Review: Types of Reproduction Sexual reproduction: two organisms produce a new unique organism = VARIABLITY!!! Asexual reproduction: one organism produces a new nearly identical organism = no variability!

Genetics The branch of biology that is concerned with the ways in which hereditary information is transmitted from parents to offspring.

How does it work? Women carry XX sex chromosomes Men carry XY sex chromosomes (technically, men determine the sex of a baby) Many diseases/conditions are carried on the X chromosome (nothing is carried on the Y) ** ColorBlindness ** Hemophilia Women can be healthy ‘carriers’ Men either have or don’t have the disease.

Mendel’s 1st experiments Trait = specific characteristic that varies from one individual to another Height (tall or short) Seed color (green or yellow) Seed texture (smooth or wrinkled) Mendel crossed plants with contrasting traits P (Parental) = original pair of plants F1 (First Filial) = first set of offspring (filius means “son” in Latin) Hybrids = offspring of parents crossed with different traits (aka HETEROzygous)

Mendel’s 1st conclusions Biological inheritance is determined by factors passed from one generation to the next = genes Each gene occurred in two contrasting forms that produced different characteristics = alleles

The Principle of Dominance Some alleles are dominant and others are recessive

Mendel’s 2nd experiments Mendel crossed the F1 hybrid plants F1 (First Filial) = first set of offspring (hybrids) F2 (Second Filial) = offspring of self-pollinated F1 Dominant vs. Recessive alleles Upper case letter = dominant allele Lower case letter = recessive allele

Mendel’s 2nd conclusions The dominant allele masked the corresponding recessive allele in the F1 generation The reappearance in the F2 generation indicated that the alleles separated during gamete (sex cell) formation Each gamete contains a single copy of each gene The recessive alleles can be paired up again in the F2 generation

The Principle of Segregation Alleles are separated (segregated) during gamete (sex cell) formation (meiosis)

Concept Map Gregor Mendel Pea plants “Factors” determine traits Law of Section 11-3 Gregor Mendel experimented with concluded that Pea plants “Factors” determine traits Some alleles are dominant, and some alleles are recessive Alleles are separated during gamete formation which is called the which is called the Law of Dominance Segregation Go to Section: