(lecture 4) Genes and Cellular Function

Vocabulary flashcards generated from MCB 244 lecture notes on Genes and Cellular Function.

Deoxyribonucleic acid (DNA)

A long, thread-like nucleic acid molecule averaging about $2\,\text{inches}$ long, existing as $46$ molecules (chromosomes) in the nucleus of most human cells to carry instructions for protein synthesis.

Purines

Nitrogenous bases possessing a double-ringed structure, consisting of adenine (A) and guanine (G).

Pyrimidines

Nitrogenous bases possessing a single-ringed structure, consisting of cytosine (C), thymine (T), and uracil (U).

Law of complementary base pairing

The structural rule that the base sequence of one DNA strand governs the base sequence of the other, pairing adenine (A) with thymine (T) via $2$ hydrogen bonds and guanine (G) with cytosine (C) via $3$ hydrogen bonds.

Gene

An information-containing segment of DNA that codes for the production of a molecule of RNA that most often plays a role in synthesizing one or more proteins.

Chromatin

Fine, filamentous material composed of DNA complexed with proteins called histones, which condenses into chromosomes during cell division.

Histones

Specialized proteins around which DNA winds, clustering in groups of eight to organize DNA into repeating granules within chromatin.

Core particle

A granular subunit of chromatin consisting of a cluster of eight histone molecules wrapped by a segment of DNA.

Sister chromatids

Two parallel, identical filaments of DNA produced when a cell replicates its nuclear DNA prior to cell division, joined together at a centromere.

Kinetochores

Protein plaques located on each side of the centromere that play a critical role in attaching to spindle fibers during cell division.

Genome

All the DNA contained within one $23$-chromosome set, comprising approximately $3.1\,\text{billion}$ nucleotide pairs in humans.

Genomic medicine

The application of knowledge of the genome to the prediction, diagnosis, and treatment of diseases such as cancer, Alzheimer disease, and schizophrenia.

Genetic code

A system that enables $4$ nitrogenous bases to code for the amino acid sequences of all proteins in the body.

Codon

A three-base sequence in mRNA that specifies a particular amino acid, a start signal (AUG), or a stop signal (UAG, UGA, UAA).

Transcription

The enzyme-driven process occurring in the nucleus by which genetic instructions from a DNA strand are copied into a complementary strand of pre-mRNA.

Alternative splicing

A process in pre-mRNA processing where nuclear enzymes splice exons together in different variations after removing introns, allowing one gene to code for multiple distinct proteins.

Translation

The process occurring in the cytoplasm in which a ribosome reads the mRNA nucleotide sequence and constructs a corresponding sequence of amino acids to form a protein.

Transfer RNA (tRNA)

A small, single-stranded RNA molecule that delivers specific amino acids to the ribosome during translation using a complementary three-nucleotide anticodon.

Polyribosome

A cluster of multiple ribosomes simultaneously translating a single mRNA molecule to rapidly synthesize identical proteins.

Chaperone proteins

Specialized proteins that guide newly synthesized amino acid chains into their functional secondary and tertiary shapes and assist damaged proteins in refolding.

Semiconservative replication

The mechanism of DNA replication in which each resulting double-stranded DNA molecule contains one original parental strand and one newly synthesized daughter strand.

Genetic mosaicism

The presence of genetically different cell populations within a single individual caused by mutations and replication errors during somatic cell division.

Interphase

The portion of the cell cycle between divisions, composed of the first gap phase ($G_1$), synthesis phase ($S$), and second gap phase ($G_2$).

$G_0$ phase

A resting phase of the cell cycle in which cells have ceased dividing either temporarily or permanently.

Mitosis

Nuclear division in somatic cells that results in two genetically identical daughter cells, serving functions in development, tissue growth, cellular replacement, and repair.

Contact inhibition

The physiological cessation of cell division in response to physical contact with adjacent neighboring cells.

Cyclin-dependent kinases (Cdks)

Enzymes that regulate cell cycle progression by phosphorylating specific target proteins when activated by binding cyclins.

Karyotype

A visual arrangement displaying an individual's full set of $46$ chromosomes ordered in $23$ homologous pairs by size and structure.

Alleles

Alternative forms of a specific gene located at the same chromosomal locus on homologous chromosomes.

Phenotype

The observable physical, physiological, or biochemical traits of an individual resulting from the interaction of its genotype with environmental factors.

Codominance

An inheritance pattern in which both alleles at a locus are fully and equally expressed in the phenotype of a heterozygous individual.

Polygenic inheritance

A pattern of heredity where multiple independent genes at different loci collectively contribute to a single observable trait, such as eye color or skin color.

Pleiotropy

A phenomenon where a single gene mutation produces multiple seemingly unrelated phenotypic effects throughout the body.

Epigenetic inheritance

The transmission of non-sequence alterations in gene expression—such as DNA methylation or chromatin packaging—from parent cells or individuals to offspring.

Metastasis

The process by which malignant tumor cells penetrate blood or lymphatic vessels, travel through the circulatory system, and establish secondary tumors at distant sites.

Cachexia

A severe syndrome of physical wasting away and loss of depleted body tissues caused by advanced cancer stealing nutrients from the body.