Mitosis and Meiosis

Bio 101 Lab Quiz

Mitosis

growth, repair, and asexual reproduction

Meiosis

sexual reproduction, producing gametes.

Interphase

• Dividing cells experience nuclear division, cytoplasmic division, and a period of time between divisions

• nucleus appears normal and the cell is performing its usual cellular functions.

• cell is increasing all of its components, including such organelles as the mitochondria, ribosomes and centriole

Centromere

chromosomes, which contain DNA, are duplicated and contain two chromatids held together here

cytokinesis

when cytoplasm divides, two daughter cells
are produced

gametogensis

production of gametes (sex cells)

chromatin

threadlike strands of DNA

nucleoplasm

transparent liquid

G1

cytoplasmic growth takes place

S

DNA is duplicated

G2

structures directly involved in mitosis are synthesized

prophase

the chromosomes condense, the nucleolus
disappears, and the nuclear envelope fragments. The spindle begins to assemble
as the centrosomes, each containing two centrioles, migrate to the poles. The already
duplicated chromosomes are composed of two sister chromatids held at the
centromere. During late prophase, the mitotic spindle occupies the region formerly occupied by the nucleus. The spindle consists of poles, asters, and fibers, which are bundles of parallel microtubules. The chromosomes become attached to spindle fibers coming from opposite poles

metaphase

The sister chromatids are attached to the spindle and the chromosomes are aligned at the spindle equator

anaphase

the centromeres split, and the sister chromatids of
each chromosome separate, and begin to move toward opposite poles of the spindle

fertilization

occurs when the nucleus of a sperm fuses with the nucleus of an egg

Crossing over

results in reshuffling of alleles on the chromatids, and occurs during prophase I. During synapsis, the chromatids break and portions of chromatids bearing genes for the same characteristics are exchanged between non-sister chromatids

Independent assortment

segregation of alleles into gametes is independent of the segregation of alleles for other traits, as long as the genes are on different sets of homologous chromosomes

Nondisjunction

one or more pairs of chromosomes fail to separate in anaphase I or
anaphase II. The result is gamete nuclei with too many (n+1) or too few (n-1)
chromosomes, and is a common mechanism for trisomy or monosomy