OAC BIOLOGYName: ___________________________________

CHROMOSOMES AND GENES IN ACTION: MICROVIEWER

Slide 1 - DNA MOLECULE

  1. Chromosomes contain _________ which carries the ______________ ____________. The genetic material on this slide was extracted from a __________. The DNA appears to be a ___________ strand in the form of a ___________, however in higher forms of life a great deal of DNA is packaged into ____________________. Therefore the DNA must be ______________ many times and twisted into spiral _____________.

  2. In your notes, sketch what you see on this slide.

Slide 2 - COILING IN CHROMOSOMES

  1. In the _________________ of a working cell the chromosomes are stretched so ______, and they are so ______________ up they are unrecognizable as individual structures. However, when a cell is _________________, the chromosomes ____________ and _______________ and they are easily seen. These spiral ___________ are chromosomes. Each spiral coil is called a _____________.

Slide 3 - LAMP BRUSH CHROMOSOMES

  1. These unusual chromosomes are found in the developing ______________ _________ cells of certain _____________________, in this case a ________________. They bear resemblance to long, thin ______________ made of a central wire strand with ____________ sticking out all around.

  2. The central strand (dark line) is composed of two ______________ fibres of ___________. At various points along the strands, the ___________ fibres are twisted about themselves many times forming thickened ________________. Each nodule can give rist to two _________ of DNA, one on each side of the chromosome.

  3. In your notes, sketch what you see on this slide.

Slide 4 - LOOP OF LAMP BRUSH CHROMOSOME

  1. Notice the strand of ___________ and the thickened _______________ where the DNA strand is _______________. Biologists think that each twisted nodule of DNA is the location of a ______________ or a group of related ______________.

  2. When a ____________ becomes active, the twisted DNA strand _______________. As the DNA strand becomes ______________, it shoots out of the __________________ in the form of loops. The open loops of DNA can synthesize and release ______________________ ______. When activity ceases, the DNA _____________ up again and the loops are withdrawn into the ________________.

  3. In your notes, sketch what you see on this slide.

Slide 5 - GIANT CHROMOSOMES

  1. According to the ___________ theory, a chromosome carries a series of ___________ arranged in single file. But nothing of the kind is visible in ordinary chromosomes. However, certain special cells of specific _________________ have giant chromosomes in which ____________ and _____________ bands are visible.

  2. The giant chromosomes on this slide come from the ____________________________.

  3. Each giant chromosome probably contains a dense bundle of many _________________ DNA fibres running the length of the __________________. In the ________________ bands these fibres are loose and straight. But in the ____________ bands the DNA is tightly twisted into _____________.

  4. In your notes, sketch what you see on this slide.

Slide 6 - CHROMOSOME PUFFS

  1. Sometimes the giant chromosomes have peculiar _______________ of puffs around certain bands. Special _______________ makes the puffs visible.

  2. These puffs probably represent _____________ in _______________. The twisted DNA strands of particular dark bands suddenly __________________ and blow up into ____________. In this untwisted condition, the DNA loops can synthesize and release molecules of ______________________ _________. Each puff you see is the sum total of many _______________ _____________. When activity is over, the DNA strands twist back into the __________ bands and the puffs __________________.

  3. The image on the right side of this slide shows a chromosome tagged with ___________________ ______________. The dark colour of the puffs indicates a high concentration of radioactive _____________. Thus it is reasonable to conclude that the puffs are synthesizing ___________.

  4. In your notes, sketch what you see on this slide.

Slide 7 - NUCLEAR PORES

  1. In this slide, "N" indicates the ________________, "C" indicates the _________________, and "E" indicates the ____________ __________________. The nucleus controls all cell __________________ by means of instructions encoded in the __________ molecules. But the DNA never leaves the ________________.

  2. Scientists believe that ___________________ ________ released by the _______ passes through __________ in the nuclear __________________ to transmit information to the ________________.

Slide 8 - RIBOSOMES

  1. The dark parallel lines are part of the ________________ ____________________ in the ________________. The tiny dots are ___________________. It is here that _____________________ synthesis occurs.

  2. Instructions from the ____________ are carried out of the nucleus by _______________ ________ to the ________________. The ribosomes now attract many molecules of _____________________ __________, each of which carries a molecule of ______________ _____________. There is a special tRNA for each of the ___________ different amino acids.

  3. Next, the proper ______________ ________________ are assembled in their correct order to form a ____________ chain of the right kind. When the chain is complete, the _________________ is released into the ________________.

  4. In your notes, sketch what you see on this slide.