1. Genetics
Mrs. Harlin

2. 3.2.2
Predict offspring ratios based on a variety of inheritance patterns (including dominance, co- dominance, incomplete dominance, multiple alleles, and sex-linked traits).

3. Mendel’s Laws of Heredity

4. Gregor Mendel
The first person to succeed in predicting how traits are transferred from one generation to the next.
Genetics: study of heredity.
Heredity: passing on of traits from parents to offspring.

5. Why Mendel Succeeded? 1. Chose his subject carefully.
Garden pea plant- > reproduces sexually.
Used cross-pollination to breed two different plants. Normally pea plants self-fertilize.
Pollination is transferring pollen grains from a male reproductive organ in a plant to a female reproductive organ.

6. 2. Mendel was a careful researcher.
Studied one trait at a time in order to control variables.
The pea plants he worked with were true-breeding.

7. P Short X Tall ↓
F ALL TALL
↓ ↓ ↓ ↓
F2 Tall Tall Tall Short
3:1 ratio

8. Why did he get these results?
3 rules:
1. The rule of unit factors: what Mendel called factor, we call a gene. Genes are located on chromosomes in cells. Different forms of a gene are called alleles.
Example: the gene for height could have alleles short and tall.

10. The rule of dominance:
dominant: trait that appears whenever an allele is present.
Write as a CAPITAL letter.
recessive: trait that only shows up when 2 forms of the allele are present.
Write as a LOWERCASE letter.

12. 3. The law of segregation: every individual has 2 alleles of each gene
3. The law of segregation: every individual has 2 alleles of each gene. When gametes (sex cells) are produced, each gamete receives one allele.

13. Phenotype: the way an organism looks and behaves. “Pheno” means to show.
Example: Tall
Genotype: the allele combination.
Example: TT

14. Homozygous (true-breeding): an organism has 2 alleles for a trait that are the SAME.
Example: TT = tall (dominant)
tt=short (recessive)
Heterozygous (hybrid): an organism has 2 DIFFERENT alleles for a trait.
Example: Tt=tall (dominant)

15. Punnett Squares
Diagrams used to predict the outcome of a genetic cross considering all possible combinations of gametes.

16. Complex Patterns of Heredity

17. Incomplete Dominance
The heterozygous individual is intermediate between those of 2 homozygotes.
Snapdragon flower
RR – red
rr- white
When these 2 are crossed you get: Rr - pink

18. Incomplete Dominance
Sometimes incomplete dominance is denoted with an apostrophe, RR’ instead of Rr.

19. Codominance
Causes the phenotype of both homozygotes to be produced in heterozygous individuals.
Chickens
BB- black feathers
WW-white feathers
When these are crossed (BW), you do not get black, white, or gray feathers, you get BLACK and WHITE feathers (checkered).

20. Multiple Alleles Traits controlled by more than 2 alleles.
3 alleles on one gene govern blood type.

21. Multiple Alleles Govern Blood Type
3 possible alleles: IA, IB, or i.
Genotypes Phenotypes
IAIA or IAi A
IBIB or IBi B
IAIB AB
ii O

22. Sex-linked Traits
Traits specifically located on the X-chromosome (not chromosomes 1-22).
Ex: color-blindness and hemophilia
Males are more likely than females to exhibit a sex- linked trait because they only have 1 X chromosome.

23. Pedigree Tracing a Sex-linked Trait

24. Polygenetic Inheritance
Inheritance pattern of a trait is controlled by 2 or more genes.
Ex: eye color or height

25. Genetic Disorders
Sometimes genes are damaged or copied incorrectly, resulting in faulty proteins. These mutations can cause disorders that may or may not be lethal.

26. Sickle-Cell Anemia Recessive
If homozygous, the oxygen- carrying protein hemoglobin differs by one amino acid than normal. It changes the shape of the red blood cells.
Heterozygous individual are protected from effects of malaria.

27. Hemophilia Recessive sex-linked Causes blood not to clot.
Mutation of 1 of the blood-clotting genes on X chromosomes.

28. Huntington’s Disease Dominant
Rare, lethal disorder in which certain areas of the brain are broken down.
Doesn’t show up until ages 30-50, so an individual may have already reproduced.
There is a test to see if you have this disease.

29. Cystic Fibrosis Recessive
Due to defective protein in the plasma membrane. Results in thick mucus in lungs and digestive track.

30. Gene Therapy
Gene therapy may soon allow scientists to correct certain recessive genetic disorders by replacing defective genes with copies of healthy ones. Basically this means inserting “good” genes into an organism with “bad” genes.

31. Changes in Chromosomes
Caused by nondisjunction.
Occurs when homologues fail to separate during anaphase I of meiosis, or sister chromatids fail to separate during anaphase II.
Results in gametes with missing or too many chromosomes.

32. Changes in Chromosomes
Normal Karyotype

33. Changes in Chromosomes
Normal Karyotype

34. What is different about this karyotype?

35. How about this one?

36. How about this one?

37. How about this one?

38. How about this one?

39. Importance of Karyotypes
What can we determine about a person by looking at a karyotype?

40. 1. Chromosomal abnormalities
2. Gender