Molecules of Life Biology Lecture Flashcards

Question

what does unwinding of DNA cause

Answer 1

Unwinding of DNA introduces torsional strain in the molecule that can lead to additional twisting of the helix, called supercoiling

Answer 2

Topoisomerases are enzymes that prevent supercoiling

Answer 3

DNA gyrase is the topoisomerase involved in DNA replication that relieves the torsional strain

Answer 4

DNA polymerase can only synthesize in the 5'-to-3' direction

Answer 5

Antiparallel nature of DNA means new DNA strands must be synthesized in opposite directions

Answer 6

Leading strand synthesized continuously from an initial primer

Answer 7

Lagging strand synthesized discontinuously with multiple priming events

Answer 8

DNA fragments on the lagging strand are called Okazaki fragments, must be connected together

Answer 9

larger amount of DNA in multiple chromosomes linear structure (versus circular structure) need to deal with ends (telomeres)

Answer 10

Biotechnology started with the ability to manipulate DNA including: Cutting at sequence specific sites * Ligating DNA fragments together * Amplifying DNA as plasmids in bacteria * Separating and visualising DNA

Answer 11

Enzymes that cleave DNA at specific sites Used by bacteria against viruses Discovery of restriction endonucleases important because of their: Ability to cut DNA into specific fragments * Use in gene cloning

Answer 12

DNA ligase joins two DNA fragments forming a stable DNA molecule Catalyzes formation of a phosphodiester bond between adjacent phosphate and hydroxyl groups of DNA nucleotides Same enzyme joins Okazaki fragments on lagging strand in replication

Answer 13

Recombinant DNA can be stably replicated using a host organism, often E. coli . Add DNA fragment of interest to a bacterial plasmid * Introduce plasmid to E. coli Bacteria will incorporate recombinant DNA into genome where it will replicate and be maintained for study

Answer 14

Allows separation of DNA fragments by size Gel made of agarose or polyacrylamide Submersed in buffer that can carry current Subjected to an electrical field * Negatively-charged DNA migrates towards the positive pole . Larger fragments move slower, smaller move faster DNA is visualized using fluorescent dyes DNA fragments can be cut from gel and purified for use in making recombinant DNA

Answer 15

when chromosome gets copied, you get two copies of each chromatid, these are sister chromatids

Answer 16

Time it takes to complete a cell cycle varies greatly Fruit fly embryos = 8 minutes Mature cells take longer to grow * Typical mammalian cell takes 24 hours. * Liver cell takes more than a year. Growth occurs during G1, G2, and S phases * M phase takes about an hour. Most variation in length of G

Answer 17

1. G/S checkpoint Cell "decides" to divide. Primary point for external signal influence. 2. G/M checkpoint Cell makes a commitment to mitosis. Assesses success of DNA replication. 3. Late metaphase (spindle) checkpoint Cell ensures that all chromosomes are attached to the spindle.

Answer 18

Cyclin-Dependent Kinases (Cdks) Cyclin-Dependent Kinases (Cdks) Enzymes that phosphorylate proteins * Primary mechanism of cell cycle control Cdks partner with different cyclins at different points in the cell cycle

Answer 19

Cdk - cyclin complex Also called mitosis-promoting factor (MPF). Activity of Cdk is also controlled by the pattern of phosphorylation Phosphorylation at one site (red) inactivates Cdk. Phosphorylation at another site (green) activates Cdk.

Answer 20

* Multiple Cds control the cycle as opposed to the single Cdk in yeasts Animal cells respond to a greater variety of external signals than do yeasts, which primarily respond to signals necessary for mating More complex controls allow the integration of more input into control of the cycle

Answer 21

unrestrained, uncontrolled growth of cells failure of the cell cycle