Cell division and Cellular Organization

Question 1

What is the stages of the cell cycle

Answer 1

G1, G1 checkpoint, S, G2, G2 checkpoint

Question 2

What happens during G1

Answer 2

Cell grows and new organelles and proteins are made

Question 3

What happens during G1 checkpoint

Answer 3

The cell check that the chemicals needed for replication are present and for any damage to the DNA before enters S phase

Question 4

What happens during S phase

Answer 4

Cell replicates its DNA ready to divide by mitosis

Question 5

What happens during G2

Answer 5

Cell keeps growing and proteins needed for cell division are made

Question 6

What happens during G2 checkpoint

Answer 6

The cell checks whether all the DNA has been replicated without any damage. If it has, the cell can enter mitosis.

Question 7

What happens during M phase

Answer 7

Mitosis and cytokinesis

Question 8

What are the stages of mitosis

Answer 8

Interphase, prophase, metaphase, anaphase, telophase, cytokinesis

Question 9

What happens during interphase

Answer 9

The cell carries out normal functions but also prepares to divide. The DNA is unraveled and replicated to double its genetic content. Organelles are replicated and ATP is increased

Question 10

What happens during prophase

Answer 10

The chromosones condense getting shorter and fatter. Centrioles (bundles of protein) start moving to opposite ends of the cell forming a protein network - spindle. The nuclear envelope breaks down and chromosomes lie free in the cytoplasm

Question 11

What happens during metaphase

Answer 11

The chromosomes line up along the middle of the cell and become attached to the spindle by their centromere. The cell check all the chromosomes are attached to the spindle before mitosis can continue

Question 12

What happens during anaphase

Answer 12

The centromeres divide separating each pair of sister chromatids. The spindles contract, pulling chromatids to opposite ends of the cell, centromere first

Question 13

What happens during telophase

Answer 13

The chromatids reach the opposite poles on the spindle. They uncoil becoming long and thin now called chromosomes. A nuclear envelope forms around each group of chromosomes so now two nuclei

Question 14

What happens during cytokinesis

Answer 14

The cytoplasm divides. In animals a cleavage furrow forms now two genetically identical daughter cells are formed.

Question 15

How do you observe the cell cycle

Answer 15

By staining the chromosomes so you can see them under a microscope and therefore be able to watch what happens during mitosis

Question 16

What does meiosis produce and where

Answer 16

The reproductive organs producing gametes

Question 17

What type of division is meiosis

Answer 17

Reduction division. This is where the cells that are formed have half the number of chromosomes (diploid)

Question 17

What happens in meiosis I

Answer 17

Prophase I = Chromosomes condense, getting shorter and fatter then arrange themselves into homologous pairs. Centrioles move them to opposite ends forming spindle fibres. Nuclear envelope breaks down

Metaphase I = The homologous pairs line up across the centre of the cell and attach to the spindle fibres by their centromeres

Anaphase I = The spindles contract separating the pairs one chromosome to each end of the cell

Telophase I = A nuclear envelope forms around each group

Cytokinesis = two haploid daughter cells produced

Question 18

What are homologous pairs

Answer 18

Pairs of chromosomes one from mum and one from dad

Question 19

What happens during meiosis II

Answer 19

Daughter cells undergo the stages again. In anaphase II the pairs of sister chromatids are separated and each new daughter cell inherits one chromatid from each chromosome

Question 20

What happens to homologous pairs during meiosis I

Answer 20

Come together and pair up, the chromatids twist around each other and bits of chromatids swap over. The chromatids still contains the same genes but now a different combination of alleles

Question 21

What are the two main events during meiosis that lead to genetic variation

Answer 21

Crossing over of chromatids - daughter cells formed contain chromatids with different alleles

Independent assortment of chromosomes

Question 22

What are stem cells

Answer 22

Unspecialized cells that can develop into different types. They divide to become new cells which specialize for a certain job called differentiation.

Question 22

Why does the independent assortment of chromones lead to genetic variation

Answer 22

1) Each homologous pair is made from one chromosome that is maternal and one paternal chromosome

2) When pairs line up in metaphase I and separated in anaphase I it is completely random which chromosome from each pair ends up in which daughter cell

3) The four daughter cells have different combinations of maternal and paternal

4) This is an independent assortment of chromosomes

5) The shuffling leads to genetic variation

Question 22

What do cells in bone marrow differentiate to

Answer 22

Blood cells - erythrocytes and neutrophils

Question 23

What do cells in meristems differentiate into

Answer 23

Xylem and phloem sieve tubes

Question 24

How does research show stem cells might cure Parkinson’s and Alzheimer’s

Answer 24

• Regrow healthy nerve cells in the brain for Alzheimer’s
• Parkinson’s suffer from tremors that they cannot control. Transplanted stem cells may regenerate the dopamine-producing cells