Central Dogma Of Molecular Biology

The central dogma of molecular biology describes the two-step process, transcription and translation, by which the information in genes flows into proteins: DNA ? RNA ? protein. Transcription is the synthesis of an RNA copy of a segment of DNA.

The central dogma of molecular biology is a phrase by Francis Crick, who proposed the double helix structure of DNA. It means that information passes from DNA to proteins via RNA, but proteins cannot pass the information back to DNA.

Transcription is the first step of gene expression, in which a particular segment of DNA is copied into RNA (especially mRNA) by the enzyme RNA polymerase. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language.

DNA synthesized mRNA in a process known as transcription.

mRNA is read at the ribosome and translated into a protein in a process known as translation.

Proteins are polymers of amino acids.

Proteins are the internal machinery of a cell. Among the many different roles that proteins serve in the cell, proteins have structural roles to help the cell keep its shape, regulatory roles to control movement of particles in and out of the cell, and repair roles to help signal and and help with repair of a cell if it is damaged. Proteins are especially important in cell division because they control when it starts, ends, and every movement in between.

Proteins are synthesized at ribosomes within the cell.

Translation

DNA directly codes for RNA: mRNA, tRNA and rRNA. DNA also codes for itself via replication.

DNA indirectly codes for polypeptides and proteins via an intermediary called messenger RNA or mRNA.

A gene is a segment of DNA that codes for a specific sequence of mRNA that is translated to produce a protein.

DNA

A gene is a segment of DNA that codes for a specific sequence of mRNA that is translated to pleotides. RNA is composed of ribonucleotides.

A nucleotides is composed of a phosphate, a sugar and a nitrogenous based. Deoxyribonucleotides have the sugar deoxyribose, while ribonucleotides have ribose. The nitrogenous bases for DNA are adenine, guanine, cytosine and thymine. RNA houses adenine, guanine, cytosine and uracil.

The nitrogenous bases for DNA are adenine, guanine, cytosine and thymine. RNA houses adenine, guanine, cytosine and uracil.

Purines and pyrimidines are nitrogenous bases that make up the two different kinds of nucleotide bases in DNA and RNA. The two-carbon nitrogen ring bases, adenine and guanine, are purines, while the one-carbon nitrogen ring bases, thymine, uracil and cytosine, are pyrimidines.

The two-carbon nitrogen ring bases, adenine and guanine, are purines, while the one-carbon nitrogen ring bases, thymine, uracil and cytosine, are pyrimidines.

DNA deoxyribonucleotides versus RNA ribonucleotides. In ribonucleotides, the sugar component is ribose while in deoxyribonucleotides, the sugar component is deoxyribose. Instead of a hydroxyl group at the second carbon in the ribose ring, it is replaced by a hydrogen atom. Secondly, DNA house the nitrogenous base thymine, whereas RNA house uracil.

The 3 prime carbon connects of one nucleotide connects to a phosphate group of an adjacent nucleotide binding them together in a phosphodiester bond.

Deoxyribose and ribose differ in the presence or absense of an oxygen at the 2 prime carbon. Ribose has an oxygen, Deoxyribose does not. Hence, deoxy-ribose.

Adenine, cytosine, guanine and uracil.

Nucleotides (ribonucleotides and deoxyribonucleotides are connected by phosphodiester bonds, a covalent bond connecting the phosphorous of one nucleotide to the 3 prime carbon of an adjacent nucleotide.

Thymine contains a methyl (CH3) group at number-5 carbon, whereas uracil contains hydrogen (H) molecule at number-5 carbon.

Nucleotides (ribonucleotides and deoxyribonucleotides are connected by phosphodiester bonds, a covalent bond connecting the phosphorous of one nucleotide to the 3 prime carbon of an adjacent nucleotide.

A phosphate group is on the 5 prime end of a nucleic acid, and the sugar is on the 3 prime end.

Ribonucleeotides compose RNA.

Ribosomes are composed of ribosomal RNA and protein.

RNA predominately assists with the production of proteins in the cell. DNA transcribes mRNA. mRNA is read at a ribosome, which is composed of rRNA and protein, by tRNA. All of these RNAs work in conjunction to produce a protein.

Ribosomes are composed of ribosomal RNA and protein.

mRNA is synthesized by a specific sequence of DNA, known as a gene. mRNA serves as a template for the production of a protein.

tRNA reads the mRNA at a ribosome synthesizing a protein.

Chargaff discovered: 1. the relative abundance of guanine equals cytosine, and 2. the relative abundance of adenine equals thymine.

James Watson and Francis Crick suggested Chargaff's evidence strongly supports base pairing in DNA, in which deoxyribonucleotides of adenine attach to thymine (A?T) and guanine attaches to cytosine (G?C). In addition, Watson and Crick hypothesized that base pairing of deoxyribonucleotides suggested that DNA was most likely double stranded.

To acquire evidence of the actual molecular shape of DNA, Rosalind Franklin and Maurice Wilkins bombarded DNA with x-rays and analyzed how the radiation scattered, a technique known as x-ray chromatography.

Analyses of the scatterplots from this technique allowed them to measure the distance between atoms in DNA and they were able to conclude three things: 1) DNA has a consistent width, 2) within DNA is a repeating pattern and 3) the molecule must be helical.

Watson and Crick suggested that DNA is composed of two strands: one running 5' to 3' connected to a second strand running 3'to 5'. This orientation is called antiparallel.

The rules of base pairing (or nucleotide pairing) are: A with T: the purine adenine (A) always pairs with the pyrimidine thymine (T) C with G: the pyrimidine cytosine (C) always pairs with the purine guanine (G).

For the width of DNA to be consistent with the variety of shapes found in nitrogenous bases, purines must connect with pyrimidines. A purine-purine base pairing creates a larger molecular width than observed, and a pyrimidine-pyrimidine base pairing would be too small.

Investigating the shapes and interactions of these four nitrogenous bases, they discovered that guanine and cytosine were geometrically complements of each other and held together by three hydrogen bonds, while adenine and thymine are held together by two hydrogen bonds. Essentially, the A-T and C-G pairing are more stable than any other combination due to the complementarity of the molecular shape and hydrogen bond orientation.

Of the more than 500 amino acids known, only 20 appear in proteins of living organisms.

Investigating the shapes and interactions of these four nitrogenous bases, they discovered that guanine and cytosine were geometrically complements of each other and held together by three hydrogen bonds, while adenine and thymine are held together by two hydrogen bonds. Essentially, the A-T and C-G pairing are more stable than any other combination due to the complementarity of the molecular shape and hydrogen bond orientation.

R groups vary between amino acids.

R-groups can vary in their size, shape and polarity.

Non-polar molecules have relatively equal distribution of electrons via covalent bonding, while polar molecules have an unequal distribution of electrons. The unequal distribution of electrons in polar molecules creates partially charged atoms (?+, ?-).

Polar R-groups are hydrophilic, meaning they have an affinity for water due to hydrogen bonds between the partial charges of the R-group and the water molecules.Non-polar R-groups are repelled by water, or hydrophobic.

Proteins are polymers of amino acids chained together by covalent bonds, known as peptide bonds.

Amino acids link via peptide bonds forming long chained molecules, or polypeptides.

The unique amino acid sequence is a protein's primary structure.

Sickled cell anemia is caused by a single different amino acid in one protein, an alteration of the proteins primary structure.

When amino acids are grouped into polypeptide chains, neighboring amino acids can interact via hydrogen bonding. These interactions can form a regular pattern, which increases the molecular stability of the polypeptide chain.

The protein's secondary structure form either corkscrew-shaped structures, known as ?-helices, or folded ribbon-shaped structures, known as ?-pleated sheets.

Within a single amino acid of an ?-helix polypeptide chain, the hydrogens of the amine groups face the opposite direction relative to the oxygens of the carboxyl groups. In a single amino acid of a ?-pleated sheet, the oxygen of the carboxyl and the hydrogen of the amine group face in the same direction. In the adjacent amino acid, the oxygen and hydrogen both face in the opposite direction relative to the first. The third amino acid is in a similar orientation to the first, and so on.

Hydrogen bonding between R groups. Hydrophobic/hydrophillic interations and ionic bonding between R groups.

Quartenary structure.