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Chapter 16 Blog: Genetics

Page history last edited by Peter Falk 13 years, 2 months ago


A.  Daily Blog

I'm gonna try something a little different. I know when you said to use the learning obejctives to help guide the summaries you didn't mean to literally put the objectives in, however I think the most effective way for me to summarize would be to briefly answer all of the points posed in the objectives. If this doesn't work out, I won't do it again and it's worth a shot change it up a bit. 


16.1 Mendel’s Laws of Inheritance

  • Explain the advantages of Mendel’s experimental system.
    • Mendel used pea pods. Pea pods are self-fertilizing (more easily bred), and have several traits that are distinguishably one or the other (e.g. wrinkled, round seeds, height of plant). Overall, pea pods proved to be very effective at demonstrating basic genetic inheritance.
  • Evaluate the outcome of a monohybrid cross.
    • Let's make a Punnet square! (Genetics professors should leave the room now.) Even though generally Punnet squares aren't the most efficient method of determining inheritance, they are useful for monohybrid crosses, and they are the only method that I can remember and use effectively. Let's try a cross between two heterzygotes.
      • So 3/4 will be phenotypically dominant
  • Explain Mendel’s principle of segregation.
  • Predict the outcome of genetic crosses by using Punnett squares.
    • See above, for different genotypes just use the different dominant and recessive lettering 
  • Interpret data from test crosses to infer genotypes.
    • This is basically analyzing a pedigree. The most effective way to do this would to give an example and then go through it, so thats what Ill do.  
  • Evaluate the outcome of a dihybrid cross.
  • Explain Mendel’s Principle of Independent Assortment.


16.2 The Chromosome Theory of Inheritance

  • Outline the tenets of the chromosome theory of inheritance.
  • Understand the physical basis of independent assortment.
  • Compare the segregation of alleles with the behavior of homologues in meiosis.


16.3 Pedigree Analysis of Human traits

  • Describe how a pedigree is used to analyze the transmission of an inherited trait over the courses of several generations.
  • Determine whether a particular trait is caused by the presence of a dominant allele or a recessive allele based on pedigree analysis.


16.4 Sex Chromosomes and X-linked Inheritance Patterns

  • Differentiate between the major categories of sex determination in animals.
  • Describe sex-linked inheritance in fruit flies.
  • Explain the evidence for genes being on chromosomes.


16.5 Variations in Inheritance Patterns and Their Molecular Basis

  • Describe how assumptions in Mendel’s model result in oversimplification.
  • Discuss a genetic explanation for continuous variation.
  • Explain the genetic basis for observed alterations to Mendel’s ratios.
  • Compare and contrast the molecular basis for variations in inheritance patterns, including relevant examples from the medical community.


16.6 Genetics and Probability

  • Understand the rule of addition and the rule of multiplication.
  • Apply the rules of probability to genetic crosses.


B.  Useful Materials




Ocular anomalies in a herd of Exmoor ponies in Canada.


This article discusses the use of pedigree analysis in Exmoor ponies (pictured left) to determine the inheritance of an ocular anomaly. Eye exams were done on thirty ponies in south-west Ontario, and following the compiling of the findings pedigree analysis was done to assess the recurrence pattern of specific anomalies in families and the data were tested for significance for breed prevalence and gender dependence, utilizing Fisher's exact test. The most common ocular finding was cataracts seen mainly in females. Statistical tests on prevalence data confirmed a significant breed and sex association. Pedigree analysis favored a sex-linked mode of inheritance for cataracts in this line of Exmoor ponies. This article shows how pedigree analysis and genetics that we learned in Dr. Weber's class is used in the real world to study equine animals. 
Fisher's exact test of independence   In my journal summary I mentioned that the biologists studying the ponies used something called "Fisher's exact test" in order to determine the statistical significance of the data.  I had no idea what that was, so I decided to do a little research to find out how biologists analyze data in the real world and the kinds of methods they use. This website details how this test works, and it is pretty dense in statistics jargon. Basically though, the test is used to determine the statistical significance of data when given two nominal variables (e.g. male/female). The site is pretty interesting if you have a passing interest in statistical analysis, and how it applies to biology. 
  This video (starting at the 14:00 mark) discusses the idea of Chromosome Inheritance Theory of Inheritance. The video as a whole discusses the basics of genetics, and serves as an effective supplement to Dr. Weber's virtual lecture. This MIT video goes over the main principles of the chapters, and it is interesting to see it presented from another angle. 



Comments (1)

Derek Weber said

at 2:52 am on Apr 1, 2011

Good start to the summary but we fell off.

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