ZOO501T Final Term Past Papers by Kainat Alvi

DEVELOPMENTAL BIOLOGY (ZOO501T) · CURRENT FINAL TERM PAPER FALL 2023(18-FEB) · SHORT QUESTIONS(3) · 1. Germ Layers

Animal development is the division of embryo into the three germ layers.

1. The ectoderm gives rise to the epidermis, nervous system, and pigment cells.
2. The mesoderm generates the kidneys, gonads, bones, heart, and blood cells.
3. The endoderm forms the lining of the digestive tube and the respiratory system.

Q2. Write the three name of vesicle formed in brain?

Neural tube balloons into three primary vesicles.

1. Forebrain (prosencephalon)
2. Midbrain (mesencephalon),
3. Hindbrain (rhombencephalon).

3. Composition of Hyaline Membrane

The hyaline layer is actually made up of two layers, an outer lamina made primarily of hyalin protein and an inner lamina composed of fibropellin proteins.

4. Deuterostomes:

In Deuterostomes ("mouth second"), the mouth opening is formed after the anal opening. Phyla in the Deuterostomes lineage include the chordates and echinoderms.

Q5. Which factor is responsible for cartilage specification?

Pax1 and Scleraxis are the transcription factors are thought to activate cartilage-specific genes.

6. Camptomelic Dysplasia

In humans, the SOX9 gene, which encodes a DNA-binding protein, is expressed in the precartilaginous condensations. Mutations of the SOX9 gene cause camptomelic dysplasia, a rare disorder of skeletal development that results in deformities of most of the bones of the body.

7. Spina Bifida

Failure to close the human posterior neural tube regions at day 27 (or the subsequent rupture of the posterior neuropore shortly thereafter) results in a condition called spina bifida, the severity of which depends on how much of the spinal cord remains exposed.

Q8. Failure to close the anterior neural tube regions results in a lethal condition called?

Failure to close the anterior neural tube regions results in a lethal condition, anencephaly.

Q9. Which type of egg present in birds or chicks?

Telolecithal egg is present in birds. It is a type of egg that has large amount of yolk that is unevenly distributed in the cytoplasm.

10.

Cleavage pattern in snail, sea urchin, nematode and tunicate?

In all four invertebrates described here, cleavage is holoblastic. In the sea urchin,cleavage is radial; in the snail, spiral; in the tunicate, bilateral; and in the nematode, rotational. In some, such as the sea urchin and tunicate, the axes are established at fertilization through determinants in the egg cytoplasm.

11.

Work of Lazzaro Spallanzani

The first evidence suggesting the importance of sperm in reproduction came from a series of experiments performed by Lazzaro Spallanzani in the late 1700s. Spallanzani demonstrated that filtered toad semen devoid of sperm would not fertilize eggs.

12.

Acrosomal Reaction

The acrosomal reaction is a process in which a sperm releases enzymes from a structure called the acrosome. This reaction helps the sperm penetrate the outer layer of the egg, known as the zona pellucida, allowing fertilization to occur.

13.

What happens when egg and sperm fuse together?

When an egg and sperm fuse, it's called fertilization. This is the moment when the genetic material from the sperm combines with the genetic material from the egg. It forms a new cell called a zygote, which is the very beginning of a new individual. The zygote then undergoes cell division and development to eventually form an embryo.

14.

Zp3 function in the fertilization process

ZP3 is a specific glycoprotein found in the outer layer of the egg called the zona pellucida. It acts as a binding site for sperm in mice. When sperm attach to ZP3, it triggers a reaction called the acrosomal reaction. This reaction allows the sperm to release proteolytic enzymes that help it penetrate and fertilize the egg.

15.

Define sub-germinal cavity and its function?

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. It gives the central part of the blastodisc a semitransparent appearance and this area is called the area pellucida.

16.

Embryonic Shield

The cells of both the epiblast and hypoblast intercalate on the future dorsal side of the embryo to form a localized thickening, the embryonic shield.

The embryonic shield is critical in establishing the dorsal-ventral axis in fishes. It can convert lateral and ventral mesoderm (blood and connective tissue precursors) into dorsal mesoderm (notochord and somites), and it can cause the ectoderm to become neural rather than epidermal.

17.

What is the Henson node?

At the anterior end of the primitive streak is a regional thickening of cells called the primitive knot or Hensen's node. The center of this node contains a funnel-shaped depression (sometimes called the primitive pit) through which cells can pass into the blastocoel. Cells migrating through Hensen’s node pass down into the blastocoel

18.

What is the umbilical cord?

The narrow connecting stalk of extra embryonic mesoderm that links the embryo to the trophoblast eventually forms the vessels of the umbilical cord

The umbilical cord connects the baby to the mother's placenta. During fetal development in the womb, the umbilical cord is the lifeline to the baby supplying nutrients. After birth, the cord is clamped and cut. Eventually between 1 to 3 weeks the cord will become dry and will naturally fall off.

19.

Function of retinoic acid:

In the retina, retinoic acid acts as a light-signaling neuromodulator and regulates gap junctionmediated coupling of retinal neurons. It has also been involved in the control of sleep and circadian clock.

Retinoic acid helps specify the ventral region of the neural tube, where motor neurons are located. It influences cell fate and positioning along the dorsal-ventral axis. Its role is crucial in the development and organization of the nervous system.

20.

Amnion sac

The amnion sac is a protective membrane that surrounds and cushions the developing fetus during pregnancy. It is filled with amniotic fluid, which provides a stable environment for the fetus to grow and move. The amnion sac plays a crucial role in protecting the fetus from external shocks and infections. It also helps regulate temperature and allows for the exchange of nutrients and waste between the mother and the fetus.

21.

Define hypoblast

Hypoblast is the term used to describe the lower layer of cells of the early bilaminar disc, most commonly in avian embryos: this layer is also termed anterior, or distal, visceral endoderm in mouse embryos.

22.

Trophoblast function?

embryonic portion of the placenta. The trophoblast helps facilitate the exchange of oxygen, nutrients, and waste products between the mother and the developing embryo. 23.

Neural plate?

During early development, a specific portion of the dorsal ectoderm is designated to become neural ectoderm. These cells can be distinguished by their columnar appearance. This region is referred to as the neural plate. The neural plate is a crucial early structure in embryonic development, serving as the precursor to the neural tube, which ultimately gives rise to the central nervous system.

24.

Neural Tube?

The neural tube develops from the neural plate. The neural tube is the rudiment of the central nervous system. It forms during embryonic development through a process called neurulation. The neural tube eventually develops into the brain at the anterior end and the spinal cord at the posterior end.

25.

Notochord

The notochord is like a flexible rod that helps shape the body of developing animals. It provides support and becomes part of the backbone in vertebrates. It helps form our skeleton.

26.

How neural grove is formed during primary neurulation?

Shortly after the neural plate has formed, its edges thicken and move upward to form the neural folds, while a U-shaped neural groove appears in the center of the plate, dividing the future right and left sides of the embryo.

The neural folds migrate toward the midline of the embryo, eventually fusing to form the neural tube beneath the overlying ectoderm. The cells at the dorsal most portion of the neural tube become the neural crest cells.

27.

Events of Primary Neurulation:

During primary neurulation, the original ectoderm is divided into three sets of cells.

1= The Internally positioned neural tube, which will form the brain and spinal cord.

2= The externally Positioned epidermis of the skin.

3= The neural crest cells. The neural crest cells form in the region that connects the neural tube and epidermis, but then migrate elsewhere; they will generate the peripheral neurons and glia, the pigment cells of the skin, and several other cell types.

28.

Difference between mantle zone and ventricular zone?

As the cells adjacent to the lumen continue to divide, the migrating cells form a second layer around the original neural tube. This layer becomes progressively thicker as more cells are added to it from the germinal neuroepithelium. This new layer is called the mantle (or intermediate) zone, and the germinal epithelium is now called the ventricular zone (and, later, the ependyma).

29.

Myogenesis

Myogenesis refers to the process of muscle formation in the body. It involves the development and differentiation of muscle cells, known as myoblasts, into mature muscle fibers. Myogenesis is regulated by various factors and signaling pathways that guide the formation and organization of different types of muscles in the body.

30.

How myotubes form?

The myotome cells producing the myogenic bHLH proteins are the myoblastscommitted muscle cell precursors. These cells align together and fuse to form the multinucleated myotubes, a characteristic of muscle tissue.

31.

Define osteoblast

During intramembranous ossification in the skull, neural crest derived mesenchymal cells proliferate and condense into compact nodules. Some of these cells develop into capillaries; others change their shape to become osteoblasts, committed bone precursor cells. The osteoblasts secrete a collagenproteoglycan matrix that is able to bind calcium salts. Through this binding, the prebone (osteoid) matrix becomes calcified.

32.

Fertilization In Mammals

In mammals, fertilization occurs internally. During sexual reproduction, the male releases sperm into the female reproductive system through sexual intercourse. The sperm then travel through the female's reproductive tract, eventually reaching the fallopian tubes, where they may encounter an egg.

If a sperm successfully penetrates the egg's outer layer, fertilization takes place. This results in the fusion of the genetic material from the sperm and the egg, forming a single cell called a zygote. The zygote then begins to divide and develop, eventually implanting itself into the uterus and continuing its growth into an embryo.

33.