Genetics Key Terms 2: Ploidy, Chromosomes, Division

Ploidy

The number of sets of chromosomes in a cell

Haploid

A cell/organism that has 1 set of chromosomes

Diploid

A cell/organism that has 2 sets of chromosomes

Polyploid

A cell/organism that has more than 2 sets of chromosomes

What does the variable n equal?

The number of chromosomes in a full set depending on the cell or organism and its state

What is the n value of a human?

n = 23, 2n = 46

Homologous Chromosomes

A chromosome pair that has the same genes in the same order, only with slight variations

Chromosome

A thread of DNA wrapped around proteins at a nucleus that carries genetic info

Chromatin

The material that composes chromosomes, roughly 40% DNA and 60% histone proteins

Histone Proteins

Proteins found in the center of eukaryotic cells; helps make up chromatin

Centromere

This is where the sister chromatids meet to create a long and short area of a chromosome; spindle fibers attach to this using the kinetochore during mitosis

Telomere

Protein and DNA structures found at the end of chromosomes that protect the DNA ends

(Sister) Chromatid

An identical copy of a chromosome that has not yet been separated after duplication

Chromosome Arms

The sections of a chromosome, split specifically by the centromere

Cohesin Protein

Protein complex that mediates sister chromatid cohesion, homologous recombination, and DNA looping.

Karyotype

A visual representation of someone’s full chromosome set, including names, sizes, and shapes

Autosomes

One of the numbered chromosomes besides those defining biological sex (humans have 22 sets)

Sex Chromosome

The 23rd set of chromosomes that helps to determine biological sets using X and Y genotypes

Genome

The total amount of all genetic info within an organism; helps to code genetic information

Somatic Cells

All cells in the body that are not related to reproduction

Meiocyte

Cells that produce gametes (reproductive cells) through the process of meiosis

Microtubule Organizing Center (MTOC)

Used during the interphase stage, these structures organize microtubular parts; creates the spindle apparatus to help divide cells

Microtubule

A thin, hollow tube structure located in the cytoplasm; helps notably with cell support and shape

Kinetochore

A complex of proteins related to the centromere of a chromosome; The microtubules attach to this area

Synapsis

The fusion of chromosome pairs at the start of meiosis

Synaptonemal Complex

A protein that forms in between and connects homologous chromosomes during meiosis

Chiasma (s.)

A point along the chromosome where non-sister chromatids entangle and swap bits of chromosomal material during meiosis

Chiasmata (pl.)

The area in which homologous chromosomes switch genetic material by crossing over during meiosis

Tetrad

2 pairs of homologous chromosomes next to each other during meiosis

Crossing Over

When genetic material is switched between paired homologous chromosomes, resulting in new genetic offspring