1. Introduction to Genetics
Mrs. Stewart
Biology

2. Standards:
CLE Investigate how genetic information is encoded in nucleic acids.
CLE Describe the relationships among genes, chromosomes, proteins, and hereditary traits.
CLE Predict the outcome of monohybrid and dihybrid crosses.

3. Objectives: Differentiate between characteristics and traits
Analyze Mendal’s principle of dominance
Predict genotype based on phenotype
Analyze characteristics and traits in this classroom

4. Decide with your partner
“shoulder” partners decide which one is the cat and which one is the dog. (it’s just a fun way of doing partner teaching without saying partner A and partner B)

5. What is heredity?
The transmission of characteristics from parents to offspring

6. Heredity is why families look alike

7. Vocabulary
Heredity - The transmission of characteristics from parents to offspring
Genetics – the study of heredity
Genes – Segments of DNA that code for a characteristic

8. Characteristics vs. Traits
Characteristic – an inheritable feature
Examples: flower color, hair color, number of fingers on your hand
Trait – a genetically determined variation of a characteristic
Examples: purple flower color vs white, brown/blonde/red hair, having 6 fingers instead of 5

9. Dogs
Give your cats two examples of characteristics that can be inherited from human parents to offspring.

10. Cats
Give your dogs an example of traits (variations) for the characteristics he/she listed.

11. Gregor Mendel (1822-1884) “Father of Genetics” Austrian Monk
Studied the inheritance of characteristics & traits using pea plants

12. Mendel’s pea plants Why pea plants? Pea plants have only 7 chromosomes
Can cross pollinate (sexual repro.) or self pollinate (asexual repro.)

13. Flower Reproduction Reminder:

14. Self-Pollination Pollen from the plant fertilizes its own eggs
Similar to asexual reproduction
Creates offspring identical to the parent

15. Cross - Pollination
Mendel removed male parts from one plant to prevent self-pollination and transferred pollen from a plant with different traits
Produces “hybrids”
Genetically different offspring
Sexual reproduction

16. Dogs
Explain the difference between self-pollination and cross-pollination to your cat.

17. Pea Plant Possibilities
Characteristics
Traits
Seed shape
Seed color
Seed coat color
Pod shape
Pod color
Flower position
Plant height
wrinkled or smooth
yellow or green
white or grey
smooth or constricted
green or yellow
axial or terminal
tall or short

18. Generations The parent generation The first generation
The second generation

19. Mendel’s Observations
He recorded the traits for each characteristic in the parent generation and which seeds came from which plants
One Observation he made:
Sometimes, short plants came from tall plant seeds

20. Mendel’s experiments Mendel’s Conclusions:
P – Purebred Tall x Purebred Short
F1 – All tall (hybrids)
F2 – 3:1 ratio tall:short
Mendel’s Conclusions:
Tall height “masks” the effects of short height.
Tall is “dominant”; Short is “recessive”.

21. Genotype VS. Phenotype
GENOTYPE: actual combination of alleles (genes) inherited from parents.
(One from MOM, and one from DAD.)
Example: Tt, TT or tt
PHENOTYPE: physical appearance/expression of the trait.
Example: Tall plant or short plant

22. Alleles We use letters to represent the variations
Capital Letters = Dominant allele
Lowercase letters = recessive allele
Example: T = tall plant, t = short plant
Most genes have two or more variations (alleles)

23. Cats and Dogs (think – pair – share)
Phenotype
Genotype
Widows Peak or straight hair line
Ww, WW or ww

24. Important Vocabulary Terms
HETEROzygous: (DIFFERENT)
have different alleles
Example: Tt
HOMOzygous : (SAME)
have the same alleles.
Example: TT or tt
HYBRID = offspring of heterozygous parents
PUREBRED (true-breeding) = offspring of homozygous parents – will produce offspring identical to parent traits

25. Principle of Dominance
some variations are dominant over others
Dominant traits will mask or hide the presence of a recessive trait
Recessive traits are hidden/masked by a dominant allele

26. Principle of Dominance – UFC style
Only one can win
Matt Hughes = Recessive
BJ Penn = Dominant

27. Principle of Dominance

28. Cats And Dogs
The dominant trait is “gray” fur, and the recessive trait is “white” fur. Lets use the following alleles: Gray is G. White is g.
If a bunny is heterozygous gray:
What is the genotype? ______________
If a bunny is homozygous white:
If a plant is homozygous dominant: Gg gg GG

29. Principles of Dominance
Predictable patterns of dominant and recessive only apply to single gene traits
Example: ONE gene is responsible for the type of hairline we have
There are 2 alleles (variations) for this gene
Possible Phenotypes: widow’s peak (W) or straight hairline (w)
Possible Genotypes: WW, Ww or ww

30. Dominance VS. Commonality
Does “dominant” mean most common?
Not necessarily
Examples:
Polydactyl – having 6 fingers
Achondroplasia – Dwarfism
O blood type (recessive)

31. Mendel’s 2 Laws Law of Independent Assortment Law of Segregation
Homologous chromosomes line up and assort independently during Metaphase/Anaphase I of meiosis
Law of Segregation
Sister chromatids are sorted into separate gametes during Anaphase II of meiosis

32. Mendel’s Laws

33. Cats
Explain how the law of independent assortment leads to gametes with different allele combinations

34. Punnett Squares
A diagram that is used to predict the possible outcomes of a particular cross (sexual reproduction union) 

35. Punnett Squares
Each square represents the possible combination of gametes during fertilization to make a baby.
4 gametes for each parent = 4 possible combinations for each trait

36. Dogs
Explain to your cat how Punnett squares work

37. Objectives: Differentiate between characteristics and traits
Analyze Mendal’s principle of dominance
Predict genotype based on phenotype
Analyze characteristics and traits in this classroom