CHAPTER 5-3

HUMAN GENETICS

The Human Genetic MakeupHumans have:

-23 pairs of chromosomes (46 individual chromosomes)

-22 pairs of autosomes

- 1 pair of sex chromosomes (X and Y)

MutationsFrom Ch. 4-3

• Any permanent change in a gene or chromosome is a mutation

A. If the gene is changed, the trait may be changed.

B. These mutations may occur during:1. DNA Replication

2. mRNA Transcription

3. tRNA Translation

4. This may result in incorrect protein production.

5. Sometimes a cell (zygote) may receive an extra chromosome.

Down’s Syndromeaka Triplody 21

Mutations cont.

C. Mutation may be caused by:1. Radiation2. Ultraviolet rays3. Chemicals

a) Herbicidesb) Insecticidesc) Drugsd) Smokinge) Alcohol

Mutations cont.

D. Mutations in body cells may or may not be dangerous.

1. Cancer is the big exception

E. Mutations in sex cells may affect any potential offspring.

F. Many organisms with mutations do not survive to birth.

G. Some mutations are good and may add variety to a species.

HUMAN GENETICSRecessive Genetic Disorders

A. Sickle-Cell Anemia1. A homozygous recessive disorder2. Red blood cells are sickle-shaped rather than disc-shaped.

a) Creates problems with oxygen delivery

b) Other tissues may be damaged due to lack of oxygen.3. Found in tropical areas and African

American populations.4.Can be treated with drugs and transfusions

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B. Cystic Fibrosis1. A homozygous recessive disorder2. An error of 3 base pairs on chromosome 73.Thick mucus is produced in the lungs and digestive system.

a) Causes damage to lungs leading to breathing problemsb) Causes damage to the pancreas leading to a reduction in digestive enzyme production

4. Common in Caucasians ,1 in 20 are carriers, Four babies are born with CF every day.5. Treated with antibiotics, diet, and physical therapy

Icf I

Icf

I

Icf Icf

I Icf

I Icf

II

I = Autosome

I Icf = Carrier for Cystic Fibrosis (does not have CF)

Icf Icf = Has Cystic Fibrosis

II = Healthy, Is not a carrier

Sex Determination

X YX XX XY

X XX XY

50% XX (female) 50% XY (male)

Sex (X) – Linked Disorders1. Color Blindness and Hemophilia

X XcX XX XcX

Y XY XcY

XX Not color-blindXY Not color-blindXcX Not color-blind but is a carrierXcY is color-blindWHY???????