InheritanceGenetic Information being

passed from one generation to the next

Gregor Mendel“Father of

Genetics”

Study of Genetics

• Mendel studied the trait of pea plant flowers and learned:– When both parent pea plants had

purple flowers, the offspring were purple

– When both parent pea plants had white flowers, the offspring were white

• He wondered what would happen if one parent pea plant had white flowers and the other had purple

What happened?•Mendel discovered that the

offspring where either ALL purple or ALL white– They were not as he

hypothesized – a light purple•He reasoned that the

offspring (baby pea plants) must be inheriting something from each parent that told them what color to be

The Cell• Story of inheritance

is told by the cell• Inside the nucleus is DNA – the inheritance messenger

• DNA is coiled into chromosomes which are the structures that carry the message of inheritance

•Nucleus contains chromosomes– Occur in

identical pairs

•Band on each chromosomes represents the allele

Genes and Alleles

•Two alleles on the paired chromosomes work together–These are a GENE

•A gene controls a trait

Genotype• Alleles are the code that determine

the trait

• Combination of alleles in an organism’s chromosomes is the

genotype– Lists the paired alleles for that organism– Examples: AA, ee, Tt

•Genetic make-up of an organism

Dominant and Recessive

•Not all alleles have an equal influence in determining traits

•Alleles with more influence are called DOMINANT ALLELES– Represented by UPPERCASE letters

(TT)

•Alleles with less influence are RECESSIVE– Represented by lowercase letters

(tt)

Phenotype•The physical result of an

organisms genotype– What an organism looks like

because of its genotype

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