GENETICSPopulations and EcosystemsInvestigation 9

INHERITANCE Passing on genetic information from one

generation to the next is called inheritance.

INHERITANCE Augustinian monk, Gregor Mendel, was the

pioneer of inheritance with his work on pea plants.

MENDEL’S OBSERVATIONS There was variation in the color of the

flowers of pea plants.

MENDEL’S OBSERVATIONS 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.

MENDEL’S OBSERVATIONS 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!

MENDEL’S CONCLUSIONS Mendel found that the flowers were either all

purple or all white. There were no pale lavender (purple) flowers.

MENDEL’S CONCLUSIONS Mendel reasoned that the offspring must be

inheriting something from each parent that told the pea plan what color

CELLS 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.

CHROMOSOMES 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.

CHROMOSOMES 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 ininherited characteristics, such as eye color or blood type.

ALLELE

GENESTwo alleles on the paired

chromosomes work together and constitute a gene.

SUMMARIZING 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.

GENE (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.

GENOTYPE 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.

DOMINANT 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.

PHENOTYPE 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.