BIOL 401 Final: Exam IV Study – Lecture 19

3 Pages

Course Code
BIOL 401
Steven P Tammariello

This preview shows page 1. Sign up to view the full 3 pages of the document.
Exam IV Study – Lecture 19 This notes set focused on developmental biology, particularly of vertebrates. The entire developmental process is carried out by ligands, which bind to receptors on a cell to trigger transduction. It’s important to note that the ligand doesn’t pass into the cell; they are entirely extracellular signals. Also remember that membrane bound receptors are not transducers, that happens inside the cell. Once bound to the receptor, the ligand will bind to another ligand/receptor complex and dimerize, triggering a secondary messenger cascade. The three ligands/receptors we HAVE to know for the exam are as follows: 1. FGF/tyrosine kinase: limb growth 2. TGFβ/serine threonine kinase: epidermal specification 3. Hedgehog/patched receptor: ventral spinal cord Possibly the most important of the above ligands is hedgehog (aka shh). It’s responsible for the induction of the ventral spinal cord via the notochord. The notochord secretes shh, causing the differentiation of certain structures to occur. Cells closest to the notochord, thus in contact with the highest concentration of shh, will develop into the floor plate. Membrane development will also occur here. Areas with low shh will develop into ventral neurons. I’ll get into this more later. Sexual development is determined by signal pathways, particularly testosterone. Before sexual development there are two ducts present: the wollfian duct and the mullerian duct. In the presence of testosterone the mullerian duct will degenerate, while the wollfian duct will develop into male structures such as the vas deferens and testes. However without exposure to testosterone, the wollfian duct will degenerate while the mullerian duct will remain intact, eventually developing into female structure such as the ovaries. Another major topic discussed is oogenesis. This process begins with oogonium, which as somatic cells destined to become eggs. First the oogonium undergoes massive growth to become a primary oocyte. At this stage yolk, which is generate in the liver, is imported into the primary oocyte. Know that the vitellogenin and VLDL are associated with this, and that they are taken up by the LR8 receptor. It then undergoes its first meiotic division to form a secondary oocyte. This splits the cell into an egg and first polar body. It’s at this stage where the cell enters developmental arrest until it’s ready for maturation. These secondary oocytes are stored in the ovaries for up to 50 years. Once ready to mature, the egg will undergo its second meiotic division to become a haploid ootid, and may undergo further maturation to become a completely mature egg. We need to know the process of chicken egg development for the exam (ugh). Beginning in the ovary, a structure called the infundibulum acts as the site of fertilization. The now fertilized egg, also called a blastodisc at this stage, travels down the oviduct. The first half of the oviduct is called the magnum, which is where egg white proteins such as albumen are added. The second half is called the isthmus, which is where a shell membrane is added. Once through the oviduct the egg passes to the uterus, where a calcium carbonate shell is added over the initial shell was added. Sperm development is another important topic discussed in class. The sperm cell, called a spermatogonium, undergoes meiosis to become a spermatozoon, which is a mature sperm. The spermatozoon contains several structures, including a sac of enzymes called the acrosome, two centrioles, and protamine
More Less
Unlock Document

Only page 1 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.