Download Chapter 12 – Human Genetics

Chapter 11, 12, and 13: Human Genetics
I.
Chromosomes and Inheritance
A. Sex Determination
1. T. Morgan (1920’s) – Fruit fly(Drosophilia) experiments.
2. Chromosome Theory
a. Autosomes – body chromosomes.
b. Sex Chromosomes – determine sex.
c. Gene arrangement – single file on the chromosome
1) Linkage group – genes located on the same
chromosome.
2) Chromosome map – diagram that shows the
genes on a chromosome.
d. Crossing over – leads to a variation of traits.
3. Sex – Linked Traits – controlled by genes located on the
sex chromosomes.
a. X-linked.
b. Y-linked.
B. Mutation – a change in DNA which results in a new
phenotype; can occur in somatic(body) cells or gametes.
1. Chromosome mutations
a. Deletion
b. Inversion
c. Translocation
d. Duplication
e. Nondisjunction
2. Gene mutations – involve the nitrogen bases.
a. Point – involves a single nucleotide.
b. Frameshift – involves the addition or deletion of
a nucleotide.
3. Mutagens – cause mutations.
a. Radiation.
b. Chemicals.
c. Viruses.
d. Natural causes (chance).
II. Human Genetics
A. Studying Human Heredity
1. Population Sampling.
2. Twin Studies – effects of environment on heredity.
3. Pedigree – a family record showing the occurrence
of a trait from one generation to the next.
4. Karyotype – picture of a person’s chromosomes.
5. Human Genome Project – world wide research
project.
a. 50,000 + genes.
b. Map and identify genes.
c. Gain information – cure, treatment,
prevention, and testing of genetic disorders.
B. Genetic Traits and Disorders
1. Single allele, dominant
a.
b.
c.
d.
e.
f.
Huntington’s Disease
Achondroplasia
Polydactyly
Cataracts
Neurofibromatosis
Spina bifida
2. Single allele, recessive
a.
b.
c.
d.
e.
Albinism
Cystic fibrosis
PKU
Tay Sachs
Sickle cell Anemia
3. Polygenic traits – controlled by many genes; many
variations; influenced by environmental factors.
a.
b.
c.
d.
e.
f.
Skin color
Hair color
Eye color
Height
Foot size
Most human traits
4. Multiple alleles – controlled by three or more alleles
of the same gene.
a. Blood type (ABO system).
5. X-Linked Traits
a.
b.
c.
d.
Color blindness
Night blindness
Hemophilia
Muscular dystrophy
6. Sex-Influenced Traits – affected by male and female
hormones.
a. Baldness
7. Nondisjunction – failure of chromosomes to
separate during gamete formation(meiosis).
a. Autosomal
1) Trisomy 21(Down’s Syndrome)
2) Trisomy 13
3) Trisomy 18
b. Sex Chromosome
1)
2)
3)
4)
Turner’s Syndrome(XO)
Klinefelter’s Syndrome(XXY)
XXX
XYY
C. Detecting Genetic Disorders
1. Genetic Screening – an exam of a person’s genetic
make up.
a. Karyotype.
b. Chemical analysis – testing a body fluid for the
presence or absence of organic compounds.
2. Genetic Counseling – medical guidance.
3. Pre-Natal Diagnosis
a. Ultrasound – sound waves reflect off the fetus
and produce an image called a sonogram.
b. Amniocentesis – analysis of amniotic fluid.
c. Chorion villi sampling – analysis of villi cells.
d. Fetoscopy – pictures of the fetus are taken by a
microscopic camera.