Bio LAB Fall 2023 - Mitosis/Meiosis Quiz Study

interphase

interphase

period of time between cell divisions. The nucleus appears normal, and the cell is performing it’s usual cellular functions. DNA replication occurs between G1 and G2 of interphase. chromosomes are then duplicated.

centromere

where the two sister chromatids are held together (the belt)

mitosis

nuclear division. The new nuclei receive the same number of chromosomes as the parent. (2n)

cytokinesis

when the cytoplasm divides and produces two daughter cells.

in multicellular organisms…

mitosis permits growth and repair of tissues.

in eukaryotic, unicellular organisms,

mitosis is asexual reproduction.

meiosis

part of gametogenesis, the production of gametes (sex cells). The daughter cells have half the number of chromosomes(n) as the parental cell.

MAKES 4 HAPLOID CELLS.

how does meiosis contribute to recombination of genetic material and variation among sexually producing organisms?

meiosis allows the crossing over of genetic material, and chromosomes occur in various combinations in daughter cells.

nucleoli

concentrated regions of RNA

chromatin

threadlike strands of DNA

at the start of mitosis/meiosis, the parental nucleus (surrounded by a double membrane) contains one or more nucleoli and chromatin suspended in a transparent liquid called

nucleoplasm

during division, chromatin condenses so that the chromosomes are visible, the nuclear envelop fragments, and a …

spindle appears

in mitosis, the most time is spent in…

interphase

interphase

G1 - cytoplasmic growth

S- DNA replication

G2 - structures involved in mitosis are synthesized

prophase (mitosis)

• chromosomes condense, nucleolus disappears, and nuclear envelope fragments.

• The spindle forms and the centrosomes (2 centrioles each) move to the poles.

• The duplicated chromosomes are two sister chromatids held together at the centromere

• Late prophase - the mitotic spindle occupies the space where the nucleus was.

• Microtubules stretch out in a star-like aster

• Chromosomes are attached to spindle fibers from opposite poles

mitotic spindle is made up of

poles, asters, and fibers (parallel microtubules)

metaphase

the sister chromatids are attached to the spindle and the chromosomes align at the metaphase plate (spindle equator)

anaphase

centromeres split, and sister chromatids at each chromosome separate, and move towards opposite poles of the spindle.

telophase

• the daughter chromosomes are at opposite poles, and the mitotic spindle dissolves.

• Nuclear envelope begins to reform around the daughter chromosomes at the poles.

• The chromosomes expand into chromosomes.

• cytokinesis - division of the cytoplasm

in plants, cytokinesis occurs by

cell plate formation. where Golgi body derived vesicles migrate to the spindle equator and fuse to contribute to the formation of the new cell wall.

in animal cells, cytokinesis occurs by

cleavage furrow, the cell pinches in two (boobies)

spermatogenesis

occurs in the testes, producing sperm.

• makes 4 sperm cells

oogenesis

occurs in the ovaries, producing eggs

• makes 1 egg and 3 polar bodies (nonfunctional cells that will dissolve)

meiosis reduces the number of chromosomes from

2n (diploid) to n (haploid).

meiosis - Prophase 1

duplicated chromatin condenses.

each chromosome is made of two sister chromatids

• homologues chromosomes (composed of two sister chromatids) are joined at the centromere

• Homologous chromosomes pair with each other (synapsis) and form a tetrad

• Crossing over (the end pieces flip, exchanging genetic material between two homologs)

meiosis - metaphase 1

homologous chromosomes align at the equatorial plate

meiosis - anaphase 1

homologous pairs separate with sister chromatids remaining together

meiosis - telophase 1

two daughter cells are formed with each daughter containing only one chromosome of the homologous pair

meiosis - prophase 2

DNA does not replicate, but the nuclear envelope disorganizes and the chromatin recondenses

meiosis - metaphase 2

chromosomes align at the equatorial plate

meiosis - anaphase 2

centromeres divide and sister chromatids migrate separately to each pole

meiosis - telophase 2

cell division is complete. Four haploid daughter cells are obtained

crossing over

occurs during prophase 1

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

when one or more pairs of chromosomes don’t separate during anaphase II.

produces gametes with too many (n+1) or too little (n-1) chromosomes and can cause trisomy or monosomy.

*

medical conditions caused by nondisjunction

• down’s syndrome - trisomy of chromsome 21

• patau syndrome - trisomy of chromosome 13

• edward syndrome - trisomy of chromosome 18

• kleinfelter syndrome - extra X chromsomes in males (XXY)

• turner syndrome - strange X chromosome dosage in females (XO, XXX)

• XXY syndrome - an extra Y chromosome in males

seminiferous tubules

where sperm formation occurs

interstitial cells

cells between the tubules, which secretes testosterone