Viruses: Genes in Packages

I AM ABLE TO: Understand the process by which a virus is created.

Viruses have genes and are highly organized, but are not able to reproduce on their own and are not made of cells.

• They are basically "genes in a box".
  
• Viruses can only survive by infecting another living cell and force it to produce more viruses.


• Bacteriophages are a type of virus that attack or "eat bacteria.
• Their reproductive cycle is known as the lytic cycle.


• An alternate route is the lysogenic cycle, where the cell doesn't burst open.


• First, the virus attaches to the bacteria.



• Then it injects phage DNA into the host bacteria.


• The cell's devices for DNA transcription and translation are made to produce phages.

The phage parts are assembled, then the cell lyses, or bursts open.

• In the lysogenic cycle, after the bacterial chromosome is inserted it becomes inactive.


• The bacteria then reproduces normally, only now it has the prophage in it.


• Once in awhile, a prophage will leave the cell and send it to the lytic cycle.


• Plant viruses can stunt the plant and force the it to yield less than normal.


• Many are rod-shaped with a covering of protein spikes.


• There are no cures for plant or animal viruses.


• Hepatits, chicken pox, and herpes are examples of animal viruses.
  
• Viruses reproduce by attaching themselves to susceptible cells.


• Then, they enter the cytoplasm and remove the protein coat from the RNA that entered


• One of the enzymes that entered with the RNA, uses the RNA as a template to create mRNA.


• The mRNA are utilized to create new viral proteins and viral genome.


• They are then assembled again and exit the cell receiving an envelope.
  
• Finding ways to make anitviral drugs is hard, because it's difficult to kill the virus wothout killing the cell.


• Retroviruses like AIDS use reverse transcriptase to create RNA from the host cells own DNA.
  
• The enzyme uses the viral RNA as a template to create a new strand of DNA.


• Then it adds a second complimentary DNA strnad to form a doucle stranded virus.


• This provirus DNA attaches itself to the host cells own DNA and creates RNA.


• The RNA is then translated into viral proteins and a new virus is assembled.

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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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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DNA: Structure and Replication

DNA and RNA Structure

I AM ABLE TO: Describe DNA, its shape, and how it creates more of itself.

• Both DNA and RNA are Nucleic Acids.
  
• Monomers are nucleotides.
  
• There are three components of a nucleotide: a sugar, a phosphate group, and a nitrogenous base.


• The Four nitrogenous Bases of DNA: Adenine, Guanine, Cytosine, and Thymine(RNA has uracil instead of thymine).


• The nucleotides in DNA are joined by covalent bonds between the nitrogenous base, and the sugar.
  
  
• The "backbone" of the structure is made of a pattern of "sugar-phosphate-sugar-phosphate".


• The sugar in DNA is deoxyribose.
• DNA= deoxyribonucleic acid.
  
  

Watson and Crick and the Double Helix

• The two have been credited for the discovery of DNA's double-helix structure.


• Watson first perceived it from a X-ray crystallographics photo by Rosalind Franklin.
Watson and Crick constructed a model using wires

They used the information from Franklin's data, as well as the current chemical knowledge of DNA.


With their models, they came up with the concept of specific base pairings.

Adenine pairs with Thymine (DNA, Uracil in RNA), and Guanine pairs with Cytosine.

DNA Replication

• Replication is the process in which more DNA is made.

• An enzyme called helicase starts at the origin of replication, and untwists the the DNA strands.

• This becomes the "replication bubble"

• Then the enzyme DNA polymerase follows and adds complimentary DNA nucleotides to the two opposite strands. (One of the old DNA strands will be used as the template for the new DNA strand.)

The product is two DNA strands, each with a new and old strand of nucleotides.

There are many replications happening at the same time, and at very fast rates.

Replication ensures that the DNA in a multicellular organism's cells are the same.

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.


All pictures from:http://wps.aw.com/wps/media/objects/3037/3110897/ebk/htm/_eb3e.htm?10

Chapter 10: The Structure and Function of DNA

Hello everybody! So this is the website for Chapter 10 in the Biology Book. It'll cover everything from the nitrogenous bases, all the way to viruses. Hope this is informational and to your use.
Kobey