Genetic JournalsGenetic Journals
• American Journal of Medical
Genetics Clinical Genetics
• Developmental Genetics Human
• Genetics European J. of Human
• Genetics Selection Evolution
• Genetika Fungal Genetics and
• Genome Cancer Genetics and
• Genomics American J. Human
• Hereditas Opthalmic Genetics
• Japanese Journal of Human
Genetics Human Genetics
• Journal of Heredity Current
• Molecular Biology and
Evolution Animal Genetics
• Molecular Ecology Brazilian J.
• Molecular and General Genetics
• Theoretical and Applied
Genetics J. of Medical Genetics
• Trends in Genetics
Basic Concepts of Genetics
Nucleus - contains genetic material
DNA - genetic material
4 bases (nucleotides G, C, A, T)
Gene - functional unit of heredity
sequence of 4 nucleotides
Chromosome -linear DNA molecule
1865 Gregor Mendel
- controlled genetic
experiments (garden peas)
- statistical regularity
- theory of inheritance
• Relationship between:
set of genes morphology
1. Attributes of the phenotype that
vary among individuals
2. Phenotypic variation caused by
Genotype and Phenotype
• The genotype is our actual genes. We
cannot see our genes.
• The phenotype is the physical expression of
• Genes - cannot be observed directly
• Phenotypes - observed directly
** inheritance of phenotypes used to
infer the inheritance of genes
Seven Pea varieties “True Breeding Lines”
Character “traits” Phenotypes
1. seed shape round, wrinkled
2. seed colour yellow, green
3. flowers (pods) axial, terminal
4. pods full, constricted
5. pods yellow, green
6. flowers violet, white
7. stem tall, dwarf
Gametes carry the genetic information about
The male gamete produce Sperm.
The female gametes produce Eggs.
The process in which one gamete is united
with another is called Fertilization.
• When an organism has both male and
female gametes, they are able to self-
• easy to grow
• matures in a season
• easy to cross-fertilize
• Some characteristics overshadow others
• This is referred to as a Dominant trait.
• The unseen trait is said to be Recessive.
• Dominant traits are represented on
charts by a capital letter.
• Recessive traits are represented by a
lower case letter
• When an organism is said to be of pure
lines, it means their genotype is two
• TT is the pure line for a tall plant.
• tt is the pure line for a short plant.
• When parents of two different pure lines
are crossed, the offspring are called
• A hybrid’s genotype consists of two
• The genotype Tt would be a tall plant
Homozygous and Heterozygous
• When an organism has identical alleles,
it is said to be homozygous.
• TT, and tt would both be homozygous
• When an organism has two different
alleles, it is heterozygous.
• Tt is heterozygous.
1. Hereditary characteristics are determined
by distinct units or factors.
2. For each characteristic, an individual
carries two factors, one inherited from each
3. The two factors of each pair segregate from
each other and end up in separate gametes.
Principle of Segregation
If a plant is short, what is its
• It must be homozygous recessive, tt.
If a plant is tall, what is its
• It could be homozygous dominant, or
heterozygous. TT, or Tt.
• To determine which genotype it is we use a
Genes: hereditary elements
• Alleles: forms of a gene: A a
• Heterozygote: Aa
• Homozygotes: AA aa
• Genotype: Genetic makeup
• Phenotype: What we actually see
• Dominance AA, Aa same phenotype
1. Two pure breeding lines
2. Cross --------> F1 hybrid
3. Self F1 ------> F2
1. F1 one phenotype
2. F2 3:1 ratio of 2 phenotypes
1. Single major gene
2. dominant phenotype
3. equal segregation
4. existence of genes inferred