1. PATTERNS OF INHERITANCE AND HUMAN GENETICSBY
DAWN M. THOMPSON

2. SIMPLE RECESSIVE INHERITANCE
CYSTIC FIBROSIS:CF
Common in white Americans 1:2000
Caused by defective protein in plasma membrane.
Mucus accumulates in lungs and digestive tract.
Controlled by physical therapy, diet, drug therapy
Life expectancy improving annually
Person must have 2 recessive alleles to suffer from CF. 1 allele carrier but shows no symptoms

3. PKU
Phenylketouria
Caused by the absence of an enzyme that converts the amino acid phenylalanine to tyrosine.
Accumulation of phenylalanine leads to mental retardation and CNS damage
Newborns are given a blood test to check for the absence of the enzyme
Milk products are high in phenylalanine
Disorder is treatable by controlling diet from birth

4. OTHER RECESSIVE TRAITS
TAY-SACHS
ATTACHED EAR LOBES
DO PROBLEM SOLVING LAB 12.1 p317

5. SIMPLE DOMINANT TRAITS
HUNTINGTON’S DISEASE:
Lethal disorder, no treatment
Certain areas of the brain breakdown
Symptoms; neurological and muscular show at the age of 30+
Genetic testing is available before symptoms show
Ethical issues
Every child of an affected person has a 50/50 chance of inheriting the disease
Only 1 defective allelle required for person to show disease

6. OTHER DOMINANT TRAITS Unattached ear lobes Tongue rolling Hapsburg lip
Hitchhiker’s thumb
Hairy fingers
Almond shaped eyes
Thick lips
Widow’s peak

7. INCOMPLETE DOMINANCE

8. INCOMPLETE DOMINANCE
Heterozygous phenotype is intermediate between those of the two homozygotes
Red flower x white flower
Intermediate phenotype is pink F1 F2 R’ R’ R R’ R R
R’R
R’R RR
R’R R R’
R’R
R’R
R’R
R’R’

9. CODOMINANCE
CODOMINANT ALLELES CAUSE THE PHENOTYPE OF BOTH HOMOZYGOTES TO BE PRODUCED IN THE HETEROZYGOTE INDIVIDUALS. BOTH ALLELES ARE EXPRESSED EQUALLY B W
B = black feathers in chickens
W = white feathers in chickens
BB = black chicken
BW = checkered chicken
WW = white chicken BB BW B BW WW W

10. CODOMINANT TRAITS SICKLE-CELL ANEMIA
Common among African Americans 1:12
Homozygous people for trait differ by 1 amino acid coding for hemoglobin compared to normal people
Abnormal hemoglobin is sickle celled
Sickle shaped cells block blood vessels reducing the amount of oxygen reaching the tissues
Shortened life span

11. HETEROZYGOUS ADVANTAGE
People who are heterozygote for the trait produce both normal and abnormal hemoglobin
Show no symptoms of sickle- cell anemia
Less likely to suffer from malaria
This explains why African’s suffer more from sickle-cell anemia

12. MULTIPLE PHENOTYPES FROM MULTIPLE ALLELES
Traits controlled by more than two alleles have multiple alleles

13. BLOOD GROUPS ABO blood group Single gene I has 3 different alleles
Blood type A genotype IA IA IA i
Blood type B genotype IB IB IB i
Blood type AB genotype IA IB (codominant)
Blood type O genotype ii (recessive)
Important in blood transfusions and paternity suits
Refer to ABO blood group information page 325

14. SEX DETERMINATION Autosomes 22 pairs of homologous chromosomes
23 rd pair of chromosomes are sex chromosomes X and Y
Female XX chromosomes
Male XY chromosomes
Gametes carry either an X or Y chromosome
Fertilization results in offspring having either XX or XY chromosomes
There is a 50:50 chance of producing a male or female each time an offspring is produced.

15. SEX-LINKED INHERTANCE
Experiments conducted by Morgan
Worked with Drosophila (fruit flies)
Easy to keep: feed on banana, live in a vial, reproduce in a few days, produce large numbers of offspring.
Observed males had white eyes more often than females
Suggested gene for eye color was carried on the X chromosome and Y chromosome has no corresponding gene for eye color

16. INHERITANCE OF EYE COLOR IN DROSOPHILA

17. COLOR BLINDNESS X-linked disorder
Inability to differentiate between two colors such as red and green
Males are more susceptible because they have to inherit 1 defective X chromosome to suffer from the disorder females needed to inherit 2 defective chromosomes.
Most serious problem is the inability to detect traffic light colors

18. HEMOPHILIA X-linked disorder
Caused by a lack of factor VIII a blood clotting enzyme
Inability to clot the blood
1:10,000 males 1:100million females
Males are more susceptible because they have to inherit 1 defective X chromosome to suffer from the disorder females needed to inherit 2 defective chromosomes.
Treated by blood transfusions and injections of factor VIII.
Treatments are expensive and some people have contracted AIDS.

19. POLYGENTIC INHERITANCE
A trait is controlled by two or more genes.
Inheritance of eye color, height, stem length, skin color.
Bell shaped curve.

20. ENVIRONMENTAL INFLUENCES
Factors that determine how genes or expressed in an organism.
External environmental: temperature, light, chemicals, and infectious agents influence gene expression. Temperature determines coat color of artic foxes
Internal environmental: males and females differ because of differences in hormones and structures. Horn size in males greater than females.
Male pattern baldness and feather color in peacocks is influenced by different hormones in different sexes

21. ENVIRONMENTAL INFLUENCES

22. CHANGES IN CHROMOSOME NUMBERS
Nondisjunction: paired chromosomes fail to separate properly during meiosis
TRISOMY: 47 chromosomes
Down’s syndrome: chromosome 21 3 copies inside of 2. Mental retardation etc, higher incidence in women over 40.
Klinfelter’s syndrome: males, extra X or Y chromosome.
MONOSOMY: 45 chromosomes
Turner’s syndrome: females, missing X chromosome, mental retardation, sterile.

23. KARYOTYPE
Chart of chromosome pairs used to evaluate unusual chromosome numbers in cells.
Amniocentesis is the procedure by which the cell are collected for analysis and production of the karyotype.