1. Mendelian Genetics
Regular Biology
Waggy

2. The Father of Genetics…
Gregor Mendel, 1850
Austrian monk who was in charge of the monestary garden
He noticed that each generation of pea plants looked like the parent generation, but with some differences

3. He collected pea seeds from each crop & carefully recorded the plants characteristics
He called these characteristics: traits
He began by testing for individual traits like height or flower color

4. For instance, he crossed a plant with white flowers with a plant with purple flowers
These is the parental generation (P1)
He found that in the first offspring generation, all the plants had purple flowers
This generation is called the filial generation (F1)
When one trait hides another the stronger trait is called: dominant
The hidden trait is called the recessive trait

5. When he crossed two flowers
from the F1 generation, the
white flowers reappeared at a
ratio of 3 purple to 1 white (3 : 1)
This final generation is called F2
Mendel concluded that the paired factors separate during the formation of gametes
And that each parent plant contributed one of the genes to the offspring
He called this the Law of Segregation

6. Next, he crossed two traits
He found that the dominant traits did not always appear together
This means that not only do the paired genes separate during meiosis but they also rearrange
He called this the Law of Independent Assortment

7. Modern Genetics Mendels work was unfortunately lost
It was rediscovered in 1900
Barbara McClintock picked up where Mendel left off
She worked with corn plants & discovered that genes did not have to stay in the same place on the chromosome

8. This added to the variability of the offspring
This is called jumping genes or transposons

9. Genetic Crosses
Genotype: an organisms genetic makeup (represented by a letter)
Phenotype: an organisms physical appearance (represented by a word)
Purple flower is represented by P (purple=phenotype & P=genotype)
White flower is represented by p (white=phenotype & p = genotype)
PP = ________ Pp = ________
pp = ________

10. Homozygous vs. Heterozygous
When BOTH alleles are the SAME it is a homozygous trait (PP, pp)
When the alleles are DIFFERENT it is a heterozygous trait (Pp)

11. Probability
Probability is the likelihood that a specific event will occur
It can be expressed as a decimal, percentage, fraction or ratio
Use this simple formula:
# of times an event is expected to occur total number of times could happen

12. In Mendel’s experiments, the dominant yellow seed color appeared 6,022 times
The recessive green seed color appeared 2,001 times
Calculate the probability of the seed being green:
2,001 = .25 (or 1/4 or 1:4 or 25% ) 8,023

13. Calculate the probability of the seed being yellow:
6,022 = .75 (or 75%, 3/4, 3:4) 8,023
Practice!

14. Monohybrid Cross
A cross between two organisms that tracks only ONE trait is a monohybrid cross
Scientists use Punnett squares to track these traits
P=purple
p =white p p P P

15. 100% What is the probability that the offsprings genotype will be Tt?
4 = 1 (100%, 4/4, :4) T T t t

16. 50% What is the probability that the offspring will be homozygous?
2 = .5 (50%, 2:4, /2) B b b b

17. -genotypes of the parents? -phenotypes of the parents?
What are the
-genotypes of the parents?
-phenotypes of the parents?
-probability of homoygous offspring?
-probability of heterozygous offspring?
-the phenotypes of the offspring? A a A a