BIO 112 — FINAL EXAM STUDY GUIDE (Ch. 15–17)

These flashcards cover key concepts related to DNA structure, replication, gene expression, transcription, and translation based on the study guide for the final exam.

A bacterium infected with a phage made of a T2 protein coat and T4 DNA will produce

T4 phages

What viruses use host cells to make.

Viral nucleic acids and proteins

Hershey & Chase used the fact that DNA contains ________ and protein contains ________.

Phosphorus; sulfur

During the experiment, the T2 phage

Injected its DNA into the host cell

 If G = 19%, thymine =

31%

Current definition of a gene.

A DNA sequence that codes for a functional product (protein or RNA)

Base-pairing combinations consistent with DNA rules.

A = T and G = C

The phosphodiester bond forms between the phosphate of the new nucleotide and the ________ of the previous one

3' hydroxyl (–OH)

A–T and C–G pairing ensures

Uniform width of the DNA helix

If DNA strands were joined by covalent bonds:

They could not separate for replication or transcription

Semiconservative model supported by ________

Meselson and Stahl

Template in semiconservative replication:

Each parent strand

Method by which DNA is synthesized.

Semiconservative replication

Correct order of DNA replication steps.

Helicase → Primase → DNA polymerase → Ligase

Enzyme that catalyzes phosphodiester bonds:

DNA polymerase

Energy for DNA synthesis comes from _______

dNTPs (nucleotide triphosphates)

Major difference between eukaryotic and prokaryotic DNA replication.

Eukaryotes have many origins of replication; prokaryotes have one

________ unwinds DNA; ________ relieves tension

Helicase; Topoisomerase

DNA polymerase III in E. coli:

Main enzyme that adds nucleotides

Leading vs. lagging strand:

Polymerase can only synthesize 5' → 3'

DNA ligase role:

Connects Okazaki fragments

Proteins that keep DNA strands separated:

Single-strand binding proteins (SSBs)

Telomeres replicate differently because ________.

Lagging strand cannot fully replicate the ends

Telomere conservation reflects ________.

Their essential protective function

Definition of a telomere.

A repetitive DNA sequence protecting chromosome ends

Lowest telomerase activity occurs in ________ cells.

Somatic cells

Telomere shortening is a problem in ________.

Frequently dividing cells

Gene expression is

Using DNA to make RNA and proteins

One-Gene, One-Polypeptide Hypothesis

Each gene encodes one polypeptide.

Scientists who proposed the One-Gene, One-Polypeptide Hypothesis.

Beadle and Tatum

Knockout mice have genes ________

Inactivated (knocked out)

Describes the flow of genetic information: DNA → RNA → Protein.

Central dogma

Not synthesized from DNA directly.

Amino acids

Transcription synthesizes

RNA

 In eukaryotes, transcription is in the ________ and translation in the ________.

Nucleus; cytoplasm

Retrovirus enzyme that makes DNA from RNA.

Reverse transcriptase

________ is to transcription as ________ is to translation.

RNA polymerase; ribosome

DNA: TTTTTTT → RNA: ________

AAAAAAA, synthesized in the nucleus

mRNA from the DNA sequence 3’ ATG GGC AAT CGC 5’.

5’ UAC CCG UUA GCG 3’

Which codon typically serves as the start signal for translation?

AUG

Stop codons that signal termination.

UAA, UAG, UGA

Reason genetic code is unambiguous.

Each codon = 1 amino acid

Reason genetic code is redundant.

Multiple codons for the same amino acid

Bases needed per amino acid:

Three

Code is nearly universal because

Most organisms use the same codons

Two-base codons would allow ________ amino acids.

16

Sickle-cell mutation type:

Missense mutation

Premature stop codon mutation:

Nonsense mutation

Silent mutation

Base change with no amino acid change due to redundancy.

Frameshift mutations occur from

Insertion or deletion

Segment inserted into another chromosome:

Translocation

Segment reversed in the same chromosome.

Inversion

Chromosome segment copied and added again.

Duplication

Without ________, RNA polymerase cannot start transcription at the correct sites.

Sigma factor

To express a eukaryotic gene in bacteria, you must include ________

A bacterial promoter

Central to bacterial transcription initiation:

The promoter

When termination occurs in transcription.

RNA polymerase reaches a termination sequence

What happens to sigma after transcription begins.

Detaches from RNA polymerase

Occurs in prokaryotes but not eukaryotes:

Coupled transcription and translation

Ribosomes can bind prokaryotic mRNA ________

Before transcription is complete

Primary purpose of RNA splicing:

Remove introns and join exons

What introns are

Non-coding sequences removed from pre-mRNA

Adapter molecule in translation:

tRNA

Explains why there are 61 codons and only 45 tRNAs.

Wobble pairing

Anticodon of tRNA is ________

Complementary to the mRNA codon

Ribosome binding site in prokaryotes

Shine–Dalgarno sequence

Site where codon is read

A site

What happens after a peptide bond forms.

Ribosome shifts; tRNA moves A → P

Missing ________ prevents translation initiation in eukaryotes.

5’ cap

Translation requires ________.

mRNA, ribosomes, tRNA, amino acids, and energy (GTP)