2.6.2 Mitosis

Question 1

what is mitosis?

Answer 1

the process of nuclear division by which two genetically identical daughter nuclei are produced that are also genetically identical to the parent cell nucleus (they have the same number of chromosomes as the parent cell)

Question 2

what the acronym for mitosis?

Answer 2

PMAT

Question 3

what are the 4 main stages of mitosis?

Answer 3

prophase
metaphase
anaphase
telophase

Question 3

what are chromosomes made up of?

Answer 3

two strands

Question 4

what are the two strands of a chromosome joined in the middle by?

Answer 4

centromere

Question 5

what are the two separate strands that make up a chromosome called?

Answer 5

chromatids

Question 6

what are two strands on the same chromosome called?

Answer 6

sister chromatids

Question 7

how many chromosomes will a cell about to go under mitosis have?

Answer 7

it will have replicated the chromosome strands so will have two

Question 8

how many chromosomes will each daughter cell have after mitosis?

Answer 8

one strand chromosome

Question 9

what happens in prophase? 5

Answer 9

-chromosomes condense
-chromosomes have replicated during S phase to form sister chromatids
-mitotic spindle fibres assemble between the two centrosomes
-the centriole (found in centrosomes) replicates and move apart to opposite poles
-nuclear envelope breaks down

Question 10

what happens in metaphase? 2

Answer 10

-sister chromatids (the chromosomes) are aligned at the equator of the spindle
-pairs of chromatids attach to the spindle threads by the centromere

Question 11

what happens in anaphase? 3

Answer 11

-centromere of the chromatids splits
-motor proteins pull each sister chromatid in opposite directions
-chromatids are now called chromosomes

Question 12

what happens in telophase? 4

Answer 12

-separated chromosomes reach the poles
-new nuclear envelope forms
-each daughter cell contains genetically identical nuclei to the parent cell
-the division of the cytoplasm begins with the contraction of the contractile ring

Question 13

what is the difference between the mitotic phase and mitosis?

Answer 13

mitosis doesn’t contain cytokinesis

Question 14

what is the main significance of mitosis?

Answer 14

-growth of multicellular organisms
-replacement of cells & repair of tissues
-asexual reproduction

Question 15

explain the significance of mitosis to the. growth of multicellular organisms

Answer 15

-the two daughter cells produced are genetically identical to one another (clones) and have the same number of chromosomes as the parent cell
-this enables unicellular zygotes (as the zygote divides by mitosis) to grow into multicellular organisms
-growth may occur across the whole body of the organism or be confined to certain regions, such as in the meristems (growing points) of plants

Question 16

explain the significance of mitosis on the replacement of cells and repair tissues

Answer 16

-damaged tissues can be repaired by mitosis followed by cell division
-as cells are constantly dying they need to be continually replaced by genetically identical cells
-in humans, for example, cell replacement occurs particularly rapidly in the skin and the lining of the gut
-some animals can regenerate body parts, for example, zebrafish can regenerate fins and axolotls regenerate legs and their tail amongst other parts

Question 17

explain the significance of mitosis on asexual reproduction

Answer 17

-asexual reproduction is the production of new individuals of a species by a single parent organism – the offspring are genetically identical to the parent
-for unicellular organisms such as Amoeba, cell division results in the reproduction of a genetically identical offspring
-for multicellular organisms, new individuals grow from the parent organism (by cell division) and then detach (‘bud off’) from the parent in different ways
-this type of reproduction can be observed in different plant, fungi and animal species