Session 1: DNA Replication, Mitosis and Meiosis Flashcards
What is aneuploidy?
Abnormal number of chromosomes in a cell.
What characterizes aneuploid cells?
Aneuploid cells have a chromosome number that is greater or smaller than a normal cell.
What is polyploidy?
Condition in which the cells of an organism have more than two paired sets of chromosomes. (3n,4n,5n)
What is the general outcome of polyploidy?
Polyploidy is generally lethal.
What is semi-conservative DNA replication?
Each daughter DNA double-helix is composed of one strand from the original and one newly synthesized.
Where does DNA replication begin?
At the origin of replication.
What marks the origins of replication?
Particular sequences of nucleotides to which initiator proteins bind to open the double helix.
How many origins of replication are there in the human genome?
There are 10,000 origins of replication in the human genome.
What is DNA ligase?
An enzyme which mediates the joining of DNA strands together by catalyzing the formation of phosphodiester bonds.
What are DNA polymerases?
A group of polymerase enzymes that** catalyze the synthesis of DNA** from mono-deoxyribonucleoside triphosphates (dNTPs).
What is the function of DNA helicase?
An enzyme which separates double-stranded DNA into single strands.
What does DNA topoisomerase do?
Relieves supercoiling of DNA ahead of replication fork
What is the role of DNA primase?
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.
What type of polymerase is DNA primase?
RNA polymerase.
In what direction is DNA synthesized?
5’ to 3’.
What is the difference between the leading and lagging strand in DNA replication?
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’
What are the fragments of the lagging strand called?
Okazaki fragments.
What are replication forks?
Asymmetrical.
What is Cisplatin?
A chemotherapy agent that cross-links DNA, inhibiting DNA synthesis and ** leading to apoptosis**.
What types of cancer does Cisplatin treat?
Testicular, ovarian, cervical, breast, bladder, esophageal, lung, brain cancers and neuroblastoma.
What is Gemcitabine?
A chemotherapy agent that inhibits DNA elongation.
What types of cancer does Gemcitabine treat?
Testicular, breast, ovarian, non-small lung, pancreatic, and bladder cancer.
What is Mercaptopurine (6-MP)?
A purine agonist therefore blocking purines during DNA replication.
What does Mercaptopurine (6-MP) treat?
Acute lymphocytic leukemia (ALL) and chronic myeloid leukemia (CML). It can also be used to treat Crohn’s disease and ulcerative colitis.
Name three therapeutic agents that inhibit DNA synthesis.
Cisplatin, Gemcitabine, Mercaptopurine (6-MP).
What are the stages of mitosis in order?
PPMAT: Prophase, Prometaphase, Metaphase, Anaphase, Telophase, Cytokinesis.
What is the contractile ring made of during cytokinesis?
Actin and myosin filaments.
What does mitosis produce?
2 genetically identical diploid daughter cells with the same chromosome content as the parental cell (2n).
Why are metaphase and anaphase important stages of mitosis?
They ensure that each daughter cell receives a copy of every chromosome.
What is meiosis?
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.
What does meiosis produce?
Four genetically different haploid cells.
What type of division is meiosis?
Meiosis is a reduction division resulting in four non-identical haploid cells with the chromosome number halved from diploid (46) to haploid (23).
What occurs during prophase 1 of meiosis?
‘Lazy Zebra Push Dumb Donkey’: Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis.
Which stage of prophase 1 in meiosis produces genetic variation?
Pachytene, due to crossing over between pairs of homologous chromosomes to form chiasmata.
What occurs during metaphase 1 of meiosis?
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.
What occurs during anaphase 1 of meiosis?
Homologous chromosomes in each bivalent are separated and move to opposite poles, while sister chromatids remain attached and some have exchanged genetic material.
What occurs during telophase 1 of meiosis?
Chromosomes become diffuse and the nuclear membrane reforms.
What occurs during cytokinesis 1 of meiosis?
Final cellular division to produce two new haploid cells.
What occurs during meiosis II?
Mitotic division of each of the haploid cells produced in meiosis I.
What are the sources of genetic variation in meiosis?
Crossing-over, independent assortment, random fertilization.
What is a genotype?
The genetic make-up of an individual, which is inherited.
What is a phenotype?
Observable characteristics of an individual resulting from the interaction of its genotype with the environment, which is not inherited.
