University:
Winston-Salem Forsyth County Schools
Course:
AP Biology
Academic year:

2011
Views:

419

Pages:

1
Author:

Kinsley Bowers

IB Biology Homework, IB Biology Exam Practice March 9, 2011 1. During the G1, S and G2 phases of the cell cycle, DNA is replicated and the cells does “normal stuff.” Give at least three examples of normal cell activities that take place during these phases. Respiration Active transport Protein synthesis Replication of DNA 3 max 2. Name two processes involving mitosis. Tissue repair Asexual reproduction 2 max 3. Colchicine is a chemical substance that prevents the formation of microtubules. What stage of mitosis would be prevented if dividing cells were treated with colchicine? Anaphase – separation of genetically identical chromosomes 1 max 4. What ensures that mitosis produces two genetically identical nuclei? during interphase DNA replicates / produces two copies of genetic material; sister chromatids are two identical DNA molecules held together by centromere; sister chromatids are separated during mitosis to form two genetically identical nuclei; in prophase chromosomes shorten / thicken / become visible as double-stranded chromosomes / joined sister chromatids; chromosomes condense by supercoiling; chromosomes attach to spindle microtubules at centromeres; chromosomes begin to move towards equator / centre of cell; during metaphase all chromosomes lined up at equator separately / not in homologous pairs; at start of anaphase centromeres divide separating sister chromatids; separated sister chromatids known as (single stranded) chromosomes; (identical sets of) chromosomes pulled to opposite poles; move by contraction of microtubules; nuclear envelope / membrane forms around each set of chromosomes; 8 max Many of these points can be shown by correctly annotated diagrams. Credit may be given for diagrams clearly illustrating these points. 5. Describe the three checkpoints in the cell cycle. (Where do they occur? How are they controlled? How do they work?)