Let the frequency of allele A be represented by q p q 1 p 2 2pq q 2 1 Apply the

Let the frequency of allele a be represented by q p q

This preview shows page 8 - 11 out of 35 pages.

Let the frequency of allele A be represented by q. p + q = 1 p 2 + 2pq + q 2 = 1 Apply the probability of marrying parent carrying gene of interest to pedigree problems. Downloaded by Nat Kp ([email protected]) lOMoARcPSD|2850388
Image of page 8
Week 3 Lecture 5 Variation in Chromosome Number and Structure: chromosome a DNA molecule with part or all of the genetic material (genome) of an organism sister chromatid pieces of identical DNA that are crucial in the process of cell replication and division homologue a chromosome that is similar in physical attributes and genetic information to another chromosome with which it pairs during meiosis nondisjunction results in daughter cells with abnormal chromosome numbers (aneuploidy) - failure of a pair of homologous chromosomes to separate in meiosis I, failure of sister chromatids to separate during meiosis II, and failure of sister chromatids to separate during mitosis aneuploidy the presence of an abnormal number of chromosomes in a cell polyploidy containing more than two paired (homologous) sets of chromosomes Diploid 2n: mitosis cell division initiates by doubling each chromatid, then chromatids are packaged and divided between daughter cells - if 2n = 46, 4n = 92 after DNA duplication meiosis I gamete production initiates by doubling each chromatid, then maternal and paternal chromatids stay together ( bivalents ) and segregate together - if 2n = 46, 4n = 92 after DNA replication meiosis II no DNA replication, segregation of sister chromatids before division Downloaded by Nat Kp ([email protected]) lOMoARcPSD|2850388
Image of page 9
Cytological Techniques geneticists use stains to identify specific chromosomes and to analyze their structures, often focuses on chromosomes in dividing cells Giesma banding lyse cell, stain with Giesma Quinacrine lyse cell, stain with quinacrine Chromosome painting fluorescent dyes stain only some chromosomes Ideogram identification of chromosome, result of staining bands Karyotype depiction of duplicated chromosomes of a cell arranged for cytogenic analysis Monoploidy n only one set of chromosomes - male ants, bees, wasps Diploidy 2n 2 sets of chromosomes - most plants and animal species Polyploidy 3n,4n, … more than the normal number of sets of chromosomes 30-35% of flowering plants are polyploids. Polyploidy is rare in the animal kingdom. Seedless varieties of fruits have an odd number of sets of chromosomes (like triploids or pentaploids). Meiosis is impaired because the organism will produce gametes with di ff erent number of chromosomes. The organism will be sterile. Instead, plants have omnipotent cells - cells that can di ff erentiate into all cell types - any cell can form a whole new plant. Problems with Polyploidy - Triploid 3n: unbalanced segregation of bivalents in meiosis I the number of chromosomes in a gamete can vary gametes that have extra chromosomes or lack certain chromosomes are not viable the gamete pairs that will re-create the 3n plants is extremely rare Meiosis in bananas! 3n = 33, 3 trivalents for every chromosome: Then consider the segregation possibilities for each set!
Image of page 10
Image of page 11

You've reached the end of your free preview.

Want to read all 35 pages?

  • Fall '13
  • DNA, Nat Kp

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture