http://www.expertsmind.com/topic/biology/biochemistry-92044.aspx

1. The Principles of Genetics
Mendelian Genetics
Monohybrid cross
Dihybrid cross
Polyhybrid cross

2. Definition, Concepts and Topics of Genetics
• The word Genetics is derived from the Greek word genetikos,
"genitive" combined with genesis, "origin"
• Genetics is the most exciting field of biology, it is the science of
genes, heredity and variation in living organisms. It is concerned
with mechanisms of heredity by which traits “characters” are
passed from generation to generation
• Genetics also deals with the molecular structure and function of
genes, e.g. gene behavior in the context of a cell or organism, patterns
of inheritance from parents to offspring, and gene distribution,
variation and change in populations
• Genes are universal to all living organisms, and are applied to
the study of all living systems, from viruses and bacteria, to
plants and animals, Special attention is given to crop plants and
domestic animals and humans

3. Characters studied by Mendel
Seven Characters in Garden peas

4. Why Garden pea (Pisum sativum) ?
• Garden pea has a short life cycle
• Garden pea has several observable contrasting characters
• Garden pea is a self pollinating plant
• The general features for a good genetic experimental
organism are:-
• short life cycle
• easy to grow and breed
• produce large number of offspring

5. The monohybrid cross, Law of segregation
Inheritance of stem length in Garden pea
Phenotype Tall Dwarf Recessive
Dominant
Parents
Tall
Genotype DD
dd
F1
Dd
Phenotype 3 Tall 1 Dwarf
F2
Genotype DD Dd Dd dd
DD = Homozygous Dd = Heterozygous dd = Homozygous

6. Explanation of the law of segregation
Inheritance of stem length in Garden pea
D d
D DD Dd
Tall Tall
d Dd dd
Tall Dwarf
3- Tall 1- Dwarf

7. Law of independent assortment
Inheritance of seed shape and color in Garden pea
Parents Tall plants, Round seeds Dwarf plants, wrinkled seeds
DDWW ddww
P. Gametes DW dw
F1 Phenotype: Tall plants Round seeds
Genotype: DdWw
W DW
F1 D
w Dw
Gametes
W dW
d
w dw

8. Mendel’s Foundations of Genetics
• Genes are found in allelic pairs
• One allele is dominant and the other is recessive
• Law ofsegregation: Each character is controlled by
a pair of (factors) genes that segregate at
meiosis and reunite in the offspring
• Law of independent assortment: Each pair of
genes segregate independently of all other
pairs during gamete formation

9. About Chromosomes
• What is a chromosome?
• Eukaryotic DNA: multiple linear diploid chromosomes
• Number of chromosomes (types) depends on species
• Chromosomes replicate
Unwound form of
DNA = Chromatin

10. • Terms: chromosome vs chromatid
chromatin vs condensed chromosome
centromere vs centriole
dulipcated chromosome vs homologous pair
• 2 cell types: 1. somatic cell: body diploid = 2 sets
2. gamete: sex cell M & F haploid = 1 set
• Human genome has 23 types of chromosome 22
autosomes + 1 sex chromosome (#23) human
conception = 23M + 23F = 46 chromosomes NOTE: these are
NOT stuck together – NOT identical
• How do corresponding M & F chromosomes compare? Same
genes in same corresponding positions…but… Are they exactly
alike? Alleles: different forms of a gene

11. Eukaryotic cell division
• 2 ways that Eukaryotic cells divide: 1.
Mitosis: cell division for growth, healing & asexual repro.
1 diploid set  2 identical diploid sets (1 round)
  replication  + 
somatic cells only
somatic cells genetically identical cloning?
2. Meiosis: cell division (2 rounds) for gamete formation
1 diploid set  2 diploid sets  4 haploid sets
NOT identical genetic variability
strategy of sexual reproduction
• What is replication? It precedes cell division 46 X 2 = 92

12. Cell cycle
90%
Replication happens here
23 x 2  23 x 2 x 2