Genetics

= The study of heredity/how characteristics are passed from

parents to offspring.

Gregor Mendel

• = The father of genetics.• Mendel was a monk who crossed pea plants

with varying traits, hence discovering simple laws of heredity.

Mendel’s Experiment:

• 1. Created pure- breeding strains of pea plants and used these as the parental generation.

• 2. Crossed plants different in a particular trait and found only dominant phenotype in the resulting F1 offspring.

• 3. Allowed F1 to self-fertilize and found a 3:1 ratio of the dominant: recessive trait in the F2 generation.

Mendel’s Laws:

• Law of Segregation = During meiosis, homologous pairs of chromosomes segregate from each other and end up in different gametes.

• Gametes are haploid reproductive cells such as the sperm and egg in humans.

• Law of Independent Assortment = Alleles for different traits are distributed to gametes independent of one another.

• ie. Inheritance of a gene for one trait does NOT affect the inheritance of the gene for a different trait.

• Exception to this law are sex-linked traits.

Important terms:

• Heredity = Biological inheritance/transmission of characteristics from parents to offspring.

• Traits = Characteristics.• Genes = Structures/segments on

chromosomes that control traits.

Alleles = Different forms of a gene.Ex. Blue vs. brown eye color.

• Dominant = Allele that prevents the expression of a recessive allele.

• Represent using a capital letter. Ex. B• Recessive = Allele that is hidden by a

dominant allele.• Represent using a lower case letter. Ex. b

• Genotype = The genetic makeup of an organism.

• Phenotype = The physical appearance of a trait.

• Phenotype is a result of the genotype.

• Homozygous = Having two of the same alleles for a single trait.

• Also known as purebred. Ex. BB or bb• Heterozygous = Having two different alleles for

the same trait.• Also known as hybrid. Ex. Bb

• P1 = Represents the parental generation.• F1 = Represents the first filial generation.• - Offspring of the P1 generation.• F2 = Represents the second filial generation.• Offspring of the F1 generation.