1. Human Genetics

2. I. 5 Human Patterns of Inheritance:
a. Complete Dominance (Basic Mendelian Genetics)
b. Incomplete Dominance
c. Co-dominance
d. Sex-Linked
e. Polygenic

3. a. Complete Dominance
• Traits inherited are either DOMINANT or
RECESSIVE
• Ex. BB, Bb, bb

4. b. Incomplete Dominance
• Traits inherited show a new phenotype
that is a BLENDING or MIXING of
parental alleles
–HETEROZYGOUS results in a blending
of two alleles
–Use 2 different CAPITAL letters to
represent (neither allele is dominant or
recessive)

5. Incomplete Dominance cont.
Ex: 4 o’clock flowers, snapdragons, Tay Sach’s Disease

6. Incomplete Dominance cont.
Ex: 4 o’clock flowers, snapdragons, Tay Sach’s Disease

7. Incomplete Dominance
cont.
Ex: 4 o’clock
flowers, snapdragons, Tay
Sach’s Disease

8. c. Co-dominance
• Trait inherited shows a new phenotype that
EXPRESSES BOTH parental alleles
–HETEROZYGOUS condition results in the
expression of both alleles
– Use 2 different capital letters to represent

9. Co-dominance continued
Ex: Roan Horse
X

10. Co-dominance continued
Ex: Roan Horse, Dalmatian

11. d. Sex Linked Traits
• Traits are controlled by genes on
the X or Y chromosomes
a. _X linked traits can be passed on
to males and females
b. _Y linked traits can only be
passed to males

12. X-Linked Traits
1. Affect the X chromosome
2. _FEMALES tend to be CARRIERS and
XtY
pass on the trait to their sons -
3. Females can be affected but BOTH X
chromosomes must have the gene for the
trait - XtXt

13. Examples:

14. Hypertrichosis –
Human Werewolf Syndrome:
Congenital generalized hypertrichosis (CGH)
Rare, X-linked dominant trait
Found in a single multigenerational Mexican
family

15. Colorblindness
Self Test:
NUMBERS: 5 | 8 | 9 | 5 | 3 | 5 | 9 | 10 |

16. Hemophilia

17. Male Pattern Baldness

18. Genotypes of Male Pattern Baldness

19. e. Polygenic Traits
• Traits are controlled by
MULTIPLE gene pairs
1.Genes may be on same or
different chromosomes
2.Expressed trait varies
greatly
Ex. Hair color, eye and skin
colors, height, weight

20. II. How to study patterns of inheritance in
families
Two Methods:
1. _KARYOTYPE: Photograph of an individual’s
chromosomes arranged in homologous pairs and
can be viewed underneath a microscope
a. Used to identify problems with chromosomes
• _ABNORMAL NUMBERS
• _DAMAGED OR BROKEN
• _TO DETECT GENETIC DISEASES

21. Typical Karyotype: Normal Individual
Pattern of Inheritance:
Normal Chromosome
Pattern
Abnormality:
None
Notation:
46, XY, Male

22. 2. _PEDIGREE CHART: Diagram to show
genetic traits and used to map genetic traits
through generations
a. Shows
SEX, PHENOTYPE
S, and
GENOTYPES of
family members
b. Can predict patterns
of inheritance
c. Uses symbols