Protein Synthesis. A gene is the basic unit of heredity in a living organism All living things depend on genes Genes hold the information to build and maintain their cells and pass genetic traits to offspring the term gene often refers to the scientific concept of an allele .
Complex molecules (macromolecules) composed of one or more polypeptide chains
The sequence of amino acids in a protein is defined by the sequence of a gene, which is encoded in the genetic code
Biochemical reactions are controlled by enzymes
Enzymes are often are organized into chains of reactions known as metabolic pathways. Loss of activity in a single enzyme can inactivate an entire pathway.
He hypothesized that a defective enzyme causes an "inborn error of metabolism“
If there is an accumulation of substance B, then enzyme 2 must be defective
If there is an accumulation of substance C, then enzyme 3 must be defective
+ Amino Acid
If the precursor accumulated, the defect was in enzyme A
If ornithine accumulated, enzyme B was defective
They showed that a lack of a particular enzyme corresponded to a mutation in a specific gene
Vernon Ingram further proved the results of Beadle and Tatum while studying the amino acid sequence of hemoglobin from individuals with sickle cell anemia
proposition put forward by Francis Crick
The information flow in the cell goes from the
deoxynucleicacid DNA, to the ribonucleic acid
messenger RNA, to protein
Never from protein to nucleic acids.
Atype of molecule that consists of a long chain of nucleotide units.
RNA is very similar to DNA, but differs in a few important structural details:
RNA Polymerase binds to the DNA at a specific site, near the beginning of the gene
Using the DNA as a template, RNA polymerase puts together the appropriate ribonucleotides
Shorty after the RNA Polymerase passes the end of a gene, it recognizes a signal to stop transcribing
Initiation occurs when a ribosome recognizes a specific sequence on the mRNA and binds to that site
A tRNA delivers the appropriate amino acid and the polypeptide chain is elongated
There are 20 amino acids found in proteins but only four different basesin mRNA
More than one codon can code for a single amino acid, indicating a redundancy in the genetic code
Codon: Sequence of three bases in DNA or complementary mRNA that serves as a code for a particular amino acid