The Molecular Basis of Inheritance

What was the design of Griffith's Transformation Experiment?

Frederick Griffith (1928) studied two strains of Streptococcus pneumoniae: S strain (pathogenic, smooth) and R strain (non-pathogenic, rough).

What were the findings of Griffith's Transformation Experiment?

transformation where R strain took on the properties of S strain.

What are Chargaff's rules?

The number of adenine (A) equals thymine (T); the number of guanine (G) equals cytosine (C).

How can Chargaff's rules be applied to determine nucleotide percentages?

If an organism’s genome has 20% adenine, then it has 20% thymine, and the remaining 60% is divided equally between guanine and cytosine, giving 30% each for guanine and cytosine.

What was the design of Meselson and Stahl's experiment?

Used heavy and light nitrogen isotopes to label DNA and observe replication in E. coli.

What were the findings of Meselson and Stahl's experiment?

Their results showed a banding pattern indicative of semi-conservative replication, where each daughter molecule contains one old strand and one new strand.

What is nucleotide excision repair?

Involves recognizing and removing damaged DNA segments.

What enzymes are involved in nucleotide excision repair?

Nucleases cut out erroneous sections, DNA polymerases fill in the gaps, and DNA ligases seal the new segments into the existing DNA strand.

What are telomeres?

Repetitive nucleotide sequences at the ends of chromosomes that protect them from erosion.

What is the impact of telomeres on cellular aging?

Shortening of telomeres over time can lead to cellular aging and loss of function.

What is telomerase?

An enzyme that extends telomeres in germ cells, which is not present in somatic cells, allowing those cells to divide more without losing important DNA.

What is euchromatin?

Loosely packed chromatin that is accessible for gene expression.

What is heterochromatin?

Densely packed chromatin that is less accessible and generally inactive.

What are the key enzymes involved in DNA replication?

Helicases, single-strand binding proteins, topoisomerase, primase, DNA polymerases, and DNA ligase.

What is the role of helicases in DNA replication?

Helicases unwind the DNA helix.

What is the purpose of single-strand binding proteins during DNA replication?

They keep unwound strands separate.

What function does topoisomerase serve in DNA replication?

It alleviates tension ahead of the replication fork.

What does primase do in DNA replication?

Primase synthesizes RNA primers for DNA polymerases.

What is the function of DNA polymerases?

They add nucleotides to the growing strand, synthesizing new DNA.

What does DNA ligase do during DNA replication?

It joins Okazaki fragments on the lagging strand.