Gene Expression Dr.Timmel Dr.Timmel

Vocabulary To truly understand how our genes and environment affect who we are, we first need to understand some content specific vocabulary. To truly understand how our genes and environment affect who we are, we first need to understand some content specific vocabulary. You should commit these terms to memory! You should commit these terms to memory! Be like the elephant, and never forget!

Genome: The complete genetic material of an organism. It can be either DNA or RNA. In humans, our genome is approximately 3,000,000,000 base pairs long! Human Genome Project Human Genome Project Human Genome Project

Gene: A segment of a chromosome which codes for one specific protein or trait. Allele: The term used to describe different versions of the same gene. For example the blue eye or brown eye allele.

Chromatin: Mass of genetic material composed of DNA and proteins that condense to form chromosomes in eukaryotic cell division. Chromatin is located in the cell's nucleus. Chromatin consists of long, thin strands that cannot be seen with a compound light microscope. Memory aid: Chromatin is thin.

Chromosome: Long, stringy aggregates of genes that carry heredity information and are formed from condensed chromatin. These become visible under a compound light microscope just prior to cell division.

Chromatid: One of the two identical parts of the chromosome. The two chromatids of a single chromosome are called sister chromatids. Centromere: The centromere is the constricted point at which the two chromatids forming the chromosome are joined together.

What does a chromosome look like? 1 chromatid

Genotype: The genetic constitution (the genome) of a cell, an individual or an organism. The genotype is all of the genes within your cells. Only identical twins (or tripets, etc.) have the same genotype.

Phenotype: The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences. Genotype + Environment = Phenotype.

The snowshoe hare. The appearance of this animal changes as the environmental conditions change. The genotype is always the same. Winter SpringSummer

Does the environment affect human phenotypes? Absolutely! Light skinned people generally are paler during the winter months. However, in the summer when they are outside and exposed to more ultra violet radiation, they tan. Absolutely! Light skinned people generally are paler during the winter months. However, in the summer when they are outside and exposed to more ultra violet radiation, they tan. Some diseases also result from a change in environmental conditions. If your body is lacking in vitamin C, you can get the disease called scurvy. Some diseases also result from a change in environmental conditions. If your body is lacking in vitamin C, you can get the disease called scurvy. As a result, the shape of the long bones in your arms and legs can become curved. As a result, the shape of the long bones in your arms and legs can become curved.

In conclusion Our outward appearance, or phenotype is determined as much by our environment as it is our genotype. Our outward appearance, or phenotype is determined as much by our environment as it is our genotype. Our genotype never changes*, though our phenotype does change over time. Our genotype never changes*, though our phenotype does change over time. *except in the case of a mutation.