DNA Replication Mr. Mah Living Environment

DNA (de-oxy-ribo-nucleic acid) a nucleic acid that stores and transmits the genetic information from one generation to the next

Where in the cell is DNA found?

People knew that DNA was made up of: Adenine (A) Guanine (G) Cytosine (C) Thymine (T)

Your Challenge: Figure out the shape of DNA

Erwin Chargaff Discovered that in any sample of DNA, the amount of A equals the amount of T and the amount of C equals the amount of G. This suggested that A binds with T and that C binds with G.

Rosalind Franklin’s X-Ray Crystallography Took x-ray photographs of crystallized DNA Discovered that the shape of DNA must be a helix, because of the x-ray pattern Died of cancer (too many x-rays?)

An example of X-Ray Crystallography

Watson and Crick Credited for discovering the structure of DNA in 1953 Used Chargaff and Franklin’s discoveries along with toy models to discover the structure

A 3-D Model of DNA

NUCLEOTIDES Made up of: A phosphate group 5 carbon sugar Nitrogenous Base (nitrogen containing)

PURINES Adenine (A) Guanine (G)

PYRIMIDINES Cytosine (C) Thymine (T)

Base Pairing in DNA A-T C-G

Write the complementary DNA strand for each of these DNA strands: DNA GAATTACA CCAATTAG ATAGACAG CCAGTACA DNA CTTAATGT GGTTAATC TATCTGTC GGTCATGT

Each of the 96 columns represents one DNA sequence. A different colored dye attached to each of the four nucleotides.

Replication The act of making an exact copy of DNA

Semi-Conservative Replication Each strand of the original molecule acts as a template for the synthesis of a new complementary DNA molecule

With semi-conservative replication, each new strand is ½ new and ½ old

Examples of DNA Replication

RNA (ribo-nucleic acid) a nucleic acid that is a messenger between DNA and the ribosomes

Differences between DNA and RNA 1.Different sugars (DNA=deoxyribose) (RNA=ribose) 2.RNA is single stranded (1 side) DNA is double stranded (2sides) 3.RNA has “U” (uracil) DNA has “T” (thymine)

Always remember… RNA loves U

Write the RNA strand for each of these DNA strands: ½ Strand of DNA GAATTACA CCAATTAG ATAGACAG CCAGTACA RNA CUUAAUGU GGUUAAUC UAUCUGUC GGUCAUGU

Transcription The process by which DNA is copied into mRNA

mRNA Messenger RNA, is the copy of the DNA that goes from the nucleus to the ribosome

FACT Proteins are made up of amino acids

tRNA Transfer RNA, matches up with mRNA and has an amino acid on its top

CODON Each combination of 3 nucleotides on a strand of mRNA

ANTICODON Each combination of 3 nucleotides on a tRNA

Translation The decoding of a mRNA message into proteins

rRNA Ribosomal RNA, glues together all of the amino acids into a polypeptide chain

Table of Codons