Gene Expression and Point Mutations

Vocabulary flashcards covering the stages of gene expression, types of point mutations (substitutions vs. frameshifts), and their phenotypic effects as discussed in Chapter 17.

Transcription

The process where DNA serves as a template for RNA polymerase to synthesize an RNA transcript in the nucleus.

RNA Processing

The modification of a pre-mRNA transcript including the addition of a $5'$ Cap, a Poly-A tail, and the removal of introns while joining exons.

Aminoacyl-tRNA synthetase

An enzyme responsible for amino acid activation by attaching a specific amino acid to its corresponding tRNA.

Translation

The synthesis of a polypeptide in the cytoplasm using mRNA, ribosomes, and tRNA, where codons are matched with anticodons.

Point mutations

DNA changes that affect single base pairs, caused by errors in DNA replication or repair, or by mutagens.

Mutagens

Physical or chemical agents that damage DNA and can cause mutations.

Nucleotide-pair Substitution

The replacement of $1$ base pair ($bp$), also known as a single nucleotide polymorphism (SNP).

Silent mutation

A nucleotide-pair substitution that results in no change to the amino acid (aa) sequence of the protein coding region.

Nonsense mutation

A mutation that changes an amino acid codon to a stop codon, resulting in a shortened protein.

Missense mutation

A nucleotide-pair substitution that results in the substitution of one amino acid for another in the polypeptide chain.

Frameshift Mutation

A mutation caused by a base pair insertion or deletion ($indel$) that shifts the downstream reading frame, unless the insertion or deletion is in a multiple of $3$.

Indel

A term used to describe the insertion or deletion of base pairs in the DNA sequence.

Neutral mutation

A mutation that has no effect on protein function or phenotype.

Gain of function

A mutation that results in a protein having a new or enhanced function.

Lactase persistence

An example of a gain of function mutation in adult humans that allows for lactose tolerance.

Sickle cell anemia (Hb S)

A severe blood disease caused by an amino acid $6$ mutation in the $\beta$ hemoglobin chain; heterozygotes are resistant to malaria.

Hb Makassar

A specific mutation at the amino acid $6$ position of hemoglobin that has no effect on the protein.

Hb C

A mutation at amino acid $6$ of the hemoglobin chain that results in mild anemia.