Molecular Genetics I: Chromosomal Structure and DNA Replication

60 flashcards covering key concepts from the lecture notes on genetic structure, DNA replication, chromatin, and foundational history.

What is the significance of genetics in medicine?

Genetics is central to understanding most major diseases; all processes are influenced by genes.

Which experiment demonstrated that genes are composed of DNA?

Avery–MacLeod–McCarty (1944).

Who described alkaptonuria as the first 'inborn error of metabolism'?

Archibald Garrod.

Who coined the term 'gene' to denote the basic unit of heredity?

Johannsen (1909).

Which scientists proposed the DNA double-helix structure?

Watson & Crick (1953).

Name two molecular tools that opened the door to genetic manipulation mentioned in the notes.

Plasmids and restriction enzymes.

What major technologies followed the discovery of DNA structure?

PCR & cloning; Human Genome; Post-genomic era.

Approximately what percentage of the human genome codes for proteins?

1–2%.

What are the two classes of repetitive DNA described?

Satellite repetitive DNA and dispersed repetitive DNA.

What are the main components of a nucleotide's backbone?

Phosphate group and sugar.

What sugar is in DNA and what sugar is in RNA?

DNA contains deoxyribose; RNA contains ribose.

Which bases are Purines and which are Pyrimidines?

Purines: Adenine (A) and Guanine (G); Pyrimidines: Cytosine (C) and Thymine (T) in DNA; Uracil (U) in RNA.

Which base is found in RNA but not in DNA?

Uracil (U).

Where is thymine found and where is uracil found?

Thymine is in DNA; Uracil is in RNA.

What is a nucleosome?

DNA wrapped around histone proteins forming a nucleosome.

What are the two chromatin states related to gene expression?

Heterochromatin and Euchromatin.

What does DNA methylation do and what is CpG island silencing?

DNA methylation can repress transcription; CpG islands are associated with silencing when methylated.

List the major enzymes/proteins involved in DNA replication as given in the notes.

Ori/ter; helicase; SSBPs; primase; DNA Pol III; DNA Pol I; DNA ligase.

In which direction is DNA synthesized?

5' to 3'.

Is DNA replication semi-conservative or conservative?

Semi-conservative.

Which enzyme has proofreading ability during replication (as noted)?

DNA polymerase III.

Which bacterial target corresponds to quinolone antibiotics like nalidixic acid and ciprofloxacin?

DNA gyrase.

What process in eukaryotes involves remodeling chromatin during replication?

Chromatin remodeling.

What are the three eukaryotic polymerases involved in replication and their roles?

Pol α (initiation/primer); Pol ε (leading); Pol δ (lagging).

Where are telomeres mainly expressed?

Germ cells.

What enzyme maintains telomere length?

Telomerase.

What is the structural unit of chromatin formed by DNA wrapped around histones?

Nucleosome.

What are the two forms of chromatin packaging affecting gene expression?

Heterochromatin and Euchromatin.

What is the effect of DNA methylation on transcription?

Methylation represses transcription.

What does histone acetylation do to chromatin?

Relaxes DNA coiling and allows transcription.

What do Ori and ter stand for in DNA replication?

Origin of replication (ORI) and terminus (ter).

In which direction do polymerases synthesize DNA?

5' to 3'.

Which role does DNA polymerase α play in eukaryotic replication?

Initiates DNA synthesis by laying down the RNA-DNA primer.

What is the function of DNA ligase during replication?

Seals nicks between Okazaki fragments on the lagging strand.

What is a key difference between prokaryotic and eukaryotic replication mentioned?

Prokaryotes use DNA gyrase; eukaryotes rely on chromatin remodeling.

Which DNA sequence is associated with mismatch repair in methylation context?

GATC sequences.

What is the role of CpG islands in gene regulation?

CpG islands are associated with transcriptional silencing when methylated.

What is the component around which DNA wraps in a nucleosome?

Histone proteins.

What does semi-conservative replication mean for the daughter DNA molecules?

Each daughter DNA has one original strand and one new strand.

What percentage of the genome is coding versus noncoding?

About 1–2% is coding; the rest is noncoding or repetitive DNA.

Which historical figure contributed to the concept of discrete hereditary units and Mendelian genetics?

Mendel.

Which scientist coined the term 'gene' in 1909?

Johannsen.

Which scientist described the first inborn error of metabolism (alkaptonuria)?

Archibald Garrod.

Which experiment established that genes are made of DNA beyond reasonable doubt?

Avery–MacLeod–McCarty (1944).

What is the relevance of the Human Genome in genetics?

It marked a milestone in mapping and understanding the human genetic blueprint and sparked post-genomic studies.

What is the difference between satellite repetitive DNA and dispersed repetitive DNA?

Satellite DNA is tandemly repeated; dispersed repeats are interspersed throughout the genome.

What are the core components of nucleotides?

Phosphate group, sugar, and base.

What sugar is unique to DNA?

Deoxyribose.

What sugar is unique to RNA?

Ribose.

Which bases are purines?

Adenine (A) and Guanine (G).

Which bases are pyrimidines?

Cytosine (C) and Thymine (T) in DNA; Uracil (U) in RNA.

Which base is present in RNA instead of thymine?

Uracil (U).

What is the role of GATC sequences in biology as mentioned?

Involved in mismatch repair (GATC).

What is the significance of CpG islands?

Associated with silencing when methylated.

What is the direction of replication fork movement relative to base pairing?

Replication proceeds with new strands synthesized 5' to 3' on both templates.

What is the role of helicase?

Unwinds the double-stranded DNA at the replication fork.

What are SSBPs and their function?

Single-strand binding proteins that stabilize exposed single strands.

What is the role of primase?

Synthesizes RNA primers to start DNA synthesis.

What is the major difference between prokaryotic and eukaryotic DNA replication in terms of chromatin?

Prokaryotes do not have chromatin; eukaryotes require chromatin remodeling.

Which antibiotic class targets DNA gyrase?

Quinolones (e.g., nalidixic acid, ciprofloxacin).

What is the primary catalytic activity of DNA polymerase III?

DNA synthesis with proofreading capability.

What is the role of DNA polymerase I?

Fills in gaps and removes RNA primers during lagging-strand synthesis.

What is the significance of telomeres in germ cells?

Telomeres help protect chromosome ends; telomerase maintains their length in germ cells.

What are core references for this course?

Schaaf et al. 2012; Jorde et al. 2016; Clark & Pazdernik 2013; Tao et al. 2025.

What does the term 'post-genomic era' imply?

A focus on genome function, regulation, and interactions beyond sequencing.

What is the relationship between DNA methylation and transcription?

Methylation generally represses transcription.

What is chromatin remodeling's role in replication and transcription?

It alters chromatin structure to permit access to DNA.

Which three polymerases are cited for eukaryotic replication and their general roles?

Pol α (initiation/primer), Pol ε (leading), Pol δ (lagging).