GEN 371 - Exam 2 Study Material

What do three-point crosses reveal?

Gene order and distances by analyzing parental, single, and double crossover offspring.

What does 1% recombination equal?

1 map unit (centimorgan).

What type of offspring reveals gene order in a three-point cross?

Double crossover offspring.

What does linkage analysis infer?

Gene distances based on recombinant frequencies.

When can genes on the same chromosome behave independently?

When they’re far apart, allowing frequent crossing over.

What are phage plaques?

Clear zones on bacterial lawns caused by viral lysis.

What are plasmids?

Small circular DNA molecules carrying accessory genes like antibiotic resistance.

Define conjugation.

DNA transfer between bacteria through direct cell contact via F plasmid.

Define transformation.

Uptake of free DNA from the environment.

Define transduction.

Gene transfer mediated by bacteriophages.

What is a prophage?

Viral DNA integrated into a host chromosome.

What are the three components of a nucleotide?

Phosphate group, pentose sugar, nitrogenous base.

DNA strands are and .

Double-stranded and antiparallel.

Chargaff’s rule states?

A = T and G = C; purines equal pyrimidines.

E. coli DNA structure?

Circular and double-stranded.

Eukaryotic chromosomes structure?

Linear and double-stranded.

RNA differs from DNA by containing what sugar and base?

Ribose and uracil.

Type of replication in DNA?

Semiconservative.

Leading vs. lagging strand synthesis?

Leading is continuous; lagging forms Okazaki fragments.

DNA polymerase III role?

Extends 3′ end during replication.

DNA polymerase I role?

Removes RNA primers and fills gaps.

Helicase function?

Unwinds the double helix.

Gyrase function?

Relieves supercoiling.

Ligase function?

Seals nicks between fragments.

Primase function?

Synthesizes RNA primers.

Telomerase function?

Extends chromosome ends in eukaryotes.

DNA runs in what directions?

5′ to 3′ with phosphate at 5′ and hydroxyl at 3′.

The genetic code is __.

Triplet, universal, non-overlapping, and degenerate.

What does the wobble hypothesis explain?

Flexibility of tRNA pairing at the third codon position.

What forms codon–anticodon pairing?

mRNA codon with tRNA anticodon.

Role of promoters and enhancers?

Help RNA polymerase bind to specific DNA regions.

Purpose of gel electrophoresis?

Separates DNA fragments by size.

Direction smaller DNA fragments move?

Toward the positive electrode faster.

VNTRs were used in what?

Early DNA fingerprinting.

Common markers for mapping genes?

Microsatellites and RFLPs.

Why are histones positively charged?

Rich in lysine and arginine.

What do nucleosomes contain?

Histones H2A, H2B, H3, H4 with DNA.

Role of histone H1?

Links nucleosomes.

Effect of histone acetylation?

Loosens chromatin; promotes expression.

What are introns?

Noncoding sequences removed during RNA splicing.

What is mRNA’s role?

Carries coding information to ribosomes.

tRNA and rRNA function?

Involved in translation.

snRNA function?

Aids in RNA splicing.

Avery, MacLeod, and McCarty discovered what?

DNA is the transforming principle.

Hershey–Chase confirmed what?

DNA, not protein, is genetic material.

Why were proteins once suspected as genetic material?

Greater complexity and variability.

Four functions of genetic material?

Stores info, replicates, expresses traits, allows mutation.

Coding portion of human genome?

Small; most is noncoding.

Repetitive DNA makes up about what percent of human genome?

~5%.

Does genome size correlate with organism complexity?

No, it does not.