Decoding DNA :Decoding DNA : Transcription, Translation Transcription, Translation and Gene Regulationand Gene Regulation

How do we get information from DNA?

DNA is the genetic plan for each cell and a blueprint for every characteristic in an organism.

The instructions needed to make proteins are coded in the nucleotides that make up a gene.

What are some body parts that contain protein?

Hair

Skin

Nails

Internal organs

PHYSIOLOGY

-Hemoglobin in blood

-Enzymes

Functions of proteins?

Traits such as eye color are determined by proteins

Proteins are built by instructions in the DNA.

Some act as enzymes.

Some act as cell membrane channels.

RNA is involved in making proteins

RNA- RIBONUCLEIC ACID

RNARNA DNADNA

• consists of a single strand

• two strands (double).

• 5 carbon sugar ribose

• 5 carbon sugar deoxyribose

• nitrogen base Uracil (U)

• nitrogen base Thymine (T)

3 types of RNA

mRNA – (messenger) - copies DNA

rRNA – (ribosomal) – reads codons on mRNA

tRNA – (transfer) – places amino acid on each codon of mRNA

2 Steps of Protein Synthesis

1 2

Steps in making proteins

Step 1 – Transcription- Take a gene composed of DNA and made (write down) the mRNA.

Step 2 – Translation- Translate (Decode) the mRNA into amino acid sequences.

Step 3- Gene expression- when the proteins are made.

DNA mRNA tRNA

protein

Transcription (Step 1)

Transcription occurs in the nucleus (eukaryotes) or the cytoplasm (prokaryotes).

Only part of the DNA (a gene) serves a template.

When the RNA is transcribed the DNA double helix will reform.

TRANSCRIPTION

Transcription

RNA polymerase (ENZYME) adds complementary RNA nucleotides

1st RNA polymerase binds to DNA

2nd Elongation unwinds DNA & adds/links RNA nucleotides.

3rd Reaches a stop signal and is finished

Transcribe mRNA from the DNA given:

DNA 3’ ATGCTCAA 5’mRNA 5’ UACGAGUU3’

Give the segment of DNA that this mRNA was transcribed from.

mRNA: UGAUUCDNA: ACTAAG

Introns- long segments of nucleotides that have no coding information.

Exons- portions of genes that are translated. (expressed in proteins).

Introns get cut out of mRNA by proteins and the Exons are pasted together.

Introns and Exons

Genetic Code The genetic code (codons) used by most organisms to translate mRNA is nearly universal.

Codons consist of three nucleotide “words” (three bases)

One codon codes for 1 Amino Acid

The genetic code

There are 20 amino acids

64 possible mRNA codon combinations

“Start” and “Stop” signals also:

- Start : AUG (Methionine)

- Stop : UAG, UAA, UGA

Each protein is coded for by a gene in a specific location on DNA

Translation (Step 2)Takes place in the cytoplasm.

Transfer RNA (tRNA)- a strand of RNA that carries an amino acid on one end and an anticodon on the other.

Anticodon - a three-nucleotide sequence of tRNA that is complementary to a codon on mRNA.

mRNA

Protien

Amino Acid

Anticodon

Codon

tRNA

Steps in Translation

Step 1: mRNA leaves nucleus and enters cytoplasm. The ribosome and and tRNA carrying amino acid form a complex.

Determine the Amino Acid Code that this mRNA codes for.

GUUCAGAACUGU

Valine, Glutamine, Asparagine, Cysteine

What is the maximum number of amino acids that could be coded for by this section of mRNA?

4

Gene Regulation and Structure

Gene Regulation and Structure

Not all genes get expressed all the time. (Translated and transcribed)

If a cell does not need that protein at the time why waste energy to make it.

In prokaryotic organisms the lac operon allows bacterium to build proteins needed for metabolism only when lactose is present.

MUTATIONS

Changes in an organism’s hereditary information. Rare but they can occur.

Mutations in gametes (sex cells) can be passed on the the offspring. Mutations in body cells only affect the individual.

Fruit Flies

TYPES OF MUTATIONS that change genes

Frame shift

Point mutations

Insertion and Deletions

MUTATIONS can be caused by exposure to ultraviolet radiation (tanning)

Point Mutation

Only a single nucleotide changes.

Insertion and Deletion

Insertion - a sizable length of DNA is inserted into a gene.

Deletion - segments of a gene are lost. Often during Meiosis.

DNA Electrophoresis

DNA fingerprint – help determine how closely related members of a population are.

The segments of DNA move down the gel. The smaller pieces move the furthest down the gel.

Each individual has a unique pattern of banding.

A B C D E

DNA fingerprinting is used in forensic science to identify victims or criminals

A human’s genome is all the base A human’s genome is all the base pairs that compose the DNA of the pairs that compose the DNA of the organism, and their location on the organism, and their location on the chromosome.chromosome.

Human cells contain about Human cells contain about 30,000 to 40,000 genes.30,000 to 40,000 genes.

Genetic Engineering in Medicine

Can be used to manufacture human proteins for use as drugs and to make safer and more effective vaccines.

Treat human genetic disorders.

Genetic Engineering in Agriculture

Crops can be genetically engineered to have favorable characteristics, including improved yields and resistance to herbicides and destructive pests.

Genetically engineered growth hormones.

Cloning

DOLLY

GFP (Green Fluorescent Protein)Comes from the jellyfish Aequorea victoria

In modified forms it has been used to make biosensors.

Organisms are given this as proof-of-concept that a gene can be expressed throughout a given organism.

The big picture:The big picture:

DNA is coiled into chromosomes (found in the nucleus).

DNA is responsible for inherited characteristics.

Genes are found on chromosomes and consist of DNA, made of four nitrogen bases.

- mRNA “reads” DNA and transcribes the message for a protein.

- mRNA makes a complex with a ribosome. tRNA anticodons match with mRNA codons and a protein is made.