ZOO501 Midterm Past Papers Complete

1)Differnce b/w Karyokinesis and Cytokinesis

Karyokinesis the mitotic division of the nucleus. The mechanical agent of this division is the mitotic spindle, with its microtubules composed of tubulin (the same type of protein that makes up the sperm flagellum). The second process is cytokinesis the division of the cell. The mechanical agent of cytokinesis is a contractile ring of microfilaments made of actin (the same type of protein that extends the egg microvilli and the sperm acrosomal process). The relationship and coordination between these two systems during cleavage, in which a sea urchin egg is shown undergoing first cleavage. The mitotic spindle and contractile ring are perpendicular to each other, and the spindle is internal to the contractile ring. The contractile ring creates a cleavage furrow, which eventually bisects the plane of mitosis, thereby creating two genetically equivalent blastomeres.

2)Polyadenylation

is the addition of a poly(A) tail to an RNA transcript, typically a messenger RNA (mRNA). The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. ... In many bacteria, the poly(A) tail promotes degradation of the mRNA. The poly(A) tail Confers stability on the messenger RNA. Allows the mRNA to exit the nucleus. Permits the mRNA to be translated into protein.

3)Marginal Zone/Belt

deep cells constitutes the area opaca. Between the area pellucida and the area opaca is a thin layer of cells called the marginal zone (or marginal belt).

4)Area Pellucida

Between the blastoderm and the yolk is a space called the subgerminal cavity. This space is created when the blastoderm cells absorb fluid from the albumin ("egg white") and secrete it between themselves and the yolk. At this stage, the deep cells in the center of the blastoderm are shed and die, leaving behind a onecellthick area pellucida.

5)Area Opaca

deep cells constitutes the area opaca

6)Dendrites

The fine extensions of the neuron that are used to pick up electrical impulses from other cells are called dendrites. Some neurons develop only a few dendrites, whereas other cells (such as the Purkinje neurons) develop extensive dendritic trees.

7)Fertilization:

The process of combining the male gamete, or sperm, with the female gamete, or ovum. The product of fertilization is a cell called a zygote.

8)Somites

Once the neural tube has formed, it induces changes in its neighbors, and organogenesis continues. The mesodermal tissue adjacent to the notochord becomes segmented into somites, the precursors of