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BIOL102 Principles of Biology
Exam 3 Review Sheet

Exam date: Friday Dec 1 2006

A reminder of my make-up policy: If a scheduled exam must be missed, I should be contacted as soon as possible to explain your absence--it should be BEFORE the next scheduled class period.  A make-up exam will be rescheduled at MY convenience. The make-up test may differ substantially from the original. For exam 3, the makeup exam will consist entirely of short answer questions (no multiple choice).  There can be only one make-up exam during the semester – NO EXCEPTIONS.

Disclaimer:

This exam review sheet is intended to help you prepare for the exam but should not be considered your only source of study.  It is possible I have inadvertently left off some items of importance, so you should use your notes to help you prepare for the exam. You are still responsible for any material we covered in class, whether on this sheet or not.  This lists serves only to highlight the main points.

Material on exam:

Cell Cycle

• Interphase
  • G1, S, G2
  • DNA replication/chromosome duplication (during S phase of interphase)
  • DNA is in chromatin form
• Cell Division = mitosis + cytokinesis

Chromosomes/mitosis

• Be able to distinguish between chromatin, chromosomes, and chromatids

• Chromosome are composed of both DNA and protein
• DNA is compacted 10,000 times to form chromosomes
• What are centrosomes?
• What is a centromere?
• What role do microtubules play in mitosis?
• Be familiar with the order of the stages of mitosis (prophase, metaphase, anaphase, telophase)
• Know what happens in each stage of mitosis
• Be able to identify a drawing of a particular stage of mitosis
• Functions of mitosis:
  • asexual reproduction
  • growth
  • repair and renewal of cells

Cytokinesis

• When does cytokinesis occur?
• How does cytokinesis occur in animal cells?  in plant cells?
• what is a cleavage furrow? what is a cell plate?

Meiosis

• Know what is meant by the term homologous pair.  What does it look like? Be able to draw a homologous pair. 
• Know what is meant by diploid and haploid
• Be able to tell me how many chromosomes or chromatids would be present in a diploid or haploid cell
• Be familiar with the terms: zygote, gamete, fertilization
• Be familiar with the order of the stages of meiosis
• Know what happens in each stage of meiosis
• Be able to identify a drawing of a particular stage of meiosis
• Where does meiosis occur? 
• Functions of meiosis:
  • production of gametes (and reducing # of chromosome in half)
  • increase genetic diversity
    • crossing over
    • independent assortment of chromosomes
• Review egg formation and sperm formation
• What is the same between mitosis and meiosis?  What is different?
• What is crossing over?  When does crossing over occur?
• What does independent assortment of chromosomes mean?
• What is spermatogenesis?
•  What is oogenesis?  What is unique about oogenesis?

• Know what a karyotype is
• A Karyotype is a photographic inventory of an individuals chromosomes; Chromosomes are are arranged in homologous pairs, and from large to small
• Humans have 46 chromosomes - 23 homologous pairs; 22 homologous pairs are autosomes, the remaining pair are the sex chromosomes
• males = XY. Female = XX
• Why do researchers isolate chromsomes in metaphase?

• Accidents during meiosis can alter chromosome number
• Nondisjunction - an accident in meiosis in which members of a chromosome pair fail to separate
  Nondisjunction can result in an abnormal number of chromosomes (See Figure 8. 21, 8.22 p136,136)
• Abnormal numbers of autosomes is often lethal and miscarried before birth, only extra copies of the smaller chromosomes are tolerated (like 21) but the effects are quite serious
• An extra copy of chromosome 21 causes Down Syndrome; people with Downs syndrome have three copies of chromosome 21  - this condition is called trisomy 21

• An extra copy of chromosome 13 causes Patau syndrome; people with this syndrome have three copies of chromosome 13 -- this condition is called trisomy 13
• An extra copy of chromosome 18 causes Edwards syndrome; people with this syndrome have three copies of chromosome 18-- this condition is called trisomy 18
• Abnormal numbers of sex chromosomes do not usually affect survival
• Abnormal numbers of sex chromosomes are better tolerated than abnormal numbers of autosomes
• Klinefelters syndrome -XXY
• Turners syndrome - XO
• 47 XYY
• Presence of Y = male; absence of Y = female

Genes on Chromosomes

•  genes are located on chromosomes
• carry information about heritable traits
• In a homologous pair, 1 chromosomes carries one allele for a given gene, and the other carries the second allele.  The two alleles may be different or the same.  See figure 9.9, p. 146 and  figure 9.23, p. 160.