1. Genetics: Branch of biology dealing with genes and heredity
Genes: bits of DNA on chromosomes
Usually 2 genes for a trait
Dominant Gene: always seen in the population – represented by a capital letter
Recessive Gene: overpowered by the dominant gene – represented by a small letter
Trait: a feature or characteristic (eye color, hair color)
Alleles: different forms of a gene on a homologous chromosome

2. Gregor Mendel (1822-1884) The “Father of Genetics”
Austrian monk who worked with pea plants (28,000 plants in a 10 year span)
Use of favorable material (easy to raise)
Self-pollination (creation of pure strains) and cross-pollination possible
Discontinuous traits (2 contrasting forms)
Could study 1 trait at a time
Large numbers of offspring produced

3. Mendel’s Three Laws:
Law of Dominance: One gene can mask another gene (dominant versus recessive)
Phenotype: the appearance of the organism
Genotype: the arrangement of genes
Homozygous Dominant (FF)
Homozygous Recessive (ff)
Heterozygous (Hybrid) (Ff)
Law of Segregation: In gamete formation, genes are separated
Rule for # of gametes: 2n (n= # of hybrids)
Law of Independent Assortment: In gamete formation, genes separate independent of each other
Exception: linkage (blonde hair, blue eyes)

4. Rules for Problem-Solving:
Write down dominant and recessive genes
Write down parents’ genes (P generation)
Get parents’ gametes
Do the cross on a punnett square (board for offspring possibilities – F1 generation)
Get results and label answer

5. Types of Problems: Simple 1 trait cross Monohybrid Cross (Ff X Ff)
Genotype: 1:2:1 Phenotype: 3:1
Simple 2 trait cross
Dihybrid Cross (FfDd X FfDd)
Phenotype: 9:3:3:1
Incomplete Dominance (3 phenotypes present)
Andalusian Fowl FF (black) ff (white) Ff (blue)
Roan Cattle FF (brown/reddish) ff (white) Ff (brown with white)
Four O’Clock Flowers FF (red) ff (white) Ff (pink)

6. Multiple Alleles: traits with more than one pair of alleles
Examples: Rabbits (coat color) Humans (blood groups)
Human Blood Groups Karl Landsteiner
Also called Codominance (2 dominant alleles/1 recessive allele)
A and B = dominant O = recessive
4 Human Blood Types: A B AB O (phenotypes)
Type A: AA AO (genotypes)
Type B: BB BO (genotypes)
Type AB: AB (genotype)
Type O: OO (genotype)
Test Cross: used to determine the genotype of an organism
Use homozygous recessive X the unknown genotype

7. 1903 Walter Sutton: factors as genes
1909 Thomas Hunt Morgan: Colombia University - used Drosophila melanogaster as a research animal
Easy to raise
Eat simple food
Life cycle (10-15 days) many generations
Easy to distinguish the sexes
4 pairs of chromosomes (3 pairs of autosomes)
Large salivary gland chromosomes
Easy storage
1 pair of sex chromosomes with sex-linked traits (white eyes) XX, XY
Genetic Maps: specific location of genes on chromosomes
Crossing over of genes (“jumping genes”)
Barbara McClintock: research with corn

8. Mutations A change in DNA (a “mistake” in DNA)
Add diversity
Most are recessive
Not usually positive
Inherited
Caused by mutagens (chemicals, food additive, radiation, viruses)
Somatic Mutation: in body cells (not passed on)
Germ Mutation: in sex cells (passed on)
Gene Mutation:
Deletion (a gene is omitted) agethol agetol
Insertion (a gene is added) agethol agethoyl
Frameshift (a section is reversed) agethol aolgeth

9. Chromosomal Mutation:
Inversion: piece of a chromosome breaks off and reattaches itself to the same chromosome backwards
Translocation: piece of one chromosome breaks off and reattaches itself to a different chromosome (Stillbirths)
Human chromosome number = 46 (2n)
n = # of chromosomes in a sperm or egg
Aneuploidy = 1+ or - the 2n number (either 45 or 47 chromosomes)
Monosomy: 45 (2n-1)
Turner’s Syndrome (X_) Sterile female underdeveloped
Trisomy: 47 (2n+1)
Down’s Syndrome (extra #21 chromosome)
Kllinefelter’s Syndrome (XXY) Sterile male feminized
(XYY) Tall male with acne (criminal tendencies)
(XXX) Fertile female (mentally challenged)

10. Human chromosome number = 46 (2n)
Polyploidy: whole sets of chromosomes are inherited (3n, 4n, etc.) plants
Human chromosome number = 46 (2n)
n = # of chromosomes in a sperm or egg cell
Sex Linked Condition: recessive abnormality on the X chromosome Hemophilia: XHXH XHXh XhXh XHY XhY
Colorblindness XCXC XCXc XcXc XCY XcY
Sex Influenced Condition: not sex linked; not attached to the X chromosome; patterned baldness (influenced by female hormones)
Genetic Abnormalities:
PKU: affects infants; lack an enzyme; problems with amino acids
Sickle Cell Anemia: Pain at joints, fatigue; affects Black Americans; red blood cell shape of sickle; (1 in 500 is a carrier)
Cystic Fibrosis: Caucasian disease; excess mucus during digestion
Tay Sachs: Jewish infants (1 in 3 is a carrier)

11. Genetic Counseling: Genetic Engineering:
Galactosemia: problems with sugar breakdown
Huntington’s Disease: causes insanity; dominant gene
Genetic Counseling:
Sonagrams of fetuses
Amniocentesis: technique in which amniotic fluid is extracted and examined
Karyotype: a picture of the chromosomes
Pedigree: a family history of genes
Genetic Engineering:
Cloning/Gene splicing
Human Genome Project
“Green Revolution”