ZOO501 Midterm Solved Papers

Zoo501 mid term papers solved

AAMIR ALI AAMIR AND MALIK’S

What are the event of Fertilization?

Although the details of fertilization vary from species to species, conception generally consists of four major events:

• Contact and recognition between sperm and egg. In most cases, this ensures that the sperm and egg are of the same species.
• Regulation of sperm entry into the egg. Only one sperm can ultimately fertilize the egg
• Fusion of the genetic material of sperm and egg.
• Activation of egg metabolism to start development.

What are two main startegie of developmental commitment?

There appear to be two major strategies for establishing commitment and hence initiating the series of events that result in cell differentiation.

The inheritance of cytoplasmic determinants: Cytoplasmic determinants are the molecules in cytoplasm that can help to determine cell fate. The asymmetric distribution of cytoplasmic determinants indicates that the mechanism of differentiation is entirely intrinsic The perception of external inductive signals: The process where one cell or group of cells changes developmental fate of another is termed induction. It is extrinsic process that depends on the position of a cell in the embryo.

How Egg is protected form sunlight? Which of Egg protected form sunlight?

Many eggs contain ultraviolet filters and DNA repair enzymes that protect them from sunlight; some eggs contain molecules that potential predators find distasteful; and the yolk of bird eggs even contains antibodies.

Composition of Egg Yolk? Explain composition of Egg Yolk?

Yolk vitamins and minerals. Yolks hold more than 90% of the calcium, iron, phosphorus, zinc, thiamine, vitamin B6, folate, vitamin B12, and pantothenic acid of the egg. In addition, yolks cover all of the fat-soluble vitamins: A, D, E, and K in theegg, as well as all of the essential fatty acids.

What is gastrulation?

Gastrulation is a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a multilayered structure known as the gastrula.

Who discover sperm?

A.V Leeuwenhoek, the Dutch microscopist who co-discovered sperm in 1678

Name the three germ layer in animals?

1. Ectoderm 2. Mesoderm 3. Endoderm

How many type of mRNA are present in sea urching egg?

sea urchins contain 25,000 to 50,000 different types of mRNA.

Differentiate B/W Promoter and Enchancer?

Promoter: A region, which is responsible for the binding of RNA polymerase and for the subsequent initiation of transcription. Enhancer: It is a DNA sequence that can activate the utilization of a promoter, controlling the efficiency and rate of transcription from that particular promoter. The human β-globin gene has an enhancer in its 3´ UTR, roughly 700 base pairs

What are Somites?

Somites are precursor populations of cells that give rise to important structures associated with the vertebrate body plan and will eventually differentiate into dermis, skeletal muscle, cartilage, tendons, and vertebrae. ... Formation begins as paraxial mesoderm cells organize into whorls of cells called somitomeres.

What is different B/W Sex and Fertilization?

Fertilization: Fertilization is the process whereby two sex cells (gametes) fuse together to create a new individual with genetic potentials derived from both parents. Sex involves the combining of genes from two different individuals into new arrangements.

Conditional Specification?

Conditional specification: o Characteristic of all vertebrates and few invertebrates. o Specification by interactions between cells. Relative positions are important. Variable cleavages produce no invariant fate assignments to cells. o Massive cell rearrangements and migrations precede or accompany specification. o Capacity for "regulative" development: allows cells to acquire different functions.

What is difference B/W protocadherin and other Cadherin?

Protocadherins: Calcium-dependent adhesion proteins that differ from the classic Cadherins in that they lack connections to the cytoskeleton through catenins. Protocadherins have been found to be very important in separating the notochord from the other mesodermal tissues during Xenopus gastrulation. E-cadherin: Epithelial cadherin is expressed on all early mammalian embryonic cells, even at the 1-cell stage. Later, this molecule is restricted to epithelial tissues of embryos and adults. P-cadherin: Placental cadherin appears to be expressed primarily on the trophoblast cells (those placental cells of the mammalian embryo that contact the uterine wall) and on the uterine wall epithelium. N-cadherin: Neural cadherin is first seen on mesodermal cells in the gastrulating embryo as they lose their Ecadherin expression. It is also highly expressed on the cells of the developing central nervous system.

Describe anatomical approachesof developmental biology?

The basis of all research in developmental biology is the changing anatomy of the organism. What parts of the embryo form the heart? How do the tissues that form the bird wing relate to the tissues that form the fish fin or the human hand? Following important parameters weave together to form the anatomical approaches to development. Comparative embryology Evolutionary embryology Teratology Mathematical modeling

What is Microvilli? Microfilaments?

Microfilaments are necessary for cell division, and they also are used to extend the egg surface into small projections called microvilli, which may aid sperm entry into the cell.

Difference B/W Somatic Cell and Germ Cell?

Germ Cell: In many species a specialized portion of egg cytoplasm gives rise to cells that are the precursors of the gametes (the sperm and egg). The gametes and their precursor cells are collectively called germ cells, and they are set aside for reproductive function. Somatic Cell: All the other cells of the body are called Somatic cells. This separation of somatic cells (which give rise to the individual body) and germ cells (which contribute to the formation of a new generation) is often one of the first differentiations to occur during animal development.