Mitosis

Front 1

How long does the total mitotic cycle usually take to complete?

Back 1

Around 18-24 hours

Front 2

How long does the average S phase of mitosis take to complete?

Back 2

Around 6-8 hours in length

Front 3

What is the average length of time that the M phase lasts?

Back 3

Usually around 30-45 minutes

Front 4

What is the stage that cells become arrested?

Back 4

G0 phase

Front 5

What does terminal differentiation mean?

Back 5

Cells become committed to differentiating and will never divide again.

Front 6

In what manner is DNA replicated?

Back 6

Semiconservative

Front 7

How was the semiconservative nature of DNA illustrated?

Back 7

By equilibrium density centrifugation of a sample grown initially in N (isotope 15)

Front 8

How do Eukaryotes replicate their genomes so quickly despite the size?

Back 8

They have multiple replication origins (replicons).

Front 9

What is an autonomously replicating sequence?

Back 9

A sequence that functions as a replication origin.

Front 10

What is replication licensing?

Back 10

It is the process by which the cell ensures that DNA is not replicated again until the cell has first passed through mitosis

Front 11

DNA Pol I

Back 11

Synthesizes DNA, 3'->5' exonuclease (proofreading), 5'->3' exonuclease removes RNA primer; excision repair system (Bacteria)

Front 12

DNA Pol III

Back 12

DNA synthesis, 3'->5' exonuclease (proofreading) (Bacteria)

Front 13

DNA Pol alpha

Back 13

Nuclear DNA synthesis; forms complex with pri0mase and begins DNA synthesis at RNA primers (Eukaryotes)

Front 14

DNA Pol gamma

Back 14

Mitochondrial DNA synthesis (Eukaryotes)

Front 15

DNA Pol delta

Back 15

Nuclear DNA synthesis; proofreading exonuclease (3'->5'); DNA repair (Eukaryotes)

Front 16

DNA Pol epsilon

Back 16

Nuclear DNA synthesis; proofreading exonuclease (3'->5'); DNA Repair (Eukaryotes)

Front 17

Primase

Back 17

RNA synthesis; makes RNA oligonucleotides that are used as primers for DNA synthesis (Eukaryotes and Prokaryotes)

Front 18

DNA helicase

Back 18

Unwinds double-stranded DNA (Eukaryotes and Prokaryotes)

Front 19

Single-stranded DNA binding protein (SSB)

Back 19

Binds to single-stranded NA; stabilizes strands of unwound DNA in an extended configuration that facilitates access by other proteins (Eukaryotes and Prokaryotes)

Front 20

DNA topoisomerase (type I)

Back 20

Makes single-strand cuts; induces and/or relaxes DNA supercoiling; can serve as swivel to prevent overwinding ahead of the DNA replication fork; can separate linked DNA circles at the end of DNA replication (Eukaryotes and Prokaryotes)

Front 21

DNA topoisomerase (type II)

Back 21

Makes double-strand cuts; induces and/or relaxes DNA supercoiling; can serve as swivel to prevent overwinding ahead of the DNA replication fork; can separate linked DNA circles at the end of DNA replication (Eukaryotes and Prokaryotes)

Front 22

DNA gyrase

Back 22

Type II DNA topoisomerase that serves as a swivel to relax supercoiling ahead of the DNA replication fork in E. coli

Front 23

DNA ligase

Back 23

Makes covalent bonds to join together adjacent DNA strands, including the Okazaki fragments in lagging strand DNA synthesis and the new and old DNA segments in excision repair of DNA (Prokaryotes and Eukaryotes)

Front 24

Initiator proteins

Back 24

Bind to origin of replication and initiate unwinding of DNA double helix (prokaryotes and eukaryotes)

Front 25

Telomerase

Back 25

Using an integral RNA molecule as template, synthesizes DNA for extension of telomeres (sequences at ends of chromosomal DNA in eukaryotes)

Front 26

In what direction is DNA synthesized?

Back 26

5'->3'

Front 27

Why is DNA polymerase not capable of synthesizes DNA in the absence of a primer?

Back 27

DNA pol requires a 3' hydroxyl group and template to bind to in order to begin replication

Front 28

DNA is always synthesized from 5'->3' and bidirectionally. One strand is easily synthesized, the other is performed discontinuously. How does the cell accomplish this?

Back 28

The DNA sequence is replicated in smaller sequences called Okazaki fragments. This requires more work by DNA ligase and Pol I.

Front 29

What is the primosome in E. coli?

Back 29

A protein complex where primase is accompanied by 6 other enzymes to function.

Front 30

What enzyme is primase tightly bound to for function in Eukaryotes?

Back 30

DNA pol alpha

Front 31

What is a telomere?

Back 31

A noncoding region at the end of linear chromosomal DNA that serves as protection for exonucleases and prevents loss of information during replication

Front 32

How is telomere shortening related to cancer?

Back 32

Many long-living lines of cancer cells have been found to replicate indefinitely. This is because the cell does not signal them to stop when the telomeres become to short.

Front 33

What is the sequence "TTAGGG?"

Back 33

It is an example of a telomeric (TEL) sequence in humans.

Front 34

How many copies of the TEL are present in human chromosomes?

Back 34

Typically 100-1500.

Front 35

What is translesion synthesis?

Back 35

DNA pol eta can catalyze DNA synthesis across a region of a thymine dimer, correctly inserting two adenines. This avoids introduction of mutations. (damage tolerant mechanism)

Front 36

Base excision repair

Back 36

corrects single damaged bases in DNA by removal of nitrogenous base

Front 37

Nucleotide excision repair

Back 37

Corrects errors in DNA by cuts the DNA backbone and inserts the correct nucleotides using NER endonuclease (excinuclease)

Front 38

Transcription-coupled repair

Back 38

NER system is specifically recruited to DNA regions where transcription has been halted because the transcription machinery encountered an area of DNA damage

Front 39

Mismatch repair

Back 39

Detection of incorrectly inserted bases and removing the INCORRECT base. In E. coli the enzymes recognize the newly synthesized strand because the original strand was methylated preceding replication (at GATC sequences)

Front 40

Why is thymine present in DNA and uracil in RNA?

Back 40

The only difference between uracil and thymine is methylation at the sp2 hybridized alpha carbon. (cytosine can be converted to uracil by deamination)

Front 41

Nonhomologous end-joining

Back 41

Proteins bind to the ends of two broken DNA fragments and join them together; nucleotides are lost from he end and cannot ensure that the correct ends are being joined together

Front 42

homologous recombination

Back 42

Uses the other copy of the chromosome present in the cell as a template for correction

Front 43

Prophase

Back 43

Chromosomes condense and become visible

Front 44

Prometaphase

Back 44

Fragmentation of the membranes of the nuclear envelope and the spindle may make contact with chromosomes

Front 45

Metaphase

Back 45

Chromosomes are aligned at the metaphase plate

Front 46

Anaphase A

Back 46

shortening of microtubules for separation of chromatids

Front 47

Anaphase B

Back 47

Spindle poles move away from each other

Front 48

Telophase

Back 48

Nucleus reforms

Front 49

What is a centromere?

Back 49

Tightly bound regions of DNA where kinetochore protein is located

Front 50

What is a kinetochore?

Back 50

Protein to which the microtubules bind during mitosis

Front 51

Cytokinesis

Back 51

Division of the cytoplasm. Formation of two daughter cells.

Front 52

Apoptosis

Back 52

Form of cell death triggered by activation of death receptors, withdrawal of survival factors, or as a result of DNA damage

Front 53

Growth factors

Back 53

Coordinate messages for cell state. May serve to inhibit or stimulate cell proliferation

Front 54

Ultraviolet light (UV radiation)

Back 54

Causes thymine dimers in DNA->mutagen/carcinogen