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’sX-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

NUCLEOTIDESMade 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.

ReplicationThe 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…

RNAloves

U

Write the RNA strand for each of these DNA strands:

½ Strand of DNA

• GAATTACA• CCAATTAG• ATAGACAG• CCAGTACA

RNA

• CUUAAUGU• GGUUAAUC• UAUCUGUC• GGUCAUGU

TranscriptionThe process by which DNA is

copied into mRNA

mRNAMessenger RNA, is the copy of the DNA that goes from the nucleus

to the ribosome

FACTProteins are made up of amino acids

tRNATransfer RNA,

matches up with mRNA and has an

amino acid on its top

CODONEach combination of 3

nucleotides on a strand of mRNA

http://ghs.gresham.k12.or.us/science/ps/sci/soph/nucleic/pics/codon.gif

ANTICODONEach combination of 3 nucleotides on

a tRNA

TranslationThe decoding of a

mRNA message into proteins

rRNARibosomal RNA, glues

together all of the amino acids into a polypeptide chain

Table of Codons