DNA & RNADNA & RNA

DNA STRUCTUREDNA STRUCTURE

• Double Helix• Phosphate ( PO4)• Deoxyribose sugar• Nitrogen Bases: A-

adenine, C-cytosine,

T-thymine, G-guanine

NUCLEOTIDENUCLEOTIDE

RNARNA

• Single stranded• Phosphate (PO4)• Ribose sugar• Nitrogen Bases:U-uracil, C-cytosine, G-guanine, A-adenineThree TypesmRNA-messenger RNArRNA- ribosomal RNAtRNA- transfer RNA

DNA REPLICATIONDNA REPLICATION

• DNA makes DNA

DNA Replication Cont…DNA Replication Cont…

• DNA unwinds and unzips• Free floating nucleotides bond to the

unattached bases on both sides of the DNA• There are now two DNA strands that are

identical.• http://www.mcb.harvard.edu/losick/images/

trombonefinald.swf

How To View DNAHow To View DNA

• http://learn.genetics.utah.edu/content/labs/gel/

ElectrophoresisElectrophoresis• DNA is cut by restriction enzymes which

creates different size pieces of DNA

• The DNA is placed in a gel

• DNA is charged negatively so the gel is plugged in with a positive charge near the bottom of the well

• The negative pieces of DNA move through the gel

• The small pieces end up at the bottom and the larger pieces end up near the top.

DNA Protein SynthesisDNA Protein Synthesis

• DNA unwinds and unzips• Free RNA nucleotides in the nucleus bond

to the DNA strand, creating the m-RNA strand. U-A, C-G.

• This is called transcription• The m-RNA leaves the nucleus goes into

the cytoplasm• The m-RNA comes in contact with the r-

RNA inside a ribosome.

Protein Synthesis cont..Protein Synthesis cont..• The job of the r-RNA is to find the start codon (3

bases) on the m-RNA• Once the start codon is found the t-RNA’s attach

their 3 base anti-codon to the codon on the m-RNA.

• They bring with them their amino acids which are attached to the t-RNA on the top.

• All the codons after the start codon are then attached to their own t-RNA’s, until the stop codon is recognized by the r-RNA.

• The amino acids are bonded together by a peptide bond creating a polypeptide (protein).

• This process is called translation.

DNA TRANSCRIPTION & TRANSLATION

DNA TRANSCRIPTION & TRANSLATION

•Animations•http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a3.html

DNA MutationsDNA Mutations

• What Causes DNA Mutations?

Mutations in DNA sequences generally occur through one of two processes:

1.DNA damage from environmental agents such as ultraviolet light (sunshine), nuclear radiation or certain chemicals

2.Mistakes that occur when a cell copies its DNA in preparation for cell division.

What Kind of Mutations Are There?What Kind of Mutations Are There?

• Point MutationA point mutation is a simple change in one base of the gene sequence. This is equivalent to changing one letter in a sentence, such as this example, where we change the 'c' in

cat to an 'h':

Original The fat cat ate the wee rat.

Point Mutation The fat hat ate the wee rat.

• Frame-shift mutations. In a frame shift mutation, one or more bases are inserted or deleted, the equivalent of adding or removing letters in a sentence. But because our cells read DNA in three letter "words", adding or removing one letter changes each subsequent word. This type of mutation can make the DNA meaningless and often results in a shortened protein. An example of a frame-shift mutation using our sample sentence is when the 't' from cat is removed, but we keep the original letter spacing:

Original The fat cat ate the wee rat.

Frame Shift The fat caa tet hew eer at.

Frame-shift mutationFrame-shift mutation

Deletion&Insertion Deletion&Insertion

• Deletion -Mutations that result in missing DNA are called deletions. These can be small, such as the removal of just one "word," or longer deletions that affect a large number of genes on the chromosome. Deletions can also cause frameshift mutations. In this example, the deletion eliminated the word cat.

• Original- The fat cat ate the wee rat.

• Deletion -The fat ate the wee rat.• Insertion - Mutations that result in the addition of extra DNA are

called insertions. Insertions can also cause frameshift mutations, and general result in a nonfunctional protein.

• Original- The fat cat ate the wee rat.• Insertion- The fat cat xlw ate the wee rat.

InversionInversion

• In an inversion mutation, an entire section of DNA is reversed. A small inversion may involve only a few bases within a gene, while longer inversions involve large regions of a chromosome containing several genes.

• Original -The fat cat ate the wee rat.• Insertion -The fat tar eew eht eta tac.