CH 16: How Do Genes Work?

This set of vocabulary flashcards covers concepts from molecular biology, including the gene-to-protein pathway, properties of the genetic code, and various types of mutations based on Chapter 16 of the lecture notes.

Molecular biology

The branch of biology that seeks to understand life by studying the molecules that create cells.

Gene expression

The process of converting information coded in DNA into molecules that actually do things.

Null alleles

Also known as loss of function alleles, these are alleles that do not function at all.

One gene-one enzyme hypothesis

Proposed by George Beadle and Edward Tatum, it states that each gene specifically codes for the production of a single, unique enzyme which controls a specific step in a metabolic pathway.

Metabolic pathways

A linked series of chemical reactions occurring within a cell, catalyzed by enzymes, that convert a starting molecule into a final product through intermediate steps.

Genetic code hypothesis

Proposed by Francis Crick, it suggests that the sequence of bases in DNA acts as a code where DNA serves as an information storage molecule.

mRNA

Single-stranded molecules of RNA that carry information out of the nucleus from DNA to the site of protein synthesis in the cytoplasm.

RNA polymerase

An enzyme that polymerizes ribonucleotides into strands of RNA during transcription.

mRNA hypothesis

Proposes that mRNA is the unstable intermediate molecule carrying genetic information from DNA in the nucleus to ribosomes for protein synthesis.

Central Dogma

A set of core principles articulated by Francis Crick summarizing the one-way flow of biochemical information: $DNA \rightarrow RNA \rightarrow Proteins$.

Transcription

The process of using a DNA template to make an RNA molecule that has a base sequence complementary to the DNA.

Translation

The process of using information in the base sequence of mRNA to synthesize proteins, performed by ribosomes; also known as protein synthesis.

Genotype

Determined by the sequence of bases in an organism's DNA.

Phenotype

The physical traits of an organism, largely produced by the proteins it produces.

Reverse transcriptase

A viral enzyme that synthesizes a DNA version of the RNA genes, reversing the typical flow of information.

Genetic code

The rules specifying the relationship between a sequence of nucleotides in nucleic acids and the sequence of amino acids in a protein.

Triplet code

A three-base code, which is the shortest genetic word length capable of coding for at least $20$ different amino acids.

Codon

A group of three bases that specifies a particular amino acid.

Reading frame

A specific way of dividing a nucleotide sequence into consecutive, non-overlapping triplets (codons).

Start codon

The sequence $AUG$, which signals that protein synthesis should begin at that point on the mRNA molecule.

Stop codons

Sequences ($UAA$, $UAG$, and $UGA$) that do not code for amino acids but signal the end of the polypeptide chain.

Redundancy (Degeneracy)

A property of the genetic code where most amino acids are coded for by more than one codon.

Unambiguous

A property of the genetic code where a single codon never codes for more than one amino acid.

Non-overlapping

A property of the genetic code where ribosomes read each separate codon one after another once the reading frame is established.

Universal

A property of the genetic code where, with minor exceptions, all codons specify the same amino acids in all organisms.

Conservative

A property of the genetic code where the first two bases are usually identical when several codons specify the same amino acid.

Mutation

Any permanent change in an organism's DNA, serving as the source of diversity and variation.

Point mutation

A mutation that alters the sequence of one or a small number of base pairs.

Missense mutation

A point mutation that changes the identity of an amino acid in a protein.

Silent mutation

A point mutation that does not change the amino acid sequence of the gene product.

Frameshift mutation

Mutations caused by insertions or deletions that shift the reading frame and often destroy protein function.

Nonsense mutation

A point mutation that changes an amino-acid-specifying codon into a stop codon, causing early polypeptide termination.

Chromosomal deletion

The loss of a segment of a chromosome, resulting in missing genes.

Chromosome inversion

A structural rearrangement where a chromosome segment breaks in two places, rotates $180^{\circ}$, and reinserts itself.

Chromosome duplication

A genetic alteration where a segment of a chromosome is copied, resulting in extra genetic material.

Chromosome translocation

A genetic abnormality where a chromosome segment breaks and attaches to a different chromosome or exchanges segments with another.