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03.05 DNA Replication
Transcript of 03.05 DNA Replication
-a molecule that encodes the genetic instructions used in the development and functioning of all known living organisms and many viruses.
-a large family of RNA molecules that convey genetic information from DNA to the ribosome, where they specify the amino acid sequence of the protein products of gene expression,
-also known as DNA-dependent RNA polymerase, is an enzyme that produces primary transcript RNA
-form between specific nitrogenous bases, are the building blocks of the DNA double helix and contribute to the folded structure of both DNA and RNA.
- the first step of gene expression, in which a particular segment of DNA is copied into RNA by the enzyme RNA polymerase.
-the process in which cellular ribosomes create proteins.
-an adaptor molecule composed of RNA, typically 73 to 94 nucleotides in length, that serves as the physical link between the nucleotide sequence of nucleic acids (DNA and RNA) and the amino acid sequence of proteins.
-the RNA component of the ribosome, and is essential for protein synthesis in all living organisms.
-a large and complex molecular machine, found within all living cells, that serves as the primary site of biological protein synthesis (translation).
-are biologically important organic compounds composed of amine (-NH2) and carboxylic acid (-COOH) functional groups, along with a side-chain specific to each amino acid
-large biological molecules, or macromolecules, consisting of one or more long chains of amino acid residues
DNA consists of four nucleotide bases [ adenine (A), guanine (G), cytosine (C), and thymine (T) ] that are paired together (A-T and C-G) to give DNA its double helical shape. Nucleotide base sequences are the genetic code or instructions for protein synthesis. There are three main steps to the process of DNA transcription. RNA Polymerase Binds to DNA. DNA is transcribed by an enzyme called RNA polymerase. Specific nucleotide sequences tell RNA polymerase where to begin and where to end. RNA polymerase attaches to the DNA at a specific area called the promoter region.
Elongation,Certain proteins called transcription factors unwind the DNA strand and allow RNA polymerase to transcribe only a single strand of DNA into a single stranded RNA polymer called messenger RNA (mRNA). The strand that serves as the template is called the antisense strand. The strand that is not transcribed is called the sense strand. Like DNA, RNA is composed of nucleotide bases. RNA however, contains the nucleotides adenine, guanine, cytosine, and uracil (U). When RNA polymerase transcribes the DNA, guanine pairs with cytosine and adenine pairs with uracil. Termination,RNA polymerase moves along the DNA until it reaches a terminator sequence. At that point, RNA polymerase releases the mRNA polymer and detaches from the DNA. Since proteins are constructed in the cytoplasm of the cell, mRNA must cross the nuclear membrane to reach the cytoplasm. Once in the cytoplasm, ribosomes and another RNA molecule called transfer RNA work together to translate mRNA into a protein. Protein synthesis is accomplished through a process called translation. After DNA is transcribed into a messenger RNA (mRNA) molecule during transcription, the mRNA must be translated to produce a protein. In translation, mRNA along with transfer RNA (tRNA) and ribosomes work together to produce proteins ,transfer RNA plays a huge role in protein synthesis and translation. Its job is to translate the message within the nucleotide sequence of mRNA to a specific amino acid sequence. These sequences are joined together to form a protein. Transfer RNA is shaped like a clover leaf with three loops. It contains an amino acid attachment site on one end and a special section in the middle loop called the anticodon site. The anticodon recognizes a specific area on a mRNA called a codon. Translation occurs in the cytoplasm . After leaving the nucleus , mRNA must undergo several modifications before being translated. Sections of the mRNA that do not code for amino acids, called introns, are removed. A poly-A tail, consisting of several adenine bases, is added to one end of the mRNA, while a guanosine triphosphate cap is added to the other end. These modifications remove unneeded sections and protect the ends of the mRNA molecule. Once all modifications are complete, mRNA is ready for translation!