1. Happy Thursday! Please do the following: have out your Karyotyping lab
pick up the handouts

2. Genetics and Heredity

3. Watch this video before completing your foldable or taking notes.

4. Use slides 4 – 18 to aide you in completing your Genetics Foldable

5. Heredity
The study of how traits are passed from parents to offspring.

6. Genes and Alleles
A gene is a segment of DNA that codes for a specific trait.
Ex. Gene for hair color
An allele is an alternative form of a gene
Ex. Allele for brown hair

7. Dominant
Trait that is always observed; masks the recessive form of a trait.
Represented by CAPITAL LETTERS
W : Widow’s Peak
H : Hitchhikers thumb
E : Unattached earlobes

8. Recessive Only observed when TWO recessive alleles are present.
Represented by a lower case letter.
w : Straight hair line
h : Absent hitchhikers thumb
e : Attached earlobes

9. Homozygous Same alleles joined together Examples: Homozygous Dominant
RR, HH, TT, LL
Homozygous Recessive
rr, hh, tt, ll

10. Heterozygous
Different alleles joined together
Examples:
Ww, Hh, Ee

11. Genotype
Combination of alleles in an organism

12. Phenotype The physical appearance The outward expression of a gene
What an organism looks like

13. Interpreting a Genotype
G: dominant allele for green pea
g: recessive allele for yellow pea
GG Gg gg

15. Theory of Heredity Inherited allele for purple P
HOMOZYGOUS purple flower PP

16. Theory of Heredity Inherited allele for purple flower (P)
Inherited allele for pink flower (p)
HETEROZYGOUS purple flower (Pp)

17. Theory of Heredity Inherited for pink flower (p)
HOMOZYGOUS pink flower (pp)

18. Phenotype for Fur Color
G = Gray fur, g= White fur
Subject A
Subject B
Subject C
Genotype for Fur Color GG Gg gg
Phenotype for Fur Color

19. Now, read through slides 22 – 29
Now, read through slides 22 – 29. In your notebook or on the back of your foldable, summarize Mendel’s conclusions and define: - Law of Segregation - Law of Independent Assortment

20. Gregor Mendel
Studied patterns of heredity (passing on of characteristics from parent to offspring)
Used the common garden pea in experiments

21. Why did Mendel use peas?
Sexually reproducing: able to isolate both male and female gametes
Easy to identify traits (characteristics that are inherited)
Short life cycle: able to be grown quickly

22. Tall true breed x short true breed 75% tall hybrids, 25% short hybrids
Mendel’s Experiment
PARENT GENERATION (P1)
Tall true breed x short true breed
FILIAL GENERATION (F1)
All tall hybrids
FILIAL GENERATION (F2)
75% tall hybrids, 25% short hybrids

23. What did Mendel observe?
When a true-breeding tall plant is crossed with a true-breeding short plant in the P generation, the F1 height trait is always predictable. 100% are tall plants.
P generation F F2

24. What happens when the F1 tall plants are crossed together?
Mendel observed that the F2 generation, the offspring of F1 plants, are always in a fixed ratio of 3:1 tall:short.
Why?
P generation F F2

25. Mendel’s Conclusions
There must be two variations for every trait, where each variation is called an allele.
Each offspring inherits only one allele from each parent.
The alleles are either dominant or recessive.
To show the recessive trait, two recessive alleles must be inherited.

26. Mendel’s Conclusions - Law of Segregation
Mendel concluded only one allele is passed from parent to offspring for each trait.
F1 plants must be heterozygous because the P generation only passed on one tall allele and one short allele.
The F1 plant will then pass on to its offspring either a tall or a short allele, never both.

27. Mendel’s Conclusions - Law of Independent Assortment
Because organisms are made up of more than one trait, Mendel concluded that the inheritance of one trait does not influence the inheritance of a second trait.
Example: Height of the pea plant does not influence the color of the peas
Height is independently assorted from color.