Mendelian Genetics 1 Gregor Mendel The Father of

Gene • A gene is a discrete unit of heredity, which transmits a set

Alleles • Different or alternate forms or expressions of the same gene. • Example:

Genotype • The letters that represent the trait being investigated. • Examples: Bb, BB,

Phenotype • The actual representation of the genes as a physical trait. • Examples:

Dominant allele • An allele that is fully expressed in the phenotype of a

Recessive allele • An allele that is not fully expressed in the phenotype of

Homozygous • When both genes (letters) are the same. • BB = Homozygous Dominant

Heterozygous • Having two different alleles for a given gene. • One upper case

Hybrid • Another name for individuals that are heterozygous for a trait. 13

Example Problem • Round = R • wrinkled = r • If a plant

Punnett Square • A method for finding predicted outcomes and probabilities for offspring from

Example Problem B b b Bb bb B = Brown b = blue 16

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Mendelian Genetics 1

Gregor Mendel The Father of Genetics 2

Gene • A gene is a discrete unit of heredity, which transmits a set of specifications from one generation to the next; consisting of a specific nucleotide sequence in DNA (or RNA in some viruses) that codes for a specific product • Ex: a gene for blood type. 4

Alleles • Different or alternate forms or expressions of the same gene. • Example: Blood type A, B, and O. Tall or short. Round seed or smooth seed. • Every trait has 2 alleles one from each parent • The location of an allele on a chromosome is known as the locus (loci) 5

Genotype • The letters that represent the trait being investigated. • Examples: Bb, BB, bb 6

Phenotype • The actual representation of the genes as a physical trait. • Examples: brown eyes, blond hair, freckles 7

Dominant allele • An allele that is fully expressed in the phenotype of a heterozygous organism. Represented by capital letters. 8

Recessive allele • An allele that is not fully expressed in the phenotype of a heterozygous organism. Represented by lower case letters. 9

Homozygous • When both genes (letters) are the same. • BB = Homozygous Dominant • bb = Homozygous recessive 10

Heterozygous • Having two different alleles for a given gene. • One upper case letter and one that is lower case. • Bb = Heterozygous 11

Hybrid • Another name for individuals that are heterozygous for a trait. 13

Example Problem • Round = R • wrinkled = r • If a plant has round seeds, do we know what its genotype is? • It could be RR or Rr • If a plant has wrinkled seed, do we know what its genotype is? • Yes, it is rr. 14

Punnett Square • A method for finding predicted outcomes and probabilities for offspring from any cross. • A chart for predicting the traits of offspring. 15

Example Problem B b b Bb bb B = Brown b = blue 16