Session 1: DNA Replication, Mitosis and Meiosis

Question 1

What is aneuploidy?

Answer 1

Abnormal number of chromosomes in a cell.

Question 2

What characterizes aneuploid cells?

Answer 2

Aneuploid cells have a chromosome number that is greater or smaller than a normal cell.

Question 3

What is polyploidy?

Answer 3

Condition in which the cells of an organism have more than two paired sets of chromosomes. (3n,4n,5n)

Question 4

What is the general outcome of polyploidy?

Answer 4

Polyploidy is generally lethal.

Question 5

What is semi-conservative DNA replication?

Answer 5

Each daughter DNA double-helix is composed of one strand from the original and one newly synthesized.

Question 6

Where does DNA replication begin?

Answer 6

At the origin of replication.

Question 7

What marks the origins of replication?

Answer 7

Particular sequences of nucleotides to which initiator proteins bind to open the double helix.

Question 8

How many origins of replication are there in the human genome?

Answer 8

There are 10,000 origins of replication in the human genome.

Question 9

What is DNA ligase?

Answer 9

An enzyme which mediates the joining of DNA strands together by catalyzing the formation of phosphodiester bonds.

Question 10

What are DNA polymerases?

Answer 10

A group of polymerase enzymes that** catalyze the synthesis of DNA** from mono-deoxyribonucleoside triphosphates (dNTPs).

Question 11

What is the function of DNA helicase?

Answer 11

An enzyme which separates double-stranded DNA into single strands.

Question 12

What does DNA topoisomerase do?

Answer 12

Relieves supercoiling of DNA ahead of replication fork

Question 13

What is the role of DNA primase?

Answer 13

Catalyzes the synthesis of short RNA primers complementary to a single-strand DNA template.

Short RNA sequences made by primase to allow DNA polymerase to start DNA synthesis.

Question 14

What type of polymerase is DNA primase?

Answer 14

RNA polymerase.

Question 15

In what direction is DNA synthesized?

Answer 15

5’ to 3’.

Question 16

What is the difference between the leading and lagging strand in DNA replication?

Answer 16

Leading strand: Synthesized continuously in the 5’ to 3’ direction because DNA polymerase moves toward the replication fork.
Lagging strand: Synthesized discontinuously in short Okazaki fragments (5’ to 3’) because DNA polymerase works away from the replication fork. These fragments are later joined by DNA ligase.

DNA polymerase moves from 3’ to 5’

Question 17

What are the fragments of the lagging strand called?

Answer 17

Okazaki fragments.

Question 18

What are replication forks?

Answer 18

Asymmetrical.

Question 19

What is Cisplatin?

Answer 19

A chemotherapy agent that cross-links DNA, inhibiting DNA synthesis and ** leading to apoptosis**.

Question 20

What types of cancer does Cisplatin treat?

Answer 20

Testicular, ovarian, cervical, breast, bladder, esophageal, lung, brain cancers and neuroblastoma.

Question 21

What is Gemcitabine?

Answer 21

A chemotherapy agent that inhibits DNA elongation.

Question 22

What types of cancer does Gemcitabine treat?

Answer 22

Testicular, breast, ovarian, non-small lung, pancreatic, and bladder cancer.

Question 23

What is Mercaptopurine (6-MP)?

Answer 23

A purine agonist therefore blocking purines during DNA replication.

Question 24

What does Mercaptopurine (6-MP) treat?

Answer 24

Acute lymphocytic leukemia (ALL) and chronic myeloid leukemia (CML). It can also be used to treat Crohn’s disease and ulcerative colitis.

Question 25

Name three therapeutic agents that inhibit DNA synthesis.

Answer 25

Cisplatin, Gemcitabine, Mercaptopurine (6-MP).

Question 26

What are the stages of mitosis in order?

Answer 26

PPMAT: Prophase, Prometaphase, Metaphase, Anaphase, Telophase, Cytokinesis.

Question 27

What is the contractile ring made of during cytokinesis?

Answer 27

Actin and myosin filaments.

Question 28

What does mitosis produce?

Answer 28

2 genetically identical diploid daughter cells with the same chromosome content as the parental cell (2n).

Question 29

Why are metaphase and anaphase important stages of mitosis?

Answer 29

They ensure that each daughter cell receives a copy of every chromosome.

Question 30

What is meiosis?

Answer 30

Specialized cell division of germline cells to produce oocytes (eggs) and spermatozoa (sperm), consisting of one round of DNA replication followed by two rounds of division: meiosis I and meiosis II.

Question 31

What does meiosis produce?

Answer 31

Four genetically different haploid cells.

Question 32

What type of division is meiosis?

Answer 32

Meiosis is a reduction division resulting in four non-identical haploid cells with the chromosome number halved from diploid (46) to haploid (23).

Question 33

What occurs during prophase 1 of meiosis?

Answer 33

'Lazy Zebra Push Dumb Donkey': Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis.

Question 34

Which stage of prophase 1 in meiosis produces genetic variation?

Answer 34

Pachytene, due to crossing over between pairs of homologous chromosomes to form chiasmata.

Question 35

What occurs during metaphase 1 of meiosis?

Answer 35

Homologous pairs of chromosomes are arranged as a double row along the metaphase plate, with random alignment of maternal and paternal homologues, leading to genetic variation through random assortment.

Question 36

What occurs during anaphase 1 of meiosis?

Answer 36

Homologous chromosomes in each bivalent are separated and move to opposite poles, while sister chromatids remain attached and some have exchanged genetic material.

Question 37

What occurs during telophase 1 of meiosis?

Answer 37

Chromosomes become diffuse and the nuclear membrane reforms.

Question 38

What occurs during cytokinesis 1 of meiosis?

Answer 38

Final cellular division to produce two new haploid cells.

Question 39

What occurs during meiosis II?

Answer 39

Mitotic division of each of the haploid cells produced in meiosis I.

Question 40

What are the sources of genetic variation in meiosis?

Answer 40

Crossing-over, independent assortment, random fertilization.

Question 41

What is a genotype?

Answer 41

The genetic make-up of an individual, which is inherited.

Question 42

What is a phenotype?

Answer 42

Observable characteristics of an individual resulting from the interaction of its genotype with the environment, which is not inherited.