Unit 5 Reflection

Unit 5 was about protein synthesis, mutations, and how genes are regulated.

For this section, I had to look into my notes, but only to see how to spell some words so that doesn't count! Protein synthesis is how proteins are created from DNA. RNA polymerase makes a copy of the DNA, which is deoxyribose nucleic acid. DNA is made from a sugar, the deoxyribose, a phosphate group, and a nitrogen base, which can be either Adenine, Thymine, Guanine, or Cytosine. DNA has two strands, and twists into a double helix shape, with bases matching together. The bases match with each other, Cytosine with Guanine, and Adenine with Thymine. The copy is called RNA, which is very similar, except Thymine is replaced with Uracil, and it is single stranded instead of double stranded. This is messenger RNA. It goes out of the nucleus and to a ribosome, where it is read. Each codon, which is 3 bases, codes for one amino acid. An amino acid can be coded for by several different codons. Transfer RNA brings the amino acid to the ribosome to build the protein, and matching base pairs for the messenger RNA.


Mutations are changes in DNA. They can be deadly, or do nothing at all, which is called a silent mutation. One type of mutation is a point mutation, where a single base pair is changed. One type of point mutation is a substitution, where one base pair is substituted for another one. This type of mutation causes little to no damage, because some amino acids can be coded for in several ways, and if it does change the amino acid, it only changes one of them, which will have a small effect. The other type of point mutation is a frameshift mutation, where one base pair is added or removed. This has a large effect, and can completely ruin a protein because  in addition to changing the current codon, it shifts over all following codons, which can cause a completely different protein to be made, or cause no protein to be made at all. There are other mutations that aren't point mutations, such as inversions, which cause a piece of DNA to become unattached, and reattach backwards. Translocations are when DNA from one chromosomes attaches to a different chromosome. Mutations are caused by mutagens, such as UV, (checks notes for other mutagens) nuclear radiation, X-rays, and toxins(closes notebook).

Example of a mutation.

Gene regulation was probably the most complex part of the unit, so I will obviously be referring to my notes for this paragraph. All cells have DNA for all genes, but they don't express all genes at all times because cells don't want to waste energy by over expressing genes. A group of genes that work together is called an operon. A good example of gene regulation is the Lac Operon. The RNA attaches to the part of the DNA called the operator, and copies the gene from there. But, in Lac Operon, there is a repressor, which is like a road block, attached to the promoter. The repressor is removed when lactose appears, and attaches to it. Then, the gene can be read to create the enzyme lactase, which breaks down lactose for food. In eukaryotes, the process is more complex, and several proteins can bind before a gene. After RNA copies a gene, sections called introns, which don't code for anything, are cut out, leaving the exons, which are expressed.

1: RNA polymerase. 2: Repressor. 3: Operator. 4: Promoter. 5: Lactose

That's all we covered in unit 5. The only part I really need to study is gene regulation, and the spellings of thymine, adenine, guanine, and cytosine.