Decoding DNA : Transcription, Translation and 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

RNA DNA 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 12

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 mRNAtRNA 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 1 st RNA polymerase binds to DNA 2 nd Elongation unwinds DNA & adds/links RNA nucleotides. 3 rd 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: UGAUUC DNA: 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

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 pairs that compose the DNA of the organism, and their location on the chromosome. Human cells contain about 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: 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.