Q.Correct the statement, if necessary, by changing the underlined word only: Yeasts generally reproduce asexually by fission.
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🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Asexual Reproduction
Asexual reproduction is the production of offspring by a single parent, without the formation and fusion of gametes from two individuals. Because only one parent's genetic material is involved and no new genetic combinations are created, the offspring are genetically and morphologically identical to the parent and to each other — a group of such identical individuals is called a clone. This is the dominant reproductive strategy among single-celled organisms and among plants and animals with relatively simple body …
Yeasts are unicellular fungi whose typical mode of asexual reproduction is distinct from the binary fission characteristic of bacteria and some protists. …
The statement is incorrect as given; "fission" must be replaced with "budding", the characteristic mode of asexual reproduction in most yeasts.
Yeasts are unicellular fungi, and Saccharomyces cerevisiae (baker's/brewer's yeast) - the organism relevant to this chapter's discussion of fermentation - reproduces asexually mainly by budding:
- A small outgrowth (bud) forms on the parent cell, its nucleus divides mitotically, one daughter nucleus moves into the bud, and the bud eventually enlarges and separates (or in some cases remains attached, forming a chain) to become a new yeast cell. …
Showing the 12 most recent of 13 on this concept.
- CBSE 2026Set ANNUAL1 markMCQQ.Assertion (A) : In nature many organisms produce clones through asexual reproduction. Reason (R) : By this process, genetically identical individuals are produced.(a) Both Assertion and Reason are false.(b) Assertion is true, but Reason is false.(c) Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.(d) Both Assertion and Reason are true and Reason explains Assertion correctly.
›Reveal solutionSolution
Asexual reproduction genuinely produces clones because it relies on mitotic division from a single parent with no genetic recombination -- making both the Assertion and its explanatory Reason true.
Asexual reproduction is a mode of reproduction in which a single parent produces offspring without the fusion of gametes, through mechanisms such as budding (Hydra, yeast), binary fission (Amoeba, Paramecium), fragmentation (Planaria) or vegetative propagation in plants. Because these offspring arise purely through mitotic cell divisions of the parent's own cells, there is no opportunity for genetic recombination or the mixing of genetic material from two parents (as happens in sexual reproduction via meiosis and fertilisation). As a result, the offspring produced are genetically identical to the parent organism and to one another -- by definiti …
- CBSE 2025Set ANNUAL1 markMCQQ.Most common special asexual reproductive structure seen in members of algae is(a) Zoospore(b) Conidia(c) Sporangiospore(d) Gammule
›Reveal solutionSolution
Zoospores — flagellated, motile asexual spores — are the most common special asexual reproductive structures in algae.
Many algae (e.g. Chlamydomonas, Vaucheria, Ulothrix) reproduce asexually by producing zoospores: naked, flagellated, motile spores formed inside a parent cell (zoosporangium) that are released into water and swim using their flagella before settling down and developing into a new individual.
- Conidia are non-motile asexual spores typical of fungi (e.g. Penicillium), not algae. …
- CBSE 2023Set BOTANY1 markQ.Correct the statement, if necessary, by changing the underlined word only: Bacteria mostly reproduce by gemmules (underlined word: 'gemmules').
›Reveal solutionSolution
The commonest mode of bacterial reproduction is binary fission (asexual cell division); gemmules are a completely different structure found in sponges (Porifera), not bacteria.
Binary fission is the predominant mode of asexual reproduction in bacteria: the single circular DNA molecule replicates, the cell elongates, and a septum forms in the middle, dividing the parent cell into two genetically identical daughter cells. Under favourable conditions this can occur very rapidly (bacterial cells can divide every 20 minutes).
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- CBSE 2023Set ANNUAL1 markMCQQ.The term 'parthenogenesis' was coined by whom?(a) Boveri(b) Owen(c) Sutton(d) Johannsen
›Reveal solutionSolution
'Parthenogenesis' was coined by Richard Owen.
Parthenogenesis is the development of a new individual from an unfertilised egg (as in honeybee drones, some rotifers and aphids). The term was introduced by the English biologist Richard Owen. Boveri, Sutton (chromosome theor …
- CBSE 2022Set HE2201 markQ.Match the following (Column I with Column II): Budding — choose the matching term from:(a) Obelia(b) Hydra(c) Transgenic(d) Gender linked disease(e) Amoebiasis(f) Antimicrobial substance(g) Male sterilization(h) Genetic disorder.
›Reveal solutionSolution
Budding, the classic NCERT example of which is Hydra, is a form of asexual reproduction where a new individual grows out of the parent's body as an outgrowth.
This match-set (Column I: Budding, Vasectomy, Colour blindness, Entamoeba histolytica, Interferon, Gene therapy, Transgenic animal; Column II: (a) Obelia (b) Hydra (c) Transgenic (d) Gender-linked disease (e) Amoebiasis (f) Antimicrobial substance (g) Male sterilization (h) Genetic disorder — a distractor with no pair) is answered item-by-item across questions 22–28. This topic (asexual reproduction/budding) is itself from the pre-rationalisation 'Reproduction in Organisms' chapter, which is not in MP's current syllabus, but the correct pairing is: in ***H …
- CBSE 2021Set D1 markMCQQ.When offspring is formed by single parent, it is called as(a) Sexual reproduction(b) Asexual reproduction(c) Both (A) and (B)(d) Internal fertilization
›Reveal solutionSolution
Reproduction by a single parent is asexual reproduction.
In asexual reproduction only one parent is involved and no gametes are formed or fused. The offspring are genetically identical to the parent (clones) — e.g. binary fission in Amoeba, budding in yeast/Hydra, and vegetative propagation in plants. Sexual reproduction, in contrast, requires two parents (or two mating typ …
- CBSE 2020Set ANNUAL1 markQ.What is a Clone ?
›Reveal solutionSolution
A clone is a population of morphologically and genetically identical individuals or cells derived from a single ancestor by asexual reproduction (mitotic division), so all members are exact genetic copies of the parent.
In asexual reproduction, a single parent produces offspring using only mitotic cell division, with no fusion of gametes and no exchange or recombination of genetic material. As a result, the offspring are morphologically and genetically identical to the parent organism as well as to each other. Such a group of genetically identical individuals is called a clone. Examples include the offspring produced by vegetative propagation in plants (e.g …
- CBSE 2020Set ANNUAL1 markMCQQ.Asexual reproduction structure of hydra is OR Amoeba is called Immortal because(a) It cannot reproduce sexually(b) It reproduce by binary fission(c) The body of parent is distributed among the offspring(d) It is microscopic(a) Buds(b) Gemmules(c) Conidia(d) None of the above
›Reveal solutionSolution
Hydra's usual mode of asexual reproduction is budding: a small outgrowth develops on its body wall, grows into a miniature Hydra, and then detaches to live independently.
Under favourable conditions, a bud arises as a localised outgrowth on the body wall of Hydra, formed by repeated mitotic cell divisions at that site. The bud enlarges, develops tentacles and a mouth of its own, and eventually constricts at its base and detaches from the parent body to become an independent, miniature individual identical to the parent.
This is different from the other structures listed: gemmules are internal asexual reproductive/resistant bodies formed by sponges (Porifera) to survive adverse conditions, conidia are asexual spores produced by fungi such as Penicillium, and none of these are the structure Hydra uses.
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- CBSE 2019Set 57/3/11 markQ.Why are no variations seen in clones ? State two reasons.
›Reveal solutionSolution
Clones are genetically identical copies, so no genetic variation arises from sexual reproduction; the two key reasons are the absence of meiosis (no crossing over or independent assortment) and the absence of fertilisation (no combining of different parental genomes).
The Concept: Why Clones Are Carbon Copies
When we talk about clones, we mean organisms produced by asexual reproduction — not by the fusion of male and female gametes. In nature, this happens in bacteria (binary fission), yeast (budding), plants (runners, cuttings), and even some animals (starfish regeneration). In the lab, it’s done via techniques like somatic cell nuclear transfer (think Dolly the sheep).
The core idea is simple: no mixing of DNA from two parents means no new combinations of genes. But let’s dig deeper into the two specific biological processes that normally create variation — and why they are completely absent in clones.
Step-by-Step Reasoning
1. Absence of Meiosis (No Crossing Over or Independent Assortment)
In sexual reproduction, gametes (sperm and eggs) are produced by meiosis. During meiosis, two major events shuffle the genetic deck:
- Crossing over in prophase I: Homologous chromosomes exchange segments, creating new combinations of alleles on a single chromosome.
- Independent assortment in metaphase I: The way homologous pairs line up at the equator is random, so each gamete gets a unique mix of maternal and paternal chromosomes.
In a clone, the new individual is formed by mitosis — a simple, exact duplication of the parent cell’s DNA. Mitosis produces two daughter cells with identical genetic material. No crossing over, no independent assortment. The clone’s genome is a perfect copy of the parent’s.
Watch outA common mistake is to think that mutations during mitosis could create variation. While mutations can occur, they are rare and random — not a systematic source of variation like meiosis. The question asks why no variations are seen in clones, meaning the normal, predictable process produces zero variation. Mutations are exceptions, not the rule.
2. Absence of Fertilisation (No Combining of Two Genomes)
Even after meiosis, variation in sexual reproduction isn’t complete until fertilisation — the fusion of two genetically different gametes. This brings together chromosomes from two distinct parents, creating a new, unique diploid genome. …
- CBSE 2019Set BOTANY1 markQ.Correct the statement, if necessary, by changing the underlined word only: Yeasts generally reproduce asexually by fission.
›Reveal solutionSolution
The statement is incorrect as given; "fission" must be replaced with "budding", the characteristic mode of asexual reproduction in most yeasts.
Yeasts are unicellular fungi, and Saccharomyces cerevisiae (baker's/brewer's yeast) - the organism relevant to this chapter's discussion of fermentation - reproduces asexually mainly by budding:
- A small outgrowth (bud) forms on the parent cell, its nucleus divides mitotically, one daughter nucleus moves into the bud, and the bud eventually enlarges and separates (or in some cases remains attached, forming a chain) to become a new yeast cell. …
- CBSE 2019Set ANNUAL1 markQ.Why is offspring formed by asexual reproduction referred to as clone?
›Reveal solutionSolution
Asexual offspring are genetically identical to their single parent because they arise by mitosis, not by fusion of two different gametes -- this genetic identity is what defines a clone.
In asexual reproduction a single parent produces offspring through mitotic cell division (e.g., budding in yeast/Hydra, fragmentation, vegetative propagation), without any fusion of male and female gametes. Since mitosis is a copying process that produces daughter cells with the same DNA sequence as the parent cell, every offspring so produced carries an identical genotype to the parent and to each other. A morphologically and genetically identical group of individuals …
- CBSE 2016Set ANNUAL1 markMCQQ.When a gamete without any fusion develop into a new organism the phenomenon is called(a) Syngamy(b) External fertilization(c) Parthenogenesis(d) Parthenocarpy
›Reveal solutionSolution
Parthenogenesis is asexual development of an unfertilised gamete into a new individual; it is neither true fertilisation (syngamy) nor a mode of fruit formation.
Let's examine each option:
- Syngamy is the fusion of a male and a female gamete to form a zygote — the opposite of what the question describes, since here there is 'no fusion'.
- External fertilization refers to the site where two gametes fuse (outside the body, e.g. in many fishes and amphibians) — it still requires fusion of two gametes, so it does not fit either.
- Parthenocarpy is the development of a fruit without fertilisation of the ovule (a seedless fruit, e.g. banana) — this concerns fruit formation, not the development of a new organism from a gamete. …
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