Mendelian Genetics April 3rd 2017

Important Vocabulary to Know Trait – physical characteristic on an organism (e.g. eye color)

Important Vocabulary to Know Gene – the hereditary unit that codes for a trait category (e.g. gene for hair color)

Important Vocabulary to Know Allele – The specific expression of a gene (e.g. BROWN hair). For every gene in an organism, there are two alleles present – each allele is present on it’s OWN chromosome in the homologous chromosome pair (this explains why chromosomes must come in pairs!)

Important Vocabulary to Know Genotype – the actual gene makeup of an organism (e.g. Tt) Phenotype – the physical appearance that is expressed despite the combination of alleles.

Important Vocabulary to Know Dominant trait – the allele that will be expressed in an organism if it has that allele.

Important Vocabulary to Know Recessive trait – the allele that will not be expressed in an organism, or seem hidden, unless it is purebred that has two recessive alleles.

The “Father of Genetics” – Gregor Mendel (1822 – January 6, 1884) Gregor Mendel was a german Monk that studied the inheritance of pea plants. He used pea plants because they grew quickly and they could reproduce at at a fast rate, seeing more generations in a shorter amount of time.

The “Father of Genetics” – Gregor Mendel (1822 – January 6, 1884) They also many identifiable characteristics (traits) that he could recognize from one generation to the next. This work led to identifying Dominant and RecessiveTraits.

The Principles of Genetics Traits, or characteristics, are passed on from one generation or organisms to the next generation. 2. The traits of an organism are controlled by genes. 3. Organisms inherit genes in pairs, one gene from each parent. ( In diploid organisms)

The Principles of Genetics Some genes are dominant, whereas other genes are recessive. Dominant genes hide recessive genes when both are inherited by an organism. Some genes are neither dominant nor recessive. These genes show incomplete dominance

Predicting Genetics . In order to predict what will happen from one generation to a next, we use a Punnett Square (Named after Geneticist Reginald C. Punnett).

To make a Punnett Square you need to do the following: Draw a square and divide it into four boxes. List the one allele from the gene pair from one parent next to the two boxes on the left side of the square. For the example we are starting with one parent that is a hybrid tall pea plant. List the other two alleles from the gene pair of other parent above each box at the top of the large square. For the example, we are supposing that we are crossing our hybrid with a purebred tall pea plant. Write the alleles from the top and sides of the square in the boxes where they intersect. Remember only ONE allele comes from EACH parent! Use your results to predict the probable PHENOTYPES and GENOTYPES of your four possible organisms! Use percentages or fractions to explain the probability of getting certain phenotypes and genotypes in the offspring.