Gametogenesis Flashcards
o Each of us began life as a single cell called a ____.
o A human embryo at about ___ weeks after conception shows development of distinctive features.
zygote
6–8
o The question of how a zygote becomes a fully developed human has been asked for centuries.
o In the 18th century, the prevailing theory for development was called ______.
preformation
What is preformation?
Preformation- the egg or sperm contains a miniature infant, or “homunculus” which becomes larger during development.
The preformation hypothesis was discredited through studying model organisms: What are model organisms? (3)
o These are species that are chosen for the ease with which they can be studied in the laboratory.
o Model organisms for developmental studies are Sea urchins, Frogs, Chicks and roundworms.
o Humans are not model organisms, but we are interested in our own development.
Development assures two main functions: self-____and self-____, which are intertwined.
organization
replication
What is growth?
The generation of cell number.
What is differentiation?
The generation of cell diversity.
What is morphogenesis?
The organization of differentiated cells into tissues and organs.
Development in many organisms consists of 6 stages. What are these stages?
- Gametogenesis
- Fertilization,
- Cleavage
- Gastrulation,
- Organogenesis
- Morphogenesis
How is development determined?
Development is determined by the zygote’s genome and molecules in the egg called cytoplasmic
determinants.
o ___ _____ is the specialization of cells in structure and function.
o _________ is the process by which an animal takes shape.
Cell differentiation
Morphogenesis
True or false
Gametogenesis (formation of gametes) is not necessarily considered part of embryonic development. Gametes are however important for reproduction.
True
Gamete cells have a ____ number of chromosomes. Both gametes contribute an ____ number of
chromosomes to the offspring.
haploid
equal
o Female gamete cells (eggs) are produced in the _____.
o Male gametes cells (sperm) are produced in _____.
ovaries
testes
Explain the function of the function of:
the yolk, cortisol granules, vitelline envelope. (3)
o The yolk or yolk granules which provide nutrients.
o Cortisol granules, small vesicles involved in fertilization.
o In addition, this sea urchin egg has Vitelline envelope and a jelly layer that protects the egg.
Sperm cells are small and _____.
motile
These ‘DNA with a propeller’ cells have four main components: (4)
o The head contains the nucleus and enzyme-filled structure called acrosomes
o The neck and middle piece contains mitochondria which provide ATP to power the tail
o The tail has flagellum which works as a propeller
What is spermatogenesis? (4)
o Formation of sperm is called spermatogenesis.
o Occurs throughout adolescence and adulthood.
o All four products of meiosis develop into mature gametes.
o Sperm production is continuous and prolific.
Steps of spermatogenesis (6)
Where is sperm produced?
o Sperm is produced inside the seminiferous tube.
o Stem cells that give rise to sperm are in the outer edge of the tube and are diploid.
What is oogenesis?
o Formation of eggs is called oogenesis.
o Production of primary oocytes is complete before birth.
What are the products of oogenesis?
o Only one of the products of meiosis develop into egg, the rest are called polar bodies and they degenerate.
o There are long interruptions in oogenesis
Production of mature gametes ceases at ___.
50
_____ divide via mitosis before birth to form primary oocyte.
During puberty the Primary Oocyte divide via meiosis to form _____ oocyte which get arrested at metaphase II.
During puberty the Primary Oocyte divide via meiosis to form secondary oocyte which get arrested at metaphase II
