DNA - Introduction Deoxyribonucleic

Acid Structure: Replication Transcription Translation

DNA

DNA- Deoxyribonucleic Acid

What is this?

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POLYMER

A polymer is a large molecule made up of smaller molecules called monomers

DNA is a polymer made up of Nucleotides.

NUCLEOTIDES

Nucleotides are the smaller sub-units that make up a DNA

Each Nucleotide is made up of a

Sugar, Phosphate and Nitrogen Base

4 NITROGEN BASES

A d en in e(A )

G u an in e(G )

Th ym in e(T)

C ytos in e(C )

D N A N itrog en B ases4 B ase P a irs

H e ld Tog e th er b y H B on d s

Complementary Base Pairs: Cytosine always

bonds with guanine by forming three hydrogen bonds. (C-G)

Adenine always bonds with thymine by forming two hydrogen bonds. (A-T)

DOUBLE HELIX

The DNA molecule consists of two nucleotide chains that wrap around each other to form a double spiral

Looks like a twisted ladder

DNA makes you UNIQUE :) The order of nucleotides

(NB) will vary in every organism

The closer you are in Evolutionary History- the closer your DNA will resemble

The sequence of nucleotides forms the unique genetic information of an organism

DNA Replication: The process of copying DNA Takes place during the “S” phase of the cell

cycle…Remember?

Steps of DNA Replication

DNA will unwind DNA will “unzip”

down the middle separating the sides of the ladder

Steps of DNA Replication

Free-Floating nucleotides will come in and attach to each existing side of the original DNA

This process will continue until the entire molecule has replicated

Outcome of DNA Replication Replication will make 2 identical

strands of DNA which can then be passed on to a new cell during mitosis or meiosis

When all the DNA in all the cells has replicated, there are 2 copies of the organism’s genetic information.

DNA

DNA is the “Master” copy of an organisms information code. This information contains instructions used to form nearly all enzymes and proteins.

DNA- Major Functions

Directing Protein Synthesis Controlling Cell Division Inheritance

Why is it called Universal?

The codons represent the same amino acids in all organisms

Same in humans and virtually every other known organism

Figured out by studying the DNA of the bacteria E. Coli

The Other Nucleic Acid- RNA

RNA stands for Ribonucleic Acids RNA and DNA are very similar but

they do have three key differences.

Differences between RNA & DNA

RNA: Single Sided Sugar molecule

called RIBOSE 4 Bases- Cytosine,

Guanine, Adenine and URACIL

DNA: Double sided Sugar molecule

called DEOXYRIBOSE

4 Bases-Cytosine, Guanine, Adenine and THYMINE

RNA in involved in an important process called transcription.

The process in which RNA makes a copy of DNA

Similar to Replication.

Transcription!! Proteins are

made on ribosomes in the cytoplasm of the cell. Yet DNA is found only in the nucleus. How is information brought to the ribosomes for protein synthesis?

RNA Transcription .

DNA must first unwind. Enzymes unzip DNA molecule Free-floating RNA nucleotides pair

with complementary DNA nucleotides on one of the DNA strands

Guanine pairs with Cytosine Adenine pairs with Uracil

RNA Transcription .

When the process of base pairing is completed, the mRNA molecule breaks away as the DNA strands rejoin

The mRNA leaves the nucleus and enters the cytoplasm to a ribosome.

RNA Transcription

(Messenger) mRNA is the form in which information moves from DNA in the nucleus to the ribosomes in the cytoplasm

Enzymes make a RNA copy of a DNA strand

The Genetic Code

DNA holds the instructions to make proteins.

Like DNA..Protein is also a polymer made up of smaller subunits called Amino Acids

There are 20 A.A. They combine in various ways to make various proteins.

The Genetic Code You need to look at DNA as being similar to

the alphabet. The alphabet has 26 letters which combine to

form 1000’s of words. The DNA alphabet only has 4 letters and all

the words are made up of only 3 letters. When you “read” DNA you read in group of 3

Nitrogen Bases at a time. Groups of 3 are called CODONS Each codon will code for a specific Amino

Acid

Translation- Protein Synthesis

The process of converting the information of mRNA into a sequence of Amino Acids that will make a protein

On your ribosome is your mRNA with all the codons and information from DNA

Another Form of RNA

tRNA Transfer RNA Single strand Purpose is to bring the

appropriate amino acid to the ribosome

Carries the anti-codon

Mutations Gene: sequence of DNA nucleotide bases Gene Mutation: any change in this DNA

sequence of nucleotide bases Point Mutation: a change in a single base

pair, mistake may or may not interfere with protein function

Frameshift Mutation: where a single base pair is added or deleted, this causes a shift in the reading of the codons by one base

These mutations can occur when the DNA is replicated, during transcription and translation