BIOL 11100 Lecture Exam 2 Review

Vocabulary flashcards covering cytokinesis, meiosis, Mendelian genetics, gene expression, and RNA processing as presented in the BIOL 11100 lecture notes.

Cytokinesis (animal cells)

Division of the cytoplasm via a contractile ring of actin filaments and myosin motors that tightens to form a cleavage furrow.

Contractile ring

Actin-myosin structure that constricts the middle of an animal cell during cytokinesis.

Cleavage furrow

Indentation produced by the contractile ring that deepens until an animal cell splits in two.

Cytokinesis (plant cells)

Division of the cytoplasm by assembling a cell plate from vesicles that deposit callose, later replaced by cellulose to form a new wall.

Cell plate

Precursory structure of a new plant cell wall formed from vesicles carrying callose.

Callose

Polysaccharide first laid down in the cell plate of plant cytokinesis; later converted to cellulose.

Chromosome (human)

Linear DNA molecule; typical somatic human cell contains 46 chromosomes.

Homologous chromosomes

Pair of chromosomes, one maternal and one paternal, that carry the same genes but may possess different alleles.

Allele

Alternative form of the same gene occupying the same locus on homologous chromosomes.

Ploidy

Number of homologous chromosome sets present in a cell.

Diploid (2n)

Cell containing two homologs of each chromosome.

Polyploid

Cell containing more than two homologs of each chromosome.

Monoploid / Haploid (n)

Cell containing one of each chromosome.

Mitosis (ploidy)

Nuclear division that maintains the original ploidy of the parent cell.

Meiosis (ploidy)

Reductional division that halves the ploidy of the parent cell to produce haploid gametes.

Gametogenesis

Overall process of producing gametes (sperm or eggs) through meiosis.

Spermatogenesis

Meiotic process generating four haploid sperm from one diploid primary spermatocyte.

Oogenesis

Meiotic process generating one mature haploid egg and three haploid polar bodies from one diploid primary oocyte.

Reduction division

Meiosis I event where one diploid cell divides into two haploid cells.

Prophase I

Stage of meiosis where nuclear envelope breaks down, chromosomes condense, spindle forms, homologs pair, and crossing over occurs.

Bivalent

Paired structure of homologous chromosomes joined during prophase I.

Synaptonemal complex

Protein lattice that physically holds homologous chromosomes together in a bivalent.

Metaphase I

Stage where homologous chromosome pairs align randomly at the metaphase plate.

Independent assortment

Random orientation of homologous pairs in metaphase I that creates genetic variation.

Anaphase I

Stage where homologous chromosomes separate to opposite poles.

Telophase I

Stage where nuclei reform, spindle disassembles, and chromosomes may decondense after meiosis I.

Interkinesis

Brief interphase-like pause between meiosis I and meiosis II with no DNA replication.

Meiosis II

Equational division separating sister chromatids to yield four haploid cells.

Nondisjunction

Failure of chromosomes or chromatids to separate properly during meiosis, producing gametes with abnormal numbers.

Aneuploidy

Condition of having an abnormal chromosome number.

Amphitelic attachment

Correct kinetochore-microtubule attachment in which each chromatid connects to opposite spindle poles.

Syntelic attachment

Erroneous attachment where both kinetochores of a pair connect to microtubules from the same spindle pole.

Gregor Mendel

Monk who established the fundamental laws of inheritance through pea-plant experiments.

Gene

DNA segment that encodes or influences a trait.

Monogenic trait

Trait controlled by a single gene.

Polygenic trait

Trait governed by multiple genes.

Locus

Specific physical location of a gene on a chromosome.

Homozygous

Having identical alleles for a given gene.

Heterozygous

Having two different alleles for a given gene.

Genotype

Set of alleles carried by an individual.

Phenotype

Observable characteristics resulting from a genotype.

True-breeding organism

Individual that produces offspring with the same phenotype when self-crossed.

Parental generation (P0)

Original parents in a genetic cross.

F1 generation

First-generation offspring produced by crossing the P0 individuals.

F2 generation

Offspring produced by interbreeding F1 individuals.

Monohybrid cross

Genetic cross tracking the inheritance of a single trait.

Dihybrid cross

Genetic cross tracking two traits simultaneously.

Law of dominance

Mendelian principle stating one allele can mask the expression of another.

Law of segregation

Mendelian principle that alleles separate during gamete formation so each gamete carries one allele per gene.

Incomplete dominance

Inheritance pattern where heterozygotes express an intermediate phenotype.

Anthocyanin

Pigment whose differential production causes red, pink, or white flowers in four-o’clocks.

Codominance

Inheritance pattern where heterozygotes express both parental phenotypes simultaneously.

Galactosamine

Sugar present on type A blood cell surface antigens.

Galactose

Sugar present on type B blood cell surface antigens.

Glycosyltransferase (I gene product)

Enzyme that adds specific sugars to red-blood-cell surface molecules, determining ABO blood type.

Epistasis

Interaction where one gene affects or masks the expression of another gene.

Phaeomelanin

Pigment that imparts yellow coloration in Labrador coats.

Eumelanin

Pigment providing brown or black coloration in Labrador coats.

B gene (Labs)

Gene controlling amount of eumelanin pigment produced.

E gene (Labs)

Gene controlling whether the B gene’s eumelanin production is expressed.

Central dogma

Flow of genetic information: DNA → RNA → Protein.

Retrovirus

Virus with an RNA genome that is reverse-transcribed into DNA within host cells.

Reverse transcriptase

Viral enzyme that synthesizes DNA from an RNA template.

Protein-coding gene

Gene transcribed into mRNA that is translated into a protein.

Non-protein-coding gene

Gene transcribed into functional RNA that is not translated (e.g., rRNA, tRNA).

Promoter region

DNA sequence where RNA polymerase binds to start transcription.

Coding region (gene)

DNA segment whose sequence is transcribed by RNA polymerase into RNA.

Termination sequence

DNA segment signaling RNA polymerase to end transcription.

Template strand

DNA strand read by RNA polymerase to synthesize complementary RNA.

Coding strand (sense strand)

DNA strand with sequence identical to the RNA transcript (except T ↔ U).

RNA polymerase (prokaryotic)

Single multi-subunit enzyme that carries out transcription in bacteria.

Sigma factor

Prokaryotic initiation subunit that recognizes the promoter and unwinds DNA, then dissociates.

Core enzyme

α₂ββ′ catalytic portion of prokaryotic RNA polymerase that elongates RNA after initiation.

Holoenzyme

Complete prokaryotic RNA polymerase consisting of core enzyme plus sigma factor.

Monocistronic mRNA

mRNA encoding one protein-coding region.

Polycistronic mRNA

mRNA encoding multiple protein-coding regions.

Operon

Cluster of prokaryotic genes under one promoter and terminator, transcribed as a unit.

Lac operon

E. coli operon with three genes necessary for lactose transport and metabolism.

RNA Polymerase I

Eukaryotic enzyme transcribing rRNA genes.

RNA Polymerase II

Eukaryotic enzyme transcribing mRNA genes.

RNA Polymerase III

Eukaryotic enzyme transcribing tRNA and some rRNA genes.

Transcription factor

Eukaryotic DNA-binding protein that recruits RNA polymerase to the promoter.

5′ cap

Modified guanine nucleotide added via 5′-5′ linkage to the pre-mRNA’s 5′ end for stability.

Poly-A tail

~200-adenine chain added to the 3′ end of pre-mRNA by poly-A polymerase for protection.

Intron

Non-coding sequence removed from pre-mRNA during splicing.

Exon

Coding sequence retained in mature mRNA after splicing.

Splicing

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

Spliceosome

RNP complex of snRNA and snRNP proteins that catalyzes pre-mRNA splicing.

snRNA

Small nuclear RNA component of the spliceosome.

snRNP

snRNA complexed with proteins, forming key spliceosome subunits.

Lariat structure

Looped intron released during splicing, held by a 5′-2′ phosphodiester bond.

Alternative splicing

Process in which different combinations of exons are joined to generate multiple mRNAs from one gene.

Splice-site activator protein

Regulatory protein that promotes use of a nearby splice site during alternative splicing.

Splice-site repressor protein

Regulatory protein that inhibits use of a nearby splice site during alternative splicing.