Genetics and Cell Division: Key Concepts for Biology

Allele

- Different forms of the same gene that can lead to different traits (like eye color variations)

Gene

- A segment of DNA that contains instructions for making proteins and determining traits

Genome

- The complete set of DNA in an organism, including all of its genes

Cell cycle -

The full sequence of stages a cell goes through to grow, copy DNA, and divide

Interphase

- The longest stage of the cell cycle where the cell grows and prepares for division

G1 phase -

First part of interphase where the cell grows and performs normal functions

S phase -

Part of interphase where DNA is replicated (copied)

G2 phase -

Final part of interphase where the cell prepares for division

M phase -

Stage when the cell actually divides (includes mitosis and cytokinesis)

Cell division -

The process where one parent cell splits into two daughter cells

Parent cell -

The original cell that divides

Daughter cells -

The two new cells formed after division

Mitosis

- A type of cell division that produces two identical diploid cells

Prophase

- Chromosomes condense, nuclear envelope breaks down, spindle begins forming

Metaphase

- Chromosomes line up in the middle of the cell

Metaphase plate -

The imaginary line where chromosomes align during metaphase

Anaphase

- Sister chromatids are pulled apart to opposite sides of the cell

Cytokinesis

- The division of the cytoplasm, forming two separate cells

Cleavage furrow -

The pinching in of the cell membrane during cytokinesis in animal cells

Chromosome

- A tightly coiled structure of DNA that carries genetic information

Chromatid

- One half of a duplicated chromosome

Sister chromatids -

Identical copies of a chromosome joined at the centromere

Centromere

- The region where sister chromatids are attached

Histones

- Proteins that DNA wraps around to stay organized

Condense(Condensation) -

When chromosomes coil tightly and become visible during division

Locus

- The specific position of a gene on a chromosome

Homologous chromosomes -

Pairs of chromosomes with the same genes (one from each parent)

Nuclear envelope -

The membrane that surrounds and protects the nucleus

Plasma membrane -

The outer boundary of the cell that controls what enters and leaves

Centrosome

- Structure that helps organize spindle fibers during cell division

Microtubules

- Protein fibers that move chromosomes during cell division

Meiosis

- A type of cell division that produces four haploid gametes (sex cells)

Meiosis I -

First division where homologous chromosomes separate

Prophase I -

Homologous chromosomes pair up and exchange DNA (crossing over)

Crossover

Exchange of genetic material between homologous chromosomes

Metaphase (Meiosis) -

Homologous pairs line up in the center

Anaphase (Meiosis I) -

Homologous chromosomes separate

Meiosis II -

Second division where sister chromatids separate

Gamete

- A sex cell (sperm or egg) with half the number of chromosomes

Germ cell -

A cell that undergoes meiosis to form gametes

Ova

- Female gametes (egg cells)

Haploid

- A cell with one set of chromosomes (n)

Diploid

- A cell with two sets of chromosomes (2n)

Ploidy

- The number of sets of chromosomes in a cell

Independent assortment -

Random distribution of chromosome pairs during meiosis

Sexual reproduction -

Reproduction involving the fusion of two gametes

Fertilization

- The joining of sperm and egg to form a zygote

Zygote

- A fertilized egg cell with a full set of chromosomes

Embryo

- An early stage of development after the zygote begins dividing

Down Syndrome -

A genetic condition caused by an extra copy of chromosome 21 (Trisomy 21)

Edwards Syndrome -

A genetic disorder caused by an extra chromosome 18

Turner Syndrome -

A condition where a female has only one X chromosome (XO)

Identical Twins -

Twins formed when one fertilized egg splits; genetically identical

Fraternal

Twins - Twins formed from two separate eggs fertilized by two sperm; genetically different