Deoxyribonucleic Acid (DNA) &

Ribonucleic Acid (RNA)

DNA is a non-living stable molecule. The DNA code is universal, allowing it to work the same in all living things. This is a critical fact that makes genetic engineering possible

DNA Structure

• DNA is a long molecule made up of nucleotides.– Each nucleotide is

made up of three basic parts:

• a 5-carbon sugar

• a phosphate group

• a nitrogenous base

Nucleotide

• Consists of:- a phosphate group- a 5 carbon sugar- a nitrogen base

adenine (A)guanine (G)cytosine (C)thymine (T)

NITROGEN BASES• Purines = adenine and guanine

• Pyrimidines = thymine and cytosine– Adenine (A) always pairs with Thymine (T)

– Guanine (G) always pairs with Cytosine (C)

A

T C

A G

C

• A group of three nucleotides is called a codon.– Codon codes for a specific amino acid.

• There are 20 different amino acids. – Their abbreviations are listed in the right half of each

column. – The codons coding that particular amino acid are listed on

the left half.

DNA - Deoxyribonucleic Acid• Genetic Code• Model of DNA was

first constructed by Watson and Crick in 1953

• Spiral shaped = double helix

• Composed of nucleotides

DNA

• Double strand-Double Helix• Sides: repeating

phosphate groupdeoxyribose (sugar)

• Rungs: base pairsadenine-thymine

A---T

guanine-cytosine G---CHeld together by

hydrogen bonds

DNA in a nutshell…

• DNA is composed of nucleotides bonded to a sugar-phosphate backbone. Double stranded DNA forms a double helix structure.

• The DNA double helix coils up into compact structures called chromosomes. Small segments of the chromosome that encode a single protein are called genes.

• Chromosomes are microscopic. There are thousands of genes on each chromosome and hundreds of nucleotides in the DNA sequence of each gene.

• The role of DNA is to store and pass on genetic information.

DNA

• Carries genetic code

• Sequence of nucleotide bases determines type of protein

• makes RNA

DNA Extraction

•

• DNA extraction is necessary because genetic engineers need to be able to work with the DNA, cut it, locate and clone a single gene, and modify the gene before they insert it into another organism. The steps in DNA extraction are:

• Plant tissue is crushed to break open the cells and release the DNA. • Buffered salt solution is added into which the DNA easily dissolves. • Organic solution is added into which other molecules, such as proteins and

fats, easily dissolve purifying the DNA solution. • The purified DNA solution is separated from the organic waste solution. • Alcohol is added to the DNA solution causing the DNA to precipitate out into

a solid string that can be spooled out with a glass hook and stored indefinitely.

Replication

• occurs before a cell divides

• makes two exact copies

DNA Replication

• DNA makes an exact copy of itself this takes about 8 hours.

• Enzyme tell the DNA to unzip

• Unpaired bases react with free floating bases

• Bonds form resulting in 2 new DNA molecules

• Single strand of nucleotides bonded into a chain

– Each nucleotide contains • Ribose, sugar

• Phosphate

• Nitrogen base: adenine, guanine, cytosine or uracil

• Adenine pairs with Uracil/ Cytosine pairs with Guanine

Structure of RNA

Types of RNA

• messenger RNA (mRNA)– carry instructions for assembling amino acids

• ribosomal RNA (rRNA)– rRNA and proteins make up ribosomes

• transfer RNA (tRNA)– transfers amino acids to the ribosomes

TRANSCRIPTIONTRANSCRIPTION• When DNA gives RNA the code • RNA enzyme unzips DNA• RNA nucleotides join the DNA complimentary bases• mRNA nucleotides bond and leave the nucleus

Transcription

When transcription begins, the DNA code is in the nucleus while the amino acids, which will compose the protein to be produced, are in the cytoplasm.

A molecule called mRNA polymerase reads the gene to be produced and makes a copy of the DNA sequence

called RNA.

The mRNA strand is able to travel outside of the nucleus into the cytoplasm with

the amino acids.

Codon Table Wheel• To decode a codon,

start at the middle of the circle and move outwards.– Ex: CAU and CAC

both code for Histidine

START & STOP SIGNALS

• To start the protein synthesis the codon AUG must be present

• To stop the protein synthesis there’s a stop codon UAA, UGA, UUC

TRANSLATION• Process of assembling proteins from the

information encoded in RNA

• mRNA leaves the nucleus and goes to the ribosome– the codon ( 3 bases in sequence on the

mRNA)

• tRNA, transfer RNA leaves the nucleus and picks up an amino acid– the anticodon is the compliment to the codon

on mRNA

TRANSLATION

mRNA codon

ribosome

Amino acid

tRNA

Proteins in a nutshell…

• Proteins are chains of amino acids bonded together and folded into a 3-dimensional structure.

• Proteins do the 'work' in a cell and function in 3 ways:

– Enzyme=catalyze reactions

– Structure=influence cell shape and tissues

– Regulate=regulate the expression of other genes

How are Proteins made from DNA?

• A ribosome, present in the cytoplasm, reads the RNA strand three nucleotides at a time.

The codon codes for a specific amino acid. The ribosome reads the RNA strand and places the proper amino acids together in the order encoded in the strand.

The protein folds up into the shape dictated by the amino acids. This shape gives the protein its function and allows it to do its work in the cell.

Cloning page 332-333

Cloning activity: http://www.sciencecases.org/dog_cloning/dog_cloning_notes.asp

Chromosomes

-The other two chromosomes, X and Y, are the sex chromosomes. The above picture of the human chromosomes lined up in pairs is called a karyotype.

-The 22 autosomes are numbered by size.

Chromosomal Disorders• A genetic disorder is a disease caused by a

different form of a gene called a variation, or an alteration of a gene called a mutation. – Some, including many cancers, are caused by a mutation

in a gene or group of genes in a person's cells. • These mutations can occur randomly or because of an

environmental exposure such as cigarette smoke.

– Other genetic disorders are inherited. A mutated gene is passed down through a family and each generation of children can inherit the gene that causes the disease.

– Still other genetic disorders are due to problems with the number of packages of genes called chromosomes. In Down syndrome, for example, there is an extra copy of chromosome 21.

• Down syndrome is a genetic disorder resulting from three chromosomes instead of two in chromosome pair 21