Cytogenetics Lesson 4: Meiosis, Development, & Aging

Comprehensive vocabulary flashcards covering the reproductive system, stages of meiosis, spermatogenesis, oogenesis, prenatal development milestones, and factors affecting maturation and aging.

Gametes

Sex cells, namely sperm and oocytes, which are the first cells that lead to the development of a new individual.

Gonads

Paired tubular structures where sperm and oocytes are made, which also produce hormones and secretions that control reproduction.

Testes (Testicles)

Male gonads containing seminiferous tubules, located within the scrotum to keep them cooler than the rest of the body for sperm development.

Epididymis

A tightly coiled tube where male sperm cells mature and are stored.

Ductus Deferens

A tube that bends behind the bladder to join the urethra, serving as the exit path for sperm and transporting seminal fluid.

Prostate Gland

Gland that produces a thin, milky, acidic fluid which activates sperm to swim.

Seminal Vesicles

Glands that secrete fructose for energy and prostaglandins which may stimulate female contractions to help gametes meet.

Bulbourethral Glands

Pea-sized glands that secrete an alkaline mucus to coat the urethra before sperm release.

Ejaculation

The discharge of sperm from the penis, delivering between $200$ million to $600$ million sperm cells.

Fallopian Tube

One of two uterine tubes with finger-like projections that carry the oocyte toward the uterus.

Meiosis

Reproductive cell division occurring in the gonads that reduces the number of chromosomes by half to produce gametes.

Germline Cells

Special cells where gametes form.

Homologous Pairs (Homologs)

Chromosome pairs that have the same genes in the same order but may carry different alleles or variants.

Haploid ($1n$)

A cell containing only one of each type of chromosome.

Diploid ($2n$)

A cell containing two copies of each chromosome type.

Polyploid

A genetically overloaded cell that usually undergoes only a few divisions before stopping.

Meiosis I: Reduction Division

The first division of meiosis which reduces the number of replicated chromosomes from $46$ to $23$.

Meiosis II: Equational Division

The second division of meiosis which splits replicated chromosomes to produce four cells from the two formed in the first division.

Synapsis

An event during Prophase I where homologs line up next to one another gene by gene.

Crossover

The process during Prophase I where homologs exchange genetic parts.

Leptotene

The first stage of Prophase I where chromosomes condense and homologs starts to pair up.

Zygotene

The stage of Prophase I where synaptonemal complexes form as homologs continue to pair.

Pachytene

The stage of Prophase I where homologs are fully paired and genetic recombination (crossing over) occurs.

Diplotene

The stage of Prophase I where synaptonemal complexes dissolve but homologs remain attached at chiasmata.

Diakinesis

The final stage of Prophase I where the nuclear envelope breaks down completely and the spindle apparatus forms.

Independent Assortment

The random alignment of chromosomes during Metaphase I ensuring the fate of a gene on one chromosome does not influence a gene on another.

Spermatogenesis

The formation of sperm cells, beginning in a diploid stem cell called a spermatogonium.

Acrosome

A membrane-covered area on the front of the sperm head containing enzymes to penetrate oocyte layers.

Oogenesis

The process of egg making, beginning with a diploid cell called an oogonium.

Polar Body

A small cell with very little cytoplasm produced during the unequal divisions of oogenesis.

Paternal Age Effect

A phenomenon where older men are more likely to produce gametes with dominant single-gene mutations due to frequent stem cell division.

Embryo

A prenatal human for the first $8$ weeks of development.

Fetus

A prenatal human organism from the start of the $9$th week until birth.

Capacitation

A process in the female reproductive tract that chemically activates sperm.

Corona Radiata

A covering of follicle cells that guards a secondary oocyte.

Zygote

A fertilized ovum.

Morula

An embryo consisting of a solid ball of sixteen or more blastomeres.

Blastocyst

A hollow ball of cells with a fluid-filled center (cyst) and an inner cell mass.

Human Chorionic Gonadotropin (hCG)

A hormone secreted by the trophoblast that prevents menstruation and is a detectable sign of pregnancy.

Gastrula

A three-layered primordial embryo consisting of the ectoderm, mesoderm, and endoderm.

Epigenetic

Changes to DNA expression that do not alter the DNA nucleotide base sequence.

Placenta

An organ that links the woman and fetus, secretes hormones, and sends nutrients to the fetus.

Monozygotic (MZ) Twins

Identical twins that descend from a single fertilized ovum.

Organogenesis

The transformation of the three germ layers into distinct organs.

Neural Tube

A structure that develops into the brain and spinal cord; a defect occurs if it does not close by day $28$.

Teratogens

Chemicals or other agents, such as Thalidomide or alcohol, that cause birth defects.

Aging

The gradual deterioration and functional physiological decline that occurs as an person gets older.