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#diploid

3 public questions tagged with this topic.

Which of the following is NOT a characteristic of meiosis?

Meiosis encompasses specialized sequence absent from mitosis distinguishing germline division that produces haploid gametes maintaining constant chromosome number across sexual generations. Hallmark events include synapsis where homologous maternal and paternal chromosomes align along entire length via synaptonemal complex comprised of SYCP2, SYCP3 lateral elements and SYCP1 transverse filaments, providing intimate pairing necessary for homology search. Parallel programmed double-strand breaks catalyzed by Spo11 recruit DMC1 recombinase promoting crossing over between non-sister chromatids, generating recombinant chromosomes with novel allele combinations contributing to evolution and adaptation. Two successive divisions without intervening S phase reduce chromosome complement from diploid 2n to haploid n: meiosis I segregates homologs reductionally, meiosis II separates sisters equationally. Independent assortment adds further shuffling. Producing diploid daughters would duplicate ploidy each generation leading to polyploid lethality, contradicting reduction purpose. Therefore generation of haploid diversity and halving underpin meiosis definition. This circuitry is highly conserved across eukaryotes, integrating growth factor signals, DNA damage surveillance, and developmental cues, and its disruption frequently underlies oncogenesis, providing targets for checkpoint inhibitors and cancer therapeutics.

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 21: Overview of Meiosis Characteristics.

Most fungal life cycle is predominantly

Most fungal life cycles are haplontic with predominant stage haploid performing growth, foraging and ecological functions. Vegetative mycelium, which performs nutrient absorption and colonization, carries haploid nuclei throughout except transient diploid zygote. Diploid phase restricted to fleeting zygote formed after karyogamy within ascus, basidium or zygosporangium, immediately undergoing meiosis to regenerate haploid spores ensuring genetic diversity. No alternation favoring diploid dominance as in animals or diplontic algae. Triploid and tetraploid uncommon except lab-induced heterokaryosis. Haploid dominance facilitates rapid expression of beneficial mutations and adaptation.

Ref: Campbell Biology 12th ed., Chapter 31: Fungal Life Cycle Haploid Dominant; NCERT Class 12 Genetics - Fungal Dominance; NCBI Haplontic Cycle

Diploid organisms contain

Diploid organisms maintain two complete chromosome sets, designated 2n, in somatic cells with homologous pairs one inherited from each parent. This state provides two allelic copies per locus, permitting dominance interactions, buffering deleterious recessives and enabling segregation. Diploidy is restored at fertilisation when haploid gametes fuse and reduced during meiosis maintaining constant chromosome number across generations. One set defines monoploid, three sets triploid and variable sets describe mixoploidy or aneuploidy, diploid condition dominates animal life cycles. This principle is routinely tested in NEET, CBSE 11-12, CUET, CSIR-NET, GATE and MSc Genetics examinations requiring clear conceptual distinction.

Ref: Pierce, Genetics, 7th ed., Chapter 2: Diploidy and Life Cycles