Exam 5 Review – Molecular Genetics & Protein Biology

Thirty-one question-and-answer flashcards summarizing key concepts from the Exam 5 review slides, covering mutations, Mendelian crosses, DNA replication, transcription, translation, gene regulation, protein structure, and epigenetic control.

Comparing 3′-AAGAGAGGA-5′ with 3′-AAGAGTGGA-5′, what kind of mutation occurred?

A point (base-substitution) mutation; specifically a G→T transversion.

When a kyky dog is crossed with a KBrky dog, what genotypic ratio is expected in the pups?

1 KBrky : 1 kyky (50 % each).

In the cross AaBb × Aabb, what fraction of the offspring will be double recessive aabb?

¼ (25 %).

The interaction between the A-locus (yellow pigment) and K-locus (black pigment) that together determine Borzoi coat color is an example of what genetic phenomenon?

Epistasis (gene interaction between two loci).

Put these proteins in the order they act during DNA replication: DNA ligase, DNA helicase, DNA polymerase I, DNA polymerase III, single-stranded binding proteins, RNA primase.

DNA helicase → single-stranded binding proteins → RNA primase → DNA polymerase III → DNA polymerase I → DNA ligase.

What is the primary role of the primer in DNA replication?

To provide a free 3′-OH so nucleotides can be added; without it DNA polymerase cannot start synthesis.

Which newly made strand at a replication fork is the leading strand?

The strand synthesized continuously in the 5′→3′ direction toward the replication fork.

Proteins are polymers of _ held together by _ bonds.

Amino acids; peptide bonds.

Where does RNA polymerase bind to initiate transcription in eukaryotes?

The promoter region (at or near the TATA box) with help from transcription factors.

Which RNA sequence is transcribed from the DNA template 3′-GCAATCG-5′?

5′-CGUUAGC-3′.

Name the three essential DNA segments that make up a prokaryotic operon.

Promoter, operator, and the structural genes they control (plus a separate regulatory gene that makes the repressor).

What does the regulatory gene of an operon typically produce?

A regulatory protein (repressor or activator) that binds the operator to control transcription.

Continuous, unregulated transcription of a gene is called _ expression.

Constitutive expression.

How are introns removed from a pre-mRNA in eukaryotic cells?

By the spliceosome during RNA splicing.

Producing different mature mRNAs (and therefore proteins) from the same gene by varying the splicing pattern is called what?

Alternative splicing.

Define a polysome (polyribosome).

A single mRNA molecule with many ribosomes attached, each simultaneously synthesizing the same protein.

After translation, what must generally occur before a polypeptide becomes a functional protein, and where does much of this occur?

Folding and post-translational modifications (e.g., cleavage, glycosylation) often begin in the rough ER and continue in the Golgi or cytoplasm.

Ultimately, what determines the 3-D shape of a protein?

Its primary amino-acid sequence and the chemical interactions between side chains.

List the four levels of protein structural organization in order.

Primary → Secondary → Tertiary → Quaternary.

Name four kinds of bonds/interactions that help stabilize tertiary protein structure.

Hydrogen bonds, ionic bonds, disulfide linkages, and van der Waals interactions.

Give three distinct biological roles performed by proteins.

Examples: enzymes (catalysis), antibodies (defense), hemoglobin (transport).

What is the typical effect of DNA methylation on gene expression?

It represses transcription, silencing the gene.

Changing 5′-TCCTCAGGG-3′ into 5′-TCACTCAGGG-3′ represents what mutation type?

An insertion (frameshift) of an A after TC.

Switching 3′-CCCGGGAGT-5′ to 3′-CCCGGGGGT-5′ is what kind of mutation?

A point mutation (base substitution of A→G).

Changing 5′-GCGCAGTGG-3′ to 5′-GCGCAGTGA-3′ is classified as what mutation type?

A point (base-substitution) mutation; G→A transition at the last base.

During DNA replication, which strand (leading or lagging) requires multiple RNA primers and why?

The lagging strand, because it is synthesized discontinuously as Okazaki fragments.

Where in the cell does translation occur in eukaryotes?

In the cytoplasm—either on free ribosomes or on ribosomes bound to the rough ER.

For a typical eukaryotic mRNA, how many different proteins does it encode?

One kind of protein (although many copies can be made).

What type of chemical bond links adjacent amino acids in a polypeptide’s primary structure?

A peptide bond (covalent).

In what direction (relative to the growing strand) does DNA polymerase synthesize new DNA?

5′→3′, adding nucleotides to the free 3′-OH.

Name the essential requirement that allows DNA polymerase to begin elongation on a template strand.

A free 3′-OH provided by an RNA primer.