1. Chapter 14 – Human Genome

2. Human Chromosomes
Karyotype – arrangement of chromosomes in their homologous pairs and by length
Humans – 23 pair
22 pair of autosomes
1 pair of sex chromosomes

3. Pedigree Graphic representation of genetic inheritance
Circle = female: square = male
Shaded = have trait; not shaded = do not have trait
Most recent generation
at bottom
Generations identified by
Roman numerals
Individuals identified by
Arabic numbers (1,2,…)

4. Simple Recessive Heredity
Most genetic disorders are caused by recessive alleles
Albinism
Cystic fibrosis (CF)
1 in 20 – carrier;
1 in 2000 – have it
Defective protein in plasma
membrane results in formation and
accumulation of thick mucus in lungs and digestive tract
Most common disorder among white Americans

5. Simple Recessive cont. Tay-Sachs disease Phenylketonuria (PKU)
Fatal disorder of central nervous system
Lipid build up on brain
Most common in US among Amish
Phenylketonuria (PKU)
Absence of enzyme that converts certain amino acids
Damage to CNS, mental retardation
Most common among people with ancestors from Norway and Sweden

6. Simple Dominant Heredity
Simple Dominant Traits
Tongue rolling, Hapsburg lip, earlobe types, hitchhiker’s thumb, almond eyes, thick lips, hair on middle of fingers
Huntington’s disease
Rare, lethal
Breakdown of brain
Onset between ages of 30-50
Achondroplasia - dwarfism

7. Codominance in humans Sickle-cell anemia
Twisted, bent (sickle-shaped) red blood cells
Cells are not able to carry oxygen normally, blood blow slows, blockage of smaller vessels, shorter life span for cells
Produces physical weakness and
damage to heart and brain
Most common in African Americans
1 out of 12 are heterozygous –
produce normal and sickle

8. Multiple Alleles in humans
Blood groups – ABO groups and Rh group
Rh – single gene with 2 alleles – positive and negative
ABO groups
Determined by presence or absence of certain molecules on surface of red blood cell
Types : A, B, AB, O
Genes : IA, IB, i
Used to determine parentage
Ex. Child AB, mom A, man w/ O can not be father

9. Transfusions – need to know type to determine compatibility
A – IAIA, IAi
Can get from A or O
Can give to A or AB
B – IBIB, IBi
Can get from B or O
Can give to B or AB
AB – IAIB
Can get from A, B, AB, or O – universal recipient
Can give to AB
O – ii
Can get from O
Can give to A, B, AB, or O – universal donor

10. Sex-linked traits Genes are found on the X or Y chromosomes
Colorblindness – most common red-green (found in 1/10 males in US)
Recessive on X chromosome
XBXB, XBXb – normal female
XbXb – colorblind female
XBY – normal male
XbY – colorblind male
Hemophilia – blood does not clot – may bleed to death from minor cuts
1/10,000 males have
1/1 million females have

11. Calico cats
X chromosome may carry either black alleles or orange alleles
Females may have spots of both colors – 2 X chromosomes
Males only have one X chromosome so they will have black spots or orange spots but not both

12. Changes in chromosome #
Nondisjunction (homologous pairs do not split) occurs resulting in unusual numbers of autosomes – normal is 22 pair
Trisomy – have 3 of a certain autosome instead of 2 – results in 47 chromosomes
Ex. Down syndrome – trisomy of chromosome 21 – occurs 1/800 births

13. Changes in # cont. Unusual numbers of sex chromosomes
Turner’s syndrome – females
Have only 1 X chromosome
Are sterile, sex organs may not develop
Klinefelter’s syndrome – males
Have an extra X – XXY
Usually sterile

14. Applications Human DNA Analysis Human Genome Project
Used to test for genetic disorders
DNA fingerprinting – used to identify individuals
Human Genome Project
Mapped the human DNA strand
Gene therapy – an absent or faulty gene is replaced by a normal, working gene
Still working on perfecting the practice