Human Reproduction and Developmental Biology

Vocabulary flashcards covering the basics of developmental biology, historical theories, the cell cycle, and the processes of human gametogenesis based on the lecture transcript.

Developmental biology

A field in science that focuses on how a single cell undergoes a series of changes to form a complex embryo and eventually a complete individual with distinct anatomical features.

Zygote

A fertilized egg that results from the fusion of sperm and egg, which subsequently transforms into an adult organism.

Differentiation

The process by which a single fertilized egg gives rise to hundreds of specialized cell types, such as muscle, nerve, and blood cells, despite sharing the same genetic blueprint.

Pattern formation

The process where cells and tissues are arranged in specific, recognizable patterns throughout the body, such as the head being positioned anteriorly.

Homunculus

A concept from the $1600s$ and $1700s$ positing that reproductive cells contained miniature adult individuals with all anatomical features already present on a smaller scale.

Preformationism

A theory suggesting that development is simply the growth of a pre-existing individual present within the sperm or egg prior to fertilization.

Epigenesis

A theory dating back to Aristotle proposing that individuals arise from a relatively formless state through a series of progressive and gradual changes.

Cell theory

A biological principle developed by Schleiden and Schwann in the $1830s$ and $1840s$ stating that all living things are composed of cells and that new cells arise from pre-existing cells.

Caspar Friedrich Wolff

Often considered the father of modern embryology, he proposed that development is a gradual process of differentiation and organization rather than pre-existing growth.

Karl Ernst von Baer

An embryologist who formulated laws describing how embryos of different species resemble each other in early stages but diverge as development proceeds.

Heinz Christian Pander

The researcher credited with the discovery of the three germ layers (ectoderm, mesoderm, and endoderm) in chick embryos.

Gene regulatory networks

Interacting genes and their regulatory elements that control precise patterns of gene expression during the development of an organism.

Signal transduction pathways

Biochemical processes by which cells respond to signals from their environment to coordinate activities like cell fate determination and pattern formation.

Gametogenesis

The process of generating reproductive cells known as gametes (sperm in males and eggs in females) through meiosis and the involvement of germline stem cells.

Embryonic cleavages

A series of rapid mitotic divisions after fertilization that increase cell number without increasing the overall size of the embryo.

Gastrulation

A significant reorganization of the early embryo into three primary germ layers: ectoderm, mesoderm, and endoderm.

Organogenesis

The stage of development where specific organs form from the interaction of cells and tissues within the germ layers.

Metamorphosis

Post-embryonic development involving significant changes in form and function, typically observed in insects and amphibians.

Interphase

The longest phase of the cell cycle, accounting for approximately $90\%$ of its duration, consisting of the $G_1$, $S$, and $G_2$ stages.

S phase

The specific stage of interphase during which DNA replication takes place, resulting in the duplication of the cell's genetic material.

Kinetochores

Specialized protein structures located at the centromeres of chromosomes that facilitate microtubule attachment and mediate chromosome movement.

Metaphase plate

An imaginary plane equidistant from the two spindle poles where chromosomes align during the metaphase stage of mitosis.

Synapsis

The process occurring in the zygotene stage of Prophase I where homologous chromosomes pair up and align along their lengths.

Crossing over

The exchange of genetic material between chromatids of homologous chromosomes at specific sites called chiasmata, increasing genetic diversity.

Spermiogenesis

The post-meiotic phase of spermatogenesis where round spermatids eject most of their cytoplasm and differentiate into streamlined, mature sperm.

Residual body

A small membrane-limited bleb of cytoplasm shed during the final stages of spermiogenesis, breaking the cytoplasmic bridges between spermatids.

Dictyate resting stage

The prolonged meiotic arrest in the diplotene stage of Prophase I where primary oocytes remain dormant, potentially for $12$ to $40\,years$.

Polar bodies

Small, typically non-functional cells produced during the asymmetric cytokinesis of oogenesis that contain minimal cytoplasm.

Aneuploidy

The condition of having abnormal chromosome numbers, the risk of which increases with maternal age due to the loss of cohesin proteins in aging oocytes.