DNA Denaturation, Hybridization, Genomes, and Chromatin – Vocabulary Flashcards

Vocabulary flashcards covering key concepts from DNA denaturation and renaturation, hybridization and probes, genome sequencing, and chromatin structure and epigenetics.

Denaturation (melting)

Disruption of hydrogen bonding and base stacking in double-stranded DNA or RNA, causing separation into single strands without breaking covalent bonds.

Annealing (renaturation)

Reformation of base pairs and restoration of the double helix when conditions return to normal; can occur in one step or, if fully separated, in two steps.

Hypochromic effect

Decrease in UV absorption of DNA when in the double-stranded form due to base stacking and hydrogen bonding limiting electronic transitions.

Hyperchromic effect

Increase in UV absorption when DNA denatures to single strands because unpaired bases absorb more UV light.

Melting point (Tm)

Temperature at which half of the DNA population denatures; higher for DNA with more GC base pairs.

GC content

Proportion of guanine and cytosine bases in DNA; GC pairs have three hydrogen bonds, increasing stability and melting temperature.

A=T rich regions (bubbles)

Regions rich in adenine-thymine base pairs that denature first, forming bubbles of single strands.

Hybridization

Base pairing between complementary nucleic acids from different sources, enabling detection of specific sequences and formation of duplexes.

Probe

Labeled nucleic acid sequence used to detect a complementary target sequence by hybridization.

Single-nucleotide polymorphisms (SNPs)

Single-base variations in the population; common genetic variations used as markers and in disease studies.

Haplotype

A group of SNPs that tend to be inherited together and serve as a genetic marker for populations or individuals.

Contigs

Long contiguous DNA sequences assembled from overlapping clones in genome projects.

BAC (Bacterial Artificial Chromosome)

A cloning vector capable of carrying large DNA fragments for genomic libraries.

YAC (Yeast Artificial Chromosome)

A cloning vector using yeast to maintain large DNA fragments for genome assembly.

Whole-genome shotgun sequencing

Sequencing of random DNA fragments across the genome and assembling overlaps to reconstruct the genome.

Public Human Genome Project

International collaboration to map and sequence the human genome using mapping and sequencing centers.

Celera Genomics

Private company that accelerated genome sequencing using whole-genome shotgun methods in collaboration with the public effort.

Genome

The complete haploid set of genetic material of an organism; includes nuclear and organelle genomes.

Genomics

The study of genomes on a cellular scale, including sequencing, structure, function, and evolution.

Diploid genome

Genome of an organism with two copies of each chromosome, one from each parent.

Introns

Noncoding sequences within genes that are removed during RNA processing (splicing).

Exons

Coding sequences of genes that remain in mature mRNA and often encode protein domains.

Splicing

Process of removing introns from pre-mRNA and joining exons to form mature mRNA.

Transposons

Mobile genetic elements that can move within the genome; include DNA transposons and retrotransposons; many are inactive but have driven evolution.

Simple sequence repeats (SSRs)

Short, highly repetitive DNA sequences (usually <10 bp) found in telomeres/centromeres and used in forensic analysis.

Short tandem repeats (STRs)

A type of SSR consisting of repeating units used as markers in forensic DNA profiling.

Nucleosome

Basic unit of DNA packaging: about 146 bp of DNA wrapped around a histone octamer, forming beads on a string.

Histone octamer

Core histones (two H2A–H2B dimers and one H3–H4 tetramer) around which DNA wraps to form a nucleosome.

Core histones

Histones H2A, H2B, H3, and H4; highly conserved and form the nucleosome core.

Linker histone H1

Histone that binds to linker DNA between nucleosomes and promotes higher-order chromatin compaction.

N-terminal histone tails

Flexible, protruding regions of histones subjected to post-translational modifications that regulate chromatin structure and gene expression.

Epigenetics

Heritable changes in gene expression not due to DNA sequence, often involving histone modifications and DNA methylation.

Beads-on-a-string

Description of beads (nucleosomes) spaced along DNA, the first level of chromatin organization.

Left-handed solenoidal supercoil

The left-handed winding of DNA around the histone core in a nucleosome, contributing to negative supercoiling.