Introduction to Genetics Genetics is all about DNA Genetics is all about DNA DNA is located in the...

Introduction to Genetics

Genetics is all about DNA DNA is located in the nucleus of cells. The actual pieces of DNA are called

chromosomes. Chromosomes contain the genetic

code for everything (traits). Chromosomes are not visible until

they are ready to “divide/reproduce” In humans, 46 is the magic number.

Reproduction

Reproduction

Making new individuals from an existing individual

How??

Chromosomes copy themselves and then “split” creating a new cell.

Methods:– Asexual (Mitosis)– Sexual (Meiosis)

Asexual Reproduction

One parent Offspring (kids) are all identical to

parent and each other

Method of Asexual Reproduction

Budding Fission Spores Vegetative Reproduction (runners)

Budding

In this form, an offspring grows out of the body of the parent.

Hydras exhibit this type of reproduction.

Example: Potatoes

Fission

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.

Common among unicellular organisms such as bacteria, many protist, some algae

(such as Spirogyra and Euglena), as well as a few higher organisms such as flatworms.

Spores

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.

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.

Examples: strawberry

Mitosis In animals (humans) this form of

reproduction is used in “body cells.” Example : Skin cells must be

replenished 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

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.