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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.
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.
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
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.
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
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
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.
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.
TYPES OF MUTATIONS that change genes
Frame shift
Point mutations
Insertion and Deletions
MUTATIONS can be caused by exposure to ultraviolet radiation (tanning)
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
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
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.