DevBioLab MA1

Sexual Reproduction

It means that the life cycle involves the union of male and female gametes to form a fertilized egg or zygote.

spermatozoon (sperm)

• male gamete

• small and motile

egg or ovum

• female gamete

• large and immotile

gametes

formed from germ cells in the embryo

Germ cells

consisting of cells that will or can become the future gametes

Germ line

Collective term for germ cells

somatic tissues or soma

all other cells, excluding the germ cells

1. germ line

2. soma

The importance of the 1 is that its genetic information can be passed to the next generation, while that of the 2 cannot.

Meiosis

• critical cellular event in gamete production

• modified type of cell cycle in which the number of chromosomes is reduced by half

four

The process starts with the nucleus possessing a total DNA content of _____ times the haploid complement.

two

Meiosis involves ____ successive cell divisions

bivalents

In the first cell division, the homologous chromosomes, which are the equivalent chromosome derived from mother and father, pair with each other. At this stage the chromosomes are referred to as ______, and each consists of four chromatids, two maternal-derived and two paternal-derived.

Decribe the daughter cells produced in mitosis

• two duaghter cells

• genetically identical

• 2 identical cells, each with 2N chromosomes and 2X DNA content

1. germline 

2. meiosis

3. gametes (eggs and sperm)

All eukaryotic cells replicate via mitosis, except ______ cells that undergo ________ to produce _________.

prophase

The phase when chromosomes condense; each chromosome consists of a pair of identical sister chromatids joined at the centromere.

metaphase

The phase when chromosomes line up at the middle of the cell, along the plane of cell division, pushed and pulled by microtubules of the spindle apparatus.

anaphase

The phase when sister chromatids separate and migrate towards opposite ends of the cell.

Telophase

The phase when chromatids cluster at opposite ends of the cell and begin to decondense.

Cytokinesis

The phase when the membrane pinches in to divide the two daughter cells.

Isogamy

A form of sexual reproduction in simple organisms

Oogamy

A form of sexual reproduction in complex organisms

The 7 essential features of human reproduction

1. Liberation of an ovum, or egg, at a specific time in the reproductive cycle,

2. Internal fertilization of the ovum by

   spermatozoa, or sperm cells,

3. Transport of the fertilized ovum to the uterus, or womb

4. Implantation of the blastocyst,

   the early embryo developed from the fertilized ovum, in the wall of the uterus,

5. Formation of a placenta and maintenance

   of the unborn child during the entire period of gestation

6. Birth of the child and expulsion of the placenta,

7. Suckling and care of the child, with an eventual return of the maternal organs to virtually their original state

1. seminiferous tubules

2. testes

In males, the gametes are produced within the _____ of the _____.

1. germline epithelium

2. spermatogonia

3. spermatids

Each seminiferous tubule is surrounded by a basement membrane which is lined by ________, which will divide by mitosis to make _______ (which divide by meiosis to make __________)

1. spermatozoa

2. lumen

The spermatids differentiate into functional ________, which are then released into the ________ of the tubule.

Sertoli cells

• Nourishes developing spermatozoa

• reside in the tubule lining.

Leydig cells

The primary source of testosterone or androgens in males

Vas deferens

It transports mature sperm to the urethra in preparation for ejaculation

Spermatocytes

Cells that arise from the immature germ cells, spermatogonia

Spermatid

• Undifferentiated sex cells that differentiate and mature to form sperm cells

• immature form of the male gamete

• non-motile and round in shape

tubule (germline epithelium)

Spermatogenesis in the seminiferous tubules starts at the outer lining of the ___________.

Ovaries

In females, the gametes are produced by the ________.

Primordial follicles

They contain egg cells that have been arrested in prophase I (primary oocytes)

1. Graafian follicle

2. corpus luteum

In each cycle, one follicle will become a dominant _______ and rupture to release the secondary oocyte. The ruptured follicle will then develop into a short-lived _________.

Corpus luteum

It secretes key ovarian hormones, primarily the progesterone

corpus albicans.

The corpus luteum eventually degenerates into this structure.

FALSE. It does not.

[TRUE OR FALSE]

Like in spermatogenesis, the outer germline epithelium of the ovaries directly contribute to gamete formation

head, mid-piece and tail

Three sections of human sperm

a haploid nucleus, an acrosome cap and paired centriole

The head region of a human sperm contains these three structures:

Haploid nucleus

The region in a sperm that contains the paternal DNA (this will combine with maternal DNA if fertilization is successful).

Acrosome cap

The region in a sperm that contains hydrolytic enzymes which help the sperm to penetrate the jelly coat of the egg.

(Paired) centrioles

These are needed by a zygote to divide.

mid-piece

This section of the sperm contains high numbers of mitochondria which provide the energy (ATP) needed for the tail to move.

tail (flagellum)

This section of the sperm bends to facilitate movement.

axoneme

A microtubule structure in a sperm that allows the sperm to bend in order to move

1. zona pellucida (jelly coat)

2. corona radiata

A typical egg cell is surrounded by two distinct layers: the __________ and the ___________.

zona pellucida (jelly coat)

A glycoprotein matrix which acts as a barrier to sperm entry.

corona radiata

An external layer of follicular cells which provide support and nourishment to the egg cel

cortical granules

Structures within the egg cell which release their contents upon fertilization to prevent polyspermy.

haploid

Egg cells commonly include a ______ nucleus

ooplasm

The cytoplasm of the egg

Alecithal

A term that refers to having little or no yolk in the cytoplasm of the egg or ovum, such as in human eggs

aneuploidy

Errors in meiosis resulting in ________ are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities.

genetic recombination

A programmed process in which DNA is cut and then repaired, which allows them to exchange some of their genetic information.

crossover

Creation of physical links between the homologous chromosomes

chiasma (sing.) / chiasmata (plural)

These are links created during crossovers between the homologous chromosomes that are essential to direct each pair of homologous chromosomes to segregate away from each other during Meiosis I, resulting in two haploid cells that have half the number of chromosomes as the parent cell

polar bodies, ovum

In female animals, three of the four meiotic products are typically eliminated by extrusion into _______, and only one cell develops to produce an _______.

Developmental control genes

These are genes that are critical for pattern formation and cell fate specification during the development of multicellular organisms and are defined by their specific mutant phenotypes in genetic screens

housekeeping genes

genes are required in all cells

effector genes

genes that have highly specialized functions and are only required in certain differentiated cells or only under certain environmental conditions

Drosophila as model system

The first systematic genetic screen for embryonic phenotypes was performed using this organism as a model system

Developmental Biology

• Formerly known as embryology (during the time of Aristotle)

• Known as modern embryology

Five Problems in Developmental Biology

1. Differentiation

2. Morphogenesis

3. Growth

4. Reproduction

5. Evolution

Abnormal Development

Occurs when the development of an organism does not follow the usual pattern of formation

Gastrulation

The most critical period in the history of any organism 

Three Germ Layers

1. Ectoderm

2. Mesoderm

3. Endoderm

Ectoderm

• the outermost layer;

• gives rise to the skin and the nervous system

Mesoderm

• middle layer

• develops into several cell types such as bone, muscle, and connective tissueGives rise to

Endoderm

• innermost layer

• becomes the linings of the digestive and respiratory system, and forms organs such as the liver and pancreasives rise to

Growth Society

• American society for DevBio

• International groups of developmental biologists

Philippine Society for Developmental Biology

Counterpart of Growth Society in the Philippines

Zygote

• Forms upon the union of an egg and sperm cell (fertilization)

• Further develops into an embryo, and finally, a more complex organisms

Teratology

The study of congenital abnormalities (may be caused by chemicals, radiation, carcinogens, etc.)

Amniocentesis

A prenatal test that takes amniotic fluid from around your baby in the uterus for early detection of diseases, like Down syndrome

Newborn screening

A prenatal test for detection of congenital diseases/birth defects

Homunculus

• “Little man”

• Fully formed miniature human thought ot be present within reproductive cells

• Miniature adult or individualt

Preformationism

Theory that reproductive cells contain preformed adult individuals

Epigenesis

• Proposed by Aristotle

• A theory that individuals acquire final form through series of progressive changes

• In support of the cell theory

Gastrulation

Reorganization of organs in the embryo into three germ layers

Post-embryonic development

1. Metamorphosis

2. Regeneration

3. Aging

Spermatogenesis

Production of sperm

Oogenesis

Production of oocyte

Etymology of morphogenesis

Morpho: general form/structure; genesis: origin

Allometric growth

Varying rates of mitosis in regions of the embryo

Isometric growth

Equal rates of mitosis throughout the embryo

Gametogenesis

Formation and maintenance of pluripotent, haploid germ cells (gametes)

Diapause

• A state of arrested growth or reproduction of many hibernating or estivating arthropods

• A period of suspended development in an insect, other invertebrates, or mammal embryo, especially during unfavorable environmental conditions.

Girolamo Fabricci 

Founder of Modern Embryology

Christian Pander

He was able to describe the “germ cells” or germ layer

Heart

The first organ to develop in an animal embryo, followed by the cardiac muscles

Ancestral gills

Where pharyngeal arches were derived

William Harvey

Physiologist that disagreed with Aristotle

Gametogenesis

• Process of creating gametes

• Germ cells are set aside early in development

• Migrate to the gonad

• Undergo meiotic divisions to make haploid germ cells

mesoderm (middle layer)

Gonads arise from the _______ and is initially composed of somatic cells.

Hermaphrodites

Organisms that are capable of producing both sperm and eggs cells within the same individual (i.e. monoecious)

dioecious

Organisms that have the male and female reproductive organs in separate individuals.

reduction division

Another term for meiosis

Spermatogonia

Are the germ cells that will eventually develop into mature sperm

spermiogenesis

The process where sperm cells differentiate into the shape we commonly know by developing a tail

65 days (nearly 2 months)

It takes _________ for human males to produce a new batch of sperm cells.