DNA, RNA, and Proteins - AP Biology

When a point mutation on the DNA strand creates a premature stop codon the RNA template will not be completely translated, resulting in a protein with a lower molecular weight due to fewer amino acid residues. As a result, the protein will also likely be nonfunctional. This is an example of a nonsense point mutation.

A slightly altered protein with the same molecular weight would be an example of a missense point mutation, resulting in the substitution of one amino acid for another.

There are four levels of protein structure. Primary structure involves the linear arrangement of amino acids. It is simply the linear sequence of amino acids created by the ribosome during translation. Secondary structure involves the hydrogen bonding of the backbone and can form alpha-helices and beta-pleated sheets. Tertiary structure involves the interaction between amino acid side chains, or R-groups. These interactions can be hydrogen bonds, hydrophobic interactions, or disulfide bridges. Quaternary structure involves the interaction between two or more folded subunits, and is not present in every protein structure.

The primary structure of a protein is a linear sequence of amino acids. Amino acids are joined by peptide bonds between the N terminus of one amino acid and the C terminus of another amino acid through a condensation reaction, which results in the release of a water molecule.

The secondary structure of protein folding is two-dimensional and can take two forms: alpha helices and beta-pleated sheets. The secondary structure is characterized by hydrogen bonds between peptide groups.

Cells have certain mechanisms to protect proteins from denaturation and ensure proper folding. The cell uses two mechanisms to protect proteins: chaperones and heat shock proteins. Chaperones are a large class of proteins that aid with protein folding and prevent folding defects under normal and stressed conditions, during which chaperone expression is up regulated. Chaperones use ATP to induce a conformational change to provide an isolated environment for the protein to fold and prevent protein aggregation. Heat shock proteins are only produced under stress conditions. Heat shock proteins have a variety of functions including functioning as a chaperone, aiding in the binding of immune antigens, and preventing platelet aggregation in the cardiovascular tract.

Aggregations of misfolded proteins contribute to degenerative diseases such as Alzheimer’s, Huntington’s, and Parkinson’s diseases. Protein misfolding and degradation lead to protein-related diseases, such as cystic fibrosis.

There are a number of ways that scientists study protein folding and structure. They include the following processes: mutation studies, x-ray crystallography, and spectroscopy. Mutation studies compare the folding patterns of wild type proteins and those with targeted point mutations. X-ray crystallography is a form of high-resolution microscopy that uses x-rays to study the atomic structure of protein crystals through diffraction patterns. Last, a number of spectroscopy methods are employed to study protein folding by comparing unfolded, folded, and partially folded proteins.

Since the interior of cell membranes are made up of the hydrophobic tails of the phospholipids, proteins that are bound in membranes need region that contains high amounts of hydrophobic amino acids residues that can contact the hydrophobic tails molecules and keep it stable. Therefore, in a membrane-bound protein, one would expect the majority hydrophobic amino acid residues to be in the portion of the protein that is buried within the cell membrane.

The formation of beta pleated sheets and alpha helices occur in the secondary structure of a protein immediate after the sequence of the polypeptide has been formed. These two structures, alpha helices and beta-pleated sheets, are formed by the hydrogen bonds that occur among the amino acids of the polypeptide.

When a point mutation results in an inadvertent stop codon, it results in a truncated, and often, nonfunctional protein. This is referred to as a nonsense mutation. A point mutation is caused by a switch of a single base pair in the DNA, which may or may not result in the substitution of an amino acid for another since the genetic code is redundant.

The folding of proteins is the second and third level of organization in a protein and determines the protein's shape and how it bonds to substrates. The sequence of amino acids does not determine the shape as much as the folding in the second and third levels. The folding does not determine how long the protein will last in a cell. It does, however, influence the shape of the enzyme, which dictates the types of interactions between the enzyme and substrate, which ultimately determines the rate of the reaction that it catalyzes.

Denaturation is the correct answer here. The denaturation of a protein occurs when a catalyst causes the disruption and/or destruction of the bonds in a protein structure. Heat is one of the ways to denature a protein because the heat causes the molecules to vibrate quickly and coagulate into the white substance we eat.

Watson and Crick were the two scientists who developed the model of DNA as a double helix in 1953.

Uracil in RNA bonds to adenine on the DNA template during transcription. These two nitrogenous bases form two hydrogen bonds.

mRNA contains uracil instead of thymine, therefore your answer should not contain the base thymine. Remember, DNA is read in the 3' to 5' direction and the corresponding strand is created in the 5' to 3' direction. It is important to pay attention to polarity of the strands. Adenine pairs with thymine, and/or uracil. Guanine pairs with cytosine.

mRNA is messenger RNA, it carries the genetic code that determines the protein. snRNA directs splicing of pre-mRNA. tRNA transports the amino acids used for assembling proteins. rRNA is a component of ribosomes (the other component is protein). pre-mRNA- single strand of RNA processed to form mRNA.

Uracil is bound to adenine in the production of RNA, while thymine is used in its place in the production of DNA. Adenine, guanine, and cytosine are all used in the production of both RNA and DNA.

Cytosine and guanine form three hydrogen bonds with each other, while adenine and tyrosine only form two hydrogen bonds. This means that strands of DNA with a higher percentage of cytosine and guanine will have higher melting points.

Since we are looking for the sequence with the lowest melting point, we want the lowest percentage of cytosine and guanine, and the highest percentage of adenine and thymine.

The operator region is the location where the repressor binds. Other parts of an operon include the promoter (where RNA polymerase binds), and structural genes.