Genes and Cellular Function - Vocabulary

Vocabulary flashcards covering key terms and concepts from the lecture notes on DNA, RNA, protein synthesis, cell cycle, and cancer.

DNA

Deoxyribonucleic acid; long, thread-like molecule that carries genetic instructions and is organized into 46 DNA molecules (chromosomes) in the nucleus.

Nucleotide

The basic unit of DNA and RNA, consisting of a sugar (deoxyribose or ribose), a phosphate group, and a nitrogenous base.

Deoxyribose

The sugar component of DNA's backbone.

Phosphate group

Part of the DNA backbone that links sugars to form the sugar-phosphate backbone.

Nitrogenous base

Purines (A, G) and pyrimidines (C, T in DNA; C, U in RNA) that form the rungs of the DNA ladder.

Purines

Adenine (A) and Guanine (G); double-ringed nitrogenous bases.

Pyrimidines

Cytosine (C) and Thymine (T) in DNA; Uracil (U) in RNA; single-ringed bases.

Adenine (A)

Purine base that pairs with thymine in DNA (via two hydrogen bonds).

Thymine (T)

Pyrimidine base that pairs with adenine in DNA (via two hydrogen bonds).

Guanine (G)

Purine base that pairs with cytosine in DNA (via three hydrogen bonds).

Cytosine (C)

Pyrimidine base that pairs with guanine in DNA (via three hydrogen bonds).

Uracil (U)

Pyrimidine base in RNA that replaces thymine.

Base pairing

Hydrogen-bonded pairing of nucleotides: A with T (or U in RNA) and G with C; enables DNA replication and transcription.

Complementary base pairing

One strand's sequence dictates the other's sequence (A–T/U, G–C) in the double helix.

Double helix

Three-dimensional shape of DNA: two backbones of sugar-phosphate with base pairs as rungs.

Gene

A DNA sequence that codes for the synthesis of a specific protein or functional product.

Genome

All the genes of an individual; about 2% code for proteins; remaining DNA is noncoding.

Chromosome

A DNA molecule packaged with proteins; 46 in human somatic cells.

Chromatin

DNA wrapped around histone proteins; chromosomal material in nondividing cells.

Nucleosome

DNA wrapped around a core histone; the basic unit of chromatin (around 11 nm).

Histone

Protein around which DNA winds to form nucleosomes.

Sister chromatids

Two identical copies of a replicated chromosome held together at the centromere.

Centromere

Constriction point where sister chromatids are joined and kinetochore proteinsassemble during cell division.

Kinetochores

Protein plaques at the centromere that attach to spindle fibers during cell division.

Chromosome territory

A chromosome’s distinct region within the nucleus in nondividing cells.

Diploid (2n)

Cells with two sets of chromosomes (46 in humans; 23 pairs).

Haploid (n)

Cells with a single set of chromosomes (23 in humans; gametes).

Karyotype

Chart of all 46 chromosomes laid out in size order.

Locus

Specific position of a gene on a chromosome.

Allele

Different forms of a gene found at the same locus.

Dominant allele

Allele that usually masks the other and is expressed in the phenotype when present.

Recessive allele

Allele whose trait is expressed only when two copies are present.

Genotype

The alleles an individual possesses for a given gene.

Phenotype

An observable trait resulting from the genotype plus environment.

Homozygous

Having two identical alleles for a gene.

Heterozygous

Having two different alleles for a gene.

Sickle-cell disease

Genetic disorder caused by homozygous recessive alleles; abnormal red blood cells.

Mutation

Change in DNA sequence; can be missense, frameshift, or other types; may have no effect or cause disease.

Missense mutation

A mutation that changes one amino acid in the produced protein.

Frameshift mutation

Insertion or deletion that shifts the reading frame of the genetic code.

Proto-oncogene

Normal gene that, when mutated, becomes an oncogene.

Oncogene

Mutated gene that promotes uncontrolled cell division.

Tumor suppressor gene

Gene that inhibits uncontrolled cell growth; when mutated, cancer risk increases.

Cancer

Malignant neoplasm; uncontrolled growth that can invade and metastasize.

Benign tumor

Noninvasive, encapsulated tumor with slower growth.

Malignant tumor

Invasive cancer that can metastasize to distant sites.

Metastasis

Spread of cancer cells from the original site to other parts of the body.

Carcinogen

Environmental agent that can cause cancer (chemicals, radiation, viruses).

Cachexia

Severe wasting of body tissues associated with advanced cancer.

DNA replication

Process of duplicating DNA prior to cell division; semiconservative, involving unwinding, unzipping, synthesis by DNA polymerase, and ligation.

Helicase

Enzyme that unwinds the DNA double helix to expose bases.

DNA polymerase

Enzyme that synthesizes new DNA strands by adding nucleotides.

Ligase

Enzyme that joins okazaki fragments on the lagging strand and seals nicks.

Semiconservative replication

Each new DNA molecule contains one old (parental) strand and one newly synthesized strand.

Transcription

Process by which RNA polymerase copies DNA into mRNA in the nucleus.

RNA polymerase

Enzyme that builds an RNA strand complementary to a DNA template.

mRNA

Messenger RNA; carries the protein-coding message from DNA to the cytoplasm.

tRNA

Transfer RNA; delivers amino acids to the ribosome and contains an anticodon.

rRNA

Ribosomal RNA; structural and functional component of ribosomes.

Codon

Three-nucleotide sequence in mRNA that specifies a particular amino acid.

Anticodon

Three-nucleotide sequence on tRNA that pairs with a codon in mRNA.

Start codon

AUG; signals the start of translation and codes for methionine.

Stop codon

UAA, UAG, or UGA; signals termination of translation.

Translation

Process by which ribosomes read mRNA and synthesize a polypeptide from amino acids.

Ribosome

Molecular machine with large and small subunits that carries out translation.

Amino acid

Building blocks of proteins; linked together to form polypeptides.

Methionine

Amino acid encoded by the start codon (AUG) at the beginning of protein synthesis.

Posttranslational modification

Processing of proteins after synthesis (folding, disulfide bonds, glycosylation) and sorting in ER and Golgi.

Rough endoplasmic reticulum (Rough ER)

ER studded with ribosomes where secreted and membrane proteins are synthesized.

Golgi apparatus

Organelle that modifies, sorts, and packages proteins for secretion or delivery.

Secretory vesicles

Vesicles that transport and release proteins by exocytosis.

Exocytosis

Process by which secretory vesicles fuse with the plasma membrane to release contents outside the cell.

Protein

A chain of amino acids that performs a vast array of cellular functions.

Interphase

Cell cycle phase where growth occurs and DNA is replicated (G1, S, G2).

Mitosis (M phase)

Nuclear division followed by cytokinesis; produces two genetically identical daughter cells.

Prophase

Chromosomes condense; mitotic spindle forms; nuclear envelope breaks down.

Metaphase

Chromosomes align at the cell equator; spindle apparatus forms.

Anaphase

Sister chromatids separate and move to opposite poles.

Telophase

Nuclei form around chromosomes; chromosomes de-condense; spindle disassembles.

Cytokinesis

Division of the cytoplasm, producing two separate daughter cells.