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Early Developmental Steps quiz

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  • What is the first step of development in fruit flies?
    The first step is fertilization, where a sperm encounters and fuses with an egg.
  • How many nuclear divisions occur in the fruit fly embryo before cell membranes form around each nucleus?
    There are 13 nuclear divisions within a single cell membrane before membranes form around each nucleus.
  • At which nuclear division do primordial germ cells begin to form in fruit flies?
    Primordial germ cells begin to form at the 10th nuclear division.
  • What is the blastoderm, and when does it form in fruit fly development?
    The blastoderm is a single cell layer that forms around the embryo about 3 hours after fertilization.
  • What process follows the formation of the blastoderm in early development?
    Gastrulation follows, forming the three major germ layers: endoderm, mesoderm, and ectoderm.
  • What are the three germ layers formed during gastrulation, and what do they become?
    The endoderm forms the gut lining, the mesoderm forms tissues like bone and muscle, and the ectoderm forms the outer layer such as skin.
  • When does segmentation of the embryo begin in fruit flies?
    Segmentation begins after gastrulation, as the embryo starts forming distinct body segments.
  • What genes are expressed during the segmentation stage of fruit fly development?
    Hox genes are expressed during segmentation, helping to pattern the embryo.
  • Why are cell-to-cell interactions important during development?
    They allow cells to respond to signals from other cells or the environment, guiding proper differentiation.
  • Why is there limited cell-to-cell interaction during the earliest stages of development?
    There are few cells present, so there is less information and fewer signals exchanged.
  • What is an asymmetric egg, and how does it affect development?
    An asymmetric egg has molecules unevenly distributed, leading to different developmental outcomes in different regions.
  • How do nurse cells contribute to asymmetry in fruit fly eggs?
    Nurse cells produce bicoid protein on one side of the egg, creating an asymmetric distribution.
  • What is a symmetric egg, and how is development direction determined in such eggs?
    A symmetric egg has molecules evenly distributed, and the sperm entry point determines developmental direction.
  • In C. elegans, what determines which end of the embryo becomes anterior or posterior?
    The location where the sperm enters the egg determines the anterior-posterior axis.
  • How does the distribution of molecules differ between asymmetric and symmetric eggs?
    In asymmetric eggs, molecules are concentrated in specific regions, while in symmetric eggs, they are evenly distributed throughout.