1. Chapter 11: Introduction to Genetics (p.306)

2. Q: Are all mutations harmful?
Write an answer with ONE SENTENCE explaining your response. Include an example that supports your claim.

3. Gregor Mendel (July 20, 1822 – January 6, 1884)
Austrian Friar
Monastery gardener who raised pea plants and traced their genes through hundreds of generations
“Father of genetics”
His work was not widely accepted until the mid 1900’s

4. Mendel’s Peas Anthers = Male structure, produce pollen
Pistil = Female structure, produces ova (eggs)
Peas can self-pollinate
Or cross-pollinate

5. Cross-pollination Mendel used true- breeders (purple)
He cut off the anthers of some before they developed pollen
Then he cross- pollinated plants with paintbrushes
Offspring now had 2 parents instead of 1

6. B. Genes and Dominance P = Parental generation
F1= First filial or first “child” generation
F2 = Second Filial generation, and so on.
Filius is Latin for “son”

7. Genes and Dominance Gene: chemical factors that determine traits
locus (loci)=location of gene on the DNA
Allele: different forms of a single gene
ex. White or purple flowers

8. Principle of Dominance
some alleles are dominant and others are recessive--recessive traits are “masked” by dominant ones.
Hybrids are offspring produced by two parents with different traits

9. Pea Traits
Mendel studied 7 traits in peas and tracked how they were passed down for many generations
He recorded the information each season for over 40 years!

10. Inheritance of Color in Pea Seeds
Yellow peas are dominant
Green peas are recessive

11. Gametes Sex cells only carry one allele each
One allele will come from each parent
Humans have sperm and eggs, plants have pollen and ova

12. Other Vocabulary words. . .
Phenotype = visible expressed trait (what does it look like or do?)
Genotype = combination of genes (letters)
The genotype determines the phenotype
Homozygous = an individual with 2 alleles for the same gene (AA or aa)
Heterozygous = an individual with both alleles (Aa)

14. II. Genetics and Probability
Probability= the likelihood that a particular event will occur
Coin Flip (Ratio of heads:tails)
Once: 50:50 (1/2 of the time it is heads, ½ tails)
Q: If you flip a coin 3 times, what is the likelihood of getting three heads?
Multiply the probability of each event
½ x ½ x ½ = 1/8

15. Punnett Squares
A table of the possible outcomes from a cross between 2 parents

16. Rules for Punnett Squares (p.316)
Start with the parents
Figure out the possible gametes
Line them up on the square
Fill in the table by combining the traits
Determine the possible genotypes and phenotypes of each offspring
Write the RATIO and PERCENT CHANCE of these possibilities

18. Punnett Squares (continued)
True-breeding = Homozygous (TT or tt)
Heterozygous (Tt) means they have both alleles
Phenotype: physical expressed characteristic
Ex: Yellow or green peas; blue or brown eyes
Genotype: genetic makeup (TT, tt, Tt)
The genotype determines the phenotype

19. C. Other genetic factors
Incomplete dominance
Cases in which neither trait is dominant and the heterozygous individual expresses an even mix of the trait
Miribalis flowers
Red = R
White = W
Pink = RW

20. Incomplete Dominance RW
In Miribalis flowers, a red parent + white parent results in all pink offspring
Red = R
White = W R R
Pink = RW W
Phenotype = 4:0
Genotype = 4:0 W RW

21. Codominance
A mix of dominant and recessive trait is expressed like a blend (ex. Roan cattle) + =

22. Codominance (use capital letters)
In cattle, a red parent + white parent results in both traits being expressed equally
Red = R
White = W R R
Roan (spots) = RW W
Phenotype = 4:0
Genotype = 4:0 W RW

23. Codominance
In people a parent with straight hair + a parent with curly hair results in both traits being expressed equally (Wavy hair)
Straight = S S S
Curly = C C
Wavy = SC
Phenotype = 4:0 C
Genotype = 4:0 SC

24. Multiple alleles
more than 2 alleles control the expression of the gene (Fur color in rabbits, see p. 273 in Blue text)

25. Polygenic traits
Traits controlled by more than 2 different genes (ex. Skin color in humans)

26. III. Exploring Mendelian Genetics
Are there relationships between the different alleles?
Mendel wondered if wrinkled seeds must always be yellow or if smooth seeds must also be round
Crossed plants and looked for patterns with 4 different alleles (2 traits) DIHYBRID CROSS

27. Dihybrid Cross (RrYy x RrYy)
Mendel tracked two traits to see if there were links between the inheritance of traits
Round = R
Wrinkled = r
Yellow = Y
Green = y
Phenotype = 9:3:3:1 RY Ry rY ry
RRYY
RRYy
RrYY
RrYy
RRyy
Rryy
rrYY
rrYy
rryy
Round Yellow: wrinked Yellow:Round green:wrinkled green

28. A. Independent Assortment
Principle of independent assortment: genes for different traits can segregate independently during the formation of gametes
We end up with a phenotype ratio of 9:3:3:1
Genotype ratio of 2:2:2:2:2:2:1:1:1
Out of 16 offspring looking at 2 traits

29. B. Mendel’s Principles
Inheritance of traits is determined by genes. In sexual reproduction, genes are passed from parents to their offspring
There are dominant and recessive forms of most genes that are expressed by different traits
Each adult has 2 alleles for each gene (1 from each parent). Genes are segregated in gametes (sex cells only carry one allele)
Alleles of genes segregate independently of one another

30. Genetic Diseases: Muscular Dystrophy
Genetic muscle disease
Dominant allele
50% chance of inheritance in offspring between an affected and an unaffected pair