Mendel s Genetics. Johann Gregor Mendel. Born 1822 Occupations: -beekeeper Mendel entered Augustinian Abbey of St Thomas in Brno, Austria

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1 Mendel s Genetics Born 1822 Occupations: -beekeeper -gardener -monk -teacher -scientist Johann Gregor Mendel 1843 Mendel entered Augustinian Abbey of St Thomas in Brno, Austria Education: 1851 sent to University of Vienna (Austria) to become a math and science teacher The Monastery's Garden 1856 to 1863 Cultivated and tested pea plants to study how inherited traits are passed from generation to generation 1865 presented his research findings to scientists 1

Mendel s research and findings in genetics were

of the monastery In 1900, his work was rediscovered by

age of 61 The next abbot burned all of Mendel s papers

conclusions (verification) Mendel s Experiments Mendel

tall or short, round or wrinkled Pea plants had 7

breeding) Controlled the breeding First experiments

Mendel used pollen to fertilize selected pea plants.

interrupted the self-pollination process by removing

of his pea plants by removing the male parts, or

2 Mendel s research and findings in genetics were rejected Mendel became the abbot (chief administrator) of the monastery In 1900, his work was rediscovered by Hugo de Vries and Carl Correns Mendel died in 1884 at age of 61 The next abbot burned all of Mendel s papers They repeated his experiments and came to the same conclusions (verification) Mendel s Experiments Mendel noticed that traits exist in one of two forms. Ex. tall or short, round or wrinkled Pea plants had 7 either-or traits Used true breeding plants (pure breeding) Controlled the breeding First experiments were monohybrid crosses (cross one trait at a time) Mendel used pollen to fertilize selected pea plants. P generation crossed to produce F 1 generation interrupted the self-pollination process by removing male flower parts Mendel controlled the fertilization of his pea plants by removing the male parts, or stamens. He then fertilized the female part, or pistil, with pollen from a different pea plant. 2

flowers and some had white Mendel s Experiments Here are the steps: Pure breeding Pure breeding tall X short pea plants pea plants All tall pea

3 Mendel allowed the resulting plants to self-pollinate. Among the F 1 generation, all plants had purple flowers F 1 plants are all heterozygous Among the F 2 generation, some plants had purple flowers and some had white Mendel s Experiments Here are the steps: Pure breeding Pure breeding tall X short pea plants pea plants All tall pea plants Out of every 4 plants 3 were tall and 1 was short I am planting some true breeding short pea plants Now I am planting some true breeding tall pea plants Now I am going to cross pollinate these parents And collect their seeds Pollen 3

4 Now I am going to take these F1 seeds and plant them What will these plants look like???? The F1 generation is all tall?? What happened to the short trait? I bet the short trait is hiding somewhere! I am going to self pollinate the F1 plants And collect their seeds Now I am going to take these F2 seeds and plant them 4

5 I wonder what the F2 generation will look like! Wow! There is the short trait! But only 1 in 4. P Generation F 1 Generation Tall Short True-breeding Tall Tall 100% tall F 2 Generation P Generation Tall Tall Tall Short Ratio = 3 talls to 1 Short Tall Short True-breeding plants 5

6 P Generation F1 Generation P Generation F1 Generation F2 Generation Tall Short Tall Tall Tall Short Tall Tall Tall Tall Tall Short Mendel s Experiments Tall X Short Plants Plants Mendel s Crosses with yellow/green All tall plants 3 tall plants to 1 short plant Mendel observed the same results every time he crossed two different forms of a trait. Mendel observed patterns in the first and second generations of his crosses. Characters investigated by Mendel 6

7 Mendel s conclusions 1. Biological inheritance is determined by factors (or GENES) that are passed from one generation to the next. 3. Principle of Dominance some alleles are dominant and some are recessive. One form of a trait, the dominant trait, prevents the expression of the recessive trait. 2. One trait = one gene = two contrasting forms (ALLELES) 4. Law of Segregation- when gametes are formed the pair of genes (alleles) responsible for each trait separate. Sex cells eggs and sperm- must contain only a single copy of each allele the parent has for a gene. Dominant Recessive Homozygous Heterozygous Genotype Phenotype Terms to Know!! Mendel s Experiments Tall X Short Plants Plants TT All tall plants Tt tt The same gene can have many versions. A gene is a piece of DNA that directs a cell to make a certain protein. Each gene has a locus, a specific position on a pair of homologous chromosomes. 3 tall plants to 1 short plant 3Tall: 1 short 1 TT: 2Tt: 1 tt 7

An allele is any alternative form of a gene occurring at a specific locus on a chromosome. Each parent donates one allele for every gene.

Alleles can be represented using letters. A dominant allele is expressed as a phenotype when at least one allele is dominant.

Dominant alleles are represented by uppercase letters; recessive alleles by lowercase letters. Punnett squares are used to predict genetic crosses.

The boxes show the possible genotypes of the offspring. The Punnett square yields the ratio of possible genotypes and phenotypes.

8 An allele is any alternative form of a gene occurring at a specific locus on a chromosome. Each parent donates one allele for every gene. Homozygous describes two alleles that are the same at a specific locus. Heterozygous describes two alleles that are different at a specific locus. Alleles can be represented using letters. A dominant allele is expressed as a phenotype when at least one allele is dominant. A recessive allele is expressed as a phenotype only when two copies are present. Dominant alleles are represented by uppercase letters; recessive alleles by lowercase letters. Punnett squares are used to predict genetic crosses. The Punnett square is a grid system for predicting all possible genotypes resulting from a cross. The axes represent the possible gametes of each parent. The boxes show the possible genotypes of the offspring. The Punnett square yields the ratio of possible genotypes and phenotypes. Monohybrid A monohybrid cross involves one trait. Ex. Height Probability In a homozygous dominant x homozygous recessive cross: Genotypic results: all heterozygous Phenotypic results: all dominant In a heterozygous x heterozygous cross Genotypic Results are: 1:2:1 (homozygous dominant: heterozygous:homozygous recessive) Phenotypic Results are: 3:1 (dominant:recessive) 8

In a heterozygous x homozygous recessive Genotypic results: 1:1 heterozygous:homozygous recessive Phenotypic results: 1:1 dominant:recessive TESTCROSS A cross between an organism with an unknown

9 In a heterozygous x homozygous recessive Genotypic results: 1:1 heterozygous:homozygous recessive Phenotypic results: 1:1 dominant:recessive TESTCROSS A cross between an organism with an unknown genotype and an organism with the recessive phenotype. A monohybrid cross involves one trait. Monohybrid crosses examine the inheritance of only one specific trait. homozygous dominant x homozygous recessive: all heterozygous, all dominant Heterozygous x heterozygous 1:2:1 (homozygous dominant: heterozygous:homozygous recessive); 3:1 dominant:recessive heterozygous-homozygous recessive 1:1 heterozygous:homozygous recessive; 1:1 dominant:recessive A testcross is a cross between an organism with an unknown genotype and an organism with the recessive phenotype. 9

Trait: characteristics to be passed from parent to offspring. Passed on from parent to offspring by the blood, in bloodlines.

Inheritance Theory Prior to Mendel Trait: characteristics to be passed from parent to offspring Passed on from parent to offspring by the blood, in bloodlines. Gregor Mendel Father of Genetics Mendel s