Mitosis and Meiosis

Genes

Smallest unit of heredity, usually referring to a segment of DNA that codes for a protein

• Also non-coding RNA

Genetic Continuity

Chromosomes are transmitted from one generation to the next very precisely

Eukaryotic Chromosomes vs Bacterial Chromosomes

Eukaryotes = linear

Prokaryotes = circular

Glycocalyx

Outside layer of animal cells made of glycoproteins and polysaccharides, which provides biochemical identity to cells

Cytosol

Liquid in which everything in the cytoplasm resides

Cytoskeleton

Tubules (microtubules and microfilaments) and filaments that give the cell its shape

Microtubules

Made of the protein tubulin

Microfilaments

Made of the protein actin

Rough ER

Ribosomes present, the site of synthesis (translation) of membrane proteins and proteins destined for export from the cell

Smooth ER

Ribosomes not present, the site of fatty acid and phospholipid synthesis

Mitochondria

The site of oxidative phosphorylation, the production of ATP

Chloroplasts

Structure associated with photosynthesis

Endosymbiosis

Bacteria developed instead of archaea and developed a symbiotic relationship

Eukaryotes

Organisms that have a nucleus and membranous organelles, ex. fungi, plants, animals

Prokaryotes

Lack a nucleus, lack membrane-bound organelles, and lack mitochondria and chloroplasts,, ex. bacteria and archaea

Nucleus

Houses genetic material

Nucleolus

Within the nucleus; where ribosomal RNA (rRNA) is made and the first steps of ribosome assembly occur

Nucleolar Organizer Region (NOR)

The portions of DNA that encode rRNA genes contain many repeats of rRNA genes

Nuclear Pore

Where molecules enter and exit the nucleus

Chromatin

Diffuse network of DNA and associated proteins in a non-condensed form

Centromere

The region of the chromosome that the spindle attaches to

Kinetochore

A protein complex that forms at the centromere and facilitates spindle attachment

Metacentric

Center of chromosome

Submetacentric

Between the center and end

Acrocentric

Towards the end

Telocentric

End

Diploid

Each cell/individual contains two complete sets of species’ genes, thus one of each chromosome

Haploid

Single set of chromosomes

Homologous Pairs

Pairs of chromosomes containing the same genes, but may have different alleles of those genes

• Length and centromere location is the same

Biparental Inheritance

One pair of chromosomes is paternally derived and one is maternally derived

Sister Chromatids

Products of a chromosome that has replicated

• Have identical sequences

Mitosis

Process by which one cell replicates its genetic material and divides to yield two genetically identical daughter cells

Karyokinesis

Separating the replicated genetic material evenly

Cytokinesis

Splitting of cytoplasm to create two daughter cells

Centrioles

Move to opposite ends of the cell to an area called the centrosome during prophase

Prophase

Centrioles move to opposite ends towards the centrosome, nuclear envelope begins to break down, chromosomes condense into visible structures,the and form sister chromatids held together by cohesin

Prometaphase

Centrioles reach opposite poles, spindle fibers form, kinetochore binds to centromere, and spindle fibers attach to kinetochore; cohesin is degraded by separase, but shugoshin protects cohesin from being degraded at the centromere. Sister chromatids migrate to the metaphase plate

Centromeric Region

A locus on a chromosome

Cohesin

Holds chromosomes together along their length in prophase

Metaphase

Refers to the moment when all chromosomes are align on the metaphase plate

Anaphase

Disjunction: Sister chromatids, held together only at the centromere, disjoin; shugoshin unbinds at the centromere, allowing for the remaining cohesin to breakdown

Telophase

Complete sets of chromosomes on both ends of the cell; cytokinesis occurs, whereby the one cell physically separates into two, nuclear envelope starts to reform, and chromosomes start to decondense

Animal Telophase

Constriction of the cell membrane along the metaphase plate, forming a cell furrow

Plant Telophase

A cell plate is formed between the two daughter cells and serves as the site for the construction of a new cell wall to divide the cells

Cyclins

Proteins expressed at different points in the cell cycle that bind to cyclin-dependent kinases, activating them and allowing them to phosphorylate their target

Binary Fission

Genetic material is replicated and partitioned into two identical daughter cells

Meiosis

The process by which gametes are produced. Reduces ploidy from diploid to haploid

Reductional Division

Pulling homologous chromosomes apart instead of having both of those chromosomes lined up on the metaphase plate, and independently pulling them apart

Crossing Over

The exchange of genetic material between homologs

Prophase I: Leptonema

Chromatin begins to condense and chromosomes become visible

Prophase I: Zygonema

Synaptonemal complex forms, and homologs are lined up end to end

Synaptonemal Complex

Variably required for homolog pairing and recombination (crossing over) to occur in eukaryotes

Pachynema

Homologs become more closely associated and undergo synapsis; crossing over occurs, each chromosome is clearly now a double structure referred to as a tetrad

Diplonema

Homologs separate slightly but are held together at recombination sites called chiasmata

Diakinesis

Terminalization: Chiasmata move to the end of chromosomes; results in non-sister chromosomes held together only at their ends; nucleolus and nuclear envelope break down

Disjunction

Homologous pairs are pulled apart during anaphase I

Nondisjunction

If homologs fail to separate

Pseudoautosomal Region (PAR)

A small region where X and Y chromosomes contain similar sequences and align as homologs

Spermatogenesis

Production of sperm; yields 4 spermatids with equal amounts of cytoplasm, continuous process in males after puberty

Oogenesis

Production of eggs; one cell receives more cytoplasm, and the second oocyte (polar body) doesn’t undergo meiosis II, unequal division of cytoplasm, only one gamete (ovum) is produced