G ENETICS Populations and Ecosystems Investigation 9

I NHERITANCE Passing on genetic information from one generation to the next is called inheritance.

I NHERITANCE Augustinian monk, Gregor Mendel, was the pioneer of inheritance with his work on pea plants.

M ENDEL ’ S O BSERVATIONS There was variation in the color of the flowers of pea plants.

M ENDEL ’ S O BSERVATIONS When both parent pea plants had purple flowers, the offspring had purple flowers When both parent pea plants had white flowers, the offspring had white flowers.

M ENDEL ’ S O BSERVATIONS What happened when one parent had purple flowers and one had white flowers? What color flowers would the offspring have? Purple? White? Pale Lavender? Make a prediction!

M ENDEL ’ S CONCLUSIONS Mendel found that the flowers were either all purple or all white. There were no pale lavender (purple) flowers.

M ENDEL ’ S CONCLUSIONS Mendel reasoned that the offspring must be inheriting something from each parent that told the pea plan what color

C ELLS ROLE IN INHERITANCE Information describing how to make you resides in the cells. Inside cells, there are smaller structures called organelles (“little organs”) that perform functions essential to life. One of the key organelles is the nucleus (a.k.a. “control center” of the cell.)

DNA Inside the nucleus is the inheritance messenger, DNA. DNA molecules are huge, containing millions of atoms.

C HROMOSOMES In order for them to fit inside the nucleus, they are coiled into structures called chromosomes. Chromosomes are the structures that carry the message of inheritance.

C HROMOSOMES Chromosomes always come in pairs. Both chromosomes in a pair have dark areas in exactly the same location called alleles (a version of a gene.) Different alleles produce variations in inherited characteristics, such as eye color or blood type.

A LLELE

G ENES Two alleles on the paired chromosomes work together and constitute a gene.

S UMMARIZING NOTES Nuclei contain chromosomes. Chromosomes come in almost identical pairs. Chromosomes have specific active locations called alleles. The two alleles in identical locations on paired chromosomes constitute a gene.

G ENE ( CONTINUED ) A gene (two alleles working together) controls a trait. A genes determine eye color, hair color, etc…. Alleles are the code that determines the traits of an organism.

G ENOTYPE The combination of alleles in an organism’s chromosomes is the organism’s genotype. The genotype lists the paired alleles that are particular to that organism.

D OMINANT AND RECESSIVE Most-influential alleles are dominant alleles. Represented by an uppercase letter. Less-influential alleles are called recessive alleles. Represented by a lower case letter.

P HENOTYPE Every organism has its unique genotype, composed of paired alleles on paired chromosomes that produce unique traits in those organisms. The traits that the genotype produces results in the organism’s phenotype.