Understanding DNA Structure and Function in Biochemistry

Nucleotide

Building block of DNA and RNA.

Nucleoside

Five-carbon sugar bonded to a nitrogenous base.

DNA

Deoxyribonucleic acid, genetic material in cells.

RNA

Ribonucleic acid, involved in protein synthesis.

Deoxyribose

Sugar in DNA, lacks an -OH at C-2.

Ribose

Sugar in RNA, has an -OH at C-2.

Phosphodiester bond

Links nucleotides via sugar and phosphate groups.

Antiparallel strands

DNA strands run in opposite directions.

5' end

End of DNA with phosphate group attached.

3' end

End of DNA with free -OH group.

High-energy bonds

Bonds in ATP due to phosphate repulsion.

Adenosine

Nucleoside formed from adenine and ribose.

Adenosine triphosphate (ATP)

Nucleotide with three phosphate groups.

Adenosine diphosphate (ADP)

Nucleotide with two phosphate groups.

Guanosine

Nucleoside formed from guanine and ribose.

Cytidine

Nucleoside formed from cytosine and ribose.

Thymidine

Nucleoside formed from thymine and deoxyribose.

Uridine

Nucleoside formed from uracil and ribose.

Nucleotide nomenclature

Naming based on number of phosphate groups.

Chromosomes

Structures containing DNA in the nucleus.

Mitochondrial DNA

DNA found in mitochondria, distinct from nuclear DNA.

Chloroplast DNA

DNA found in chloroplasts, involved in photosynthesis.

Negative charge of DNA

Result of phosphate groups in the backbone.

Nucleic Acid Strand

Sequence of nucleotides forming DNA or RNA.

Double-Stranded DNA

DNA structure consisting of two polynucleotide strands.

Single-Stranded RNA

RNA structure consisting of a single polynucleotide strand.

Purines

Nitrogenous bases with two ring structures.

Pyrimidines

Nitrogenous bases with one ring structure.

Adenine (A)

Purine found in both DNA and RNA.

Guanine (G)

Purine found in both DNA and RNA.

Cytosine (C)

Pyrimidine found in both DNA and RNA.

Thymine (T)

Pyrimidine found only in DNA.

Uracil (U)

Pyrimidine found only in RNA.

Aromatic Compounds

Stable ring structures following specific rules.

Delocalized Electrons

Electrons that can move across a molecule.

Heterocycles

Ring structures containing different elements, like nitrogen.

Watson-Crick Model

Three-dimensional structure of DNA proposed in 1953.

Base Pairing

Specific pairing of nucleotides in DNA structure.

Polynucleotide Chains

Long sequences of nucleotides linked together.

X-ray Crystallography

Technique used to determine DNA structure.

Rosalind Franklin

Scientist whose work aided DNA structure discovery.

Biological Aromatic Heterocycles

Compounds with stable rings containing different elements.

Stability of Nucleic Acids

Exceptional stability due to aromatic ring structures.

Sugar-phosphate backbone

Outer structure of DNA helix, supports stability.

Complementary base-pairing

Specific pairing of adenine with thymine, guanine with cytosine.

Hydrogen bonds

Weak interactions stabilizing base pairs in DNA.

Chargaff's rules

A=T and G=C; purines equal pyrimidines.

B-DNA

Right-handed double helix with 3.4 nm turn.

Z-DNA

Left-handed helix with zigzag appearance, 4.6 nm turn.

Denaturation

Separation of DNA strands by disrupting hydrogen bonds.

Reannealing

Process of complementary DNA strands pairing again.

Polymerase chain reaction (PCR)

Technique amplifying DNA sequences through denaturation and reannealing.

Hybridization

Binding of probe DNA to target DNA sequences.

Histones

Basic proteins around which DNA is wound to form chromatin.

Chromatin

Complex of DNA and histone proteins in eukaryotic cells.

Euchromatin

Less condensed form of chromatin, accessible for transcription.

Heterochromatin

Tightly packed form of chromatin, less transcriptionally active.

Telomeres

Protective caps at the ends of chromosomes.

Centromeres

Region where sister chromatids are joined.

Major grooves

Spaces between DNA strands, often protein binding sites.

Minor grooves

Smaller spaces between DNA strands, less accessible.

GC-content

Percentage of guanine and cytosine in DNA, affects stability.

Histone

Protein that organizes DNA into nucleosomes.

Nucleosome

DNA wrapped around a histone core.

Telomere

Repeating DNA sequence at chromosome ends.

Telomerase

Enzyme that extends telomeres during replication.

Centromere

Region of DNA at chromosome center.

Replication Fork

Y-shaped structure during DNA replication.

Origins of Replication

Sites where DNA unwinds for replication.

Replisome

Protein complex facilitating DNA replication.

S Phase

Cell cycle phase for DNA replication.

Transcription

Process of synthesizing RNA from DNA.

Microtubules

Cytoskeletal structures separating chromatids during anaphase.

DNA Replication

Process of copying DNA for cell division.

Animal Studies

Research indicating telomere shortening relates to aging.

Beads on a String

Visual representation of nucleosomes under microscopy.

DNA Blueprint

Genetic information guiding organism's functions.

Highly Repetitive Sequences

DNA segments found in heterochromatin.

Transcriptionally Active

DNA regions involved in gene expression.

Sister Chromatids

Identical copies of a chromosome.

Cell Division

Process where a cell divides into two.

Replication Forks

Points where DNA strands separate during replication.

Eukaryotic Replication

Slower process with multiple origins of replication.

Prokaryotic Replication

Faster process with a single origin of replication.

Helicase

Enzyme that unwinds DNA strands for replication.

Single-Stranded DNA-Binding Proteins

Proteins that stabilize unwound DNA strands.

Positive Supercoiling

Torsional strain caused by DNA unwinding.

Negative Supercoiling

Introduced by topoisomerases to relieve torsional stress.

Semiconservative Replication

Each new DNA molecule retains one parental strand.

DNA Polymerase

Enzyme that synthesizes new DNA strands from templates.

Antiparallel Orientation

Strands run in opposite directions in DNA double helix.

Leading Strand

Continuously synthesized strand in the same direction as fork.

Lagging Strand

Discontinuously synthesized strand opposite to replication fork.

Okazaki Fragments

Short DNA segments synthesized on the lagging strand.

RNA Primer

Short RNA strand required to initiate DNA synthesis.

Nucleases

Enzymes that degrade unprotected DNA strands.

Topoisomerases

Enzymes that relieve torsional strain in DNA.

Template Strand

Parental DNA strand used for synthesis of new strand.

Hydrogen Bonding

Attraction between bases that stabilizes DNA structure.

Replication Process

Series of steps to duplicate DNA molecules.