1. Chapter 8
Mendelian Genetics

2. What is Genetics? Genetics is the branch of Biology that studies…
The passing of traits from parents to offspring=
_____________________
How do we know that Genetics isn’t something you made up? Give me the facts….

3. It all started with a guy named…..
___________________

4. Who was he? Scientist from Austria Lived at a church=Monk
Gardener of _____________
“Father of Genetics”
His experiments with Pea plants from began our understanding of how traits, things like hair or eye color, height, weight, ect, were passed down from generation to generation.

5. He studied the offspring of pea plants in his garden.
Mendel was the 1st to PREDICT patterns of heredity.
WAIT! HOW?
He studied the offspring of pea plants in his garden.
Pea Plants? Why did he choose pea plants?

6. Pea Plant Characteristics
Two ____________ forms of characteristics
Example: Some peas have purple flowers but others have white flowers.
Pea plants have male and female parts in the ____________ flower.
(He could cross-pollinate them or self pollinate them!)
The garden pea is ___________ to work with.
(Because it is small, grows easy, grows fast )
(and produces many offspring)

7. Pea Plant Characteristics

8. Self-Pollination=pure breed

9. Cross-Polination

10. Vocab to Know
Phenotype- Your ________________ or outward appearance (what you look like)
Examples: Red hair, blonde hair, black hair, ect.
Allele (Al-leal)=one ____________ of a trait
Represented by capital or lowercase letters
Genotype- The _________ that make up your traits. (Yy, YY, or yy)

11. More Vocab Recessive=Weaker, often gets hidden.
Dominant=Stronger, aggressive, masks other traits.
Traits are determined “dominant” by scientists who study ratios.
Recessive=Weaker, often gets hidden.
Traits are determined “recessive” by mixing two pure parents and seeing which trait gets hidden.
Examples: Red hair, white pea plant flowers, blue eyes, ect.
Show Holt slide 35

12. Vocab Continued… Homozygous Heterozygous Homo=______________
If you have the same two traits (YY, or yy)
like red hair from mom and red hair from dad
Depending on the trait, if your genotype is homozygous, it can be dominant or recessive!
Heterozygous
Hetero=Different (Yy)
If you have two different forms of a traits
Like blonde hair from mom and red hair from dad
Heterozygous traits show the dominant trait.
Show Holt Slide 36

13. Mendel’s Vocab Mendel used a language of his own…
True-breeding=______ (homozygous: YY or yy)
You know something is true breeding if you self pollinate it and all the offspring look the same.
P generation= ______ flowers (or Pure Flowers)
F1 generation=First __________ of two different plants (cross pollination)
F2 generation=_______________ offspring (but really he self pollinated the F1 generation!)

14. Cross between 2 pure parents Always results in 3:1 ratio of dominant to recessive.

15. Parents
First Offspring
Second Offspring

16. Mendel’s Breeding Experiment
By breeding pea plants, Mendel found patterns.
He created RULES that scientists use when understanding heredity.
You will learn his rules….
His rules are called the Theory of Heredity.
Show Holt Slide 18

17. The Theory of Heredity
The Theory of Heredity consists of 4 hypothesis that Mendel formed. Today, scientists around the world still follow these!
For each inherited trait, an individual has two copies of the gene—one from each parent.
There are alternative versions of genes. Today the different versions of a gene are called its alleles.
When two different alleles occur together, one of them may be completely expressed, while the other may have no observable effect on the organism’s appearance.
When gametes are formed, the alleles for each gene in an individual separate independently of one another. Thus, gametes carry only one allele for each inherited trait. When gametes unite during fertilization, each gamete contributes one allele.

18. Mendel’s Results
After Step 1, each of Mendel’s F1 plants showed only one form of the trait. (They all were purple!) ***heterozygous (F1)
But after Step 2 (F1 generation self-pollination) the missing trait (white color) reappeared in some of the plants in Step 3 (the F2 generation)!!!
Mendel didn’t just study color, but seven total traits. For each of the seven traits Mendel studied, he found a 3:1 ratio of plants expressing the contrasting traits in the F2 generation.
Show Holt Slide 21

20. The Law’s Mendel’s results helped form two laws of genetics.
The Law of Segregation
This law describes when homologous chromosomes are separated. Understand that the alleles for one trait (like height) separate and gametes only get one from each parent.
Show Holt Slide 38

21. The Law’s Continued… The Law of Independent Assortment
This law has to do with one trait influencing another (they don’t!). When TWO DIFFERENT traits (like hair color and height) are being passed on, they separate independently of one another.
However, these two different traits must be on different chromosomes.
Show Holt Slide 40

22. Self Practice 1 Genotype or Phenotype? Homozygous or Heterozygous?
Black Hair?_____________________
BB? _____________________
Homozygous recessive? _____________________
Homozygous or Heterozygous?
RR? _____________________
Rr? _____________________
rr? _____________________

23. Self Practice 2 Assume that the letters Choose ONE:
Capital P=Purple and Lowercase p=White
Dominant or Recessive…..
Pp? _____________________
PP? _____________________
White flowers? _____________________
Choose ONE:
Homozygous Dominant, Homozygous Recessive, or Heterozygous?
pp? _____________________

24. Self Practice 3 Assume that T=Tall and t=short
Please what would the possible genotypes be?
Homozygous Dominant _________
Heterozygous _________
Homozygous Recessive _________