mitosis and meiosis

Question 1

What are the 3 periods of Interphase

Answer 1

G1- first growth phase

S phase - synthesis phase occurs when DNA is synthesized as sister chromosomes are duplicated

G2 phase - second growth phase ( prep for cell division)

Question 2

G2 phase

Answer 2

-A well defined nucleus bounded by a nuclear envelope
- two centrosomes adjacent to the nucleus
- In animals a pair of centrioles in each centrosome
- In animals a microtubular array (Aster) around each pair of centrioles
- Duplicate chromosomes that cannot be distinguished individually due to loosely packed chromosome fibers

Question 3

Prophase

Answer 3

• Nucleolus disappears
• chromatin fibers condense into discrete observable chromosomes , composed of two identical sister chromatids joined at the centromere
  -Mitotic spindle forms & is composed of microtubles btwn the 2 spindles
• centrosomes move apart to opposite poles

Question 4

Prometaphase (Late Prophase)

Answer 4

• Nuclear membrane breaks down allowing microtubles to condense with highly condensed chromosomes
• spindle fibers extend from each pole toward the cells equator
  -each chromatid now has a specialized structure , the kinetochore located at a centromere region
• Kinetochore microtubles become attactched to the kinetochores and put the chromosomes into agitated motion
• Nonkinetochore microtubles radiate from each centrosome toward the equator without attaching to chromosomes

Question 5

Metaphase

Answer 5

• Centrosomes are at a position at opposite poles of the cell
• Chromosomes move to the equator (metaphase plate)
• Centromeres of all chromosomes are aligned on the equator
• Kinetochores of sister chromatids are attatched to kinetochore microtubles coming from opposite poles

Question 6

Anaphase

Answer 6

• sister chromatids are split apart into seperate chromosomes and move toward opposite poles of the cell
• Chromosomes move in a “v” shape
• The poles of the cell move farther apart , elongating the cell

Question 7

Mitosis definition

Answer 7

The division of the genetic material in the nucleus and is usually followed immediately by cytokinesis.

Question 8

centrosome

Answer 8

a sub cellular region containing material that functions throughout the cell cycle to organize the cells microtubules

Question 9

aster

Answer 9

a radial array of short microtubules , extends from each centrosome

Question 10

kinetochore

Answer 10

A structure made up of proteins that have assembled on specific sections of chromosomal DNA at the centromere

Question 11

telophase

Answer 11

• two daughter nuclei form in the cell
• nuclear envelope arises from fragments of parent cells
  -nucleoli reappear
• chromosome is less condensed
• mitosis is complete

Question 12

cytokinesis

Answer 12

• occurs during late telophase
  -division of the cytoplasm which involves cleavage furrow or cell plate

Question 13

What is a haploid cell and how many chromosomes are present ?

Answer 13

Haploid cells in humans contain 23 chromosomes in a single set of chromosomes
abbreviated n=23

Question 14

What is a diploid cell ? How many chromosomes are present ?

Answer 14

Cells that contain two copies of each chromosome abbrivated 2n=46

Question 15

What are gametes and where do they come from ?

Answer 15

Gametes transmit genes from one generation to the next , they come from sperm and eggs.

Question 16

Are gametes haploid or diploid ?

Answer 16

Haploid

Question 17

Prophase I

Answer 17

• Nucleolus disappears
  -chromosomes condense and homologs loosely pair aligned gene by gene
• Nuclear membrane breaks down
  -spindle apparatus develops
  -Homologus chromosomes pair
  - called synapsis
  - forms tetrad ( four
  chromosomes )
• each homologus pair has one or more x shaped region called chiasmata
• chaismata form , nonsister chromatids touch and exchange genetic material called crossing over

Question 18

Metaphase I

Answer 18

• Homologus pairs line up on the metaphase plate
• Both chromatids of one homolog are attatched to kinetochore microtubles

Question 19

Anaphase I

Answer 19

• Homologus chromosomes seperate and move to opposite poles

Question 20

Telophase I

Answer 20

• each half of the cell has a complete haploid set of duplicated chromosomes and is composed of two sister chromatids
• nuclear membrane develops
• cytokinesis occurs