Mitosis and Meiosis

Question 1

Centromere

Answer 1

constriction on chromosome at which sister chromatids held together

Question 2

Kinetochores

Answer 2

protein structure on centromere to which spindle fibers attach

Question 3

Homologous chromosomes

Answer 3

maternal and paternal derivatives of a chromosomal pair generally containing the same genes in the same order (not same exact sequence)

Question 4

Sister chromatids

Answer 4

two strands of identical DNA

Question 5

Astral microtubules

Answer 5

radiate in all directions and aid in spindle orientation immediately before mitosis

Question 6

Centrosome

Answer 6

organelle that is primary microtubular organizing center that splits and forms spindle apparatus

Question 7

Centrioles

Answer 7

located in centrosomes and produce microtubules

Question 8

Spindle apparatus

Answer 8

network of filaments overall responsible for separation chromosomes during cell division

Question 9

Spindle apparatus

Answer 9

network of filaments overall responsible for separation chromosomes during cell division

Question 10

Mitosis

Answer 10

• process occurring during somatic cell division to generate identical diploid cells
• consists of 6 phases: prophase, prometaphase, metaphase, anaphase, telophase, and cytokinesis

Question 11

Prophase

Answer 11

chromatin condenses into chromosomes, centrosomes divide and migrate towards opposite poles of cell, nuclear envelope starts to disappear

Question 12

Prometaphase

Answer 12

polar microtubules start pushing chromosomes towards metaphase plate, kinetochore microtubules attach to kinetochores, nuclear envelope disappears

Question 13

Metaphase

Answer 13

chromosomes align at metaphase plate, kinetochore microtubules go into action and abruptly separate sister chromatids

Question 14

Anaphase

Answer 14

sister chromatids separate and centromeres divide, kinetochore microtubules shorten and draw them towards either pole, polar microtubules elongate to push poles apart

Question 15

Telophase

Answer 15

chromatin expands, microtubules start to disintegrate, nuclear envelope reforms

Question 16

Cytokinesis

Answer 16

cleavage furrow forms, remains of polar microtubules in midbody help stabilize midline during division, two daughter cells formed

Question 17

Cytokinesis

Answer 17

cleavage furrow forms, remains of polar microtubules in midbody help stabilize midline during division, two daughter cells formed

Question 18

Cell cycle

Answer 18

• G0: after mitosis, cell enters this stage of interphase if not destined to divide again
• G1: if cell destined to divide again, enters G1; no DNA synthesis
• S: DNA replication occurs
• G2: each chromosome consists of two sister chromatids; ended by mitosis
• M: mitosis begins when chromosomes start to condense and become visible

Question 19

Cell cycle regulation

Answer 19

• series of checkpoints where cell cycle can be stopped; regulated by cyclins and cyclin-dependent kinases
• G1/S checkpoint: cell monitors size and DNA integrity
• G2/M checkpoint: cell monitors DNA synthesis and damage
• M checkpoint: cell monitors spindle formation and attachment to kinetochores
• apoptosis occurs if damage occurs that is severe and not repairable

Question 20

Meiosis

Answer 20

• process occurs during gamete formation to produce four haploid gametes from a diploid progenitor cell; recombination frequent
• divided into two successive division processes: meiosis I and meiosis II

Question 21

Meiosis I

Answer 21

• prophase I: condensation of chromatin, homologous chromosomes form synaptonemal complex, crossing over occurs (for sex chromosomes, recombination happens at PARs)
• metaphase I: fused kinetochores of sister chromatids function as one, homologous pairs line up at metaphase plate, arms of sister chromatids become unglued
• anaphase I: homologous chromosomes pulled apart
• telophase I & cytokinesis: 2 haploid daughter cells form

Question 22

Meiosis II

Answer 22

• similar process as mitosis since sister chromatids separate
• 4 new haploid cells formed

Question 23

Spermatogenesis

Answer 23

• starts during puberty and continues for rest of male’s life
• 2N spermatogonium undergoes first meiotic division > secondary spermatocyte (N) undergoes second meiotic division > spermatids (N) > mature sperm

Question 24

Oogenesis

Answer 24

• occurs during embryonic development
• 2N oogonium enters first meiotic prophase during 3rd month of fetal development > 2N primary oocyte suspended in prophase I until ovulation > ovulation sparks first meiotic division (98% of nondisjunction events happen here) > secondary oocyte (N) and polar body formed > second meiotic division suspended until fertilization > once fertilized ovum (N) and polar body formed