1. Words to know…
Heredity - the passing of traits from parent to offspring.
Genetics - the study of heredity.
Trait- a specific characteristic
Gene- chemical factor that determines a trait
Allele- A segment of a gene
Hybrid- the offspring crosses between parents with different traits

2. Gregor Mendel Father of Genetics
He lived in a monastery; He was a teacher and took care of the garden
Mendel’s knowledge helped us understand heredity.
He studied the pea plant most of all.

3. Mendel's Process
Mendel took a true-breeding (or pure) plants that always produce offspring with the same trait when they self-pollinate and cross pollinated it with a true breeding plant with a different trait.
The P generation is the true-breeding generation or the parent generation.

4. Pollination
Self pollination occurs when pollen is transferred from the anthers (male) of one flower to the stigma (female) of the same flower.
Cross-pollination occurs between two plants.

5. The F1 generation is the offspring of the P generation.
Mendel called the plants in the second generation the second F2

6. Mendel established three principles (or Laws) from his research
The Principle of Dominance and Recessiveness - one trait is masked or covered up by another trait
Principle of Segregation - the two factors (alleles) for a trait separate during gamete formation
Principle of Independent Assortment - factors of a trait separate independently of one another during gamete formation; another way to look at this is, whether a flower is purple has nothing to do with the length of the plants stems - each trait is independently inherited

7. copyright cmassengale
Mendelian Genetics
3/25/2017
Mendel’s Laws
copyright cmassengale

8. Results of Monohybrid Crosses
Mendelian Genetics
3/25/2017
Results of Monohybrid Crosses
Inheritable factors or genes are responsible for all heritable characteristics
Phenotype is based on Genotype
Each trait is based on two genes, one from the mother and the other from the father
True-breeding individuals are homozygous ( both alleles) are the same
copyright cmassengale

9. copyright cmassengale
Mendelian Genetics
3/25/2017
Law of Dominance
In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation.
All the offspring will be heterozygous and express only the dominant trait.
RR x rr yields all Rr (round seeds)
copyright cmassengale

10. copyright cmassengale
Mendelian Genetics
3/25/2017
Law of Dominance
copyright cmassengale

11. copyright cmassengale
Mendelian Genetics
3/25/2017
Law of Segregation
During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other.
Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring.
copyright cmassengale

12. Applying the Law of Segregation
Mendelian Genetics
3/25/2017
Applying the Law of Segregation
copyright cmassengale

13. Law of Independent Assortment
Mendelian Genetics
3/25/2017
Law of Independent Assortment
Alleles for different traits are distributed to sex cells (& offspring) independently of one another.
This law can be illustrated using dihybrid crosses.
copyright cmassengale

14. Dominant- stronger & mask other genes; the trait that shows up more frequently
represented by a capital letter
Recessive- “weaker” the trait that shows up less frequently
represented by a lower case letter

15. A chromosome is made up of DNA
A chromosome is made up of DNA. A gene is a segment of DNA on a chromosome that controls a particular hereditary trait.
Each of two or more alternative forms of a gene is called an allele. Mendel’s factors are now called an allele.

16. Particulate Inheritance
Mendelian Genetics
3/25/2017
Particulate Inheritance
Mendel stated that physical traits are inherited as “particles”
Mendel did not know that the “particles” were actually Chromosomes & DNA
copyright cmassengale

17. Probability is the likelihood that a specific even will occur.
It is the mathematical chance that something will occur.

18. copyright cmassengale
Mendelian Genetics
3/25/2017
Punnett Square
Used to help solve genetics problems
copyright cmassengale

19. Types of Genetic Crosses
Mendelian Genetics
3/25/2017
Types of Genetic Crosses
Monohybrid cross - cross involving a single trait e.g. flower color
Dihybrid cross - cross involving two traits e.g. flower color & plant height
copyright cmassengale

20. copyright cmassengale
Mendelian Genetics
3/25/2017
More Terminology
Genotype - gene combination for a trait (e.g. RR, Rr, rr)
Phenotype - the physical feature resulting from a genotype (e.g. red, white)
copyright cmassengale

21. copyright cmassengale
Mendelian Genetics
3/25/2017
Genotypes
Homozygous genotype - gene combination involving 2 dominant or 2 recessive genes (e.g. RR or rr); also called pure 
Heterozygous genotype - gene combination of one dominant & one recessive allele    (e.g. Rr); also called hybrid
copyright cmassengale

22. ?????? What is the phenotype of a heterozygous flower?
What is the genotype of a heterozygous flower?
What is the genotype of a homozygous dominant?

23. copyright cmassengale
Mendelian Genetics
3/25/2017
Dihybrid Cross RY Ry rY ry RY Ry rY ry
copyright cmassengale

24. copyright cmassengale
Mendelian Genetics
3/25/2017
Dihybrid Cross RY Ry rY ry
Round/Yellow: 9
Round/green: 3
wrinkled/Yellow: 3
wrinkled/green: 1
9:3:3:1 phenotypic ratio
RRYY
RRYy
RrYY
RrYy
RRyy
Rryy
rrYY
rrYy
rryy
copyright cmassengale

25. copyright cmassengale
Mendelian Genetics
3/25/2017
Test Cross
A mating between an individual of unknown genotype and a homozygous recessive individual.
copyright cmassengale

26. Its not all that easy!
Multiple alleles- trait that is determined by more than two alleles (ex. Human blood types)
Polygenic traits- trait influenced by several genes; genes may be on same chromosome or on different one (ex. Human eye color, weight, skin tone)

27. Incomplete dominance
The phenotype is in between that of the parents. It is like a mixture (pink flower)
Example: Snap Dragon

28. Codominance
Both alleles are expressed. With Codominance you can see two dominant alleles.

29. copyright cmassengale
Mendelian Genetics
3/25/2017
Codominance
Two alleles are expressed (multiple alleles) in heterozygous individuals.
Example: blood type
1. type A = IAIA or IAi
2. type B = IBIB or IBi
3. type AB = IAIB
4. type O = ii
copyright cmassengale

30. copyright cmassengale
Mendelian Genetics
3/25/2017
Codominance Problem
Example: homozygous male Type B (IBIB)
x heterozygous female Type A (IAi) IB IA i
IAIB
IBi
1/2 = IAIB
1/2 = IBi
copyright cmassengale

31. Another Codominance Problem
Mendelian Genetics
3/25/2017
Another Codominance Problem
Example: male Type O (ii) x female type AB (IAIB) i IA IB
IAi
IBi
1/2 = IAi
1/2 = IBi
copyright cmassengale

32. copyright cmassengale
Mendelian Genetics
3/25/2017
Codominance
Question: If a boy has a blood type O and his sister has blood type AB, what are the genotypes and phenotypes of their parents?
boy - type O (ii) X girl - type AB (IAIB)
copyright cmassengale

33. Thomas Hunt Morgan
Discovered that females have XX chromosomes and males have XY by studying a fruit fly.
Sex Chromosomes determine the sex of an organism.
He discovered that the gene for eye color in fruit flies is a sex linked trait carried on the Y chromosome

34. copyright cmassengale
Mendelian Genetics
3/25/2017
Sex-linked Traits
Traits (genes) located on the sex chromosomes
Sex chromosomes are X and Y
XX genotype for females
XY genotype for males
Many sex-linked traits carried on X chromosome
The genes interact with other genes scattered throughout the genome
copyright cmassengale

35. Blood Type Blood Type Antigen Antibody Can donate to Can receive fromAB O

36. Karyotype of Kleinfelters and Turners

37. Pedigree

39. Sex linked