The science that deals with the heredity and the factors that affect the transmission of traits from one generation to another
Heredity
The transmission of genetic materials from the parents to offspring
Factors of Heredity
Environment
Advanced Technology
Biological Factors
Walter Sutton and Theodore Boveri
Found out that inherited trait is determined by chromosome
Chromosome Theory of Inheritance
Gene in the chromosome is responsible for the transmission of traits
Components of a cell
Nucleus
Cell
Chromosome
DNA
Genes
DNA (Deoxyribonucleic Acid)
The genetic material containing gene, also called the "blueprint of life"
Gene
The factor that control the inheritance that is responsible for the transmission of traits
Gregor Mendel
An Augustinian monk in Brunn, Austria, known as the Father of Classical Genetics who formulated the Blending Theory of Inheritance, a discredited theory
Blending Theory of Inheritance
Inheritance of traits from two parents produces offspring with characteristics that are intermediate between those of the parents
When Mendel cross pollinated the tall pea plants and short pea plants, the resulting offspring were either tall or short, not medium like what the blending theory of inheritance suggests
Mendel's Experiment on Seven Contrasting Traits of Pea Plants
1. Flower Color
2. Flower Position
3. Seed Color
4. Seed Shape
5. Pod Shape
6. Pod Color
7. Stem Length
F1
The first generation offspring
P
The parental generation
Pair of factors
Controls the appearance of a particular trait in each organism
Dominant Trait
Usually seen or expressed, symbolized by capital letters
Recessive Trait
Usually hidden or not expressed, symbolized by small letters
Homozygous (Pure-bred)
The gene pairs are identical
Homozygous Dominant
The gene pairs are both dominant, symbolized by both capital letters
Homozygous Recessive
The gene pairs are both recessive, symbolized by both small letters
Heterozygous (Hybrid)
The gene pairs are not identical, symbolized by one capital letter and one small letter
Alleles
The alternative forms of genes
Genotype
The genetic make-up of an organism usually a letter symbolizing the trait of an organism
Phenotype
The physical appearance of an organism usually an adjective or words describing a trait
Mendelian inheritance
A set of primary principles relating to the transmission of hereditary characteristics from parent organisms to their children; it underlies much of genetics
Laws of Inheritance
The laws of inheritance were derived by Gregor Mendel, a 19th century monk conducting hybridization experiments in garden peas (Pisum sativum)
Mendel's experiments
1. Between 1856 and 1863, he cultivated and tested some 28,000 pea plants
2. He deduced two generalizations that later became known as Mendel's Laws of Heredity or Mendelian inheritance
3. He described these laws in a two part paper, "Experiments on Plant Hybridization", which was published in 1866
Mendel's Law of Segregation
When two traits come together in one hybrid pair, the two characters do not mix with each other and are independent of each other. Each gamete receives one of the two alleles during meiosis of the chromosome
Mendel's law of segregations supports the phenotypic ratio of 3:1 i.e. the homozygous dominant and heterozygous offspring show dominant traits while the homozygous recessive shows the recessive trait
Gametes
The ovum and sperm cells have only one copy of each chromosome and are described as haploid
Recessive traits
Recessive traits are only visible if an individual inherits two copies of the recessive allele
Dominant and Recessive alleles
Alleles can be Dominant or Recessive
Mendel's Law of Dominance
In a heterozygous condition, the allele whose characters are expressed over the other allele is called the dominant allele and the characters of this dominant allele are called dominant characters
Mendel's Law of Independent Assortment/ Dihybrid cross
At the time of gamete formation, the two genes segregate independently of each other as well as of other traits
Dihybrid cross
A cross between two true-breeding parents that express different traits for two characteristics
Monohybrid pattern of inheritance
A pattern of inheritance from two parents which differ in ONE specific trait
Reginald Punnett
Became interested in the experimental process during his stay at Cambridge and began a scientific collaboration with William Bateson (who was doing Mendelian experimentation on plants and animals)
They both published the first account of gene linkage in sweet peas and later developed the "Punnett square"
Punnett Square
A tool used to predict the possible breeding outcomes of two genes segregate independently of each other as well as of other traits
How to use Punnett Square
1. Assign symbol for each allele
2. Determine the Genotype of each parent
3. Determine the kind of Gametes produced by each parent
4. Draw the Punnett Square
5. Identify the Genotypic and Phenotypic Ratios
There is no chance to have dwarf pea plants from the cross because all offspring are heterozygous