Exam Two Notes - Exam Two Notes 2/18/08 Mitotic Segregation...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Exam Two Notes 2/18/08 Mitotic Segregation The purpose of mitosis is to produce two genetically identical nuclei.  Is mitosis the same as cell  division?  No. Cell Division = (Mitosis + Cytokinesis) Cytokinesis: Cleaves the cytoplasm Many mitotic events occurring without the subsequent cytokinetic events produces a multi- nucleic tissue.  (spelling? Synciatium) Found in muscle. In insect development, synciatiual is multi-nucleic tissue. Mitotic Segregation: In mitosis, homologous chromosomes do not pair. Mitotic Segregation can occur in two major ways. 1) Mitotic non-disjunction: In non-disjunction, the centromere does not separate  correctly. 2) Crossover: This is rare, because homologous chromosomes do not pair in  mitosis.  They have to lie just opposed to crossover (Mitotic crossing over). This can produce variegation.  The coexistence produces different-looking sectors of somatic  tissue. Somatic tissue in the animals is the tissue that does not contribute genetically to the gametes.  In plants, since differentiation of tissues can occur, tissue that was somatic may lead to germ  line tissue (does contribute genetically).  Somatic tissue differentiates into germ line tissue. Can have an environmental cause. Slide 40: Single yellow spot versus twin spot. mosaic is an individual composed of tissues of two or more genotypes.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Variegation is a way of being mosaic. In the 1930’s, Calvin Bridges discovered some +/M Drosophila females that were variegated  because mitotic nondisjunction had produced mosaics containing sectors of two different  genotypes.  Here M causes slender bristles and it is dominant to the wildtype +. He discovered mitotic nondisjunction in Drosophila. In 1936, Curt Stern found the first case of mitotic crossing-over. y= yellow body … sn = singed bristles y+ sn/y +sn X y sn /Y Female progeny, heterozygous wild type. Slide 48.  Explain the production of a single yellow spot and a twin spot. 2/22/08 The Poisson distribution A distribution is the description of the proportions of the different types of classes that result  from sampling. The Poisson distribution describes the proportion of classes containing 0, 1, 2, 3, etc. items  when the average number of items per sample is known. The distribution is most suited to situations in which the average is small in relation to the total  number of items possible.  Eg: The number of holes in a leaf made by a certain species of  insect. $100 bill example from the text page 177.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/14/2008 for the course BIO 325 taught by Professor Saxena during the Spring '08 term at University of Texas at Austin.

Page1 / 35

Exam Two Notes - Exam Two Notes 2/18/08 Mitotic Segregation...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online