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Biology - BPT03 > Gametogenesis > Flashcards

Gametogenesis Flashcards

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1
Q

Meiosis

A 
Produce gametes.
4 genetically unique haploid cells.
Only in gonads (ovaries and testies).
2 divisions.
Meiosos 1: Separation of tetrads.
Meiosos 2: Seperation of homologous pairs(same as mitosis)
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2
Q

Prophase 1

A 
Homologues pair up: Tetrads.
Crossing over.
Mitotic spindle begins to form.
Nucleus and nuclear membrane disappear.
Chromosome start to condense.
Tetrads bind to microtubules from opposite poles.
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3
Q

Metaphase 1

A

Random alignment of tetrads on metaphase plate/equator.

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4
Q

Anaphase 1

A

Separation of tetrads into homologues. Random combination of paternal and maternal chromosomes in daughter cell.

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5
Q

Telophase 1

A

Mitotic spindle breaks.
Cytokinesis.
Two new haploid cells formed.

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6
Q

Crossing over

A

Exchange of corresponding portion of DNA between homologues chromosomes. Random. No chromatids are the same. New chromosomes with unique combination of genes.

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7
Q

Genetic variation

A

Each gamete is unique. Because of crossing over: Exchange of corresponding DNA between homologues chromosomes and random alignment on of tetrads on the equator.

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8
Q

Spermatogenesis

A 
Production  of sperm cells.
Timing: Couple of months.
Quantity: Millions per day.
Location: Produced in the seminiferous tubules in between Sertoli cells.
Production from puberty throughout life.
Presence of stem cells: Spermatogonia
Sperm cell: Spermatozoa.
Size: Smallest human cell.
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9
Q

Meiosis of sperm cells

A

Meiosis 1
Primary spermatocytes split into secondary spermatocytes.
Meiosis 2
Secondary spermatocytes split into spermatids.
Spermatids transformed into spermatozoa by spermiogenesis.

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10
Q

Oogenesis

A

Production of eggs.
Timing: at least one decade.
One secondary oocyte is produced per month.
Eggs produced upon fertilization.
Production from puberty until menopause (no stem cells: Oogonia).
Size: Largest human cell.
Ovaries are female gonads, where female gamete is produced.

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11
Q

Meiosis of eggs

A

Takes at least a decade to perform.
Meiosis 1 starts in embryonic life and stops in prophase 1.
Before ovulation, meiosis 1 is completed and meiosis 2 stops in metaphase.
After fertilization meiosis 2 is completed.
Oocytes are kept and develop in ovaries inside follicles.

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12
Q

After ovulation

A

Remnants of follicles transform into corpus luteum.
Secrete progesterone
Avoid mensturation
Prepare endometrium for implantation.

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13
Q

Fertilization

A 
Happens in distal portion of uterine tubes.
During ovulation secondary oocyte is released, surrounded by corona radiata and underlying zona pellucida.
5 steps:
1. Capacitation of sperm cells.
2. Acrosome reaction.
3. Cortical reaction
4. Completion of meiosis 2
5. DNA replication
6. Fusion of pronuclei
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14
Q
  1. Capacitation of sperm cells
A

Sperm cells become competent for fertilization.

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15
Q
  1. Acrosome reaction
A

Sperm burrows through corona radiata. Contact with zona pellucida starts the reaction. The reaction being, making a hole in the zona pellucida.

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16
Q
  1. Cortical reaction
A

Secondary oocyte move receptor for sperm cells to avoid polyspermy (more than one sperm in egg). Triggered by fusion of sperm with oocyte membrane.

17
Q
  1. Completion of meiosis 2
A

Formation of egg

18
Q
  1. DNA replication
A

Male pronuclei - 23 chromosomes

Female pronuclei - 23 chromosomes

19
Q
  1. Fusion of pronuclei
A

Male and female pronuclei fuse together. Zygote - single celled diploid.

20
Q

Early embryogenesis

A
  1. Fertilization
  2. Cleavage
  3. Implantation
  4. Gastrulation
  5. Neurulation
21
Q

Cleavage

A

Rapid mitotic division.
No increase in volume.
Zona pellucida still intact.
Cells smaller at each cleavage. Called Blastomeres.
Cells form compact mass through junctions called morula.

22
Q

Implantation

A

6-8 days after fertilization.
Morula becomes blastocyst.
Penetration in the endometrium.

23
Q

Blastocyst

A

Blastocoele - inner space
Trophoblast - cells surrounded by zona pellucida (syncitiontrophoblast, cytotrophoblast).
Zona pellucida - outer shell
Embryoblasts - former inner cell mass. totipotent embryonic stem cell.

24
Q

Trophoblasts

A

Syncitiontrophoblasts: Secretes human chorionic gonadropin. Lacunae filled with blood: uteroplacental circulation (nutrient supply). No menstration.

Cytotrophoblast

25
Q

Embryoblast

A

Epiblast: Close to amniotic cavity, close to blastocyst cavity. Primitive yolk sack.

Hypoblast

26
Q

Gastrulation

A

Formation of the 3 primary germ layers.
During week 3, totipotent until here.
Formation of the primitive streak on the embryonic disc.
Migration of cell from epiblast (source of all cells) inside the primitive streak.

27
Q

Epiblast

A

Form 3 primary germ layers

  • definitive Endoderm replaces hypoblast at the bottom.
  • Mesoderm in the middle
  • Ectoderm, cells that remain in the epiblast.
28
Q

Neurulation

A

Formation of the neural tube (will become central nervous system)

  • Formation of definitive notochord
  • Induction of neural plate
  • Development of paraxial mesoderm ->Somites
29
Q

Formation of definitive notochord

A
  • Notochordal process in mesoderm during gastrulation.
  • Notochordal canal.
  • Notochordal plate.
  • Folding of definitive notochord.
30
Q

Induction of neural plate

A

Above notochord.

  • Neural folds rise due to development of paraxial mesoderm.
  • Neural groove appears.
  • Closure forms neural tube (CNS) and neural crest (PNS).
31
Q

Development of paraxial mesoderm

A

Somites.
Sclerotome: vertebrae and ribs (surrounding neural tube).
Myotome: Skeletal muscle.
Dermatome: Dermis of skin.

31
Q

Development of paraxial mesoderm

A

Somites.
Sclerotome: vertebrae and ribs (surrounding neural tube).
Myotome: Skeletal muscle.
Dermatome: Dermis of skin.

Biology - BPT03 (15 decks)

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