cell division/ mitosis

Question 1

yeast

Answer 1

; buddingdivision

nucleus

chitin

ribosomes

Question 2

all cells have

Answer 2

ribosomes

Question 3

xylem cells do not have

Answer 3

cytoplasm and nucleus

Question 4

Describe how the structure of the cell walls in xylem vessels would differ from the cell walls shown in Fig. 2.1.

Answer 4

thicker ; lignified ; contain (bordered) pits

Question 5

Name two types of cell that can be found in phloem tissue.

Answer 5

sieve (tube) element ; companion (cell) ; parenchyma ;

Question 6

process that causes increase and decrease of mass of dna per cell

Answer 6

increase- dna replication

decrease- cytokinesis

Question 7

Discuss the ways in which genetic variation is produced, including the role of nuclear division ( 9 marks ! )

Answer 7

. genetic variations is produced via the independent assortment of chromosomes (1) in metaphase 1 (1)and of chromatids in metaphase 2 (1)

since homologous chromosoems have different allelesthat come from different parents(1), a large number of allele combinations occur (1), thus causing genetic variation

crossing over of non sister chromatids (1) also occurs in prophase 1 (1) where non sister chromatids wrap around each other and shuffle alleles around (1) causing variation

Question 8

eg of cell signalling

Answer 8

contains receptors, gylcoproteins etc…

Question 9

independent assortment

formation of the spindle apparatus

separation of sister chromatids

formation of nuclear membranes

chromosomes pulled to opposite poles

Answer 9

metaphase I and metaphase II ;

prophase I 0

; anaphase II ; (anaphase 2 : seperation of sister chromatids)

telophase II ;

anaphase I ; (chromosomes pulled to opposite poles )

Question 10

Explain why meiosis needs to have twice as many stages as mitosis.

Answer 10

to, halve chromosome number / reduce from 2n to n

; to separate homologous pairs (of chromosomes) and sister chromatids ;

because, DNA (previously) replicated / chromosomes are two chromatids at start ;

Question 11

what does mutation change

Answer 11

order of dna bases

Question 12

Discuss the possible effects that mutation can have on the structure and function of a protein. (3)

Answer 12

different, primary / secondary / tertiary, structure ; (protein )

shorter due to, deletion / stop codon OR longer due to, insertion / duplication

; (protein) unchanged due to, silent mutation / non-coding DNA altered ; (function is) lost / worse / better