Download genetics 2-2

Biology Notes
2-2-09
Baldness- a sex-influenced trait which is dominant in males, recessive in females
Color blindness- sex-linked genes in humans They are attached only to the Y
chromosomes
Hemophilia- a bleeders disease, sex-linked, attached only to the Y chromosome
When you cross a horse and a mule -> a “sterile donkey” (Jackass)
A germ mutation occurred in a reproduction cell and is transmitted to offspring.
A gene mutation is one that occurs in all our cells except the reproductive cells.
Factors that cause mutations
1. radiation
2. smoke
3. temperature changes
4. viruses
5. chemicals
6. crossing-over
Laws of Independent Assortment: the separation of gene pairs on a given chromosome
during meiosis is independent of distribution.
Law of Segregation: a pair of factors called genes segregate independently during the
formation of gametes.
Law of Dominance and Recessiveness: one gene in a pair may mask or prevent the
expression of the other.
GENETIC DISORDERS
PKU: A genetic disease due to a lack of an enzyme.
Klinefelter’s Syndrome- Results of non-disjunction when an abnormal sperm containing
both the X and Y chromosomes, fertilizes a normal X egg.
Turner’s Syndrome- Result’s from the absence of an X chromosome in an egg
Down’s syndrome- the result of an abnormal chromosome number, extra 21st pair of
chromosome.
Sickle cell anemia- a blood disease where the normal round red blood cell are shaped
like a sickle.
Fraternal twins: result from a separate eggs being fertilized by different sperm
1
Biology Notes
2-2-09
Identical twins: result from an egg being fertilized by same sperm
A mutation is a change in DNA.
Our heredity and environment both influence our genetic makeup.
Species characteristics: upright posture, speech symbols, fingers and toes for grasping.
Individual characteristics: eye color, hair color, blood types.
2