DNA replication is initiated when the enzyme helicase creates a structure called a replication fork. This is the area in which the helicase unzips and where the two strands part from each other. This is done when the helicase unwinds a strand of the DNA and breaks the hydrogen bonds between the complementary strands of DNA. After this separation occurs, the two strands can be named the leading strand and the lagging strand (see diagram to the left). From here, a different enzyme known as DNA polymerase "catalyzes the synthesis of complementary strands of DNA" (DiscoveryEducation). The enzyme completes this replication of DNA by matching up the As to the Ts and the Cs to the Gs. DNA polymerase can only build onto a "free 3’ end" of a chain. Synthesis of the leading strand proceeds continuously in the 5’ to 3’ direction. Synthesis of the lagging strand occurs in stages because it will need to go in the opposite direction. Another enzyme called DNA ligase takes care of the lagging strand. This enzyme attaches the segments of the strand, or Okazaki fragments and creates the complete replication. It does this by using and combining the backbone, which is made of sugar and phosphate groups (DiscoveryEducation).
During transcription, complementary mRNA strands are created when the base codes in DNA are copied. From here, the mRNA strands move out of the nucleus and into the cytoplasm. mRNA serves as the code for assembling amino acids in a certain order to create proteins. This takes place at the site of the ribosome and is known as translation. Ribosomes are made of another type of RNA known as rRNA, and this molecule makes protein synthesis at the ribosome possible. Another type of RNA called tRNA brings amino acids to the ribosome and attaches them in the specific order that is on the mRNA. Peptide bonds link the amino acids, and this is how proteins are formed (DiscoveryEducation).
mRNA, rRNA, and tRNA all play different roles in the process of protein synthesis. mRNA carries the copied genetic information to the ribosome. With this, mRNA serves as the code for assembling amino acids in a certain order to create proteins. The role of tRNA is to bring amino acids to the ribosome during protein synthesis, and the tRNA molecules do this by carrying and lining up amino acids according to their anticodon. rRNA plays an essential role in ribosomal function/structure. rRNA is a part of the ribosome that provides the site for protein synthesis. mRNA is used in both transcription and translation, while tRNA and rRNA are directly used in translation. Along the same lines, mRNA travels both in the nucleus and the cytoplasm, while tRNA and rRNA are used in solely the cytoplasm, or the ribosome
(DiscoveryEducation). Transcription happens in the nucleus of the cell and takes place before translation. During this process, DNA is transcribed into messenger RNA when the base codes in DNA are copied. From here, the mRNA strand moves out of the nucleus and into the cytoplasm where translation occurs. This process starts at the ribosomes which are made of rRNA. Another type of RNA called tRNA brings amino acids to the ribosome and attaches them in the specific order that is coded on the mRNA. Peptide bonds link the amino acids, and this is how the process of translation is carried out (DiscoveryEducation).
During transcription, DNA is transcribed into messenger RNA when the the base codes in DNA are copied. mRNA serves as the code for assembling amino acids in a certain order. Codons are nitrogen bases that are aligned to create amino acids, and it is these amino acids that form proteins through peptide bonds (DiscoveryEducation).
Even though RNA only contains one strand of ribonucleotides, it can, at times, form folded and distorted shapes. These RNA molecules carry out processes such as "catalyzing reactions and transporting molecules" (DiscoveryEducation). There are three types of RNA: mRNA, tRNA, and rRNA. Each type of RNA is vital to protein synthesis. The specific role of mRNA is to direct the synthesis of proteins at the ribosomes, and it does this by providing the code for assembling amino acids in a certain order. The role of tRNA is to bring amino acids to the ribosome during protein synthesis, and the tRNA molecules do this by carrying and lining up amino acids according to their anticodon. rRNA makes up the ribosome and provides the site for
protein synthesis (DiscoveryEducation). DNA is a large molecule that stands for deoxyribonucleic acid, while RNA is a large molecule that stands for ribonucleic acid. DNA is made of two intertwining strands of deoxyribonucleotides, while RNA is made up of a single strand of ribonucleotides. The 5-carbon sugar in DNA is deoxyribose, and the 5-carbon sugar in RNA is ribose. In RNA, the base uracil (U) replaces the base thymine (T) that is found in DNA. Because of this, the DNA alphabet is A-T-C-G, while the RNA alphabet is A-U-C-G. One main role of RNA is to transfer the genetic code needed for the creation of proteins at the ribosome. Other types of RNA assist protein synthesis at the ribosome by providing the synthesis site and by supplying the necessary amino acids (note: function of RNA is dependent on the RNA type). The main role of DNA is to store and transmit genetic information (DiscoveryEducation).
DNA is a large molecule that contains two intertwined, complementary strands of deoxyribonucleotides that form a double helix shape. Also included is a backbone of a 5-carbon sugar (deoxyribose) and phosphate groups. Within DNA are four different chemical bases. The four bases are: adenine (A), guanine (G), thymine (T), and cytosine (C). Certain bases can bond with each other, and these complementary bases can form hydrogen bonds. Adenine bonds only with thymine, while guanine bonds with cytosine. The configuration of these nitrogenous bases is key as it determines the characteristics that are created by DNA (DiscoveryEducation).
|