Term
| Diploid cell to haploid cell |
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Definition
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Term
| How does oogenesis occur in the embryo? |
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Definition
1. Primordial germ cells multiply during migration to the ovary
2. Some mitotic divisions of oogonia occur within the ovary
3. No further multiplication occurs and a primary oocyte is formed whereby meiosis becomes arrested in prophase 1 |
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Term
| How does spermatogenesis occur in the embryo? |
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Definition
1. Primordial cells multiply during migration to the testis
2. Here the cells are arrested in the G1 phase of the cell cycle during crossover between two cells forming a 4n cell |
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Term
| How does oogenesis occur in an adult? |
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Definition
1. The primary oocyte continues growth and development of egg coat and cortical granules
2. Ovulation occurs whereby the cell completes division 1 of meiosis and forms a secondary oocyte and the first polar body
3. Ferlitization occurs whereby the cell undergoes the completion of division 2 of meiosis forming the second polar body
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Term
| How does spermatogenesis occur in an adult? |
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Definition
1. After birth the diploid spermatogonia continually multiply by mitosis in testis
2. Two stem cells crossover forming a 4n cell
3. The spermatocyte undergoes two round of meiotic division to form 4 haploid cells
4. These differentiate to give mature sperm cells |
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Term
| What is the main difference between oogenesis and spermatogenesis with age? |
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Definition
| The number of human oocytes decreases rapidly with age- sperm does not |
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Term
| What is the structure of sperm? |
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Definition
Sperm is split into two sections- the head and the tail.
Inside the head is the acrosomal vesicle and then the nucleus.
Inside the tail is the midpeice, containing mitochondria and behind that the flagellum. |
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Term
| How does mammalian sperm develop? |
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Definition
1. Between the golgi apparatus and the nucleus the acrosomal vesicle develops, the centriole moves to the cell wall on the other side of the nucleus and begins to produce the flagellum
2. As the flagellum grows the centriole moves in towards the nuclear wall
3. The mitochondria and golgi remnant move behing the nucleus near the flagella
4. Microtubules grow either side of the nucleus growing towards the flagella and the plasma membrane elongated
5. The mitochondria line up alongside the flagella and the plasma membrane engulfs it
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Term
| What is the structure of the flagella in a sperm cell? |
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Definition
The axoneme comprises of a bundle of microtubules.
Inside there are nine outer doublet microtubules surrounding a pair of singlet microtubules.
The doublets are split into two subfibres: A (13 profillaments) and B (10 profillaments).
Therefore they have a 9+2 arrangement |
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Term
| What model organism has sperm cells that cannot swim? |
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Definition
| C. elegans (ameboid sperm) |
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Term
| The acrosome or acrosomal vesicle contains: |
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Definition
| Enzymes that digest proteins and complex sugars that make up the egg coat |
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Term
| The acrosomal process is: |
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Definition
| A region of globular actin that lies between the acrosome and the nucleus |
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Term
| The haploid nucleus contains: |
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Definition
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Term
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Definition
| Just behind the nucleus and will form one of the two spindle poles at the first division |
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Term
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Definition
| Behind the centriole shealthing the base of the flagellum |
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Term
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Definition
| The central core of the flagellum and is composed of a superstructure of tubulin protein |
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Term
| What is the structure of the egg? |
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Definition
Surrounded by and outside jelly layer and a vitelline envelope.
Inside the cell cortical granules line the plasma membrane covered in microvilli, there are also mitochondria and yolk granules. |
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Term
| What does the egg have (also) that makes it specialized? |
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Definition
Nutritive proteins
Ribosomes and tRNAs
mRNAs
Morphogenic factors
Protective chemicals |
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Term
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Definition
| May be haploid or diploid and lies within the egg cytoplasm |
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Term
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Definition
| Rich in proteins (yolk), ribosomes, RNA, and other components required for embryogenesis |
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Term
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Definition
| A specialized part of the cytoplasm lying just under the egg membrane containing cortical granules. |
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Term
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Definition
| Encloses the egg cytoplasm and regulates ion flow during fertilization. |
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Term
| The vitelline membrane is: |
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Definition
| A thin glycoprotein meshwork surrounding the egg membrane often involved in sperm egg recognition. |
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Term
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Definition
| A second glycoprotein meshwork surrounding the egg that attracts or activates sperm. |
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Term
| What are the basic steps involved in sperm-egg recognition? |
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Definition
1. Chemoattraction of the sperm to the egg
2. Exocytosis of the sperm's acrosomal vesicle (acrosomal reaction)
3. The binging of the sperm to the extracellular structures (vitelline envelope)
4. The passage through the extracellular structures
5. Fusion of the egg and cell membranes |
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Term
| Explain the sperm-egg fusion in the mouse? |
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Definition
There is a cumulus layer and a zona pelludica protecting the egg.
1. Sperm is activated by the female reproductive tract
2. Sperm binds to zona pelludica
3. Acrosomal reaction
4. Sperm lyses hole in zona pelludica
5. Sperm and egg membrane fuse |
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Term
| What interactions happen at the egg surface? |
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Definition
The protein Bindin coats the inner membrane of the acrosomal vesicle, and the outside of the acrosomal process.
Bindins are species specific.
They interact with receptors on the egg surface and mediate interaction between the sperm and the egg membranes.
Bindin rceptors on the egg are limiting- restricting the number of sperm that can bind to the membrane. |
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Term
| Explain the acrosomal reaction in sea urchin sperm. |
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Definition
1. Initiated by species-specific interaction between sperm head and glycoproteins in jelly layer
2. The interaction opens ion channels that allow the influx of Ca2+ thats leads to exocytosis of the acrosomal vesicle
3. Proteolytic enzymes digest through the egg jelly layer
4. The Ca2+ influx also leads to polymerisation of the actun globule into an extended actin filament, covered in bindin, which is the acrosomal process. |
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