Kerboodle 6

Question 1

1 a Describe how the structure of these cells is specialised to carry out a particular function: i squamous epithelial cells (2 marks)

Answer 1

flattened shape ü for rapid diffusion across cell ü

Question 2

1 a Describe how the structure of these cells is specialised to carry out a particular function:

Answer 2

thicker wall one side ü when water enters turgid cell becomes hoop shaped (forming pore for gas exchange) ü

Question 3

b State two functions of mitotic cell division. (2 marks)

Answer 3

two from: asexual reproduction ü growth ü repair/regeneration ü

Question 4

Explain why meiosis is necessary in the life cycle of sexually reproducing organisms.

Answer 4

to form haploid gametes ü so when these fuse at fertilisation the chromosome number is not doubled ü

Question 5

2 a State the term used to describe the following:

i the microtubule scaffolding on which chromosomes move in nuclear division (1 mark)

Answer 5

spindle ü

Question 6

2 a State the term used to describe the following: ii the structures in the cell that organise this scaffolding (1 mark)

Answer 6

centriole

Question 7

2 a State the term used to describe the following: iii the constricted area of a chromosome visible during iii the constricted area of a chromosome visible during mitosis

Answer 7

centromere ü

Question 8

i State where in the body Haematopoietic Stem Cells are found. (1 mark)

Answer 8

bone marrow ü

Question 9

ii Outline three possible fates of a daughter cell produced by cell division of a HSC. (3 marks)

Answer 9

HSC daughter cell could: differentiate into an erythrocyte ü differentiate into a neutrophil ü continue to divide/undergo mitosis ü

Question 10

iii Describe what occurs if the G1/S checkpoint in the Haematopoietic Stem Cells cycle ceases to operate correctly. (2 marks)

Answer 10

cell may divide even though not ready or with damaged DNA ü this may lead to cancer / lymphoma / leukemia /myeloma ü

Question 11

b Explain the difference between:

i prophase of mitosis and prophase 1 of meiosis (2 mark)

Answer 11

in prophase of mitosis chromosomes appear but do not pair up ü whereas in prophase 1 of meiosis homologous chromosomes do pair up and crossing over occurs ü

Question 12

b Explain the difference between: ii anaphase 1 and anaphase 2 of meiosis.

Answer 12

in anaphase 1 the two homologous chromosomes separate ü in anaphase 2 the two sister chromatids separate ü

Question 13

a Explain why the DNA in two sister chromatids in G2 of interphase is identical. (2 marks)

Answer 13

semi-conservative replication has occurred ü complementary copy of each old strand made ü

Question 14

b Explain why the DNA in two sister chromatids in metaphase 1 of meiosis may no longer be identical. (2 marks)

Answer 14

crossing over may occur ü swapping of sections of non-sister / maternal and paternal DNA ü

Question 15

c Suggest why axial elements are important in meiosis. (2 marks)

Answer 15

to hold bivalent / homologous chromosomes together ü close enough for crossing over ü to enable segregation of homologous pairs (in anaphase 1) ü