UNCTIONS OF DNA-REPLICATION ANDPROTEIN SYNTHESIS Diagram/label and describe the

Question

UNCTIONS OF DNA-REPLICATION ANDPROTEIN SYNTHESIS Diagram/label and describe the more important steps in the process of DNA replication. Include labels and a brief explanation of each of the following terms: complimentary base pairs, 3 and 5 antiparallel parent strands, helicase, RNA primers, DNA polymerase, DNA ligase, Okazaki fragments brief descriptions of terms such as Diagram/label and describe the important steps in the process of protein synthesis. Include labels an gene, transcription, mRNA, codon, endoplasmic reticulum, ribosome, translation, tRNA, anti-codon, amino acid, and

Explanation / Answer

Important steps

Initiation

Replication begin at a location on the double helix known as “oriC” to which certain initiator proteins

bind and trigger unwinding. Enzyme called helicases unwind the double helix by breaking the hydrogen bonds between complementary base pairs, while other proteins keep the single strands from rejoining. The “topoisomerase” proteins surround the unzipping strands and relax the twisting that might damage the unwinding DNA. The cell prepare for the next step, elongation, by creating short sequences of RNA called primers that provide a starting point of elongation.

Elongation

With the primer as the starting point for the leading strand, a new DNA strand grow one base at a time. The existing strand is a template for the new strand. Like if the next base on the existing strand is an A, the new strand receives a T. The enzymes DNA polymerase control elongation, which can occur only in the leading direction. The lagging strand unwinds in small sections that DNA polymerase replicates in the leading direction. The resulting small “Okazaki fragments” can contain 1,000 to 2,000 bases in bacteria, but eukaryotes -- organisms having cells with nuclei -- have fragments of only 100 to 200 bases. The fragments terminate in an RNA primer that is subsequently removed so that enzymes can stitch the fragments into an elongating strand.

Termination

After elongation is complete, two new double helices have replaced the original helix. During termination, the last primer sequence must be removed from the end of the lagging strand. This last portion of the lagging strand is the telomere section, containing a repeating non-coding sequence of bases. Enzyme snip off a telomere at the end of each replication, leading to shorter strands after each cycle. Finally, enzymes called nucleases “proofread” the new double helix structures and remove mispaired bases. DNA polymerase then fills in the gaps created by the excised bases.

Complementary base pair- Either of the nucleotide bases linked by a hydrogen bond on opposite strands of DNA or double-stranded RNA: guanine is the complementary base of cytosine, and adenine is the complementary base of thymine in DNA and of uracil in RNA.

5-3 anti parallel- A single strand is different at its two ends. One end is called 5' (5 prime), the other is called 3' (3 prime). The names come from the notation for the two sugar carbon atoms which participate in the phosphodiester bonds. The different strands in the helix run in opposite (anti-parallel) directions.

Helicases- are often used to separate strands of a DNA double helix or a self-annealed RNA molecule using the energy from ATP hydrolysis, a process characterized by the breaking of hydrogen bonds between annealed nucleotide bases.

Primers- are short strand of RNA or DNA (generally about 18-22 bases) that serves as a starting point for DNA synthesis. It is required for DNA replication because the enzymes that catalyze this process, DNA polymerases, can only add new nucleotides to an existing strand of DNA.

DNA polymerase- In molecular biology, DNA polymerases are enzymes that synthesize DNA molecules from deoxyribonucleotides, the building blocks of DNA. These enzymes are essential for DNA replication and usually work in pairs to create two identical DNA strands from a single original DNA molecule.

DNA ligase- is a specific type of enzyme, a ligase, that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond

Okazaki fragments- are short, newly synthesized DNA fragments that are formed on the lagging template strand during DNA replication. They are complementary to the lagging template strand, together forming short double-stranded DNA sections.

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