DNA: The Molecule of HeredityWhat is What is DNA?DNA?What is What is Replication Replication of DNA?of DNA?

• So, what's the difference between DNA and a chromosome?

•      A chromosome is made up of DNA and the proteins attached to it. 

• All of the DNA in a cell is found in individual pieces, called chromosomes. 

• The basic structure of the DNA molecule is helical, with the bases being stacked on top of each other

DNA is made up of subunits which scientists called nucleotides. • Each nucleotide is

made up of a sugar, a phosphate and a base.

• There are 4 different bases in a DNA molecule: – adenineadenine (a purine) (a purine) – cytosinecytosine (a (a

pyrimidine) pyrimidine) – guanineguanine (a purine) (a purine) – thyminethymine (a pyrimidine) (a pyrimidine)

•The number of adenine bases equals the number of thymine bases

•The number of guanine bases equals the number of cytosine bases

What pairs up?• A -- T

C -- G

Usefulness of DNA• DNA is the fundamental building

block for an individual’s entire genetic makeup.

• It is a component of virtually every cell in the human body, and a person’s DNA is the same in every cell.

• That is, the DNA in a person’s blood is the same as the DNA in his skin cells, saliva, and other biological material.

• DNA analysis is a powerful tool because each person’s DNA is unique (with the exception of identical twins).

• DNA evidence collected from a crime scene can implicate or eliminate a suspect, similar to the use of fingerprints. It also can analyze unidentified remains through comparisons with DNA from relatives..

• DNA is also a powerful tool because when biological evidence from crime scenes is collected and stored properly, forensically valuable DNA can be found on evidence that may be decades old. Therefore, old cases that were previously thought unsolvable may contain

valuable DNA evidence capable of identifying the

perpetrator.• Similar to Fingerprints