Cell division

Question 1

Describe the role of the centromere in mitosis (3)

Answer 1

1. Holds chromatids together2. Attaches (chromatids) to spindle3. (Allows) chromatids to be separated/move to (opposite) poles / (centromere) divides/splits at metaphase/ anaphase;

Question 2

Homologous chromosomes carry the same genes but they are not genetically identical. Explain why

Answer 2

(Homologous chromosomes) carry different alleles

Question 3

Other than independent segregation, give one way in which meiosis allows the production of genetically different cells.

Answer 3

Crossing over / alleles exchanged between chromosomes or chromatids / chiasmata formation / genetic recombination

Question 4

Mitosis is important in the life of an organism. Give two reasons why.

Answer 4

1. Growth / increase in cell number2. Replace cells / repair tissue / organs /body3. Genetically identical cells4. Asexual reproduction /cloning

Question 5

In prophase of mitosis, the chromosomes become visible. Describe what happens in metaphase

Answer 5

Spindle formed / chromosome/centromere/chrom atids attaches to spindleChromosomes/chromatids line up/move to middle/equator (of cell)

Question 6

In prophase of mitosis, the chromosomes become visible. Describe what happens in anaphase

Answer 6

Chromosome/centromere splits / chromatids/ ‘chromosomes’ separate/pulled apartTo (opposite) sides/poles/centrioles (of cell)

Question 7

Cells lining the human intestine complete the cell cycle in a short time. Explain the advantage of these cells completing the cell cycle in a short time.

Answer 7

Form/replace cells quickly/rapidly / divide/multiply/replicate rapidly

Question 8

Mikanolide is a drug that inhibits the enzyme DNA polymerase. Explain why this drugmay be effective against some types of cancer.

Answer 8

Prevents/slows DNA replication/doublingPrevents/slows mitosisNew strand not formed / nucleotides(of new strand) not joined together / sugar- phosphate bonds not formed

Question 9

Describe the cell cycle

Answer 9

It tells you how much the values in a single sample vary, its a measure of the spread of values about the mean.A large standard deviation means the values in the sample vary a lot. A small standard deviation tells you most of the sample data is round the mean value so varries little.

Question 10

Describe the stages of mitosis

Answer 10

Interphase = DNA replicateschromosomes invisibleProphase = chromosomes become visiblenucleolus disappearsMetaphase = spindle formschromosomes line up on equator of cellAnaphase = chromatids are pulled towards polesspindle fibres attached to chromatids contractTelophase = spindle disintegratesnucleur envelope reforms