1. Human Genetics
Chapter 12

2. Do you think this trait is dominant or recessive?
Human Genetic Traits
Do you think this trait is dominant or recessive?

3. Widow’s Peak?
DOMINANT

4. PTC Tasting
Can you taste the PTC????
DOMINANT

5. RECESSIVE Earlobe Shape? Is your earlobe attached?
Do you think this trait is dominant or recessive?
RECESSIVE

6. Dimples?
DOMINANT

7. Human Inheritance Humans - 23 pairs of chromosomes
These are made of about 100,000 genes
Scientists study disease causing genes because they can easily be traced
Pedigree – a family record that shows how a trait is inherited over several generations.

8. A Pedigree of Hemophilia in the Royal Families of Europe

9. Pedigree page 299 Carriers – usually, Heterozygous
-do not express the recessive allele, but pass it to their offspring
Square = Male
Circle = Female
No shading = normal
Shaded = displays trait
Half/Half = Carrier

10. Pedigree Practice
Construct a family pedigree of two unaffected parents with a child who suffers from cystic fibrosis.

11. Pedigree Practice
Suppose both parents can roll their tongues but their son cannot. Draw a pedigree showing this trait, and label each symbol with the appropriate genotype.

12. Pedigree Practice
Describe the pedigree of a boy who has galactosemia. His father has galactosemia, his paternal grandparents are phenotypically normal. His mother and maternal grandparents are both phenotypically normal.

13. A boy is an albino. His mother is also an albino
A boy is an albino. His mother is also an albino. His father is phenotypically normal. However, his paternal grandfather is an albino. The other 3 of his grandparents are phenotypically normal.

14. A brother and a sister both are hemophilic
A brother and a sister both are hemophilic. Neither parent shows this trait, however the maternal grandmother suffers from this disorder. The other grandparents are phenotypically normal.

15. On Your Own
Page 300
Mini Lab 11.1 – Investigate Human Pedigrees

16. Simple Dominant Heredity
Many traits are inherited just as the rule of dominance predicts.
Remember, in Mendelian inheritance, a single dominant allele inherited from 1 parent is all that is needed for a person to show the dominant trait.

17. Patterns of Inheritance
Traits controlled by a Single Allele
>200 traits are determined by a single dominant allele
Ex. Huntington’s Disease
>250 other traits are determined by homozygous recessive alleles
Ex. Cystic Fibrosis, PKU, blue
people in Eastern Kentucky

18. Sometimes Heredity Follows Different Rules
1. Incomplete Dominance: Appearance of a third phenotype
2. Sex-linked inheritance
3. Codominance: Expression of
both alleles

19. 1. Incomplete Dominance
Incomplete dominance - Cross between organisms with 2 different phenotypes
-produces offspring with a 3rd phenotype that is a blending of the parental traits. 
RED Flower x WHITE Flower ---> PINK Flower

20. R = allele for red flowers W = allele for white flowers red x white ---> pink RR x WW ---> 100% RW

21. 2. Sex determination
In humans, the diploid number of chromosomes = 46 (23 pairs)
There are 22 matching pairs of homologous chromosomes called autosomes.
The 23rd pair differs in males and females, they determine the sex of an individual (sex chromosomes)
X females (XX)
Y males (XY)
*Complete a punnett square to determine the expected ratio of males to females produced given their possible gamete contribution

22. Sex-linked inheritance
Traits controlled by genes located on sex chromosomes are called sex-linked traits
Sex-Linked Traits are found only on the X chromosome
Ex. Hemophilia (recessive)
Ex. Patterned Baldness
Homozygous baldness-both will lose hair
Heterozygous-men will lose hair but women will not
Ex. Colorblindness (recessive)

23. Color Blindness Activty
Draw your family pedigree for color blindness!
Predict what your children genotype could be if:
Boys – you married a woman who carried the trait for being color blind on her X chromosome
Girls – you married a man who was color blind

24. Patterns of Inheritance
Complete a punnett square to show how the allele for red eye color is a sex-linked trait

25. 3. Codominance
Codominance - the "recessive" & "dominant" traits appear together in the phenotype of hybrid organisms.
Example:
red x white ---> red & white spotted

26. R = allele for red flowers W = allele for white flowers red x white ---> red & white spotted RR x WW ---> 100% RW

27. Examples of Codominance
1. Roan fur in cattle
Cattle can be:
1. red (RR = all red hairs)
2. white (WW = all white hairs)
3. roan (RW = red & white hairs together)

28. 2. Human blood type: AB -2 types of protein
("A" & "B") appear together
on the surface of blood cells
How to determine Blood Types:
4 possible blood types (in order from most common to most rare):
O, A, B and AB.
O blood type = individual who is homozygous recessive (ii) and does not have an allele for A or B.

29. Blood types A and B are codominant alleles.
Recessive allele i (for blood type O) is only expressed when 2 recessive alleles are present.
Individuals who have blood type A:
Genotype = IAIA or IAi
Individuals who have blood type B:
Genotype = IBIB or Ibi
Individual who has blood type AB:
Genotype = IAIB
Individual who has blood type O:
Genotype = ii

30. Human Blood Types

31. **IMPORTANCE in Real-Life**
Blood transfusion can only take place between 2 people who have compatible types of blood.
Human blood is separated into different classifications because of the varying proteins on the surface of blood cells.
These proteins are there to identify whether or not the blood in the individual's body is it's own and not something the immunity system should destroy.

32. Blood type practice Use a Punnett Square!
A woman has type A blood. Her father has type O blood. The woman marries a man with type O blood. What is the chance that they will have a child with type A blood?
What is the chance that the couple from question 1 will have a child with type AB blood?
*Show me your answers when you are finished. Keep these in your notes!

33. Sickle Cell Anemia Read about Codominance on pg. 302-303
Define Codominance.
Explain Sickle-cell Disease in ½ page.
Complete Data Analysis Lab 11.1 on the bottom ½ of the page.

34. Sickle Cell Anemia Cont.
A Mutation Story:

35. Nondisjunction
Nondisjunction is the failure of homologous chromosome pairs to separate properly during meiosis. The result of this error is a cell with an abnormal (too few or too many) number of chromosomes.

36. Nondisjunction

37. Activity: Human Karyotype

38. Patterns of Inheritance
Disorders due to Nondisjunction
Monosomy (45 Chromosomes)
Trisomy (47 Chromosomes)
Trisomy-21 (Down Syndrome)
Trisomy-18 (Edwards Syndrome)
Trisomy-13 (Patau)
Child with Trisomy 21

39. Disorders due to Nondisjunction Cont.
Klinefelter’s (XXY)-male w/ some female traits
Turner’s (XO)-female appearance
Single Y chromosome do not survive
Typically Sterile

41. Environmental Effects
Genes are inherited from parents, but sometimes their expression is modified by environmental factors.
An example is the snowshoe hare we discussed earlier in the year-these hares have dark fur in the summer and white fur in the winter.

42. Snowshoe Hare

43. Detecting Human Genetic Disorders
Genetic Screening – examination of genetic makeup
Karyotype: a picture of chromosomes grouped in pairs and arranged in sequence.
Screening of Blood: look for certain proteins
Genetic Counseling-medical guidance informing of problems that could affect their offspring.

44. Detecting Human Genetic Disorders
Amniocentesis: removal of small amount of amnionic fluid surrounding the fetus
Chorionic Villi Sampling: tissue that grows between the mother’s uterus and the placenta (between the 8th and 10th week)
Screening Immediately after Birth:
Ex PKU (Phenylketonuria)-body cannot metabolize the amino acid phenylalanine
Special diet lacking phenylalanine

45. Karyotyping