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Structure
Interesting Questions, Facts and Information
- There are a total of 20 general entries.
Special Topics
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 Interesting Questions, Facts, and Information
 DNA and RNA
| The "genetic code" in deoxyribonucleic acid (DNA) is based on the order of four nucleic acid bases: adenine, cytosine, guanine and thymine. However, what makes up a complete DNA nucleotide? | Building Blocks of Life: DNA, RNA, and Protein
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All of these (Five-carbon, 2'-deoxyribose sugar, Phosphate group, Nucleic acid (purine or pyrimidine) base). Although it is often thought that "nucleotides" are simply the A, C, G, and T bases, they are actually made up of the 5'-phosphate group, and deoxyribose sugar (or ribose in RNA), in addition to the specific base. Nucleotides are joined together through a phosphodiester link between the two sugar residues.
Hydrogen bonds. Hydrogen bonding between bases allows for stabilization of the double helix. It is important because while these bonds are strong enough to hold the helix shape, they can also be broken under appropriate conditions in order to allow for the two strands which make up the helix to separate for replication or transcription.
Semiconservative. In DNA replication one "parental" DNA molecule generates two "daughter" DNA molecules. In semiconservative replication, each daughter DNA molecule contains one "old" strand from the parent and one "new" strand generated with free nucleotides using the enzyme DNA polymerase. The new DNA molecule is therefore the identical base sequence as the parent, using one parental strand as the template to generate a complementary new strand, and thus a new DNA molecule. This process was proved through an experiment by scientists Matthew Meselson and Franklin Stahl in 1958.
Nucleus. In eukaryotic cells, the DNA is held within the nucleus to ensure it is protected from damage. Since DNA does not leave the nucleus, and this genetic material is required for transcription, this process occurs inside the nucleus. Once the RNA transcript is generated, it is modified to ensure stability, and it leaves the nucleus to be translated into protein.
All of these (Generation of a "cap" at the 5' end, Splicing of introns from the primary transcript, Addition of a poly-A tail at the 3' end). In order for successful translation to occur in the cytoplasm of the cell, all of these modifications must occur. Introns represent RNA which does not code for protein, and are thus removed through splicing before translation. The 5' cap is used to properly position the mRNA on the ribosome for translation. The poly-A tail at the 3' end can consist of up to 200 "A" nucleotides and is related to message stability.
| Translation is the process by which proteins are generated from an mRNA sequence by attaching amino acids to one another. Which specific type of RNA includes the anti-codon loop and is bound to a specific amino acid? | Building Blocks of Life: DNA, RNA, and Protein
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tRNA. All tRNAs share generally the same structure. Each one is attached to a specific amino acid based on the anti-codon sequence which it contains. The anti-codon sequence is completmentary to the codon sequence, a series of three nucleotides in the mRNA molecule. In this way, the mRNA sequence encodes for the correct sequence of amino acids needed to make a protein!
20. Proteins are polymers of 20 different types of alpha amino acids. Every alpha amino acid contains an amino group attached to an alpha carbon which is attached to a carboxyl group. The alpha carbon is also attached to a side chain, which is different in each amino acid. Different side chains allow us to name and distinguish different amino acids!
Peptide bond. Amino acids are linked together by peptide bonds between the carboxyl group of one amino acid with the amino group of another. This can also be called an amide bond.
Ribosome. The ribosome is the site of protein synthesis. The mRNA molecule is bound to the ribosome, and this is also where the aminoacyl tRNA (tRNA bound to the appropriate amino acid) binds to the complementary codon. Ribosomes are also present in the rough endoplasmic reticulum. This is why it is called rough! One cell can contain thousands of ribosomes!
| Once a polypeptide is generated through translation, it is folded to make a functional protein molecule. How many levels of structural organization are present in proteins made up of multiple polypeptide subunits? | Building Blocks of Life: DNA, RNA, and Protein
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4. Proteins have four levels of structural organization. The "primary" level is the amino acid sequence. The "secondary" level is local regular folding of that amino acid chain, typically into alpha helices or beta sheets. The "tertiary" level is overall folding of the polypeptide in which the helices or sheets become even more compact. Finally, the "quaternary" level of protein organization is the close association of multiple polypeptide chains to form a functional protein molecule.
| In DNA replication, which enzyme(s) binds to the single stranded DNA strand and builds a short RNA primer sequence? | Discovering DNA and RNA
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primase. Primase it the enzyme that creates a short RNA primer sequence so that DNA polymerase 3 can bind to the primer and link the adjacent nucleotides together. Ligase is the enzyme that links the okazaki fragments together. Restriction enzymes are used to cut DNA in DNA recombination.
RNA contains a single phosphate group. RNA is single stranded while DNA is double stranded. DNA's double stranded nature gives it the double helix structure.
mRNA. In protein synthesis, the DNA molecule uncoils and unzips. Then the mRNA, which is also known as messenger RNA, enters the nucleus, reads the bases on the DNA molecule, and leaves through the nuclear pores. This happens in the transcription part of protein synthesis.
DNA. DNA cannot leave the cell nucleus in order to prevent loss of genetic information.
uracil. Uracil is only found in RNA while thymine is only found in DNA.
phosphodiester linkages. Nucleotides are monomers of nucleic acids. They are linked together by phosphodiester linkages between the phosphate group of one nucleotide and the sugar molecule of the next nucleotide.
uracil. In DNA, the base thymine pairs up with adenine. Since thymine is not present in RNA, uracil, which is only present in RNA pairs up with adenine in place of thymine.
sugar and phosphate groups. Sugar and phosphate groups are present at either end of the chain of bases in DNA and form the backbone of it.
hydrogen bonds. The bases of the molecule point inward and hydrogen bonds link the two chains of bases. This results in the molecule forming a double helix.
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