Cell and Molecular Bio Ch. 14 Part II

What happens during prophase of mitosis

• chromosomal materials condense to form mitotic chromosomes

• cytoskeleton disassembles and mitotic spindle assembles

• nuclear envelope disperses

what happens during PROmetaphase of mitosis

• kinetochores of chromosomes attach to mitotic spindle

• chromosomes are moved to the spindle equator

what happens during metaphase of mitosis

• chromosomes are aligned along metaphase plate

what happens during anaphase of mitosis

• chromatids split and chromosomes move to opposite spindle poles

what happens during telophase of mitosis

• chromosomes cluster at opposite spindle poles

• nuclear envelope forms around clusters

• daughter cells formed by cytokinesis

(ER and Golgi reform)

Cytokinesis in animal cells

• starts with the (blank) of the cell surface

• what is the contractile ring theory

• the site of (blank) assembly aka the plane of cytokinesis, is determined by a (blank) coming from the spindle poles

• indentation

• a thin band of actin and myosin filaments cleave the cell

• filament, signal

abscission

• final step of cytokinesis

hayflick limit

• also called the replicative senescence

• the upper limit of times a cell will divide

telomeres

• protective, repeated DNA sequences found on the ends of chromosomes

what happens when telomeres become short

• when telomeres become critically short, the cell enters a state of senescence (growth arrest)

• if cells bypass senescence, this leads to genomic instability

how do cancer cells benefit from telomerase

• some cells express and enzyme called telomerase, which allows them to maintain telomere length and bypass the hayflick limit, leading to uncontrolled growth

• During mitosis, the chromatids of each chromosomes are split apart and separate into two (blank) nuclei in a (blank) division

• During meiosis, chromosomes number is (blank) and (blank) daughter haploid cells are formed

• Meiosis consists of (blank) divisions

• daughter, single

• halves, four

• two

What happens in meiosis I

• homologous chromosomes pair and the separate, ensuring each daughter cell receives a full haploid set of chromosomes

what happens during meiosis II

• chromatids are separated

Meiosis I and II basic steps

Meiosis I

• Prophase I: homologous chromosomes condense and cross over

• Metaphase I: homologues align

• Anaphase I: homologues separate

• Telophase I: homologues separated into 2 cells

Meiosis II

• Prophase II: no DNA replication between two divisions

• Metaphase II: chromosomes align at middle of cell

• Anaphase II: chromatids separate

• Telophase II: formation of four haploid daughter cells

• in male vertebrates, meiosis occurs just prior to the differentiation of (blank)

• (blank) that are committed to undergo meiosis become primary (blank)

• then, two divisions of meiosis produces four relatively undifferentiated (blank)

• each spermatid undergoes a complex differentiation to become a highly specialized (blank)

1. spermatozoa

2. spermatogonia, spermatocytes

3. spermatids

4. spermatozoon

• in female vertebrates, (blank) become primary (blank), which then enter a greatly extended meiotic prophase

• T/F : vertebrate eggs are typically fertilized at a stage before the completion of meiosis (usually after metaphase II)

• meiosis is completed after (blank), while the sperm resides in the egg (blank)

• oogonia, oocytes

• true

• cytoplasm

• trisomy

• monosomy

• triploid

• third copy of a chromosome (2n +1)

• incomplete set of chromosomes (2n-1)

• three sets of chromosomes (3n)

aneuploidy

• chromosomes number differs from the normal count by just a few chromosomes (monosomy, trisomy)

polyploidy

• cells contain extra COMPLETE sets of chromosomes (triploid)

what is special about plants and chromosomes

• plants can tolerate extra sets of chromosomes, and many healthy plant species possess more than 8 sets

• nondisjunction

• examples of chromosomes breakage

• chromosomes don’t separate properly during meiosis

• deletion

• duplication

• inversion

• translocation

Trisomy 21

• 3 copies of chromosome 21

• chromosome 21 is the smallest human chromosome

T/F: frequency of down syndrome correlate with age of the mother

true

Klinefelter’s syndrome

• XXY male

• have male sex organs but are sterile

• breast development and lack facial hair

• normal intelligence

• tall