Genetic Variations And Phenotypic Differences At The Molecular Level

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As a population, organisms look different. Genetic variations and phenotypic differences are a direct result of the processes of transcription and translation at the molecular level. In the paragraphs that follow I will discuss how the processes at the molecular level influence traits that we see at the species level.
A human has 23 chromosomes, each of these chromosomes are a housing unit for DNA. DNA, also known as deoxyribonucleic acid, is a simple molecule found in all living organisms. DNA has a unique structure, made up of a double helix, base pairing, and hydrogen bonding, all working together to make it stable. The double helix is made up of a phosphate backbone. These phosphates create a bond between the sugars and themselves,
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DNA replication takes place in the nucleus. DNA is present here, because it allows for better protection from degradation, and provides a barrier from harmful effects. In order for DNA to be replicated, the DNA helix must be unwound. DNA helicase breaks apart the hydrogen bonds between the base pairs of the strands. Next, short strands of RNA, called the RNA primers, are synthesized by an enzyme called primase. This provides a 3’ OH group for enzyme called DNA polymerase to begin replication. Without the 3’ OH group DNA polymerase would not be able synthesis DNA. The DNA polymerase binds to a DNA strand starting at the origin of replication, and joins nucleotides together to create a new DNA strand. As the DNA is unwound, this creates a replication fork. Since replication occurs in a bi-directional way, a leading and lagging strand are produced. The leading strand is made in the same direction as the replication fork, nucleotides are added continuously. The lagging strand is made in the opposite direction of the replication fork. This discontinuous synthesis of DNA causes short segments of DNA called Okazaki fragments to be formed. As DNA polymerase continues to synthesis DNA, Topoisomerase must bind to the DNA strand in front of DNA polymerase and break the hydrogen bonds of the nucleotides to relieve the strain and prevent supercoiling of DNA. An analogy of this would be twirling a rubber band until it …show more content…
The nucleotide sequence in mRNA is read in groups of three nucleotides known as codons. The codon sequence of three nucleotides corresponds to a specific amino acid. When the mRNA leaves the nucleus and enters the cytoplasm, the codons in mRNA are recognized by the anticodons in tRNA. Anticodons are a three nucleotide sequence that is complementary to the codons in the mRNA. The tRNA is a complex that has an amino acid at one end and an anticodon recognized by the codon in mRNA at the other end. Translation occurs in three steps and takes place on a ribosome. The ribosomes are found in the cytoplasm, they have a large and small subunit, and a E, P and A site. During the initiation stage, mRNA and tRNA come together on a ribosome. The elongation stage starts when the start codon is translated, usually AUG. tRNA comes in it will be kicked to the A site, then another one will come in and kick the previous one to the P site and then one more will arrive and kick the first to the E site. When all sites are filled, another tRNA will come in and kick the original tRNA off completely to disassociate. The final step in translation is the termination step. This happens when a stop codon is reached and the newly formed amino acids, making up a polypeptide chain, this chain creates the

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