Overview of Biology 211: Biomolecules and Cellular Systems

These flashcards cover key concepts related to the structure and function of DNA and the processes of DNA replication, suitable for review in a Biology course.

DNA Structure

DNA is a polymer of deoxyribonucleotides consisting of a sugar-phosphate backbone and nitrogenous bases.

Antiparallel Strands

In DNA, the two strands run in opposite directions, described as 5' to 3' and 3' to 5'.

Watson and Crick Model

A model explaining the helical structure of DNA, incorporating molecular modeling and data from other experiments.

Semiconservative Replication

A method of DNA replication in which each daughter DNA molecule contains one original and one newly synthesized strand.

Okazaki Fragments

Short segments of DNA synthesized on the lagging strand during replication, which are later joined by DNA ligase.

Telomeres

Non-coding DNA sequences at the ends of linear chromosomes that prevent degradation.

Euchromatin

Less compacted form of chromatin where genes are actively expressed.

Heterochromatin

Highly compacted chromatin that is generally silenced and not actively transcribed.

Origin of Replication

The specific location on a chromosome where DNA replication begins.

DNA Polymerase

An enzyme that synthesizes new DNA strands by adding nucleotides to a growing chain.

Leading Strand

The strand of DNA that is synthesized continuously during DNA replication in the 5' to 3' direction.

Lagging Strand

The strand of DNA that is synthesized discontinuously, in the opposite direction to the replication fork.

Nucleosomes

Units of DNA packaging in eukaryotes, consisting of DNA wrapped around histone proteins.

Base Pairing

The specific hydrogen bonding between nitrogenous bases in DNA; adenine pairs with thymine, and guanine pairs with cytosine.

Hydrogen Bonding

Weak interactions that hold the two strands of DNA together, crucial for maintaining the helix structure.

DNA Ligase

An enzyme that joins Okazaki fragments by forming phosphodiester bonds.

Meselson and Stahl Experiment

An experiment that provided evidence for semiconservative replication of DNA using nitrogen isotopes.

Replication Fork

The area where the DNA double helix unwinds and separates during replication.

Helicase

An enzyme that unwinds the DNA double helix at the replication fork.

Primase

An enzyme that synthesizes a short RNA primer to initiate DNA replication.

Topoisomerase

An enzyme that alleviates the tension in DNA strands during replication.

Phosphodiester Bond

The bond between the 5' phosphate group of one nucleotide and the 3' hydroxyl group of another nucleotide.

Purines and Pyrimidines

Nitrogenous bases in DNA are categorized into two groups: purines (adenine and guanine, double-ringed) and pyrimidines (cytosine and thymine, single-ringed).

Nucleotide Components

The building blocks of DNA and RNA, each consisting of a nitrogenous base, a five-carbon sugar (deoxyribose in DNA), and one or more phosphate groups.

Chargaff's Rules

States that in DNA, the amount of adenine equals thymine (A=T) and the amount of guanine equals cytosine (G=C). % Purines (A+G) = %Pyrimidines (C+T).

Histones

Small, positively charged proteins around which DNA is wrapped to form nucleosomes, essential for DNA packaging in eukaryotes.

Deoxyribose Sugar

A five-carbon sugar found in DNA nucleotides, lacking a hydroxyl group on the 2' carbon, distinguishing it from ribose in RNA.

Single-strand Binding Proteins (SSBPs)

Proteins that bind to the separated DNA strands during replication to prevent them from reannealing and protect them from degradation.

Proofreading (DNA Polymerase)

The ability of DNA polymerase to check newly added nucleotides against the template strand and correct errors, enhancing replication accuracy.

Chromatin Fiber (30 nm)

The second level of DNA packaging, where nucleosomes are coiled into a compact, solenoid-like structure approximately 30 nm in diameter.

Chromosome

A highly condensed and organized structure of DNA and proteins (chromatin) that carries genetic information, visible during cell division.