed a form of a trait exactly like the parent plant.
Called these plants “purebred” plants.
purebred short plants always produced short offspring
purebred tall plants always produced tall offspring. X
Purebred Short Parents
Short Offspring X
Purebred Tall Parents
Tall Offspring

10. Mendel’s First Experiment
Crossed purebred plants (P generation) with opposite forms of a trait.
Purebred tall plants were crossed with purebred short plants.
Mendel referred to plant as a “purebred” if the plant had two identical gene codes for a particular trait.
purebred tall plant has two tall genes
purebred short plant has two short genes.
Observed that all of the offspring (F1 generation) expressed the tall plants trait, and none expressed the short parent.
Parent Tall P generation
Parent Short P generation X
Offspring Tall F1 generation

11. Mendel’s Second Experiment
Crossed two of the offspring tall plants produced from his first experiment.
Observed that the F2 generation had a mix of tall and short traits expressed in the offspring plants.
Occurred even though none of the F1 parents were short
Parent Plants
Offspring X
Tall F1 generation
3⁄4 Tall & 1⁄4 Short F2 generation

12. 3 Gregor Mendel’s research reflects basic principals of Heredity
Dominant and recessive traits
Law of Segregation
Law of Independent assortment

13. Mendel’s Discoveries
Mendel reasoned that one factor (gene) in a pair may mask, or hide, the other factor.
Today, Scientists refer to Mendel’s “factors” that control traits as genes.
Different forms of a gene are called alleles
In the picture below of Mendel’s 1st experiment, What conclusion can you make about which factor (gene) is masking and which factor (gene) is getting masked?
Parent Tall P generation
Parent Short P generation X
Offspring Tall F1 generation

14. Types of Alleles
Dominant Alleles describe a genetic factor that is always expressed.
It prevents a recessive trait from showing up in offspring.
Represented by capital letters (B)
Mendel observed a variety of dominant alleles in pea plants other than the tall allele.
For example, hybrid plants for seed color always have yellow seeds.
Yellow Seed
Green & Yellow Allele

15. Represented by lowercase letters (b)
Types of Alleles
Recessive Alleles describe a genetic factor that is not always expressed.
It only expresses itself when both of the recessive traits are inherited (PUREBRED)
Represented by lowercase letters (b)

16. Mendel’s Discoveries
Mendel’s first law, the Law of Segregation, has three parts.
Mendel concluded that:
Offspring carry two alleles for each trait because they inherit one from each parent
The allele pair segregates (separates) during the formation of sex cells by the process of meiosis.
Each sperm or egg receives only one member of the allele pair.
During fertilization each parent will pass one of the two separated alleles in the sex cells randomly giving the offspring one of the possible combinations.

18. Mendel’s Discoveries
Mendel’s Second Law, the Law of Independent Assortment, states that each pair of genes separate independently of each other in the production of sex cells during meiosis.
During meiosis the cell will donate one allele for each gene to each new sex cell allowing for two possible alleles to be inherited by the offspring for each gene.
The donation of one allele from each pair of genes is independent of any other pair.
For example, if the plant donates the yellow seed allele to one sex cell, it does not mean that it will also donate the yellow pod allele.

21. Two ways scientist study traits
Phenotype: The physical trait that an offspring expresses as a result of the genotypes
Ex. Blue Eyes
Genotype: the two alleles a person has inherited that can only be seen on the DNA
one from each parent
Ex. B from mom & B from dad = BB
Ex. B from mom & b, or bb

23. Two categories of Genotypes
Homozygous: inherited two identical alleles
BB (pure dominant) or bb (pure recessive) X
Short Offspring
short-short
Short Parents

24. Two categories of Genotypes
Heterozygous/Hybrid: inherited two different alleles
Bb (hybrid)
In Mendel’s first experiment, F1 offspring plants received one tall gene and one short gene from the parent plants.
all offspring had one short allele and one tall allele. X
Parent Tall P generation
Parent Short P generation
Offspring Tall F1 generation
short-short
short-tall
tall-tall

25. What role do chromosomes play in affecting what traits get passed from parent to offspring? L.8.2C.1
Performance Objectives:
Communicate through diagrams that chromosomes contain many distinct genes and that each gene holds the instructions for the production of specific proteins, which in turn affects the traits of the individual (not to include transcription or translation).
This objective will be developed further in L.8.2.C.1 The purpose here

26. The DNA Code Chromosomes are made of DNA.
Each chromosome contains thousands of genes.
The sequence of bases in a gene forms a code that tells the cell what protein to produce.

27. Genes on a Chromosome
Chromosomes are made up of many genes joined together like beads on a string.
Genes are small sections of DNA on a chromosomes that has information about a trait
Each chromosome has a gene for the same trait (eye color from mom & eye color from dad)
Traits are determined by alleles on the chromosomes
Each gene of a gene pair is called an allele
Inherited traits are determined by the alleles on the chromosome
The chromosomes in a pair may have different alleles for some genes and the same allele for others.

28. What if Mendel had Punnett Squares?!
How does a Punnett Square help make predictions about the possible traits that an offspring may inherit or express? L.8.2B.3
Performance Objectives:
Use mathematical and computational thinking to analyze data and make predictions about the outcome of specific genetic crosses (monohybrid Punnett Squares) involving simple dominant/recessive traits
This objective will be developed further in L.8.2.C.1 The purpose here
What if Mendel had Punnett Squares?!

29. A PUNNET SQUARE TOOL USED TO PREDICT THE POSSIBLE GENOTYPES & PHENOTYPES FOR THE OFFSPRING OF TWO KNOWN PARENTS by showing all possible combinations of alleles that children can inherit from parents Think about it…If I had 2 dice could you tell me all the possible outcomes for each roll?
PARENT’S ALLELES
PARENT’S ALLELES

30. Punnett Squares B b BB Bb bb Mom’s genotype - (Bb) Hybrid
Phenotype - brown eyes
Dad’s
Genotype - (Bb) Hybrid
Offspring’s
Phenotype: 75% brown, 25% blue
Ratio – 3:1
Genotype: 25% BB, 50% Bb, 25% bb
Ratio – 1:2:1 B b BB Bb bb
Dad
BROWN
BROWN
BROWN
BLUE

31. Other types of dominance
Codominance
Incomplete

32. Punnett Square Practice
What is the genotype and the phenotype for each parent?
What are the possible genotypes and the phenotypes for the offspring?