BIOL 01111: Cell Division, Meiosis, and Genetics

Comprehensive vocabulary flashcards covering the cell cycle, mitosis, meiosis, chromosomal inheritance, and Mendelian genetics from BIOL 01111 practice exam questions.

Cell Cycle Phase at Intermediate DNA Content ($5\,\text{pg}$)

$G_1$ phase for a cell whose nuclear DNA content ranges from $4$ to $10\,\text{pg}$, preceding genome duplication in S phase.

Consequence of Repeated Mitosis Without Cytokinesis

The production of a single multinucleated cell containing several nuclei.

Prometaphase Chromosome Configuration ($2n = 4$)

A configuration consisting of four distinct, duplicated chromosomes, each composed of two sister chromatids condensing and engaging the spindle apparatus.

Mitotic Progression Immediately Following Metaphase

The segregation of sister chromatids into daughter chromosomes that move toward opposite spindle poles during anaphase.

Centromere

The specialized, narrow region on a duplicated chromosome where sister chromatids are held most closely attached to each other.

Prophase DNA Content Given Post-Mitotic Content of $10\,\text{pg}$

$20\,\text{pg}$, reflecting that chromosomal DNA has already been replicated during the prior S phase.

Primary Target Characteristic of Cancer Chemotherapeutics

Specific inhibition of the cell division cycle in rapidly dividing cells.

Density-Dependent Inhibition

A regulatory mechanism in which crowded cells stop dividing when cell surface proteins of adjacent cells contact one another and initiate inhibitory signals.

Cell Cycle Point of Peak MPF Activity

Mitosis ($M$ phase), when cyclin concentration reaches the threshold required to activate cyclin-dependent kinase (Cdk).

Primary Genetic Event Confined to Interphase

Replication of nuclear DNA, which takes place exclusively during S phase.

Metaphase Nuclear DNA Level

Twice the baseline $G_1$ amount, maintained from the end of S phase through metaphase.

Daughter Cell Chromosome Count from $24$ Anaphase Centromeres

$12\,\text{chromosomes}$ per daughter cell following cytokinesis, as the $24$ segregated chromatids are divided equally.

Non-Proliferative Cellular Defect Leading to Tumors

Failure or absence of appropriate programmed cell death (apoptosis).

Molecular Event Initiating Anaphase

Enzymatic cleavage of cohesin proteins that hold sister chromatids together.

Sister Chromatids

Two identical copies of a chromosome produced during DNA replication, joined at the centromere until anaphase separation.

Animal Cytokinesis Disruption by Cytochalasin B

Inhibition of actin microfilament assembly, preventing cleavage furrow formation and cell cleavage.

Cell Cycle Stage Characterized by Baseline DNA Quantity

$G_1$ phase, where cells possess half the DNA content of cells in $G_2$, prophase, and metaphase.

S Phase

The synthesis subphase of interphase in which nuclear genomic DNA is fully replicated.

Decline of MPF Activity at Mitotic Exit

Targeted degradation and destruction of the regulatory cyclin protein subunit.

Cell Plate

A membrane-bound partition developing across the middle of a dividing plant cell during cytokinesis to construct the new cell wall.

Chromosome Complement in a Triploid ($3n$) Organism with $n = 6$

$18\,\text{total chromosomes}$ organized into $6\,\text{sets}$ of three homologs each.

Relative Cohesin Abundance in Post-Meiotic Cells

Virtually depleted, reflecting successive enzymatic cleavages during anaphase I and anaphase II.

Stage of Earliest Chiasmata Visibility

Late prophase I of meiosis, following crossing over between non-sister chromatids of homologous pairs.

Fundamental Difference Between Meiosis II and Animal Mitosis

Meiosis II occurs in haploid cells, whereas animal mitosis takes place in diploid cells.

Chromosomal State of Telophase I Daughter Cells

Haploid cells containing chromosomes that each consist of two joined sister chromatids.

Primary Generators of Diploid Sexual Variation

Independent assortment of maternal and paternal chromosomes combined with random fertilization between gametes.

Divisions Where Sister Chromatids Separate

Mitosis and meiosis II (specifically during their respective anaphase stages).

Telophase I

The terminal stage of meiosis I where cytokinesis generates two haploid cells containing duplicated sister chromatid pairs.

Timing of Homologous Crossing Over

Meiosis I (specifically during prophase I).

Homologous Chromosomes

A pair of maternal and paternal chromosomes possessing the same length, centromere position, and loci controlling the same inherited traits.

Evolutionary Advantage of Sexual Reproduction

Production of novel allele combinations that increase phenotypic variation and reproductive fitness under natural selection.

Gamete Comparison to a Prophase I Cell

Completed gametes carry half the number of chromosomes and one-fourth the mass of DNA.

Human Gamete Combinations from Independent Assortment ($n = 23$)

Approximately $8\,\text{million}$ possible chromosome combinations ($2^{23} = 8{,}388{,}608$).

Chromosome Distribution in a Diploid Species with $2n = 16$

Eight homologous chromosome pairs per diploid somatic cell and $8\,\text{unpaired chromosomes}$ per haploid gamete.

Genetic Basis of Interspecies Difference Despite Identical Chromosome Number

Different nucleotide sequences, gene loci, and structural genetic arrangements across the chromosomes.

Stage Where Homologs Move Toward Opposite Spindle Poles

Anaphase I of meiosis.

Shared Mechanism Between Mitosis and Meiosis II

Separation of sister chromatids into individual daughter chromosomes during anaphase.

Metaphase I DNA Content Given Baseline $G_1$ Value $x$

$2x$, resulting from DNA replication completed during interphase.

Metaphase II DNA Content Given Baseline $G_1$ Value $x$

$x$, because homologous chromosomes were segregated into separate daughter cells during meiosis I.

Human Cell Carrying $22\,\text{Autosomes}$ and One $Y\,\text{Chromosome}$

A mature male gamete (sperm cell).

Genetic Risk of Consanguineous Mating (Inbreeding)

Substantially elevated probability that rare, deleterious recessive alleles will pair into homozygous genotypes.

Epistasis

A gene interaction in which alleles at one gene locus mask or alter the phenotypic expression of alleles at an independent locus.

Expected Offspring Genotypic Ratio from $BbDD \times BBDd$

$1\,BBDD : 1\,BbDD : 1\,BBDd : 1\,BbDd$.

Genotype Probability of Affected Offspring with a Recessive Parent

Heterozygous ($Ww$) with a probability of $1$ ($100\%$), because the child obligately inherits allele $w$ from the recessive parent.

True-Breeding

Describing homozygous organisms ($DD$ or $dd$) that produce identical phenotypic offspring across generations upon selfing or like mating.

Genotype of an Unaffected Individual for an Autosomal Dominant Trait

Homozygous recessive ($ww$).

Heterozygous Proportion in a Monohybrid Cross ($Dd \times Dd$)

$50\%$ ($2/4$), represented by the two diagonal heterozygous ($Dd$) cells of the Punnett square.

Unique Gamete Count for Genotype $AaBbCCDdEE$

$8\,\text{gametes}$, derived from $2^n$ with $3\,\text{heterozygous loci}$ ($2^3 = 8$).

Phenotypic Ratio of $F_1$ Hybrid Backcrossed to Dominant Parent ($Pp \times PP$)

$4:0$ (all progeny express the dominant phenotype).

Pedigree Hallmark of Autosomal Dominant Inheritance

Expression of the trait across every generation without skipping, where affected offspring have at least one affected parent.

Fraction of Fully Homozygous Recessive Progeny from $AaBbCc \times AaBbCc$

$\frac{1}{64}$, calculated as $\frac{1}{4} \times \frac{1}{4} \times \frac{1}{4}$.

Maximum Alleles per Single Gamete for One Locus

One allele per gamete, meaning an individual produces at most $2\,\text{different gamete genotypes}$ for that locus.

Pleiotropy

The capability of a single gene locus or mutation to exert multiple, diverse phenotypic effects across an organism.

Epistatic Basis for Sharp Progeny from Spineless and Dull Cacti

The true-breeding spineless parent ($nn$) carried masked dominant sharpness alleles ($S$) that were unmasked in $Nn$ progeny.

Valid Gamete Genotype from Dihybrid $HhTt$

A haploid allele combination containing one allele per locus, such as $Ht$, $HT$, $hT$, or $ht$.

Expected Genotypic Ratio of a Monohybrid Testcross ($Yy \times yy$)

$1:1$ ($1\,Yy : 1\,yy$).

Recessive Epistatic Dihybrid Phenotypic Ratio ($SsNn \times SsNn$)

$9:3:4$ (e.g., $9\,\text{sharp-spined} : 3\,\text{dull-spined} : 4\,\text{spineless}$).

Genotypes of Blue Budgies Yielding White Offspring

$yyBb \times yyBb$, requiring both blue parents ($yyB\_$) to be heterozygous carriers of the recessive allele $b$.

Heterozygote Advantage in Malaria-Endemic Regions

Natural selection maintaining sickle-cell heterozygosity ($HbA/HbS$) due to conferring resistance against malaria.

Addition Rule of Probability

A rule stating that the probability of any one of two or more mutually exclusive events occurring is the sum of their individual probabilities.

Morgan Drosophila Eye Color Cross Findings

Classic genetic experiments where white eyes segregated solely to males in the $F_2$ generation, establishing X-linkage.

Trisomy X ($47, XXX$) Phenotype

A clinically healthy, fertile female possessing three X chromosomes, typically of slightly above-average stature with two Barr bodies.

Map Distance (Centimorgan)

A metric of chromosomal distance where $1\,\text{map unit}$ corresponds to a $1\%$ recombinant progeny frequency.

Philadelphia Chromosome

An abnormally shortened chromosome 22 created by reciprocal translocation with chromosome 9 ($t(9;22)$), linked to leukemia.

Random X Inactivation

The early epigenetic silencing of either the maternal or paternal X chromosome in female mammalian cells, yielding mosaic phenotypes.

Only Viable Human Monosomy

Monosomy X (Turner syndrome, $45, X$).

Sex Ratio Under Embryonic Recessive Z-Linked Lethality

$2:1\,\text{male-to-female ratio}$ among surviving offspring, as hemizygous females receiving the lethal Z allele perish.

Map Distance Between Genes $L$ and $S$ on Pandora

$3\,\text{map units}$, calculated from $30\,\text{recombinants}$ out of $1{,}000\,\text{total progeny}$ ($3\%$).

Son Risk for X-Linked Recessive Trait from a Carrier Mother

$\frac{1}{2}$ ($50\%$), because the mother passes her mutant X chromosome to half of her sons.

Transmission Route of Paternal X-Linked Alleles

Transmitted to $100\%$ of his biological daughters and $0\%$ of his biological sons.

Recombinant Progeny in a Three-Point Testcross

Progeny phenotypes displaying non-parental allele arrangements between the two loci being evaluated.

DMD Risk in Daughters of an Affected Father and Carrier Mother

$\frac{1}{2}$ ($50\%$), as all daughters receive paternal $X^d$ and have a $50\%$ chance of receiving maternal $X^d$.

Primary Etiology of Trisomy 21 (Down Syndrome)

Chromosomal nondisjunction occurring during parental gametogenesis in meiosis.

Relationship Between Gene Proximity and Crossover Frequency

The closer two linked loci are situated on a chromosome, the lower the probability of crossing over occurring between them.

Progeny Phenotypes from Black Female ($X^B X^B$) and Orange Male ($X^O Y$) Cats

Tortoiseshell females ($X^B X^O$) and black males ($X^B Y$).

Physical Cause of Gene Linkage

Close physical proximity of two or more gene loci along the same chromosome preventing independent assortment.

Primary Driver of Mammalian Embryonic Sex Differentiation

Activation of the $SRY$ gene on the Y chromosome, triggering bipotential embryonic gonads to develop into testes.

Diagnostic Utility of a Genetic Testcross

Offspring phenotypes directly reveal the allele combinations contributed by the unknown parent because the tester contributes only recessive alleles.

Carcinogenic Mechanism of Chromosomal Translocations

Translocating a proto-oncogene adjacent to active promoter/enhancer elements, resulting in inappropriate and excessive cell division.

Genetic Cause of $46, XX$ Karyotypic Male Phenotype

Translocation of the sex-determining $SRY$ gene from the Y chromosome onto an X chromosome during paternal gametogenesis.