Patterns of Inheritance

Heredity and the Environment Organisms are products of their heredity and of their surroundings. Ex: Your height and built are probably similar to you parents, but they are also influenced by environmental factors like nutrition and exercise.

Heredity and the Environment (cont.)

A once popular theory was “blending”, an individuals genetic makeup was formed when the parents’ genes mixed at fertilization. Resulting in a sort of averaging of parent’s genes. Genetics no longer includes this theory.

Who is this?

Gregor Mendel was a monk, gardener, high school science teacher, mathematician, and scientist.

Mendel & the Idea of Alleles In the 1860’s, Gregor Mendel used garden peas to study heredity. Peas are very easy to grow, are self-fertilizing, and he could study many generations during his 8 yrs. of experiments.

Mendel & the Idea of Alleles (cont.) Mendel concentrated on traits that did not fit the blending theory. He found several different characteristics of pea plants that he could study in an either or form.

Mendel & the Idea of Alleles (cont.) Mendel classified and isolated true-breeding plants which produced offspring identical to themselves generation after generation.

Mendel & the Idea of Alleles (cont.) He then crossbred his plants, classified all the offspring, and looked for patterns of inheritance

Mendel & the Idea of Alleles (cont.) He demonstrated with pea plants that both parents pass on to their offspring genetic factors that remain separate generation after generation. Today the concept of genes has replaced Mendel’s vague idea of factors. Gene: is a segment of DNA whose sequence of nucleotides codes for a specific functional product.

Mendel & the Idea of Alleles (cont.) Most genes exist in more than one form, or allele. Each allele of a particular gene has a different base sequence. All organisms have genes that exist as several different alleles.

Mendel & the Idea of Alleles (cont.) Most traits – such as hair color, skin color, nose shape, and handedness – result from the complex interactions of several genes with each other and the environment.

Genes and Chromosomes Homologous chromosomes carry the same genes, although their genes may be present as different alleles. Stains help identify homologous chromosomes by binding to specific regions to create unique banding patterns.

When we have 46 chromosomes lined up by size and shape, it is called karyotype.