Lesson 2 DNA, Cells, & How Cells Are Made

Deoxyribonucleic acid

Deoxyribonucleic acid, or DNA is a large molecule in the nucleus of all eukaryotic cells.  Along with various proteins, DNA is "packaged" into chromosomes that reside in the nucleus of every cell in the human body. DNA is important for two vital processes:

1.   Replication (making a copies of itself)

2.   Protien sysnthesis (the manufacture of proteins)

These two processes (replication and protein synthesis) are important for growth and development, and for the passage of genetic information from parent to offspring, or on a macro-scale, from generation to generation.

Knowledge of DNA structure and function, and how DNA sequences are inherited allows us to: 1) be aware of the risks of transmitting genetic diseases to our children, 2) identify biological relationships between individuals and species, 3) track evolutionary shifts within our own human species, and 4) identify perpetrators of various crimes.


Nucleic Acids

Within all eukaryotic cells there are two types of nucleic acids, DNA, and RNA.  DNA contains our actual genetic information, while RNA, consisting of similar substances is a vital  "helper" of DNA.

The building blocks of DNA are known as nucleotides, comprised of 1) a sugar molecule [deoxyribose], 2) a phosphate molecule, and 3) a base.

You should know that there are four base types particular to DNA and RNA, made of simple atoms of hydrogen, carbon, oxygen, and nitrogen.  

The four bases of DNA are:

1.  A = adenine
2.  T = thymine
3.  C = cytosine
4.  G = guanine
5.  U = uracil (only found in RNA)

The building blocks of DNA

The Structure of DNA

The number of nucleotides strung together (2) are known as a polynucleotide chain.  All DNA consists of two polynucleotide chains.  Lastly, the DNA molecule is called a double helix, because it appears as a helical-twisted structure that gives the appearance of a twisted ladder.

The "backbone" or sides of the ladder are comprised of phosphates, while the "steps" of the ladder are comprised of base pairs (adenine, guanine, cytosine, and guanine).  The phosphates of the ladder are held together by strong chemical bonds, while the base pairs are held together by weak hydrogen bonds which can be easily broken by enzymes during cell replication.

It is important to know that the pair of bases in DNA adhere to specific "rules."  Adenine and thymine consistently bond together, as do cytosine with guanine.



Summary of Genetic Material


Protein Synthesis:  How Genes are Expressed



HOW ARE CELLS MADE?

All humans start their lives as a fertilized egg called a zygote from which we derive all cells in our body.