Genetics Biology I

The Science of Heredity The scientific study of heredity is called GENETICS

Gregor Mendel Father of genetics

Gregor Mendel- The Man Personal history 1. Austrian monk 2. Teacher of high school natural science- lover of evolution, nature, meteorology 3. Crossed pea plants and saw inheritance patterns

Gregor Mendel Pea Plant Experiment Gregor Mendel chose pea plants to conduct genetic experiments because of their plant life special properties. For example: When pollen fertilizes an egg cell, a seed for a new plant is formed. (Pollen is plant sperm cells) Pea plants normally reproduce by self- pollination.

Gregor Mendel Pea Plant Experiment To perform his experiments, how did Mendel prevent pea flowers from self-pollinating and control their cross-pollination? He cut away the pollen-bearing male parts of a flower and dusted that flower with pollen from another plant.

Gregor Mendel Pea Plant Experiment What does it mean when pea plants are described as being true-breeding? If the plants are allowed to self-pollinate, they would produce offspring identical to themselves.

Vocabulary Traits - Specific characteristics that vary from one individual to another Hybrids-The offspring of crosses between parents with different traits Genes - Chemical factors that determine traits Alleles - The different forms of a gene

Trait Consist of 2 alleles For example: BB or Bb or bb Alleles come in two forms: DOMINANT- Capital letter recessive – Lower cased letter If a trait has 2 recessive alleles, then the traits is recessive. bb, aa, ff If a trait has one dominant allele then the trait is dominant. Bb, BB

Traits If both alleles are the SAME then the trait is homozygous. BB, bb, NN, nn If the alleles are DIFFERENT then the trait is heterozygous. Bb, Nn, Gg BB- homozygous dominant bb- homozygous recessive Bb- heterozygous dominant

Steps of Mendel's Experiment

1. Mendel studied the inheritance. of one trait (for example a plant's 1.   Mendel studied the inheritance of one trait (for example a plant's height, color of flowers, seed color, and shape of seeds).

A cross in which only ONE contrasting trait is studied is called a monohybrid cross . Only one alphabet can be used . For Example: Tall – TT or Tt Short - tt ONLY THE LETTER T IS USED.

2. Mendel first cross pollinated tall pea plants with each other. (TT)

In every generation of this plant, only tall plants were produced.

3. Mendel then cross pollinated short pea plants with each other. (tt)

X

In every generation of this plant, only short plants were produced.

The next step of Mendel's. experiment was to crossed tall The next step of Mendel's experiment was to crossed tall pea plants (TT) with short pea plants (tt). T t Tt

He then crossed two pea plants which contained both tall and short alleles. Tt TT tt

¾ of the pea plants were tall, ¼ were short.

Mendel named every generation: 1) Starting generation   Mendel named every generation: 1) Starting generation P (parent) generation. 2) first generation F1 generation (offspring of the P generation) 3) second filial generation F2 generation (offspring of the F1 generation)

F1 F2 P

Genotype vs. Phenotype Phenotype Physical characteristic of an organism Example: tall or short Genotype Genetic makeup of an organism Example: Tt or TT or tt