Unit 5 Reflection

      In this unit we learned about genes and mutations. DNA is the code of life. It is made with a double helix which is two strands twisted around each other. It is made up of nucleotides which is made of a nitrogen base, phosphate group, and a sugar. The nitrogen bases wither come in double rings called purines such as adenine and guanine or single rings called pyrimidines such as thymine and cytosine. Semi-conservative replication is the process of creating two identical strands of DNA from one strand. the two strands end up with half of the original strand. The first step is unzipping, where the enzyme unzips DNA by breaking hydrogen bonds that hold nitrogen bases together. Then DNA polymerase adds matching nucleotides to each strand. The central dogma of biology is DNA to RNA which is transcription, then RNA to proten which is translation, and finally, protein to organism which is the phenotype. Transcription is the process where RNA polymerase reads and copies the DNA code for a protein as mRNA copy. The three steps of transcription are first DNA unzips, then RNA polymerase matches spare nucleotides to make an RNA strand, and finally, messenger RNA is produced and leaves the nucleus for the cytoplasm. Then in translation, mRNA arrives at the ribosome which reads the mRNA three bases at a time and translates DNA language to protein language.Each base sequence is known as a codon and each codon codes for one amino acid. The result is a long chain of amino acids which twists, folds, and combines with other chains and becomes a protein.
      We also learned about mutations, which is a change in the DNA code. Point mutations are a change in one or two base pairs of DNA. This is very small and common. The two main types are substitution and frameshift mutation.
     The most difficult part of this unit was about gene expression and regulation. Gene expression is the process of a gene ceing used to produce a gene product or phenotype. Gene regulation is mechanism used by cells to increase or decrease the expression of a gene. Every cell in our body has the same DNA but not all cells look the same. Cells look different because each type of cell expresses genes specific to those cells. Cells don't want to waste energy so thy have a variety of steps to control gene expression. There is a promoter, location on DNA where RNA polymerase attaches. The operon is a series of genes used to control the expression of a single gene.  The operator is a switch or segment of DNA at the start of a gene that prevents of allows RNA polymerase from attaching and reading the gene. An example would be the lac operon, where bacteria uses lactase to break down lactose.