1. Genes and Inheritance

2. Where does an organism get its unique characteristics?
An individual’s characteristics are determined by factors that are passed from one parental generation to the next.

3. Genes
the units that determine traits; it is a segment of DNA that contains information.

4. Alleles
Different forms of a gene that determine a specific trait

5. Mendelian Genetics- simple dominant and recessive cases

6. Identifying Alleles
Alleles are represented by either an uppercase or a lowercase letter

7. 1. Dominant Allele
Allele that will always be expressed when present

8. Dominant Expressed by Uppercase Letters Ex
Dominant Expressed by Uppercase Letters Ex. Dominant allele for tall: “T”

9. 2. Recessive Allele
Allele that will be expressed only when the dominant allele for that trait is not present. Represented by lowercase letters

10. Recessive
Example: Recessive Allele for short “t”, where tall is dominant, or T

11. Homozygous Alleles
Have 2 same alleles for a trait; the organism will have a pair of identical alleles—either two dominant or two recessive

12. Homozygous Tall—TT Homozygous short—tt TT—homozygous dominant tt—homozygous recessive

13. Heterozygous Alleles
Have 2 different alleles; the organism will have one dominant & one recessive allele

14. Tt—heterozygous tall; the plant will be tall, but will carry one dominant & one recessive allele

15. Punnett Square
a table that illustrates test-crosses between organisms; it is a determination of what traits may result after two parent alleles combine.
Probability

16. Phenotype
The form of the trait that an organism displays Ex>A plant can express a phenotype for either tall or short; it may be homozygous dominant or heterozygous, both tall, or homozygous recessive, short

17. Genotype An organism’s genetic composition
It will specify the actual alleles that make up the genetic trait.

18. Genotype affects Phenotype
A plant will express a phenotype, either tall or short, linked to it’s genotype, either TT, Tt, or tt.

19. What are some exceptions to Mendel’s principles?
Some alleles are neither dominant nor recessive.
Many genes exist in several different forms, and therefore have multiple alleles.
Many traits are produced by the interaction of several genes.

20. Despite the importance of Mendel’s work, there are important exceptions to most of his principles. Mendel’s principles alone cannot predict traits that are controlled by multiple alleles or multiple genes.

21. 1.Incomplete Dominance
Cases in which one allele is not completely dominant over another are called incomplete dominance.
Third phenotype produced that is a blending of the parental traits. (2 alleles produce 3 phenotypes.)
Example: straight hair, wavy, curly
Red, pink, white flowers

22. 2. Codominance
Cases in which the phenotypes produced by both alleles are clearly expressed are called codominance.
For example, in certain varieties of chicken, the allele for black feathers is codominant with the allele for white feathers.
Heterozygous chickens have a color described as “erminette,” speckled with black and white feathers. The heterozygous organism displays both phenotypes.

23. ABO blood group
Your blood type is determined by the presence or absence of a carbohydrate group attached to a protein on the surface of red blood cells. Type A and Type B blood each have a different carbohydrate group. Type O blood has no carbohydrate group, and is recessive. Type AB blood has both carbohydrate groups present, displaying codominance of Type A and Type B.

24. 3. Polygenic Traits
Traits controlled by two or more genes are said to be polygenic traits.
Polygenic means “many genes.”
Often show a wide range of phenotypes. Human examples: Hair, eye and skin color- the variety of skin color in humans comes about partly because more than four different genes probably control this trait.

25. 4. Multiple Alleles
A gene with more than two possible alleles is said to have multiple alleles.

26. ABO Blood Groups
There are 3 blood type alleles: IA, IB, and i. Each person has only two of the possible three alleles. Instead of three possible genotypes, there are a larger number of genotypes.

27. A pedigree is a diagram that follows the inheritance of a single gene through several generations in a family.
The information gained from pedigree analysis makes it possible to determine the nature of genes and alleles associated with inherited human traits. Based on a pedigree, you can often determine if an allele for a trait is dominant or recessive, autosomal or sex-linked.

28. Symbols
Females
(Circles)
Males
(Squares)

29. Individuals showing the trait (homozygous dominant or recessive): shaded circle or square
Heterozygous: ½ shaded circle or square; carrier of the recessive trait
Vertical line—connects parents & their children
Horizontal line—connects male & female parents

30. A recessive trait / disorder

31. Before genetic testing or complete understanding of DNA, observers noticed that genetic traits were passed from one generation to another in predictable patterns.

32. Autosomal Disorders
The genetic mutation is on an autosome, one of the chromosomes that are not an X or Y.

33. Autosomal dominant
– only need one copy of abnormal gene to inherit disease
Ex> Huntington’s Disease
Neurofibromatosis
Dwarfism

34. Autosomal recessive
– need two copies of abnormal gene to inherit disease
Ex>Tay-Sachs
Albinism
PKU
Cystic Fibrosis

35. A sex-linked gene is a gene located on a sex chromosome.
Genes located on the X chromosome are found in both sexes, but the fact that men have just one X chromosome leads to some interesting consequences.

36. A normal male inherits an X chromosome from the mother and a Y chromosome from the father. Therefore, males inherit sex-linked traits only from their mothers.

37. For each of the genes that are exclusively on the X chromosome:
Females, who are XX, would obviously have two alleles
Males, who are XY, would have only one allele.
Therefore, females with one recessive allele and one dominant allele for a gene that is unique to the X chromosome will display the dominant phenotype.
A male with a recessive allele for a gene unique to the X chromosome will always exhibit that recessive trait because there is no other corresponding allele on the Y chromosome.

38. XHXH
Chromosome with 2 dominant alleles
female
Non-hemophilia

39. XhXh
Chromosome with two recessive alleles
female
hemophilia

40. XHXh
heterozygous alleles –female
carrier
Non-hemophilia

41. XHY
Chromosome with one dominant allele
male
Non-hemophilia

42. XhY
Chromosome with recessive hemophilia allele
Male
hemophilia

43. ABO Blood Groups
Determined by a multiple allele system

44. Antigen
molecules which can be recognized by the body’s immune system on the surface of the red blood cell

45. Antibody
proteins in the human body which fight foreign objects that do not belong in the body

46. Some blood type antigens are seen as foreign in the blood of other humans
The antibodies will actually destroy the red blood cells like they are diseases.

47. If a person with type A blood (which has B antibodies) receives blood from a person with type B blood (which has A antibodies) the antibodies will attack the blood, and the person blood may begin to clump or agglutinate.

48. Blood type A & B are codominant
Blood Type O is recessive

50. Blood Types & Genotypes
Type A Blood
IAIA or IAi
Type B Blood
IBIB or IBi
Type AB Blood
IAIB
Type O Blood ii

51. B A, O B, O A & B None A, B, AB, O Blood Group Antigens Antibodies
Safe Transfusion From A B
A, O
B, O AB
A & B
None
A, B, AB, O O

52. Rh Factor
Protein substance present in the red blood cells of most people, capable of producing intense antigenic reactions

53. When 2 blood types are mixed in an Rh- negative individual, difficulty arises; the Rh factor acts as an antigen in the Rh- negative person, causing the production of antibodies.