SEM02_Gametogenesis_and_Fertilization
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Questions and Answers

What is gametogenesis?

  • The process of chromosomal abnormalities during fertilisation
  • The process of DNA replication in precursor cells
  • The process of yolk formation in female gametes
  • The process of origin, development, and maturation of gametes (correct)

    • What is the ploidy of mature gametes?

  • Tetraploid (4n)
  • Haploid (1n) (correct)
  • Triploid (3n)
  • Diploid (2n)

    • What is the significance of fertilisation?

  • It increases the ploidy of gametes
  • It reduces the genetic diversity within a species
  • It leads to the formation of haploid gametes
  • It produces a diploid zygote, the beginning of a new individual (correct)

    • What is the role of gametes in providing continuity of life between generations?

    <p>Passing on chromosomal DNA containing developmental information for the species</p> Signup and view all the answers

    What is the crucial trade-off in egg production?

    <p>Number of eggs vs. size of eggs</p> Signup and view all the answers

    What is the difference in yolk proportion between altricial and precocial birds?

    <p>25% and 40%</p> Signup and view all the answers

    What is a result of lactation in mammalian evolution?

    <p>Progressive loss of egg yolk</p> Signup and view all the answers

    What is the diploid number of chromosomes in humans?

    <p>46</p> Signup and view all the answers

    What is the sex determination system in birds?

    <p>ZW system</p> Signup and view all the answers

    What happens if an egg receives an X chromosome from the sperm in mammals?

    <p>The resulting individual is female</p> Signup and view all the answers

    Which organelle is included in the cytoplasm of the zygote?

    <p>Mitochondria</p> Signup and view all the answers

    What is the primary function of the pellucid zone in mammals?

    <p>Facilitate fertilization</p> Signup and view all the answers

    What is the function of the corona radiata in the zygote?

    <p>Protect the zona pellucida</p> Signup and view all the answers

    What is the vitelline membrane's composition in birds?

    <p>Layer of proteins and receptors</p> Signup and view all the answers

    What is the function of white albumen in eggs?

    <p>Nourish the embryo</p> Signup and view all the answers

    What is the primary component of shell membrane in eggs?

    <p>Keratin</p> Signup and view all the answers

    What is the main function of yolk or vitellus in eggs?

    <p>Nourish the embryo</p> Signup and view all the answers

    Which type of vertebrate eggs has an enormous amount of yolk?

    <p>Polylecithal or macrolecithal eggs</p> Signup and view all the answers

    In which type of vertebrate eggs is yolk uniformly distributed through the cytoplasm?

    <p>Isolecithal eggs</p> Signup and view all the answers

    Where does yolk tend to concentrate in telolecithal eggs?

    <p>On one hemisphere of the egg</p> Signup and view all the answers

    What impact has yolk had on animal evolution?

    <p>Embryonic development depends on nutritional reserves stored in egg yolk.</p> Signup and view all the answers

    During spermatogenesis, which cells proliferate by mitosis to produce primary spermatocytes?

    <p>Spermatogonia</p> Signup and view all the answers

    What is the function of the acrosome in sperm cells?

    <p>Contains digestive enzymes for fertilization</p> Signup and view all the answers

    Where does oogenesis occur?

    <p>Ovaries</p> Signup and view all the answers

    When does oogenesis start in females?

    <p>Before birth</p> Signup and view all the answers

    What happens during ovulation?

    <p>Secondary oocyte is released from the ovary</p> Signup and view all the answers

    What is produced after fertilization during oogenesis?

    <p>Zygote</p> Signup and view all the answers

    Where does fertilisation take place in mammals?

    <p>Inside the fallopian tube</p> Signup and view all the answers

    What stimulates the liver to produce yolk material for growing follicles in birds?

    <p>Oestrogen</p> Signup and view all the answers

    What is the function of the largest follicle in birds?

    <p>Produces high levels of progesterone and induces ovulation</p> Signup and view all the answers

    What happens during ovulation in birds?

    <p>Only the yolk is released from the ovary</p> Signup and view all the answers

    What occurs at the beginning of the oviduct in birds?

    <p>Fertilisation with multiple sperms binding and fusing with the oocyte</p> Signup and view all the answers

    What happens during follicular development in birds?

    <p>Accumulation of yolk without formation of a fluid-filled follicle</p> Signup and view all the answers

    What is a characteristic feature of bird's ovary during breeding season?

    <p>Resembles a bunch of grapes</p> Signup and view all the answers

    What stimulates luteinising hormone surge leading to ovulation in birds?

    <p>High levels of progesterone produced by largest follicle</p> Signup and view all the answers

    What happens during fertilisation in mammals?

    <p>Sperm-zona pellucida binding followed by zygote cell division initiation</p> Signup and view all the answers

    What is the process by which diploid precursor cells produce mature haploid gametes?

    <p>Meiosis</p> Signup and view all the answers

    What is the term for female gametes in sexual reproduction?

    <p>Ovum</p> Signup and view all the answers

    What is the significance of gametes in providing continuity of life between generations?

    <p>They carry half of the normal number of chromosomes of the species</p> Signup and view all the answers

    What occurs at fertilization in sexual reproduction?

    <p>The fusion of haploid gametes produces a diploid zygote</p> Signup and view all the answers

    What is the process of forming sperm called?

    <p>Spermatogenesis</p> Signup and view all the answers

    Where does meiosis occur in females?

    <p>Ovaries</p> Signup and view all the answers

    What is the role of the acrosome in sperm cells?

    <p>Contains digestive enzymes for fertilization</p> Signup and view all the answers

    When does oogenesis start in females?

    <p>Before birth</p> Signup and view all the answers

    What is produced from secondary spermatocytes after meiosis II?

    <p>Spermatids (1n)</p> Signup and view all the answers

    What happens during ovulation in females?

    <p>Release of secondary oocyte from the ovary</p> Signup and view all the answers

    What is the process that produces haploid gametes for sexual reproduction?

    <p>Meiosis</p> Signup and view all the answers

    What is the primary function of oocyte II?

    <p>Storage of cytoplasm and nutrients</p> Signup and view all the answers

    What occurs after fertilization during oogenesis?

    <p>Completion of meiosis II producing a fertilized egg and a second polar body (n)</p> Signup and view all the answers

    What leads to reproductive senescence in females?

    <p>Depletion of follicles determined early in life</p> Signup and view all the answers

    What drove developmental innovations in amphibians?

    <p>Increase in egg size and yolk content</p> Signup and view all the answers

    What complication arose due to the increased yolk content in reptiles and birds?

    <p>Gastrulation</p> Signup and view all the answers

    What distinguishes the eggs of altricial and precocial birds?

    <p>Yolk content</p> Signup and view all the answers

    What led to the degeneration and loss of yolk genes and content in mammalian eggs?

    <p>Development of placenta</p> Signup and view all the answers

    What does the number of chromosomes in an animal correlate with?

    <p>Apparent complexity of an animal</p> Signup and view all the answers

    How is sex determined at fertilization in mammals?

    <p>Presence of Y or X chromosome</p> Signup and view all the answers

    Where does fertilisation occur in birds?

    <p>At the beginning of the oviduct</p> Signup and view all the answers

    What is the primary function of the largest follicle in birds?

    <p>Produces high levels of progesterone</p> Signup and view all the answers

    What happens during ovulation in birds?

    <p>The yolk is released from the ovary</p> Signup and view all the answers

    What happens during fertilisation in mammals?

    <p>Sperm-zona pellucida binding initiates fertilisation</p> Signup and view all the answers

    What is a characteristic feature of bird's ovary during breeding season?

    <p>Enlarged and yellowish in appearance</p> Signup and view all the answers

    What is the primary function of the pellucid zone in mammals?

    <p>To facilitate species-specific fertilization</p> Signup and view all the answers

    What is the primary role of the corona radiata in the zygote?

    <p>To assist in sperm penetration during fertilization</p> Signup and view all the answers

    What is the composition of the vitelline membrane in birds?

    <p>Protein and lipids</p> Signup and view all the answers

    When does oogenesis start in females?

    <p>At birth</p> Signup and view all the answers

    What happens during follicular development in birds?

    <p>Growth and maturation of ovarian follicles</p> Signup and view all the answers

    What is the primary component of shell membrane in eggs?

    <p>Calcium carbonate and keratin</p> Signup and view all the answers

    What is the function of white albumen in eggs?

    <p>Nourishment and cushioning for the embryo</p> Signup and view all the answers

    What happens if an egg receives an X chromosome from the sperm in mammals?

    <p>Development of a female offspring</p> Signup and view all the answers

    What is the crucial trade-off in egg production?

    <p>Resource allocation between egg size and number produced</p> Signup and view all the answers

    What is produced after fertilization during oogenesis?

    <p>Polar bodies</p> Signup and view all the answers

    Study Notes

    • In mammals, fertilisation takes place inside the fallopian tube, while in birds, only the left ovary and oviduct remain functional in adults.

    • In birds, oogenesis starts with a number of primary follicles, each containing a primary oocyte surrounded by a granulosa layer.

    • Follicular development in birds involves the accumulation of yolk without the formation of a fluid-filled follicle.

    • The oocyte increases in size and moves closer to the ovary surface as it accumulates yolk.

    • During ovulation, only the yolk is released from the ovary, while the rest of the egg components are added along the oviduct.

    • Fertilisation occurs at the beginning of the oviduct in birds, with multiple sperms typically binding and fusing with the oocyte, but only one reaching the female pronucleus and fusing with it.

    • In mammals, the zygote is the fertilised egg that results from the union of a sperm and an egg, and the single cell undergoes cleavage to become subdivided into smaller cells.

    • The zygote contains all the essential factors for development, but they exist in encoded genetic instructions within the chromosomes.

    • In birds, follicular development involves the production of oestrogen, which stimulates the liver to produce yolk material for the growing follicles.

    • The largest follicle produces high levels of progesterone, which induces the luteinising hormone surge and leads to ovulation.

    • The ovary in the breeding season resembles a bunch of grapes, while outside of the breeding season, it resembles a collection of millet seeds.

    • In mammals, fertilisation begins with sperm-zona pellucida binding and ends with the initiation of zygote cell division.

    • In birds, multiple sperms bind and fuse with the oocyte, but only one reaches the female pronucleus and fuses with it.

    • In mammals, the zygote undergoes a brief stage before cleavage, during which all the essential factors for development exist in encoded genetic instructions.

    • The oviduct reduces in size outside of the breeding season and the ovary resembles a collection of millet seeds.

    • The yolk in birds appears as a viscous fluid with suspended granules and globules as the oocyte increases in size.

    • The largest follicle in birds produces high levels of progesterone and induces ovulation.

    • The oocyte in birds is activated by the fusion of the sperm head with the oocyte plasma membrane and undergoes meiosis, giving rise to an ovum and a second polar body.

    • The male and female haploid nuclei (pronuclei) fuse in the zygote in birds, restoring the diploid condition in the zygote nucleus.

    • In birds, the oviduct adds the white (protein) and the shell to the egg as it passes along it.

    • In mammals, the zygote immediately cancels its membrane potential and undergoes the cortical reaction, releasing enzymes and preventing polyspermy.

    • In birds, multiple spermatozoa bind and fuse with the oocyte membrane, but only one reaches the female pronucleus and fuses with it, initiating amphimixis.

    • Both sperm and egg contribute DNA, but the egg provides most of the cytoplasm for the zygote.

    • Egg cytoplasm is rich in nutrients and organelles for embryo survival, including nucleic acids, proteins, and mRNAs.

    • Egg provides membranes that protect the embryo before implantation, produced by the egg itself or follicle cells.

    • Primary membrane of the zygote is equivalent to the cytoplasmic membrane.

    • In mammals, secondary membranes include the pellucid zone and corona radiata, and in birds, the vitelline membrane.

    • Pellucid zone is a specialized glycoprotein layer surrounding the oocyte and consists of four types of zona pellucida glycoproteins.

    • Corona radiata is a layer of cells adhering to the outer surface of the zona pellucida.

    • In birds, the secondary membrane is equivalent to the vitelline membrane, which plays a crucial role in species-specific fertilization.

    • Tertiary membranes are specific to egg-laying animals, including the white albumen and shell membrane.

    • White albumen is a protein-rich fluid that surrounds the yolk in the egg.

    • Shell membrane is a double membrane surrounding the albumen and shell, formed of keratin and protecting the egg.

    • Shell is the outer covering of eggs in land animals, made of calcium carbonate and porous for gas exchange.

    • Yolk is the nutritive material in the cytoplasm of the female gamete, providing nourishment for the embryo.

    • Depending on the quantity and distribution of yolk, eggs are classified as oligolecithal, mesolecithal, or polylecithal.

    • Yolk has influenced animal evolution by providing essential nutrients for embryonic development.

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