Day 20 Cellular Reproduction
All Cells Come From Preexisting Cells!
When cells reproduce it is generally called Cell Division
-A parent cell splits into two daughter cells
(Everything in life is female. There is only one time you need a male!)
-Both daughter cells are genetically identical to each other
-Each cell receives at least one of all the organelles and half of the cytoplasm
The Hereditary information in every cell is DNA
-Deoxyribonucleic Acid contains all genetic instructions
From smallest to largest, here are the parts of DNA genetics.
Nucleotide-Codon-Gene-DNA Strand-Chromosome
-A nucleotide is a monomer, or single piece of DNA. A codon is 3 nucleotides. A gene is a group of codons that together code for a specific protein. A Chromosome is a single strand of DNA wound up.
-If we think of DNA as a written language, think of the nucleotide as a letter, a codon as a word, a gene as a sentence, and a chromosome or strand of DNA as the paragraph.
The DNA of a cell is contained in one or more chromosomes
-A Gene is a segment of DNA that codes for something
-A gene can be a few hundred nucleotides long or it can be thousands
-Different versions of the same gene are called alleles
A cell needs to have a complete copy of DNA to function
-So before a cell can divide into two cells it needs to make two copies of its DNA
-One set for each daughter cell
In Eukaryotic cells, when a cell divides into two daughter cells it is called Mitotic Cell Division
Mitotic Cell Division
Mitotic cell division happens through the process of Mitosis
Once a cell divides the new daughter cells differentiate
-When a cell divides the new cells need to become a "type" of cell for example skin cell or liver cell
-When a cell becomes a certain type of cell it is stuck as that type of cell. This is called differentiating
-A normal cell grows, divides, and then differentiates. This process is called the Cell Cycle
Three Types of Cells
There are three category of cells:
Stem cells
-Stem cells can divide and differentiate into any type of cell
-They are great for repair and renewal
Other cells capable of dividing
-Some cells can divide but can only differentiate into one or two types of cells
-For example liver cells can only make liver cells
Permanently differentiated cells
-Some cells cannot divide
-They differentiate and never divide again
-For example the human brain and heart cells
Watch this short video on the 3 different types of cells. Make sure you understand what a stem cell is, why damage to a permanently differentiated cell is bad, and which cells divide.
Asexual and Sexual Reproduction
Asexual Reproduction
-Asexual reproduction is reproduction with DNA from only one parent
-Asexual reproduction produces genetically identical offspring to the parent
-Clones
-Asexual reproduction happens through mitotic cell division
Sexual Reproduction
-Sexual reproduction is the fusion of Gametes
-Gametes are sex cells
-Usually a sperm and egg
-Gametes are made through Meiotic Cell division
-Meiotic cell division is different than mitotic cell division because the cells in meiosis only receive half the DNA
-It is important that gametes only have half of the DNA because two gametes are going to fuse together. If they had the full amount when they join there would be double the DNA