Introducing genes Genetics is the study of inherited traits and their variations. Genetics is not genealogy! Genealogy is the study of family relationships What types of characteristics can be inherited? Name some. What types of characteristics are not inherited? Name some.

Introducing genes (continued) Genes are the units of heredity (Heredity is the transmission of inherited traits) They are biochemical signals that provide instructions to the cell on how to manufacture proteins. The central dogma of genetics is genes→proteins →you!

Introducing genes (continued) How is that possible? Proteins are responsible for your physical characteristics. This happens mainly through the action of a special class of proteins called enzymes, which control chemical reactions in the cell. More on that later!

Introducing genes (continued) Genes are long molecules of DNA or deoxyribonucleic acid The complete set of genetic instructions for an individual is called the genome. The entire human genome has been decoded by the research of the Human Genome project. This effort has located 20,325 protein encoding genes!!

Introducing genes (continued) Comparing genomes of individuals can reveal information about relationships.

Introducing genes (continued) The development of the field of genetics has forced us to wrestle with concepts such as benefit and risk , right and wrong. The field of bioethics was founded in the 1970’s to address ethical questions surrounding genetics and medical technology.

Levels of genetics Through this course we will examine the transmission of traits at several levels The molecular level The body (cells, tissues, and organs) Within families Within populations and the evolution of species.

Levels of genetics (continued) At the molecular level… Genes are regions of DNA They are made up of different sequences of the bases that make up DNA A = adenine T = thymine C = cytosine G = guanine

Levels of genetics (continued) In addition to DNA, there is another molecule in cells that codes for proteins: RNA DNA is located inside the nucleus of cells, RNA is located both in the nucleus and cytoplasm.

Levels of genetics (continued) The same protein encoding gene may vary from person to person For example, all people have genes that code for eye color, but some of them have genes for blue eyes, while others have genes that code for brown Variants of a gene are called alleles.

Levels of genetics (continued) How do these variants arise? Through mutation. Mutation can be defined as an error in the copying of DNA. Some mutations have no effect, some can create harmless variations of a trait (such as brown to blue eyes) and some can cause disease (such as sickle cell anemia or Down syndrome. )

Levels of genetics (continued) All genes (which means all DNA) are stored in the nucleus in the form of chromosomes. Chromosomes are made up of a strand of DNA wound around proteins, much in the same way that thread is wound around a spool. The proteins around which the DNA is wound are called histones.

Levels of genetics (continued) Different species of organisms have different numbers of chromosomes. Humans have 23 pair for a total of 46 chromosomes a person. In humans, 22 pair (44 total) are autosomes. These are the same in both genders. The remaining two are sex chromosomes (X and Y).

Levels of genetics (continued) Moving from the molecular level to the whole body level…. The human body consists 50 to 100 trillion cells! All of these (except red blood cells) contain all your genetic information. However, cells differ in appearance (there are only 260 types of cells that make up four basic tissue types) Why is that?

Levels of genetics (continued) Because cells only use some of their genes…. For example, an adipose cell is filled with fat, but a skin cell is filled with a scaly protein keratin. Therefore, genetic defects can affect some parts of your body while others remain healthy!

Levels of genetics (continued) Many organs include rare, unspecialized cells called stem cells. These cells are special because they are undifferentiated and can became many different cell types. These cells are at the forefront of genetic and medical research and

Levels of genetics (continued) Moving from the body to the family level…. Many genes are inherited in a dominant/recessive fashion Each person has two copies of each gene in their bodies If one copy masks the other, the alleles is said to be recessive If only one copy of the gene needs to be present in order for a trait to be expressed then the allele is said to be dominant

Levels of genetics (continued) We can trace the inheritance of these types of genes within a family lineage using a chart called a pedigree. These charts can also help us predict future inheritance of traits within a family.

Levels of genetics (continued) Moving from the family level to the population level…. In much the same way that we can use an entire genome to determine how closely individuals are related, we can apply the same principle to determine how closely different species are related to one another. In this way we can make hypotheses about evolutionary relationships between species.

Levels of genetics (continued) The evolution of populations can also be described using genetics. If the physical characteristics of a population begin to change, then we know that represents a change at the genetic level. Therefore, evolution can be defined as a change in genes over time. Mutations drive evolution!