Molecular Biology Quiz: Key Terms

A set of VOCABULARY-style flashcards covering the key terms and definitions from the lecture notes.

Nucleosome

The fundamental DNA-histone complex in which DNA is wrapped around an octamer of histones.

Heterochromatin

A highly condensed form of chromatin that is generally transcriptionally inactive, often found near centromeres and telomeres.

Chromosomes

The macroscopic functional units for DNA transcription, replication, recombination, gene assortment, and cellular division.

Histones

Small, basic proteins that DNA associates with to induce condensation, forming nucleosomes, and also participate in gene regulation.

Alleles

The DNA sequence variant for a gene, which, if different on homologous chromosomes, can lead to heritable genetic linkage differences after a crossover event.

Telomerase (enzyme)

The enzyme responsible for maintaining the length of telomeres, which is related to viral RNA-dependent DNA polymerases.

Okazaki fragments

Segments of newly synthesized DNA on the lagging strand during replication, which are short (1-5 kb in eukaryotes) and require an RNA primer.

RNA splicing

The process by which introns are removed from primary mRNA transcripts and exons are joined together to form mature mRNA.

Moderately repetitive sequences

DNA sequences that are transcriptionally inactive and are interspersed with unique sequences, classified as LINEs or SINEs.

Origin of replication (ori)

The specific region on a chromosome where DNA replication begins, characterized by an association of sequence-specific DNA-binding proteins.

DNA replication

The cellular process where DNA content is doubled in preparation for cell duplication.

Single-stranded DNA-binding proteins (SSBs)

Proteins that prevent the premature reannealing of single-stranded DNA back into double-stranded DNA during replication.

Telomerase complex

A multisubunit RNA template-containing complex that synthesizes telomeres.

Euchromatin

The transcriptionally active form of chromatin, which stains less densely and is generally replicated earlier in the mammalian cell cycle.

DNA topoisomerases

A class of enzymes that relieve torsional strain during DNA unwinding by introducing temporary "nicks" in one strand of the double helix.

S phase

The period in the eukaryotic cell cycle during which DNA replication occurs.

Microsatellite instability

A type of DNA mutation caused by trinucleotide repeat sequences increasing in number, associated with diseases like Huntington chorea and fragile X syndrome.

DNA ligases

Enzymes that seal single-strand nicks between nascent DNA chains and Okazaki fragments on the lagging strand, requiring ATP hydrolysis.

p53

The tumor suppressor protein that plays a key role in G1 and G2 checkpoint control, stabilizing in response to DNA damage and inducing cell-cycle arrest or apoptosis.

Retroposons

A mobile genetic element that arose from movement through an RNA intermediate by reverse transcriptase, such as LINEs and SINEs.