cell division

Question 1

What does the cell cycle consist of?

Answer 1

Interphase (G1, S, and G2) mitosis and cytokinesis

Question 2

What does the cell cycle lead to?

Answer 2

Genetically identical cells

Question 3

How is the cell cycle regulated?

Answer 3

Checkpoints which control the cycle.

Question 4

Where are the checkpoints in the cell cycle located?

Answer 4

After G1, after G2 and during metaphase

Question 5

What does the G1 checkpoint check for?

Answer 5

The chemicals needed for replication are present, any damage to DNA and growth

Question 6

What does the G2 checkpoint check for?

Answer 6

If all of the DNA has been replicated properly, if there is any damage, and if it is big enough.

Question 7

What does the metaphase checkpoint check for?

Answer 7

The cell checks chromosomes are attached to the spindle before mitosis can continue

Question 8

What are the main stages of mitosis?

Answer 8

Prophase, metaphase, anaphase, telophase

Question 9

Why is mitosis important for life cycles?

Answer 9

It’s important for growth, tissue repair and asexual reproduction in plants animals and fungi

Question 10

Why is meiosis significant in life cycles?

Answer 10

It produces haploid cells and genetic variation by independent assortment and crossing over

Question 11

What happens in G1?

Answer 11

The cell grows and new organelles and proteins are made.

Question 12

What happens during S phase?

Answer 12

S phase strands for synthesis, the cell replicates its DNA and gets ready to divide by mitosis

Question 13

What happens in G2?

Answer 13

The cell continues to grow and proteins needed for cell division are made

Question 14

What happens in M phase?

Answer 14

Mitosis and cytokinesis

Question 15

What happens in interphase?

Answer 15

The cell prepares to divide, is DNA is unraveled and replicated to double its genetic content. The organelles are also replicated and ATP content is increased

Question 16

What happens during prophase?

Answer 16

The chromosomes condense, and tiny bundles of protein called centrioles move to opposite ends of the cell. This forms a network of protein fibres called the spindle. The nuclear membrane breaks down and chromosomes lie free in the cytoplasm

Question 17

What happens in metaphase?

Answer 17

The chromosomes each with two chromatids line up along the middle of the cell. They become attached to the spindle by their centromere. The metaphase checkpoint also occurs where the cell checks that the chromosomes are attached to the spindle.

Question 18

What are chromosomes made from?

Answer 18

Two chromatids joined by a centromere

Question 19

Why are there two chromatids in a chromosome?

Answer 19

Each chromosome has made an identical copy of itself during interphase.

Question 20

What happens to the chromosomes at the end of mitosis?

Answer 20

The chromatids end up as one strand chromosomes in the new daughter cells

Question 21

What happens during anaphase?

Answer 21

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

Question 22

What happens during telophase?

Answer 22

The chromatids reach the opposite poles on the spindle, they uncoil and become long and thin again. The chromatids become chromosomes again and a nuclear envelope forms around each group of chromosomes, so there are two nuclei

Question 23

What happens during cytokinesis in animal cells?

Answer 23

The cytoplasm divides and a cleavage furrow forms to divide the cell membrane, forming two daughter cells that are genetically identical to the original cell.

Question 24

When does cytokinesis begin and end?

Answer 24

It begins in anaphase and ends in telophase, it’s a separate process to mitosis.

Question 25

What happens during cytokinesis in plant cells?

Answer 25

A cell plate forms by microtubules transporting vesicles to the centre of the cell. The vesicles fuse together and a new cell wall is built, separating the cells

Question 26

What does mitosis produce?

Answer 26

Two genetically identical diploid cells

Question 27

What does meiosis produce?

Answer 27

Four genetically different haploid cells

Question 28

How can you observe the cell cycle?

Answer 28

You can stain chromosomes and view them with a microscope.

Question 29

What happens during sexual production?

Answer 29

Two gametes join together to form a zygote. This divides and develops into a new organism, meiosis occurs to produce gametes.

Question 30

How many chromosomes do the cells at the end of meiosis have?

Answer 30

Half the number of cells, they are haploid. This is because they are gametes

Question 31

What is mitosis 1?

Answer 31

Reduction division - it halves the chromosome number.

Question 32

What happens during prophase 1 in meiosis?

Answer 32

The chromosomes condense becoming shorter and fatter. They then arrange themselves into homologous pairs, and crossing over occurs. Centrioles start moving to opposite ends of the cell and form spindle fibres, and the nuclear envelope breaks down.

Question 33

What happens during crossing over?

Answer 33

Homologous pairs cross over and pair up in meiosis 1. The chromatids twist around each other and bits of chromatids swap over. The chromatids still contain the same genes but have a different combination of alleles

Question 34

What happens in metaphase 1?

Answer 34

The homologous pairs line up across the centre of the cell and attach spindle fibres by their centromeres.

Question 35

What happens in anaphase 1?

Answer 35

The spindles contract which separate the homologous pairs. One chromosome goes to each end of the cell.

Question 36

What happens in telophase 1?

Answer 36

A nuclear envelope forms around each group of chromosomes

Question 37

What happens in cytokinesis one?

Answer 37

The cytoplasm divides and two haploid daughter cells are produced.

Question 38

What happens in anaphase 2?

Answer 38

The pairs of sister chromatids are separated and each new daughter cell inherits one chromatid from each chromosome. Four haploid daughter cells are produced (gametes)

Question 39

What happens in meiosis 2?

Answer 39

The same as mitosis apart from anaphase 2.

Question 40

What two processes in mitosis cause genetic variation?

Answer 40

Crossing over of chromatids and independent assortment of chromosomes

Question 41

What happens during independent assortment?

Answer 41

Each homologous pair of chromosomes is made up of one maternal and one paternal chromosome. When the homologous pairs line up in metaphase one and are superstates in anaphase one it’s completely random which chromosome from each pair ends up in which daughter cell. This means that the four daughter cells produced have completely different combinations of maternal and paternal chromosomes

Question 42

What are stem cells?

Answer 42

Stem cells are a renewing source of undifferentiated cells. They can develop into different types of cells.

Question 43

Where stem cells found in animals?

Answer 43

They’re found in embryos and bone marrow. In embryos, the stem cells can differentiate into any type of human cell, but adult stem cells can only differentiate into any type of human cell.

Question 44

What is differentiation?

Answer 44

The process by which a cell becomes specialised for its job.

Question 45

What are adult stem cells used for?

Answer 45

To replace damaged cells, and to make new skin or blood cells

Question 46

What are stem cells in plants used for?

Answer 46

They make new roots and shoots, and plant tissues such as the xylem and phloem.