Fundamental Genetics Intro to genetics Genetics A branch

Fundamental Genetics

Intro to genetics Genetics - A branch of biology that deals with heredity and variation of organisms. Heredity, also known as inheritance, is the passing of traits to the next generation. Chromosomes carry the heredity information DNA RNA Protein

Gregor Mendel FATHER OF GENETICS � Austrian Monk � Began his research in 1860 � Used pea plants � He concluded that characteristics (traits) are determined by discrete factors Discrete Factors = Genes

Why Peas? Self-fertilization produces true breeding generations Female parts Male parts

Why pea plants? Pea plants self-pollinate Fertilization occurs with female gametes uniting with male gametes of the same flower. Mendel could easily manipulate the plants by cross-pollinating.

Why Peas?

Chromosomes & Genes Characteristics (traits) are determined by genes. These genes are found on homologous chromosomes. As crossing over occurs, new combinations of genes are formed

Genes & Alleles � Genes – A unit of heredity; a � Alleles – Two genes that occupy specific section of DNA that the same position on a codes for a single protein. homologous chromosome, and cover the same trait.

Mendel’s Work 1. Traits are passed on by factors (genes) 2. Factors (genes) have more than 1 form called alleles 3. There at least 2 alleles for each trait

Law of Segregation Mendel found that two alleles for each trait separate during meiosis. The two alleles unite during fertilization.

Law of Independent Assortment Random distribution of alleles occurs during gamete formation Genes on separate chromosomes sort independently during meiosis Each combination is equally likely to occur.

Generations The parent generation is also known as the P generation The offspring of this P cross are called the first filial (F 1) generation. The second filial (F 2) generation is the offspring from the F 1 cross.

Dominant & Recessive � A characteristic that is expressed (seen) is labeled as dominant. � A characteristic that is masked (unseen) is labeled as recessive. � Yellow = Dominant � Green = Recessive

Mendel’s Work Alleles are represented by the first letter of the dominant trait Pea plant flower color (trait) Purple or white Purple is dominant over white Alleles are represented as P=purple p=white

Which is Dominant/Recessive?

Which is Dominant/Recessive? Black = Dominant White = Recessive

Dominant & Recessive We use capital letters to show dominance For example – T, R, B, D, A ▪ Y = dominant yellow pea We use lower case letters to show recessive traits For example – t, r, b, d, a ▪ y = recessive green pea

Homozygous & Heterozygous An organism with two of the same alleles for a particular trait is homozygous. Homo = Same TT, rr, BB, DD, aa An organism with two different alleles for a particular trait is heterozygous. Homozygous Heterozygous organisms are known as hybrids. Heterozygous Homozygous Hetero = Different Tt, Rr, Bb, Dd, Aa Ex. Liger

Phenotype & Genotype An organism’s allele pairs are called its genotype. TT, Rr, bb The observable characteristic or outward expression of an allele pair is called the phenotype. Tall, Short, Round If bb is the allele pair for being tall, then: bb = genotype being tall = phenotype

Monohybrid Cross- tool used to predict the traits of a cross between 2 parents A cross that involves hybrids for a single trait is called a monohybrid cross. Crossing two heterozygous organisms: ▪ Yy x Yy ▪ Tt x Tt ▪ Rr x Rr Dihybrid- cross 2 traits