CHAPTER 7
CELL DIVISION
PART 2
DNA. Replication (Semi-conservative, DNA helicase, DNA polymerase, DNA ligase,
MEIOSIS -I.P.M.A.T x2 , Daughter cells – Haploid MITOSIS X1
Daughter cells - Diploid
Linked genes , Crossover,
Questions
1. Describe the DNA replication process.
2. When does replication occur in the life cycle of the cell?
3. Compare DNA replication and PCR by listing the similarities and differences between the two processes.
4. Why is meiosis significant to sexually reproducing organisms?
5. Compare Meiosis and Mitosis – number of cell divisions, chromosome number in daughter cells (n,2n)
Stages when crossover occurs, Non-disjunction can happen. Note- when chromosomes are doubled the
whole thing is called a chromosome and the parts are called chromatids.
6. How are the terms ‘ segregation of alleles” and ‘independent assortment of chromosomes’ related?
7. During meiosis, crossing over and recombination occur between homologous chromosomes. Describe the outcome
of recombination.
8. What are linked genes?
9. Describe what may happen to linked genes during the ‘crossing over’ process. Why is crossing over
important?
10. Which is most likely to be affected by crossing over- closely or distantly linked genes?
MEIOSIS
I___________
P__________
M_________
A_________
T_________
C_________
I__________
P_________
M________
A________
T_________
C_________
1. (Q110 (Q8,2000)
A goldfish has 94 chromosomes in its somatic cells. The diploid number for gold fish is
A 47
B 94
C 188
D 376
2
(Question 4)
The cell could come from
A. skin.
B. liver.
C. testes.
D. bone marrow.
3. During DNA replication
A. messenger RNA (mRNA) is produced.
B. reverse transcriptase enzymes play an important role.
C. bonds between phosphate and sugar molecules break.
D. each of the DNA strands acts as a template strand.
4.
(Question 3)
In specialised cells in the ovary and testis, cells divide by the process of meiosis to produce gametes. A cell with a
diploid number of 4 underwent meiosis. The following images illustrate different stages throughout the total process
of meiosis in this cell
a. Using the letters under each cell (A–F),
put the cells in order commencing with the
earliest stage of meiosis shown.
b. During meiosis, crossing over and
recombination occur between homologous
chromosomes. Describe the outcome of
recombination.
c. During meiosis the nucleus undergoes two
divisions.
i. Which of the cells, E or F, represents
anaphase 1? Explain
The list 1–4 below describes events and outcomes of the replication of DNA within a eukaryotic cell.
1. Complementary nucleotides bind to each of the two strands.
2. Sugar phosphate bonds form between the nucleotides.
3. The newly formed DNA molecules are semi-conserved.
4. Unwinding of the DNA molecule forms two single strands.
5.
(Question 12)
The correct order of these events during DNA replication, with the earliest event first, is
A. 1, 2, 3, 4
B. 1, 4, 3, 2
C. 4, 2, 1, 3
D. 4, 1, 2, 3
6.
(Question 1)
In some species of locusts the female has a ‘diploid chromosome number’ of 16.
a. What is meant by the diploid chromosome number?
b. In this species a male locust has a diploid number of 15.
What is the chromosome number of each of the two daughter cells produced during a mitotic division in a male?
The difference in chromosome number between the sexes is the result of a difference in the number of sex
chromosomes (X chromosomes in this case). Female locusts have two X chromosomes (XX) and male locusts have
only one X chromosome and no other sex chromosome (XO).
c. At the end of a meiotic division, how many chromosomes would you expect in the gametes of
i. a female?
ii. a male?
7. (Question 5)
In bees, females are diploid and males are haploid.
This means that male bees
A. produce gametes with half the haploid number of chromosomes.
B. produce gametes by meiosis.
C. produce gametes by mitosis.
D. do not produce gametes.
8. During meiosis
A Genetically identical daughter cells are produced.
B Homologous chromosomes line up along the equator
C DNA is replicated when the chromosomes are
visible.
D One diploid cell makes four haploid cells.
9. During mitosis
A Homologous chromosomes line up along the equator
B Haploid cells are produced
C Non-disjunction produces greater variation.
D Crossing over occurs.
10. Which of the following
statements is correct?
A Cell 1 could be either mitosis or
meiosis
B Cell 11 could be either mitosis
or meiosis
C Cell 11 could be either mitosis
or meiosis.
D The order of cells in mitosis
would be II,I, III.
I
II
III
11. Question 14
DNA was incubated with radioactive nucleotides. After one cycle of replication the distribution of radioactive
and non-radioactive nucleotides in the DNA would be
12. Question 1
The Zenkey is a hybrid animal produced from a cross between a species of zebra with a diploid number of 44
and a donkey with a diploid number of 62.
a. What is the diploid number of the Zenkey?
b. By what process are gametes formed?
c. Starting with the cell shown below with a pair of homologous chromosomes, draw what happens to the
cell and its chromosomes during the process by which gametes are produced.
d. Zenkeys are unable to produce offspring. Using your knowledge of gamete formation, suggest why the
Zenkey is sterile.