RNA and protein synthesis review
|RNA (ribonucleic acid)||Single-stranded nucleic acid that carries out the instructions coded in DNA|
|Central dogma of biology||The process by which the information in genes flows into proteins: DNA → RNA → protein|
|Polypeptide||A chain of amino acids|
|Codon||A sequence of three nucleotides that corresponds with a specific amino acid or start/stop signal during translation|
|Transcription||Process during which a DNA sequence of a gene is copied to make an RNA molecule|
|Translation||Process during which an mRNA molecule is used to assemble amino acids into polypeptide chains|
|Mutation||A change in a genetic sequence|
Structure of RNA
- RNA uses the sugar ribose instead of deoxyribose.
- RNA is generally single-stranded instead of double-stranded.
- RNA contains uracil in place of thymine.
Types of RNA
|Messenger RNA (mRNA)||Carries information from DNA in the nucleus to ribosomes in the cytoplasm|
|Ribosomal RNA (rRNA)||Structural component of ribosomes|
|Transfer RNA (tRNA)||Carries amino acids to the ribosome during translation to help build an amino acid chain|
Central dogma of biology
The genetic code
Transcription and translation
- Silent mutations do not affect the sequence of amino acids during translation.
- Nonsense mutations result in a stop codon where an amino acid should be, causing translation to stop prematurely.
- Missense mutations change the amino acid specified by a codon.
Insertions and deletions
Common mistakes and misconceptions
- Amino acids are not made during protein synthesis. Some students think that the purpose of protein synthesis is to create amino acids. However, amino acids are not being made during translation, they are being used as building blocks to make proteins.
- Mutations do not always have drastic or negative effects. Often people hear the term "mutation" in the media and understand it to mean that a person will have a disease or disfigurement. Mutations are the source of genetic variety, so although some mutations are harmful, most are unnoticeable, and many are even good!
- Insertions and deletions that are multiples of three nucleotides will not cause frameshift mutations. Rather, one or more amino acids will just be added to or deleted from the protein. Insertions and deletions that are not multiples of three nucleotides, however, can dramatically alter the amino acid sequence of the protein.