Genetics Exam 3

Semiconservative DNA Replication

Each new DNA helix has one old and one new strand.

Conservative DNA replication

The original strands stay together; two new strands form.

Dispersive DNA replication

New DNA strands contain mixed pieces of old and new DNA.

What is the start codon?

AUG (met)

What are the three stop codons?

UGA, UAA, and UAG.

What does UGA code for in mitochondrial DNA?

Tryptophan instead of a stop signal.

What does AUA code for in mitochondrial DNA?

Methionine instead of isoleucine.

What does Ori stand for?

Origin of Replication.

What is a replication fork?

The area where DNA opens during replication.

What do SSBPs do?

Stabilize single-stranded DNA.

Where does DNA polymerase add nucleotides?

To the 3′ end of a growing DNA strand.

How is the leading strand synthesized?

Continuously in the 5′ to 3′ direction.

How is the lagging strand synthesized?

Discontinuously in short sections.

What are Okazaki fragments?

Short DNA segments formed on the lagging strand.

What does primase do?

Makes RNA primers to begin DNA replication.

What shape is bacterial DNA?

Circular, with one origin called OriC.

What is the function of DNA helicase?

Opens and unwinds the DNA double helix.

What is the function of DNA gyrase?

Relieves twisting and tension during DNA replication.

Which enzymes require ATP during DNA replication?

DNA helicase and DNA gyrase.

What does DNAa do?

Binds to OriC to initiate bacterial DNA replication.

What does exonuclease activity do?

Helps remove and replace incorrect nucleotides.

What is a nonsense mutation?

A mutation that creates a premature stop codon.

What is the wobble hypothesis?

The third codon base can be more flexible.

What is transcription?

The process of converting DNA into RNA.

What enzyme synthesizes RNA without a primer?

RNA polymerase.

What does the sigma subunit do?

Helps bacterial RNA polymerase recognize promoters.

What can happen during bacterial transcription termination?

RNA may fold into a hairpin structure.

Where does eukaryotic transcription occur?

In the nucleus.

What do enhancers do?

Increase transcription.

What do silencers do?

Decrease transcription.

What does RNA polymerase II synthesize?

Eukaryotic mRNA.

What protein binds to the TATA box?

TBP (TATA-binding protein).

What must happen to chromatin before transcription?

Chromatin must uncoil so DNA is accessible.

What happens to nucleosomes before transcription?

They must be removed or displaced to expose DNA.

What are the three stages of transcription?

Initiation, elongation, and termination.

What happens during transcription initiation?

RNA polymerase binds the promoter and begins transcription.

What happens during transcription elongation?

RNA polymerase synthesizes RNA using DNA as a template.

What happens during transcription termination?

Transcription ends and the RNA transcript is released.

What is the structure of tRNA?

Cloverleaf

What does a tRNA anticodon pair with?

An mRNA codon.

What does aminoacyl-tRNA synthetase do?

Attaches the correct amino acid to its tRNA.

Where is the Shine-Dalgarno sequence found?

Prokaryotes.

Where is the Kozak sequence found?

Eukaryotes

What are the three main parts of an amino acid?

Amino group, carboxyl group, and R group.

How does a peptide bond form?

Between the carboxyl group of one amino acid and the amino group of another.

What does phenylalanine hydroxylase do?

Converts phenylalanine into tyrosine.

What happens in phenylketonuria (PKU)?

Phenylalanine hydroxylase cannot properly convert phenylalanine to tyrosine.

What builds up during PKU?

Phenylalanine levels increase, potentially causing brain deficiencies.

What is the function of tRNA?

Carries amino acids to the ribosome and pairs its anticodon with mRNA.

What is aminoacylation?

The process of attaching an amino acid to its corresponding tRNA.

What is epigenetics?

Heritable changes in gene function without changing the DNA sequence.

What can control gene expression through epigenetics?

Environmental influences can change gene activity.

What is an example of a nonsense mutation?

Angus cattle dwarfism.

What can Angus cattle dwarfism cause?

A short, stout body and fused ulna/radius.

What are housekeeping genes?

Essential genes needed for normal cellular functions.

How do methyl groups affect gene expression?

They can silence genes by blocking transcription factor binding.

Where are amino acids modified?

On the N-terminal of the histone tail.

What happens at the Avy locus in orange mice?

A methylation mutation causes differences in color and size.

Which developmental period is most critical for developmental plasticity?

The embryonic period.

What is developmental programming?

Early environmental influences can affect later development and health.

What health effect was associated with babies born during the Dutch Hunger Winter?

A higher chance of developing type-2 diabetes.