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Chapter 11 Notes

Human Heridity

Links !

PBS link to 16 part video Cracking the Human Code.

Help with a animated tour of DNA and genes.

The new science of forensic DNA analysis starting in 1987

The power of DNA evidence lies in statistics. Certain chromosome sites contain unique sequences of base pairs. Forensics technicians typically analyze three to five of these sites, called polymorphic markers, making a probability that only one person in, say, 100,000 or 1,000,000 could have the same profile.

Banding on chromosomes and activity to 'match' pairs of chromosomes

Mutations, changes in the DNA sequence of a gene and the impacts on health

 



Chapter 11

Human Genetics

I.                    Types of Chromosomes

A.     autosomes-22 pairs per somatic cell

B.     sex chromosomes-1 pair, pair #23

1.      females=XX

2.      males=XY

C.     Y chromosome is responsible for maleness characteristics.

II.                 Sex-Linked Genes

A.     Genes are located on the X sex or Y chromosome. x-linked

B.     Colorblindness:

1.      Females are often carriers

2.      Occurs most often in men

3.      ex: Normal vision=C (dominant)

Colorblindness = c (recessive)

                                    Problems: Normal male X carrier female.

C.     Hemophilia- clotting factor is missing in blood.

h=hemophilia

H=normal

D.     Muscular Dystrophy- progressive wasting away of muscle tissue due to genetic defect of gene.

III.               Sex Influenced Traits

A.     Gene located on autosomes that differs when expressed in a male or female.

B.     Baldness: B= normal hair, b=baldness

1.      bb=male and female bald

2.      Bb-male bald only

Problem: Hetero. Male X hetero. Female

IV.              Chromosomal Abnormalities

A.     Nondisjunction- failure of a chromosome pair to separate during meiosis.

1.      Downs Syndrome- (Trisomy 21)

a.       Extra #21 chrom.

2.      Klinefelters Syndrome

a.       47 chromosomes-XXY

3.      Turners Syndrome

a.       45 chromosomes-XO

V.                 Genetic Diseases

A.     Huntington disease- H   h=normal

1.      single dominant allele is responsible

2.      slow destruction of nervous system.  The only way 2 not have Huntingtons is hh.

B.     Sickle Cell Anemia

1.      abnormal shape of red blood cells

2.      normal allele is codominant with sickle allele.

3.      heterozygous genotype is partially  resistant to malaria.