1. GAMETES and ZYGOTE Sex cells: sperm and egg that are haploid.
Contain 1 allele from each gene
Contain 1 chromosome of each type
Male gametes are smaller than female
Fuse to create a zygote
Zygote contains 2 chromosome of each type so are diploid
Zygote have homologous pairs
2 alleles of each gene

2. Gregor Mendel Father of Genetics
Crossed Pea Plants to show inheritance
Conducted Good Science Research
Lots of replicates and reliable data
Law of segregation:
During meiosis 2 alleles of each gene separate from each other to produce 4 haploid nuclei.
Segregation allows new combinations in offspring.

3. Dominant, Recessive and Codominant Alleles
Dominant masks recessive
Dominant usually codes for a functional protein whereas recessive for a non- functional protein.
Codominant have joint effects

4. phenotype
Homozygous dominant
genotype
Homozygous recessive
heterozygous

5. Genetic Diseases
Most genetic disease are rare because they are caused by a recessive allele
Must inherit a recessive allele from each parent to show the disease and this chance is very small.
Heterozygous parents who do not show the disease are called carriers.
Some diseases are result of sex- linkage, dominance or codominance.

6. Possible Allele Combinations
Disease
Alleles
Possible Allele Combinations
Cystic Fibrosis
Recessive allele, must be inherited from both parents
FF – normal
Ff – normal, but carrier
ff – cystic fibrosis
Huntingtons Disease
Dominant allele, no carriers
HH- huntingtons
Hh –huntingtons
hh - normal

7. Possible Allele Combinations
Disease
Alleles
Possible Allele Combinations
Sickle Cell Anemia
Codominant, gives 3 phenotypes
HbAHbA – normal, not anemic
HbAHbS – mild anemia, resistant malaria
HbSHbS – severe anemia, susceptible malaria

8. Possible Allele Combinations
Disease
Alleles
Possible Allele Combinations
Color Blindness
Sex-linked on the X chromosome, more common in males
Female’s father must have it for female to show
XBXB – normal female
XBXb – normal female, but carrier
XbXb – color blind female
XBY – normal male
XbY – color blind male
Hemophilia
XHXH - normal female
XHXh – normal female, but carrier
XhXh – hemophilia female
XHY – normal male
XhY – hemophilia male