Genes, Alleles, and Gene Structure

What is a gene

A unit of heredity containing information to produce a functional RNA or protein.

What is the locus of a gene

The fixed location of a gene on a chromosome.

What is an allele

An alternative form of a particular gene.

What is a wild-type allele

The most commonly observed allele in a population or reference context.

What is a homozygote

An individual with two identical alleles of a gene.

What is a heterozygote

An individual with two different alleles of a gene.

Why do diploid organisms generally have two copies of each gene

They possess two homologous copies of each chromosome, one inherited from each parent.

Can a gene have more than two alleles in a population

Yes, a gene can have many alleles across a population, although a diploid individual typically carries two.

What is the central dogma of molecular biology

Genetic information generally flows from DNA to RNA to protein.

What is DNA replication

The process of copying DNA to produce new DNA molecules.

What enzyme carries out DNA replication

DNA polymerase synthesizes new DNA strands.

What is transcription

The process of producing RNA from a DNA template.

What enzyme carries out transcription

RNA polymerase.

What is translation

The process of using mRNA information to synthesize a polypeptide.

What structures are involved in translation

Ribosomes and transfer RNAs (tRNAs).

What is a promoter

A DNA region that helps recruit and position RNA polymerase to initiate transcription.

What is the transcriptional start site (+1)

The first nucleotide transcribed into RNA.

What is the transcriptional termination site

The location where transcription ends.

What is the coding region of a protein-coding gene

The region translated into a polypeptide, beginning at a start codon and ending at a stop codon.

What is the start codon in DNA

ATG on the coding DNA strand; it corresponds to AUG in mRNA.

What are the three stop codons in DNA

TAA, TAG, and TGA on the coding DNA strand.

What are the three stop codons in mRNA

UAA, UAG, and UGA.

What is the 5′ untranslated region (5′ UTR)

The transcribed region before the start codon that is not translated into protein.

What is the 3′ untranslated region (3′ UTR)

The transcribed region after the stop codon that is not translated into protein.

What is the difference between transcription and translation

Transcription makes RNA from DNA; translation uses mRNA to make a polypeptide.

How can a mutation in a promoter affect gene expression

It may alter RNA polymerase binding and change the amount of transcript produced.

How can a mutation in a coding region affect a protein

It may change an amino acid, introduce a stop codon, shift the reading frame, or have no effect on the protein sequence.

How can a mutation in a UTR affect gene expression

It may alter RNA stability, translation efficiency, or other regulatory processes.