The Flow of Genetic Information from DNA to RNA to Protein

I AM ABLE TO: Describe the process through which proteins are synthesized.

• An organism's phenotype comes from a variety of proteins.


• Structural proteins help make up the organism's body, while enzymes help facilitate metabolic actions.


• RNA programs protein synthesis, with two phases: transcription and translation.


• Transcription is the transfer of info from DNA to RNA.
  
• Translation is the transfer from RNA to proteins.
  
• The function of a gene is to dictate the production of a polypeptide.


• Both DNA and RNA have specific "languages".


• DNA is written in linear strands of nucleotide bases.


• A typical gene consists of thousands of nucleotides.


• One molecule can have thousands of genes.


• When a DNA is transcribed it produces an RNA molecule.


• Transcribed means to rewrite, and DNA is simply rewritten in another type of nucleic acid language.
  
• Translation is how the "language" of nucleic acids is turned into the "language" of the polypeptides.


• Since there are only four kinds of nucleic acids, they are grouped into triplets.


• The codons are able to make 64, allowing for several triplets to code for the same animo acid.


• The codon AUG is known as the start codon,
  
• UAA, UAG, and UGA are the three stop codons.

Transcription uses RNA polymerase.

It attaches to the promoter region of DNA where it receives signals.

• RNA is built using DNA as a template.
  
• Complimentary nucleotides are added to the DNA template, peeling away as it lengthens.
  
• The DNA then fuses back together.


• It ends when the RNA polymerase reaches the termination signal.
  
• The product is a strand of pre-mRNA and includes exons and introns.
  
• A cap and tail are added to the strand, and the introns are removed.


• The mRNA then leaves the nucleus via the nuclear pores.


• Translation uses three things, tRNA, mRNA, and ribosomes or rRNA.
  
• mRNA holds the information, tRNA "interprets", and the ribosome is the site of the actions.


• tRNA is rope-like and has two ends, one that attaches to the amino acid on that recognizes the codon: the anti-codon.


• A special tRNA attaches itself to the start codon AUG, and goes in the "P" site of the ribosomal unit.


• The elongation phase has three parts.


• The first, codon recognition, is the incoming of tRNA matching with their codon sequence.
Next is the peptide bond formation, where the old tRNA hands off the amino acid sequence to the next one.

The "P" tRNA then leaves the ribosome to pick up more amino acids to continue the cycle.

With the "P" slot open, the "A" slot tRNA move in to allow another tRNA to come in.

Termination is reached when when a signal is received from one of the stop codons, UAG, UAA, and UGA.

The amino acid sequence is then let go, and the ribosome separates.

Polypeptides may come together and form proteins.

Scientists have, since discovering the translation process, determined many differences on the molecular basis.

Diseases like sickle-cell have been found to be a change in a certain gene.

A change in the nucleotide sequence is called a mutation.

Most mutations are harmful, though some will increase the capabilities of the protien that can be passed down genetically.

There are three types of gene mutations: base substitution and insertion, or deletion.

The way that a nucleotide is translated depends on if the protein is changed.

Some are trivial, while others affect the organism totally.

If the mutation changes the sequence, but they code for the same amino acid, they are called silent mutations.

Some mutations cause the codon to become a stop codon.

This may cause the sequence to terminate too early, not have the protein function properly.

Insertion and deletion tend to cause the most damage, because they damage the triplet groupings.

Mutagenesis is how a mutation is created and can occur through many ways.

Physical and/or chemical agents that cause mutations are called mutagens.

Mutations are responsible for the different alleles needed for genetic research.

Strand:Life and Environmental Sciences

Standard 5: Life and Environmental Sciences: DIVERSITY, GENETICS, AND EVOLUTION: Understand genetics and biological evolution and their impact on the unity and diversity of organisms.

Topic: Unity and Diversity

Benchmark SC.BS.5.3 Explain the structural properties of DNA and the role of DNA in heredity and protein synthesis

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