B2

Question 1

what is the role of chromosomes

Answer 1

-chromosomes are made up of DNA and contain a large number of genes

-each gene controls a characteristic or part of a characteristic of an organism

Question 2

what are the 3 stages of cell division

Answer 2

stage 1= interphase

stage 2= mitosis

stage 3= cytokinesis

Question 3

explain the stage 1 of the cell cycle

Answer 3

stage 1:
-longest stage
-replication of DNA to form two copies of each chromosome ready for cell division
-increase the number of sub cellular structures (mitochondria, ribosomes chloroplasts)

Question 4

explain stage two of the cell cycle

Answer 4

-Mitosis
-One set of chromosomes is pulled to each end of the dividing cell and the nucleus divides

Question 5

explain stage three of the cell cycle

Answer 5

-this is when the cytoplasm and the cell membrane also divide to form two identical daughter cells

Question 6

why is cell division important?

Answer 6

-growth
-repair
-development of multicellular organisms

Question 7

what is a steam cell

Answer 7

-undifferentiated cells that divide to produce many identical cells which may differentiate to form different types of specialised cells

Question 8

mitosis in plant cells

Answer 8

-stem cells are produced in meristem found in the shoot and root tips

-plants have the ability to differentiate throughout life

-Differentiation is not permanent

-you can move plant cells from one plant to another. There it can re-differentiate and become a completely different type of cell

Question 9

cloning of animal and plant cells

Answer 9

-cloning animal cells is difficult because most animal cells differentiate permanently early in embryo development and the cell cannot change back

-you can clone a plant just from one tiny piece of relief tissue
-this is because in the right conditions a plant will become unspecialised and undergo mitosis many times

Question 10

differentiation in animal cell

Answer 10

-by time a baby is born most of cells are specialised to carry out a particular job

-many specialised cells to divide by mitosis forming more of the same sort of cell
-but some differentiated cells cannot divide at all so adult stem cells replaced dead cells

-some do not divide or have the ability to be replaced for example nerve cells