Mitosis/meiosis SAC

Question 1

What does the cell cycle include?

Answer 1

• interphase, mitosis and cytokinesis.

Question 2

What is the cell cycle?

Answer 2

The time it takes for a cell to go from being born to dividing itself into new cells.

Question 3

Cell reproduction

Answer 3

• cell replication is responsible for production of new cells within an organism for purposes of maintenance, growth and repair.
• cells spend time in either interphase or mitosis.
• every new cell must have an exact copy of DNA in it.

Question 4

Checkpoints:

Answer 4

• DNA being copied is checked for mistakes.
  In G1, looks at mistakes in the DNA that might have occurred when the cell was duplicated.
  In G2 checks for mistakes that might have been made when chromosomes were copied in S phase.

Question 5

Interphase:

Answer 5

G1, cell grows and organelles are copied.
S (synthesis), DNA is copied (interphase) the process is known as DNA replication
G2, cell keeps growing, gets ready for mitosis.

Question 6

Chromosome:

Answer 6

Packaged and organised structure containing the DNA of a living organism.
- when double stranded, each strand is called a chromatid, and centromere is where they’re connected.

Question 7

Prophase (MITOSIS)

Answer 7

• chromosomes start to get shorter and thicker (condense) and become visible under a microscope
• nuclear membrane breaks down
• spindles form at each end of the cell.

Question 8

Metaphase (MITOSIS)

Answer 8

• tentacles hook onto centromeres

- a centromere is grabbed by a spindle from each end of the cell and they are lined up in the middle of the cell.

Question 9

Anaphase (MITOSIS)

Answer 9

• spindles contract and they break apart the chromatids, one goes to one end of the cell and the other goes to the other end of the cell
• now back to being called single stranded chromosomes

Question 10

Telophase (MITOSIS)

Answer 10

• opposite of prophase.
• nuclear membrane forms around chromosomes at end of the cell.
• spindles disappear, chromosomes become long and thin n

Question 11

Cytokinesis (after MITOSIS)

Answer 11

• cytoplasm is divided so that each nucleus can be its own cell.
• in animals: plasma membrane is pinched in the middle
• in plants: a new plasma membrane and a cell wall is built between 2 nuclei.

Question 12

MEIOSIS:

Answer 12

Diploid cells to haploid cells (eg. 46-23)
Only occurs in tested and ovaries (produced gamete cells)
Somatic cells about to undergo meiosis are called germ cell.
Meiosis results in 4 new cells

Question 13

Prophase 1 (MEIOSIS)

Answer 13

• chromosome makes a copy of itself and becomes double stranded forming 2 chromatids.
• the homologous chromosomes pair up close together, it’s during this that crossing over occurs.

Question 14

Metaphase 1 (MEIOSIS)

Answer 14

• chromosomes line up in the middle of the cell next to their pair.

Question 15

Anaphase 1: (MEIOSIS)

Answer 15

• homologous pairs are separated and pulled to opposite ends of the cell
• chromosomes on left hand side aren’t always pulled to that side, it’s independent and completely random.

Question 16

Disjunction:

Answer 16

When homologous pairs go to opposite ends of the cell, during anaphase 1.

Question 17

Telophase 1 (MEIOSIS)

Answer 17

• nuclear membranes form

- chromosomes stay visible, preparing to split again.

Question 18

Cytokinesis: (occurs in telophase 1)

Answer 18

Cells split so there are two cells each with 2 copies of each type of chromosome. However they aren’t the same as when they started as a result of the crossing over.

Question 19

Prophase 2.

Answer 19

• same as prophase 1

Question 20

Metaphase 2:

Answer 20

Chromosomes line up in middle of cell (in a single line)

Question 21

Anaphase 2:

Answer 21

Each chromatid is ripped apart by the spindles and moved to opposite ends of the cell (separation independent of others)

Question 22

Telophase 2:

Answer 22

• leaves you with 4 cells each having a haploid (n) number of chromosomes
• 4 daughter cells (gametes) are not identical.

Question 23

Recombination:

Answer 23

Re- assortment of genetic material to produce new genetic combinations. Homologous pairs crossing over making each gamete slightly different.

Question 24

Binary fission:

Answer 24

Process bacteria uses to divide
Binary- 2
Fission- splitting

Question 25

PROKARYOTES

Answer 25

• no nucleus or membrane bound organelles
• don’t undergo mitosis
• they have a circular piece of DNA (a chromosome.

Question 26

Process of BINARY FISSION:

Answer 26

• chromosome is copied
• each is attached to a different part of plasma membrane.
• cell begins to lengthen and constrict in the middle forming 2 new cells, each with a chromosome
• takes about 20 mins, called exponential growth because it doubles each time