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Mendelian Genetics Genetics 2018
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The Science of Heredity
The scientific study of heredity is called GENETICS
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Gregor Mendel Father of genetics
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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
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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.
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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.
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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.
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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
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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
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Trait continued……… If both alleles are the SAME then the trait is homozygous (also known as true-bred or purebred). Ex. BB, bb, NN, nn If the alleles are DIFFERENT then the trait is heterozygous (also known as carrier or hybrid). Ex. Bb, Nn, Gg BB- homozygous dominant bb- homozygous recessive Bb- heterozygous dominant
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Steps of Mendel's Experiment
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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, OR color of flowers, OR seed color, OR shape of seeds).
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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.
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2. Mendel first cross pollinated tall pea plants with each other. (TT)
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In every generation of this plant, only tall plants were produced.
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3. Mendel then cross pollinated short pea plants with each other. (tt)
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X In every generation of this plant, only short plants were produced.
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The next step of Mendel's
The next step of Mendel's experiment was to crossed tall pea plants (TT) with short pea plants (tt). T t Tt
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He then crossed two pea plants which contained both tall and short alleles.
Tt TT tt
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¾ of the pea plants were tall, ¼ were short.
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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)
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F1 F2 P
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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
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Example Monohybrid Cross
In rabbits, brown fur is dominant to white fur. Two heterozygous brown rabbits mate. Determine the possible genotypes and phenotypes of their offspring.
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Another Example of a Monohybrid Cross
A white and a heterozygous brown rabbit mate. Determine the possible genotypes and phenotypes of their offspring.
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