1. What a monk and his peas taught us about ourselves
Mendelian Genetics
What a monk and his peas taught us about ourselves

2. Gene Expression
Talk with your lab partner about the following questions:
What is a gene?
What does a gene code for?
What is gene expression?

3. Gene Expression Mechanism: Protein Synthesis
Protein synthesis is regulated by other genes

4. Human Traits Roller Non-Roller Right Handed Left Handed Dimples
Non-dimples
Taster
Non-taster
Widow’s Peak
Non-Widows Peak

5. PTC: one gene – one protein- one trait (taster or non-taster)
Phenylthiocarbamide (PTC) is not found in nature, but the ability to taste it correlates strongly with the ability to taste other bitter substances that occur naturally, especially toxins. Eons ago, the ability to discern bitter tastes developed as an evolutionary mechanism to protect early humans from eating poisonous plants

6. Human Traits Either the trait was expressed or it wasn’t – why?
This map shows the prevalence of the ability to taste a bitter chemical, phenylthiocarbamide (PTC),
The darker the area in this map the higher the percentage of the native population of the area who can taste PTC.
As you can see, the percentage varies considerably, being over 85% in the darkest areas, and as low as 5% in the lightest.

7. Chromosomes Chromosomes are located in the nucleus
Chromosomes are made up of DNA – coded (or divided) into genes
Each organisms gets 1 set of chromosomes from one parent and 1 complimentary set from another parent
In humans there are 46 chromosomes in each cell – 23 from each parent

8. Meiosis: Cell division in sex cells

9. Meiosis Animation Showing Crossing Over

11. Meiosis: creates sex cells (eggs & sperm) Mitosis: creates all cell types except for sex cells

12. Meiosis Cell division in sex cells (eggs, sperm, pollen etc.)
Results 4 separate, haploid (1N) gametes
Creates variation in a population from
Crossing over
Different orientations of chromosomes

13. Mendel worked out the rules of genetics by breeding pea plants.

14. Mendels Experiments

18. Law of Independent (Random) Assortment
-Chromosomes sort independently of each other during meiosis 1
-Alleles on the same chromosome will “move together”

19. Law of Segregation
One allele from each gene pair (one from mom/one from dad) will separate during meiosis and end up in separate sex cells
Occurs during anaphase I

20. How did Mendel infer that alleles must separate independently?

21. What about alleles on the same chromosome?
A monohybrid cross represents the inheritance pattern of a single trait, whereas a dihybrid cross represents the inheritance patterns of two traits that are linked because they are on the same chromosome.

22. Traits are coded for in DNA
Taster or Non-taster
A gene codes for the tasting trait
Each person receives a copy of the PTC gene from each parent – so you have two copies.
Each copy is called an allele of the gene

23. Alleles An allele is an alternate form of a gene (PTC)
you either have two taster alleles (TT), one taster and one non-taster allele (Tt), or two non-taster alleles (tt)

24. Genes (alleles) are either dominant or recessive
Recessive copies of a gene can be masked by a dominant gene
Dominant genes mask recessive genes
PTC GENE
Tasting=Dominant form of gene
Non-tasting=Recessive form of gene
If you have two recessive genes (tt) you cannot taste PTC
If you have two dominants (TT), or one dominant and one recessive (Tt) you can taste PTC

25. What PTC genotypes could you have inherited from your biological parents?
TT - taster
Tt - taster
Tt – non-taster

26. Principles of Dominance – Some alleles mask the presence of other alleles
Bay (brown with black hair) is dominant in horses over chestnut (brown with blonde hair) -

27. Some traits are controlled by multiple genes Skin Pigment and Height are examples

28. Genetic Crosses
A genetic cross can be done using a punnett square to help determine the chances of offspring. Let cross the two original parents above using a punnett square

29. Genetic Crosses Blue eyes: Recessive Brown eyes: Dominant
1. A blue eyed man has a child with a brown eyed woman. What are the chances their child will have blue eyes?

30. White coat color: Dominant
Black coat color: Recessive
A white mare with a black father is crossed with a black stallion. What are the chances for a white foal?

31. Freckles are a dominant trait in humans
3. Cross a homozygous dominant male with a heterozygous female for the freckle trait. What are all of the possible genotypes and phenotypes for this couple?