pre-midterm content

What information can be obtained from a genetic approach to studying mutants defective in a particular process?

You can approach the amino acid confirmation defective in a particular process.

How would you define permissive conditions for temperature-sensitive mutants?

Permissive conditions allow the mutated gene product to behave normally, meaning the phenotype isn't observed, even with a mutant allele present.

What are the roles of model organisms in molecular biology studies?

Model organisms provide valuable insights into biological systems at the cell, tissue, organ, and system level.

What are the three main functions of DNA?

The three main functions of DNA are to replicate faithfully, store information, and to mutate.

Why must DNA replicate faithfully?

To allow the organism to grow properly by cell division.

What stabilizes the structure of DNA?

Phospho-diester bonds stabilize the DNA by linking phosphate and sugar molecules in the backbone.

What role do hydrogen bonds play in DNA structure?

Hydrogen bonds connect the strands of DNA by joining nucleotide bases.

What are the types of non-covalent interactions involved in maintaining the double-helical conformation of DNA?

Ionic interactions, hydrogen interactions, van der Waals interactions, and hydrophobic interactions.

Describe the Meselson-Stahl experiment and its conclusion about DNA replication.

The experiment involved E. coli growing in N-15 medium and then transferred to N-14 medium. It showed that DNA replication is semiconservative, with each daughter molecule comprising one 'old' and one 'new' strand.

What does it mean for a DNA strand to have polarity?

It means that the two complementary strands run in opposite directions, which is referred to as antiparallel orientation.

If the C content of a double-stranded DNA preparation is 20%, what is the T content?

The T content is 30%, since C and G pair with each other, making up 40% together.

What is the difference between nucleoside and nucleotide?

Nucleosides contain only sugar and base, while nucleotides contain sugar, base, and a phosphate group.

What does dNTP stand for?

dNTP stands for deoxynucleotide triphosphate.

How does high salt concentration influence the denaturation kinetics of DNA?

It stabilizes the negatively charged phosphates in the DNA backbone, reducing strand repulsion and allowing for a higher melting temperature.

What are the classes of DNA sequences in genomic DNA based on renaturation kinetics?

Highly repetitive genomic DNA, moderately repetitive genomic DNA, and unique genomic DNA.

What is Cot analysis?

Cot analysis measures the complexity of DNA/genome.

How does the concentration of single-stranded DNA compare to that of double-stranded DNA at equivalent absorbance at 260 nm?

Single-stranded DNA would have double the concentration compared to double-stranded DNA.

How does the complexity of bacterial genomes differ from that of eukaryotic genomes?

Bacterial genomes typically contain no repetitive genome and feature fast association, while eukaryotic genomes contain multiple highly and moderately repetitive sequences.

Explain the C-value paradox.

The C-value paradox explains that there is no correlation between the amount of DNA and the complexity of organisms.

What factors influence DNA renaturation kinetics?

High salt concentration, low temperature, DNA concentration, size of DNA fragments, and complexity of DNA.

How many classes of DNA are found in the new insect species you evaluated?

Three classes of DNA: highly repetitive (25%), moderately repetitive (25%), and unique (50%).

What are the differences between prokaryotic Topoisomerase I and Gyrase?

Topoisomerase I introduces positive supercoiling, while Gyrase introduces negative supercoiling and makes double-stranded cuts.

Define topological isomers of DNA.

Topological isomers of DNA differ in their state of supercoiling.

Why is DNA supercoiling important for cell survival?

Supercoiling allows for efficient DNA packaging, protects DNA from damage, and enables transcription and replication activities.

What are the distinctions between the primary, secondary, and tertiary structures of RNA and DNA?

Primary structure differences include base composition, with thymine in DNA and uracil in RNA; secondary structure differences include DNA's double helix and RNA's folding into base-paired segments.

What is the relationship between histones and their amino acid composition?

Histones are rich in lysine and arginine, allowing them to stabilize the negatively charged DNA backbone.

What is the significance of heterochromatin and euchromatin in DNA replication and transcription?

Heterochromatin is tightly packed and less susceptible to replication/transcription, while euchromatin is loosely packed and more actively transcribed.

How many homologous chromosomes are present in a woman and man’s germ cells?

Both have 23 homologous chromosomes.

What is the purpose of cell division in prokaryotes and eukaryotes?

In eukaryotes, it is for tissue growth and repair; in prokaryotes, it is for reproduction.

What is the purpose of checkpoints in the cell cycle?

They ensure proper cell conditions and DNA integrity before allowing progression through the cycle.

What can trigger a cell cycle arrest?

DNA damage, insufficient cell size, improper DNA replication, or lack of necessary enzymes and nutrients.