Reproduction and Cell Division Essentials

Comprehensive vocabulary covers reproduction types, genetic structures, human chromosomes, the cell cycle stages, and fundamental inheritance terminology.

Asexual Reproduction

A form of reproduction characterized by rapid population growth, low energy requirement, and offspring that are genetic copies of the single parent.

Primary Disadvantage of Asexual Reproduction

There is no genetic diversity.

Gametes

Specialized sex cells required for sexual reproduction; in animals these are sperm (male) and ovum (female), and in plants they are pollen (sperm) and ovum (egg).

Fusion

The process in sexual reproduction where two sex cells join together to create a new and genetically different offspring.

Advantages of Sexual Reproduction

Includes more genetic diversity, adaptability, variation, and a greater chance of survivability when faced with environmental change.

DNA

Deoxyribonucleic acid; the molecule that carries genetic information.

Nitrogen Bases of DNA

Adenine, Guanine, Thymine, and Cytosine.

Gene

A segment of DNA that carries instructions for a trait.

Chromosome

A thread-like structure made of DNA and proteins that carries genes.

Centromere

The region of a chromosome that joins sister chromatids and serves as an attachment point for spindle fibers.

Telomere

The structure found at the ends of the short and long arms of a chromosome.

Autosomes

The first 22 pairs of human chromosomes that are not sex chromosomes.

Sex Chromosomes

The 23rd pair of chromosomes that determine the sex of an individual, represented as $XX$ or $XY$.

Somatic Cells

Body cells that divide continuously and receive an exact copy of all the parent cell's DNA through mitosis.

Mitosis

The process of somatic cell duplication.

Diploid

$2n$; containing the full number of chromosomes in pairs, which is $46$ (23 pairs) in humans.

Haploid

$n$; containing half the number of chromosomes, which is $23$ in human eggs and sperm.

Interphase: $G1$

The phase where the cell grows, produces proteins, performs normal functions, and makes more organelles.

Interphase: $S$

The phase where DNA is copied (DNA Replication) and each chromosome now has two identical sister chromatids.

Interphase: $G2$

The phase where cells grow more, organelles increase, the cell checks copied DNA for errors, and produces proteins for mitosis.

Prophase

The first stage of mitosis where chromatin condenses into chromosomes, sister chromatids become visible, the nuclear membrane disappears, and spindle fibers begin forming.

Centriole

Cylindrical protein tubes that play a vital role in organizing the spindle fiber.

Spindle Fiber

Fibers whose purpose is to equally separate and distribute chromosomes into two new daughter cells.

Metaphase

Stage of mitosis where chromosomes align at the equator (metaphase plate) and spindle fibers attach to centromeres.

Anaphase

Stage of mitosis where sister chromatids separate and move to opposite poles.

Cleavage Furrow

The indentation that forms on the surface of an animal cell during cytokinesis which pinches the parent cell until it splits into two separate daughter cells.

Telophase

Final stage of mitosis where chromosomes reach opposite poles, nuclear membranes reform, and chromosomes uncoil.

Chromatin

A complex combination of DNA, RNA, and proteins whose primary role is to tightly package long DNA molecules to fit into the nucleus.

Heredity

The passing of traits from parents to offspring.

Trait

A characteristic or feature of an organism.

Fertilization

The joining of sperm and egg cells to form a zygote.

Variation

Differences in traits among individuals of the same species.

Allele

A different form of a gene.

Dominant

An allele that is expressed when at least one copy is present.

Recessive

An allele that is expressed only when two copies are present.

Genotype

The genetic makeup of an organism; the combination of alleles it has.

Phenotype

The observable traits or appearance of an organism.

Homozygous

Having two identical alleles for a trait.

Heterozygous

Having two different alleles for a trait.

Punnett Square

A diagram used to predict possible offspring genotypes and phenotypes.