Introduction to Genetics Genetics is all about DNA Genetics is all about DNA DNA is located in the nucleus of cells. DNA is located in the nucleus of cells. The actual pieces of DNA are called chromosomes. The actual pieces of DNA are called chromosomes. Chromosomes contain the genetic code for everything (traits). Chromosomes contain the genetic code for everything (traits). Chromosomes are not visible until they are ready to “divide/reproduce” Chromosomes are not visible until they are ready to “divide/reproduce” In humans, 46 is the magic number. In humans, 46 is the magic number.

Reproduction

Reproduction Making new individuals from an existing individual Making new individuals from an existing individual

How?? Chromosomes copy themselves and then “split” creating a new cell. Chromosomes copy themselves and then “split” creating a new cell. Methods: Methods: –Asexual (Mitosis) –Sexual (Meiosis)

Asexual Reproduction One parent One parent Offspring (kids) are all identical to parent and each other Offspring (kids) are all identical to parent and each other

Method of Asexual Reproduction Budding Budding Fission Fission Spores Spores Vegetative Reproduction (runners) Vegetative Reproduction (runners)

Budding In this form, an offspring grows out of the body of the parent. In this form, an offspring grows out of the body of the parent. Hydras exhibit this Hydras exhibit this Hydras type of reproduction. type of reproduction. Example: Potatoes Example: Potatoes

Fission The simplest form or reproduction and involves the division of a single organism into two complete organisms. The simplest form or reproduction and involves the division of a single organism into two complete organisms. Each identical to the other and to the parent. Each identical to the other and to the parent. Common among unicellular organisms such as bacteria, many protist, Common among unicellular organisms such as bacteria, many protist, some algae (such as Spirogyra and (such as Spirogyra and Euglena), as well as a Euglena), as well as a few higher organisms few higher organisms such as flatworms. such as flatworms.

Spores Are DNA-containing capsules capable of sprouting into new organisms. Are DNA-containing capsules capable of sprouting into new organisms. Spores are another form of asexual reproduction and are common among bacteria, protists, and fungi. Spores are another form of asexual reproduction and are common among bacteria, protists, and fungi.

Runners Common among plants and consists of certain parts that grow out from a main parent plant and eventually root and sprout to form new, independent plants. Common among plants and consists of certain parts that grow out from a main parent plant and eventually root and sprout to form new, independent plants. Examples: strawberry Examples: strawberry

Mitosis In animals (humans) this form of reproduction is used in “body cells.” In animals (humans) this form of reproduction is used in “body cells.” Example : Skin cells must be replenished Example : Skin cells must be replenished Constant process Constant process The DNA of the cell copies itself and then splits using a process called mitosis creating a new cell identical to the original The DNA of the cell copies itself and then splits using a process called mitosis creating a new cell identical to the original 1 cell with 46 chromosomes – doubles (92) – splits into 2 cells with 46 chromosomes each (identical) 1 cell with 46 chromosomes – doubles (92) – splits into 2 cells with 46 chromosomes each (identical)

Example of Mitosis: Root Cells of a Broad Bean (Vicia faba ) In the "resting" phase the chromosomes are not obvious within the nucleus. Just before cell division starts, a lot of metabolic activity occurs, the chromosomes start to gradually shorten and thicken. Each chromosome has divided to produce 2 identical chromatids, joined at a structure called the centromere. They begin to move towards the equator of the cell.

Once at the equator of the cell, the centromeres attach to threads of a spindle structure that has formed. (The spindle spans from one end of the cell to the other). Contraction of the spindle fibers begins to cause the chromatids to pull apart from one another and move towards opposite ends of the cell. The chromatids separate further. Energy for this is provided by mitochondria.

A new nuclear membrane begins to form round the 2 groups of chromatids. A new cell wall begins to be laid down. The chromosomes begin to lengthen and uncoil. Two new cells, identical to each other and to the parent cell. The cells now grow to full size.