1. Ch. 14 The Human Genome

2. Ch. 14 Outline 14-1: Human Heredity Human Chromosomes Human Traits
Human Genes
From Gene to Molecule

3. Ch. 14 Outline 14-2: Human Chromosomes 14-3: Human Molecular Genetics
Human Genes and Chromosomes
Sex-linked Genes
X-Chromosome Inactivation
Chromosomal Disorders
14-3: Human Molecular Genetics
Human DNA Analysis
The Human Genome Project
Gene Therapy
Ethical Issues in Human Genetics

4. Human Chromosomes Karyotypes:
A Picture of chromosomes arranged in rows is a karyotype

5. Human Chromosomes Humans have 23 pairs (46 total) chromosomes.
Two of the 46 chromosomes are called sex chromosome because they determine an individual’s sex.
In Human’s:
Female – two copies of large X chromosome
Male – one X and one small Y chromosome

6. Karyotype

7. Human Chromsomes
Autosomes: the remaining 44 chromosomes. They do not determine the sex of the organism.
All Human egg cells carry a single X chromosome.
Half of all sperm cells carry an X chromosome and half carry the Y.
This ensures that about half of the zygotes will be female XX and half will be male XY.

8. Human Traits
Biologists must identify an inherited trait controlled by a single gene
Must establish that the trait is actually inherited and not the result of environmental influences

9. They study how the trait is passed from one generation to the next
Human Traits
They study how the trait is passed from one generation to the next
Scientists use a pedigree chart to help study how a trait is passed from one generation to the next.
Pedigree: a chart that shows the relationships within a family.

10. How to read a pedigree A square represents a male.
A circle represents a female.
A vertical line and a bracket connect the parents to their children.
A horizontal line connecting a male and female represents a marriage.
A circle or square that is not shaded indicates that a person neither expresses the trait nor is a carrier of the trait.
A half-shaded circle or square indicates that a person is a carrier of the trait.
A completely shaded circle or square indicates that a person expresses the trait.

11. Pedigrees
These Charts are used to infer the genotypes of family members.
They can reveal if traits are sex-linked, dominant or recessive.

12. Using a Pedigree
A human geneticist determined the pedigree shown in the diagram with filled symbols showing the affected individuals. How is this pattern of inheritance described?

13. Using a Pedigree
Below is a pedigree for an inherited lung disease.  Provide the genotypes of each of the individuals marked with lower case letters.

14. Using a Pedigree
Below is a pedigree for an inherited brain disease.  Provide the genotypes of each of the individuals marked with lower case letters.
Brain Disease

15. Human Genes
Biologists were able to identify genes that directly control a single human trait. Some of the very first genes to be identified were those that controlled blood type.
Blood Group Genes
Knowing a person’s blood group is important during transfusions.
Two blood groups:
Rh groups
ABO groups

16. The Rh Blood Group
The Rh blood group is determined by a single gene with two alleles: Positive and negative
Rh+ is dominant to Rh-
The Rh factor is named after the Rhesus Monkey where the factor was first isolated
Very important for females to know during pregnancies.

17. ABO Blood Groups There are three alleles for the ABO Blood Group:
IA, IB, I
“i” is the recessive allele. ii  type O blood
IAIB are codominant  type AB blood
IAIA or IAi  type A Blood
IBIB or IBi  type B Blood

18. ABO Blood Groups Safe Transfusions Phenotype (Blood Type Genotype
Antigen on
Red Blood Cell To
From

19. Antigens and Blood

20. Disorders in Humans Genetic Disorders may be caused by:
Recessive Alleles
Ex. CF, PKU, Tay-Sachs
Dominant Alleles
Huntington’s Disease
Codominant Alleles
Sickle Cell Anemia

21. Concept Map Autosomol Disorders caused by Recessive alleles
Dominant alleles
Codominant alleles
include
include
include
Albinism
Galactosemia
Tay-Sachs disease
Huntington’s disease
Sickle cell disease
Cystic fibrosis
Phenylketonuria
Achondroplasia
Hypercholes-
terolemia

22. Sex-Linked Genes
Sex-linked genes: Genes Located on the sex chromosomes
Many genes are located on the X chromosome
Males have just one X chromosome. Thus, all X linked alleles are expressed in males, even if they are recessive.
Sex-linked disorders are caused by genes on the X or Y chromosome
Colorblindness, Hemophilia

23. Sex-Linked Genes : Pedigree for Color Blindness

24. X-Chromosome Inactivation
Females have two X chromosomes but males only have one. How do females cells “adjust” to having an extra X if males can survive with just one?
One of the X chromosomes in female cells are randomly switched off. Those are called Barr bodies.

25. Chromosomal Disorders
Nondisjunction: failure of chromosomes to separate correctly in meiosis
This leads to an abnormal number of chromosomes in gametes
Ex: Down Syndrome (3 copies of chromosome 21  “trisomy”)

26. Homologous chromosomes fail to separate
Nondisjunction
Homologous chromosomes fail to separate
Meiosis I:
Nondisjunction
Meiosis II

27. Nondisjunction can occur with autosomes or sex Chromosomes during meiosis

28. Chromosomal Nondisjunction Disorders

29. Down Syndrome Trisomy 21 Down Syndrome
1 in 31,000 births 46 chromosomes
XY=97% XX=3%
1 in 1,250 births
47 chromosomes XY or XX
#21 Trisomy Nondisjunction

30. Down Syndrome Short, broad hands Stubby fingers Rough skin
Impotency in males
Mentally impaired
Small round face
Protruding tongue
Short lifespan

31. Patau’s Trisomy Syndrome
1 in 14,000 births
47 chromosomes XY or XX
#13 Trisomy Nondisjunction

32. Patau’s Trisomy Syndrome
Small head
Small or missing eyes
Heart defects
Extra fingers
Abnormal genitalia
Mentally impaired
Cleft palate
Most die a few weeks after birth

33. Edward’s Trisomy Syndrome
1 in 4,400 births 47 chromosomes
XX =80% XY=20%
#18 Trisomy Nondisjunction

34. Edward’s Trisomy Syndrome
Small head
Mentally impaired
Internal organ abnormalities
90% die before 5 months of age

35. Turners Syndrome 1 in 5,000 births 45 chromosomes X only
#23 Monosomy Nondisjunction

36. Turners Syndrome 96-98% do not survive to birth No menstruation
No breast development
No hips (curve)
Broad shoulders and neck

37. Jacob’s Syndrome
1 in 1,800 births
47 chromosomes XYY only
#23 Trisomy Nondisjunction

38. Jacob’s Syndrome Normal physically Normal mentally?
Normal physically Normal mentally
Increase in testosterone
More aggressive
Normal lifespan

39. Kleinfelter Syndrome 1 in 1,100 births 47 chromosomes XXY only
#23 Trisomy Nondisjunction

40. Kleinfelter Syndrome Scarce beard Longer fingers and arms Sterile
Delicate skin
Low mental ability
Normal lifespan

41. Triple X Syndrome 1 in 2,500 births 47 chromosomes XXX only
#23 Trisomy Nondisjunction

42. Triple X Syndrome
Normally physically Normal mentally
Tall
Fertile
Short lifespan

43. The Human Genome Project
A research project to sequence (identify in order) all the bases in Human DNA ~3.2 BILLION pairs!
Some discoveries:
A large amount of DNA does not code for proteins
Humans only have 30,000-40,000 genes (scientists expected 100,000)

44. The Human Genome Project Website
Really interesting Information about the Human Genome Project. It might help you understand stuff better.
EDUCATE YOURSELF!

45. Gene Therapy
Information about the human genome might be used to cure genetic disorders though the use of gene therapy.
Gene therapy: the process of changing a gene that causes a genetic disorder
It replaces the faulty gene with a normal, working gene

46. Ethical Issues
If Human cells can be manipulated to cure disease, should biologists try to engineer people with specific traits?
What will happen to the human species if we design our own bodies?
Should we clone humans?