Cell Division/Cell Cycle Cells Make New Cells Hey teacher, I keep counting, but that’s not the answer I come up with…

TEAM QUESTION 1: What are the stages that people go through during their life, starting with infancy (newborn) and ending in their elderly years (old age)?

Cells undergo life cycles too. It is called a CELL cycle. UNLIKE the life cycle, it begins again when the cell divides. Living organisms are constantly making new cells. They make new cells in order to grow and also to replace old dead cells. The process by which new cells are made is called cell division. Cell division is occurring all the time. Around two trillion cell divisions occur in the average human body every day! 

Mitosis Mother Cell Skin Blood Muscle Daughter Cells Mitosis is used when a cell needs to be replicated into exact copies of itself. Everything in the cell is duplicated. The two new cells have the same DNA, functions, and genetic code. The original cell is called the mother cell and the two new cells are called daughter cells. The full process, or cycle, of mitosis is described in more detail below.  Examples of cells that are produced through mitosis include cells in the human body like skin and muscles.  Daughter Cells A cell makes EXACT replicas or copies of itself.

Meiosis ENTIRE organism reproduces. FOUR cells NOT two. Meiosis is used when it is time for the entire organism to reproduce. There are two main differences between mitosis and meiosis. First, the meiosis process has two divisions. When meiosis is complete, a single cell produces four new cells instead of just two. The second difference is that the new cells only have half the DNA of the original cell. This is important for life on Earth as it allows for new genetic combinations to occur which produces variety in life. ENTIRE organism reproduces. FOUR cells NOT two.

Two types of cell division Mitosis Happens in all body cells Produces 2 cells that are identical to the parent cell Meiosis Only happens in sperm and egg cell production Produces 4 cells Each cell contains half of the chromosomes needed to make a working cell

Cell Division Overview Process cells go through in order to make new cells The cell cycle has 3 parts Interphase Mitosis/Meiosis Cytokinesis Cell Animation

Interphase Interphase is where the cell spends most of its life. During this stage the cell is performing its normal functions and is not dividing. It is growing and getting prepared to divide

Interphase Interphase has 3 stages G1 –Cell doubles in size and organelles get larger or duplicate Synthesis –DNA replicates (makes a copy) G2 –Cell double checks to make sure it is ready to divide

Mitosis –Making an exact copy Mitosis is where the nucleus divides into two.Happens in body cells (skin, liver, stomach etc.) Creates cells with the same number of chromosomes as original cell (humans=46) Needed for growth and repair of cells Has 4 stages(PMAT)

Mitosis -Prophase Nucleolus disappears Nuclear membrane breaks down and starts to disappear Chromatin (DNA strands) shorten and thicken into chromatids and connect together at the centromere to form chromosomes Spindle Fiber Apparatus (SFA) forms

Mitosis - Metaphase Chromosomes move to the center of the cell and attach to spindle fibers

Mitosis -- Anaphase Chromatids separate and move to opposite side of the cell The spindle fibers pull them apart

Mitosis -- Telophase Animal Cells – cell membrane pinches in and reforms Plant Cells – plate forms in middle of the cell Nuclear membrane reforms Chromosomes uncoil back to chromatin

Meiosis – Making Sex Cells Happens when sperm and egg cell are being formed. A type of cell division that results in ½ the chromosomes needed (humans =23) Goes through 2 divisions, but only makes one copy of DNA (PMAT PMAT)

Cytokinesis The cell is completely split. In mitosis 2 cells are formed that are identical (diploid = 46 chromosomes) In meiosis 4 cells are formed that contain half of the DNA (haploid = 23 chromosomes)