Molecular Cell Biology - Lecture 4 Study Questions

What discoveries led to the understanding that DNA is the genetic material?

Experiments by Avery, MacLeod, and McCarty showed DNA is the transforming principle, and studies by Hershey and Chase demonstrated that DNA carries genetic information.

How does the Watson-Crick model for DNA incorporate Chargraff’s rules and Franklin’s X-ray structure?

The model explains that adenine pairs with thymine and guanine pairs with cytosine (Chargraff’s rules), and the helical structure and base pairing were supported by Franklin’s X-ray diffraction data.

What are the defining characteristics of the Watson-Crick structure?

It is a double helix, consists of two strands running antiparallel, has a sugar-phosphate backbone, and includes specific base pairing.

How does genome and proteome size relate to organism complexity?

Generally, a larger genome size allows for more genes, while a larger proteome can indicate more complex regulation and protein interactions.

What are the three classes of DNA? How are they distinguished and what is their function?

The three classes are: coding DNA (encodes proteins), non-coding DNA (regulates gene expression), and repetitive DNA (structural functions and genome stability).

What factors influence the denaturation of DNA?

Factors such as temperature, pH, and ionic strength can influence the separation of DNA strands by disrupting hydrogen bonds.

What is the ‘FISH’ technique? How is it performed and what can it be used for?

Fluorescence In Situ Hybridization (FISH) uses fluorescent probes to bind to specific DNA sequences; it can be used for locating specific genes or regions on chromosomes.

What is PCR?

Polymerase Chain Reaction (PCR) is a technique used to amplify specific DNA sequences.

How can PCR be used to quantify mRNA?

Quantitative PCR (qPCR) measures the amount of mRNA by amplifying cDNA generated from the mRNA.

How can PCR be used to identify individuals?

PCR can amplify variable regions of DNA, such as STRs (Short Tandem Repeats), which can be used for genetic profiling.

How is DNA organized into nucleosomes?

DNA wraps around histone proteins to form nucleosomes, which are the basic unit of chromatin.

How are nucleosomes packaged into metaphase chromosomes?

Nucleosomes are further coiled and stacked to form more compact structures that ultimately form metaphase chromosomes.

What is the difference between heterochromatin and euchromatin?

Heterochromatin is densely packed and transcriptionally inactive, while euchromatin is less dense and active in transcription.

How is DNA availability regulated by histone modifications?

Histone modifications, such as acetylation and methylation, can either promote or inhibit access to DNA for transcription based on their impact on chromatin structure.