DNA and Cell Cycle

DNA and Chromosomes  DNA is in the nucleus of every living thing.  A Chromosome is coiled DNA.  Humans have 46 chromosomes.

Chromosomes in living things Black Mulberry Plants308 Agrodiaetus Agrodiaetus butterfly Animals268

Cell Cycle  Cells are damaged, lost or die all the time. New cells must be created to replace them.  Cells make complete copies of themselves including an exact copy of their DNA.  The steps that cells go through are called the Cell Cycle and each step is a phase.

New daughter cell

Interphase This is the normal state of a cell or the resting state.

What is Mitosis? A cell and its nucleus divide and produce two identical cells. This process is important for growth, to repair or replace damaged tissue. The two daughter cells have the same genetic information (DNA) as the original cell.

The phases of mitosis

Sexual Reproduction Sexual reproduction is when chromosomes from two different cells combine, producing offspring. eggsperm zygote

What is Meiosis Meiosis is the type of cell division by which gametes (eggs or sperm) are formed. Two divisions result in 4 different daughter cells that have half of the total number of chromosomes (23). When an egg and sperm combine during fertilization, the embryo will have the normal amount of chromosomes (46).

Meiosis

Comparing the two types of cell division