Cell and Molecular Biology Exam 2

Chromatin-remodeling Complex

A family of enzymes that use ATP hydrolysis to alter nucleosome arrangement in eukaryotic chromosomes, changing DNA accessibility.

Base Pair

Two complementary nucleotides in an RNA or DNA molecule held together by hydrogen bonds, typically G with C, and A with T or U.

Cell Cycle

The orderly sequence of events by which a cell duplicates its contents and divides into two.

Centromere

A specialized DNA sequence that allows duplicated chromosomes to be separated during M phase; seen as the constricted region of a mitotic chromosome.

Chromatin

The complex of DNA and proteins that makes up chromosomes in eukaryotic cells.

Chromosome

Long, threadlike structure composed of DNA and proteins carrying the genetic information of an organism; becomes visible during cell division.

Cohesin

A ring-shaped SMC protein complex organizing interphase chromosomes into large chromatin loops and holding sister chromatids together after DNA replication.

Complementary

Describes two molecular surfaces that fit closely together and form noncovalent bonds.

Condensin

A ring-shaped SMC protein complex that compacts duplicated chromosomes for segregation by forming loops.

Double Helix

The typical structure of a DNA molecule in which two complementary polynucleotide strands are wound around each other.

Epigenetic Inheritance

The transmission of a heritable pattern of gene expression from one cell to its progeny without altering the DNA nucleotide sequence.

Euchromatin

Less compact chromatin prevalent in gene-rich areas, allowing access for proteins involved in transcription.

Gene

Unit of heredity containing instructions dictating the characteristics of an organism; in molecular terms, a DNA segment directing the production of a protein or functional RNA.

Gene Expression

The process by which a gene makes a product useful to the cell or organism by directing the synthesis of a protein or RNA molecule.

Genetic Code

The rules by which the nucleotide sequence of a gene and RNA is translated into the amino acid sequence of a protein.

Genome

The total genetic information carried by all chromosomes of a cell, including all nucleotide pairs.

Heterochromatin

Highly condensed regions of interphase chromosomes that are generally gene-poor and transcriptionally inactive.

Histone

Proteins around which DNA wraps to form nucleosomes, fundamental structures in chromatin packing.

Histone-modifying Enzyme

Enzyme that catalyzes the addition of small molecules like methyl or acetate groups to specific amino acids on histones.

Karyotype

An ordered display of a cell's full set of chromosomes arranged by size and number.

Nucleolus

Large structure within the nucleus where ribosomal RNA is transcribed and ribosomal subunits are assembled.

Nucleosome

Structural unit of a eukaryotic chromosome composed of DNA wrapped around a core of histone proteins.

Replication Origin

Nucleotide sequence at which DNA replication begins.

SMC Ring Complex

A large ring-shaped structure containing two SMC protein subunits; major types include cohesins and condensins.

Cancer

Disease caused by abnormal and uncontrolled cell proliferation followed by the invasion of other body sites.

DNA Helicase

Enzyme that unwinds the DNA double helix, exposing single strands for replication.

DNA Ligase

Enzyme that seals nicks in the phosphodiester backbone of DNA molecules.

DNA Polymerase

Enzyme that catalyzes the synthesis of DNA from a template at a replication fork.

DNA Repair

Collective term for enzymatic processes that correct damage to DNA.

DNA Replication

The process by which a copy of a DNA molecule is made.

Homologous Recombination

Repair mechanism for double-stranded breaks in DNA using homologous chromosomes.

Lagging Strand

DNA strand synthesized discontinuously in short fragments at a replication fork.

Leading Strand

DNA strand synthesized continuously in the 5'-to-3' direction at a replication fork.

Mismatch Repair

Mechanism for recognizing and correcting incorrectly paired nucleotides.

Mutation

Permanent change in the nucleotide sequence of DNA, which can result in abnormal proteins.

Nonhomologous End Joining

Error-prone mechanism for repairing double-strand breaks in DNA.

Okazaki Fragment

Short lengths of DNA produced on the lagging strand during DNA replication.

Primase

RNA polymerase that generates short RNA fragments serving as primers for DNA synthesis.

Proofreading

Process by which DNA polymerase corrects its own errors during DNA synthesis.

Replication Fork

Y-shaped DNA junction at the site where replication occurs.

RNA

Molecule produced by transcription of DNA, usually single-stranded.

Telomerase

Enzyme that elongates telomeres in eukaryotic chromosomes.

Telomere

Repetitive nucleotide sequence at the ends of linear chromosomes; protects against chromosome erosion.

Template

Molecular structure serving as a pattern for the production of other molecules.

Alternative Splicing

Production of different mRNAs from the same gene by splicing RNA transcripts differently.

Aminoacyl-tRNA Synthetase

Enzyme attaching the correct amino acid to a tRNA molecule.

Anticodon

Set of three nucleotides in tRNA that base-pairs with the codon on mRNA.

Codon

Group of three nucleotides specifying a particular amino acid in mRNA.

Exon

Transcribed segment of a eukaryotic gene that dictates part of a protein's amino acid sequence.

General Transcription Factor

Proteins that assist in assembling on promoters of eukaryotic genes.

Initiator tRNA

Special tRNA that starts translation.

Cell Memory

Ability of differentiated cells to maintain their identity.

Combinatorial Control

Groups of transcription regulators working together to regulate gene expression.

Differentiation

Progressive change of pluripotent cells into specialized cell types.

DNA Methylation

Enzymatic addition of methyl groups to cytosine bases in DNA, generally inhibiting genes.

Epigenetic Inheritance

Transmission of heritable gene expression patterns that do not involve altering DNA sequence.

Induced Pluripotent Stem (iPS) Cell

Somatic cell reprogrammed to resemble pluripotent embryonic stem cells.

Long Noncoding RNA

RNA molecules over 200 nucleotides long that do not encode proteins.

microRNA (miRNA)

Small, noncoding RNA regulating gene expression by binding specific mRNA.

Positive Feedback Loops

Form of regulation where the end product stimulates continued production.

Post-transcriptional Control

Regulation of gene expression occurring after gene transcription.

Promoter

DNA sequence that initiates gene transcription.

Regulatory DNA Sequence

DNA segment where transcription regulators bind to dictate gene expression.

Regulatory RNA

RNA molecule involved in gene expression control.

Reporter Gene

Gene encoding a protein whose activity is easy to monitor experimentally.

RNA Interference (RNAi)

Mechanism activated by double-stranded RNA that leads to destruction of complementary mRNAs.

Small Interfering RNA (siRNA)

Short RNA fragments that degrade complementary RNA, involved in gene regulation.

Transcriptional Activator

Protein that binds to DNA to stimulate transcription.

Transcriptional Repressor

Protein that binds to DNA to inhibit transcription.

Transcription Regulator

Protein that binds to regulatory DNA to switch genes on or off.

Alu Sequence

Family of mobile genetic elements constituting about 10% of the human genome.

Conserved Synteny

Preservation of gene order in the genomes of different species.

Exon Shuffling

Mechanism for creating new genes by combining coding sequences from different genes.

Gamete

Haploid cell specialized for sexual reproduction.

Gene Duplication and Divergence

Formation of new genes through accidental DNA duplication and mutation.

Gene Family

Set of related genes arising from gene duplication and divergence.

Germ Line

Lineage of reproductive cells contributing to new organism generations.

Homologous Genes

Genes with similarities due to common evolutionary origin.

Horizontal Gene Transfer

DNA transfer between organisms, even of different species.

L1 Element

Retrotransposon constituting 15% of the human genome, also known as LINE-1.

Mobile Genetic Element

Short DNA segments that can move within genomes, providing genetic variation.

Open Reading Frame (ORF)

Long DNA sequence without a stop codon, used to identify protein-coding regions.

Phylogenetic Tree

Diagram showing evolutionary relationships among organisms or proteins.

Point Mutation

Change in a single nucleotide pair in the DNA sequence.

Purifying Selection

Preservation of specific nucleotide sequences by eliminating harmful mutations.

Retrotransposon

Mobile genetic element that moves by being transcribed into RNA and back to DNA.

Retrovirus

RNA virus replicating via a double-stranded DNA intermediate integrated into the host chromosome.

Reverse Transcriptase

Enzyme creating DNA from an RNA template; present in retroviruses and retrotransposons.

Single-nucleotide Polymorphisms (SNP)

Genetic variations at a single nucleotide position in the genome.

Somatic Cell

Any cell not involved in reproduction or germ-line cell formation.

Transposon

General term for DNA segments that can move to new genome locations.

Virus

Particle of nucleic acid enclosed in a protein coat, capable of replicating within host cells.

Intron

Non-coding sequence within a gene excised during RNA processing.

Messenger RNA (mRNA)

RNA that carries the code specifying the amino acid sequence of a protein.

Noncoding RNA

RNA that does not translate into proteins but serves various functions in the cell.

Polyadenylation

Addition of multiple adenine nucleotides to the 3' end of an mRNA molecule.

Protease

Enzyme that hydrolyzes peptide bonds in proteins, degrading them.

Proteasome

Large protein complex that degrades damaged or unnecessary proteins.

Reading Frame

One of three ways nucleotide triplets are translated into proteins.

Ribosomal RNA (rRNA)

RNA forming the structural and catalytic core of the ribosome.