lesson 8 and 9

mitosis, meiosis and sexual reproduction

Cyclins

Proteins that regulate the cell cycle by activating Cyclin-Dependent Kinases (CDKs).

MPF (Maturation Promoting Factor)

A complex of cyclin and CDK that drives the cell past the G2 checkpoint into mitosis.

Apoptosis

Programmed cell death, a mechanism used to eliminate damaged or unnecessary cells.

Contact Inhibition

A process that stops cell division when cells become crowded and touch one another.

Cell Theory

All living organisms are made of cells; cells are the fundamental unit of life.

Karyotype

Chromosome structure consisting of DNA and proteins, arranged as histones.

Histones

Positively charged proteins that bind to DNA and assist in its condensation.

Autosomes

Chromosomes 1-22, not involved in determining the sex of an organism.

Sex chromosomes

Chromosomes 45 and 46 that determine the sex (XX or XY) of an organism.

P-arm

The short arm of a chromosome.

Q-arm

The long arm of a chromosome.

Centromere

The region where the two arms of a chromosome attach and replicate.

Homologous chromosomes

Chromosomes of the same number that have similar genetic content.

Sister chromatids

Identical copies of a chromosome, attached at the centromere.

Non-sister chromatids

Chromatids from different homologous chromosomes.

Prokaryotic Cells

Simplistic, smaller cells without organelles, dividing by binary fission.

Eukaryotic Cells

More complex cells that contain organelles and divide by mitosis or meiosis.

Mitosis

Cell division resulting in two identical daughter cells.

Meiosis

Cell division producing four genetically different gametes.

Diploid

A cell with two sets of chromosomes.

Haploid

A cell with half the number of chromosomes (23).

Cell Cycle

The series of events that take place in a cell leading to its division and duplication.

Interphase

The longest phase of the cell cycle, encompassing G1, S, and G2 phases.

G1 Phase

Cell growth phase before DNA replication.

S Phase

Phase where DNA replication occurs.

G2 Phase

Phase following DNA replication, where the cell prepares for mitosis.

Prophase

First phase of mitosis where chromosomes condense and the nucleus degrades.

Metaphase

Phase of mitosis where chromosomes align at the metaphase plate.

Anaphase

Phase where sister chromatids are pulled apart to opposite poles.

Telophase

Phase where the nucleus reforms and chromosomes begin to decondense.

Cytokinesis

Final step in cell division where the cytoplasm splits to form two daughter cells.

Cancer

Uncontrolled cell growth leading to the formation of tumors.

Mitosis

A type of cell division that results in two identical daughter cells, serving processes like growth and repair.

Meiosis

A specialized form of cell division that produces haploid sex cells (gametes) from diploid germline cells.

Cytokinesis

The process where the cytoplasm of a parental cell divides into two daughter cells after mitosis or meiosis.

Interphase

The phase of the cell cycle where the cell spends the majority of its life, preparing for division.

G0 phase

A resting phase where a cell is not actively dividing and may remain metabolically active but does not prepare for cell division.

Diploid

A cell or organism that has two sets of chromosomes, one from each parent (e.g., humans have 46 total chromosomes).

Haploid

A cell that contains a single set of chromosomes (e.g., human gametes have 23 chromosomes).

Somatic cells

Non-reproductive cells in an organism that are diploid.

Germline cells

Reproductive cells that can give rise to gametes, capable of undergoing meiosis.

Reduction division

The first meiotic division, which reduces the chromosome number by half, creating haploid cells.

Homologous chromosomes

Pairs of chromosomes that are similar in shape, size, and genetic content.

Spermatogenesis

The process of forming sperm cells from germline cells in males.

Oogenesis

The process of forming egg cells from germline cells in females.

Zygote

The fertilized egg resulting from the fusion of a sperm and an egg cell.

Bivalents

Structures formed by homologous chromosomes during prophase I of meiosis, consisting of two homologs.

Crossing over

The exchange of genetic material between non-sister chromatids during prophase I of meiosis.

Nondisjunction

The failure of chromosomes to segregate properly during cell division, leading to aneuploidy.

Aneuploidy

A condition in which there is an abnormal number of chromosomes in a cell.

Trisomy 21

A genetic disorder caused by the presence of an extra chromosome 21, commonly known as Down syndrome.

Apoptosis

The process of programmed cell death that allows for the removal of damaged cells.

Gametes

Reproductive cells (sperm and eggs) produced through meiosis.

Tetrad

A group of four chromatids formed during prophase I of meiosis by the pairing of homologous chromosomes.

Phenotype

The observable characteristics or traits of an organism, often influenced by genetic variation.

Ova

The plural term for ovum, referring to female gametes (eggs).

Polar bodies

Cells produced during oogenesis that are non-functional and typically degenerate, leaving one mature egg.

Biological clock

The concept referring to the limited timeframe in which an organism can reproduce, especially relevant for females.

Microtubules

Cytoskeletal filaments that play a role in the movement of chromosomes during cell division.

Cohesin proteins

Proteins that hold sister chromatids together until they are separated during cell division.

Loci

The fixed position of a gene or genetic marker on a chromosome.

Karyotype

A visual representation of an individual's complete set of chromosomes, often used to identify chromosomal abnormalities.

Alleles

Different forms of a gene that can exist at a specific locus on a chromosome.

Menstrual cycle

The monthly cycle in females that involves oogenesis and preparation for potential fertilization.

Chiasma

The point at which paired homologous chromosomes exchange genetic material during crossing over in meiosis.

Cleavage furrow

The indentation that forms during cytokinesis in animal cells, leading to cell division.

Actin

A protein that forms filaments and is involved in muscle contraction and cellular movements, including cytokinesis.