Lecture 1

History of Genetics

who is the father of genetics

Gregor Mandel

who discovered Mandels experiments after his death

Hugo de Vries

what characteristics did Mandel work with in his Peas experiments

Shape of seed, Color of seed, Color of pod, Shape of pod, Plant height, Position of flower, Flower color

why were peas prefect for Madels experiment

1. Primarily self pollinated but can be cross pollinated easily

2. pure variation of peas are available

3. Have several phenotypically contrasting characteristics

4. Annual plant with a short life span

5. Large number of seeds are produced

6. Grown easily and do not require much after care

7. F1 hybrids are fertile

What is the life span of a pea plant

3 to 4 months

How did Mendel cross pollinated the flowers

1. removed stamens from the purple flower

2. transferred pollen from the stamen from the white flower to the carpel of the purple flower

3. pollinated carpel matured into pods

4. planted the seeds from the pod

hybrids

the offspring of crosses between parents with different traits

why did all the offsprings in the F1 generation have the characteristics of only one parent

1. inheritance is determined by factors that are passed from generation to generation

2. some allelels are dominant and some are recessive

gene

Discrete factor of inheritance

Chromosome

Long piece of double- stranded DNA

Homologous Chromosome

Chromosome with the same type of gene

Locus

Location long the chromosome

Allele

Alternative forms of genes

Genotype

the combination of allelels that an individual has

Phenotype

A trait or appearance

Heterozygote

two different alleles for a trait

Homozygote

Two identical alleles for a trait

Pure-Breeding

An individual or strain that is homozygote for a particular gene

Whats the phenotypical ratio when you cross Hh x Hh

Ratio = 3:1

what is the phenotypical ratio when crossing HH X hh

Ratio= 100%

what is the phenotypical ratio when crossing Hh X hh

Ratio= 1:1

what is the genetical ratio when crossing Hh X Hh

Ratio = 1:2:1

Mendels Law of Inheritance

1. Law of Dominance

2. Law of Segregation

3. Law of Independent Assortment

Law of Dominance

Controlled by two factors where the dominate trait only needs one factor to show but a recessive trait needs both factors to show

Law of Segregation

During the formation of gametes the two factors separate. only one ends up in each sex cell one from the mother and the other from the father

Punnet Square

Predict the outcome of a cross by showing all the possible gametes

Test Cross

The crossing of an organism, with an unknown genotype, to a homozygote recessive organism