6: Meiosis, Germ Cells, And Fertilization Flashcards Preview

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Flashcards in 6: Meiosis, Germ Cells, And Fertilization Deck (23):

What occurs in leptotene phase of prophase?

Homologs begin to condense/pair


What occurs in zygotene phase of prophase?

Homologs pair and synaptonemal complex forms


What occurs in pachytene phase of prophase?

Synapsis is complete, crossing over occurs


What occurs in diplotene phase of prophase?

Synaptonemal complex begins to break down, homologs begin to separate but remain attached at chiasmata


What occurs in diakinesis phase of prophase?

Maximum condensation. Separate homologs and transition stage into metaphase


What is the synaptonemal complex?

Structure of transverse filaments that help with crossing over


What is nondisjunction?

Homolog fail to separate properly.
-common in egg development that worsen with maternal age


What is aneuploid?

-cells with abnormal chromosome number
- 90% trisomy 21, due to additional maternal chromosome


The primordial germ cell is not responsible for determining sex. What is?

-the genital ridge uses cell signaling to pull PGCs to their area
- the location of the genital ridge therefore, has large role in determining sex of individual


What is contained on the Y gene that promotes the formation of male sex?

-sex determining region located on Y chromosome
- causes cells to proliferate to form sertoli cells


Which protein is specific in activating sertoli-specific genes, such as anti-Mullerian hormone?



If SRY is present at the genital ridge, and we start with PGC, and somatic cells. What are the resulting 1) germ cells 2) supporting cells 3) sex-hormone producing cells 4) hormones produced?

1. PGC--> sperm
2. Somatic cell--> Sertoli Cells
3. Somatic cells---> Leydig cell
4. Testosterone formed from leydig cells


If SRY is absent at the genital ridge, and we start with PGC, and somatic cells. What are the resulting 1) germ cells 2) supporting cells 3) sex-hormone producing cells 4) hormones produced?

1. PGC--> egg
2. Somatic cell--> follicle cell
3. Somatic cell-->theca cell
4. Theca cells produce estrogen after differentiation


What are the five phases of prophase?

1. Leptotene
2. Zygotene
3. Pachytene
4. Diplotene
5. Diakinesis


What are the stages of oogenesis

1. PGC becomes oogonium
2. diploid oogonia proliferates in ovary
3. primary oocyte formed after entering meiosis
4. growth and development of primary oocyte
5. meiosis I completes and occyte is mature
6.secondary oocyte is arrested in meiosis II and completes after fertilization


What are the stages of spermatogenesis?

1. PGC enters gonad to become spermatogonium
2. diploid spermatogonia proliferate inside testes
3. primary spermatocyte forms
4. meiosis I completes to produce secdondary spermatocytes
5. meiosis II completes to form spermatids
6. spermatids differentiate into mature sperm


What cells are in close contact with the developing sperm, until they become mature?

sertoli cells in the seminiferous tubules


What components are required to maximize the odds of having fertilization occur?

1. albumin: extract cholesterol from the membrane, increasing the ability for acrosome to fuse
2. calcium and bicarbonate: activate adenyl cyclase for sperm to produce cAMP to power their flagella.


What are the major steps in fertilization?

1. sperm bind to the zona pellucida, using HAnidase to penetrate HA layer
2. acrosome reaction occurs, to reach the egg membrane
3. sperm and egg PM binds
4.sperm empty contents into the egg


What are crucial membrane proteins that are crucial to binding?

1. ZP 2,3 form long filaments
2. ZP 1: cross-links with those filaments


What is majorly affected in the cortical reaction?

1. zona pellucida releases enzymes to prevent more sperm binding
2. ZP3 is inactivated
3. ZP is cleaved, which further prevents sperm penetration


What is one method for men who have non-motile sperm to father children?

1.intracytoplasmic sperm injection, where an egg is injected with a single sperm


What type of men would benefit from intracytoplasmic sperm injection?

men who suffer from:
1. capacitation
2. low-motility
3. poor acrosome reaction sequence
4. poor PM fusion