bio 105 - fertilization and development 1

Development

Growth and maturation of individual organisms within their lifespan (single generation)

What does it mean to say that development is highly conserved?

It means that the processes involved in an organisms development from embryo to adult remain largely similar across different species, even if they are distantly related (indicating that these core developmental pathways have been preserved throughout evolution with minimal changes) (basic blueprint for development = shared among many organisms)

One haploid sperm fuses with one haploid egg to form what?

A diploid zygote

What gets regulated within the embryo?

The cell cycle is regulated to control rates of growth and cell division in the developing embryo.

How do embryo cells grow and divide?

They use energy and nutrients provided by the egg to grow and divide rapidly.

What does differentiation occur due to?

Changes in gene regulation caused by the activity of the cell signaling pathways.

As development proceeds, what occurs to the embryo's cells?

They become more differentiated as development proceeds with most eventually being locked into different cell fates.

Phases of frog development

fertilization, cleavage, gastrulation, & neurulation

Fertilization

Fusion of two gametes to form a zygote.

Gametogenesis

production of gametes

Where are gametes formed?

gonads (testes and ovaries)

What do primary spermatocytes and primary oocytes undergo to form haploid gametes?

These diploid cells undergo meiosis 1 and meiosis 2 to form haploid gametes.

Is gametogenesis different in males and females?

Yes, gametogenesis is different in males and females.

How do spermatocytes divide?

They divide SYMMETRICALLY, each diploid primary spermatocytes will go through meiosis 1 and meiosis 2 to produce 4 mature sperm.

How do oocytes divide?

They divide ASYMMETRICALLY, only one mature egg will be produced from meiosis 1 and meiosis 2 of a primary oocyte (polar bodies)

polar bodies

Cells produced in females that do not participate in reproduction.

How do sperm and egg cells initially interact?

Sperm swims toward eggs by following attractant molecules secreted by the eggs (detected by receptors on the sperm cell membrane).

As sperm contact the egg, what do sperm release?

Sperm release enzymes that digest the outer covering of the egg.

What happens at the end of fertilization?

The plasma membrane of one sperm fuses with the plasma membrane of the egg, leading to cytoplasmic fusion.

After the sperm releases enzymes that digest the outer covering of the egg, what happens?

An intracellular signaling cascade is initiated that permanently blocks the ability of other sperm to enter the egg diploid and initiates development. At this point, the cell is now diploid, and is referred to as a zygote.

Cells divide quickly without doing what?

Without growing, therefore, the resulting ball of cells stays roughly the same size.

Once the embryo begins to form a fluid filled internal cavity (blastoceol), what is it now called?

A blastula

Major cell development occurs within what?

It occurs within the embryo.

In gastrulation, blastula ___ into a gastrula and cells differentiate into 3 _____ ______

Invaginates, germ layers.

Gastrulation begins what?

The large scale differentiation of embryonic cells.

Endoderm

(Inner germ layer) Forms lining of gut, liver, pancreas, thyroid, lungs, and bladder.

Mesoderm

(Middle germ layer) forms limbs, muscles, kidneys, connective tissues, and notochord.

Ectoderm

(Outer germ layer) forms skin and nervous system.

germ line cells are…

…specialized on the production of gametes.

The zygote and early subsequent cells are totipotent, what does this mean?

This means that they are undifferentiated and capable of generating any kind of mature cell.

By what stage do cells start differentiation and have a restricted set of possible final cell fates?

By the blastula stage, cells are locked in!

Pluripotent

Able to give rise to multiple, but not all, cell types.