Review Comparing Mitosis and Meiosis

With our next quiz rapidly approaching (tomorrow!) we used the first half of class to compare mitosis and meiosis.  Our work is shown below:

After the review, students had the opportunity to complete the dihybrid cross Gizmo.  Those who finished received a copy of a dihybrid cross practice worksheet for further review.  A copy of the completed front side of the worksheet can be viewed by clicking here.

Ask all the questions!

Our review of Units 1 and 2 culminated today.  Notes from both classes are provided below:

Functional groups with naming and smell
Amino acid base structure
Ester synthesis and peptide bonds are examples of dehydration synthesis reactions
Flow chart for predicting which molecules have a smell
Electron domains
Molecules can consist of multiple shapes

Diybrid Crosses (two-trait Punnett Squares)

As a review from last week’s  work on monohybrid crosses (single-trait Punnett Squares) and to extend student learning of Punnett Squares to dihybrid crosses (two- traits Punnett Squares), we began class with the following video by Mr. Anderson of Bozeman Science:

We then applied these concepts to a Two-Trait Punnett Square Gizmo in which students worked together in pairs to complete a work packet which included an additional review and application of the vocabulary learned thus far.

Notes from the white board for determining the alleles in a diybrid cross:

Modeling Meiosis

We reviewed problems 1, 2, 8, and 9 from yesterday’s Punnett Square worksheet at the start of class (work shown at the bottom of the post).  Next, we watched the Amoeba Sisters video about meiosis (below) and students worked through a guided worksheet.  After the video, students had the remainder of class to use the Inside the Cell books to help them complete the worksheet and to investigate the processes of independent assortment and crossing over.

Students then had the remainder of class to complete the worksheet, complete the meosis reading assignment from last Thursday, and to get both assignments checked off in Illuminate.

Punnett Squares (one trait)

To reinforce concepts introduced in the video yesterday but not covered in the reading assignment, we spent today learning and applying the vocabulary of inheritance.  We dusted off the cobwebs from student memories from middle school, reviewing the vocabulary words of:

  • genotype: the genetic makeup of an organism
  • phenotype: the physical appearance of an organism
  • allele: one of two or more forms that a gene could take
  • dominant allele: an allele that is always expressed when it is present (usually represented by a capital letter)
  • recessive allele: an allele that is not expressed when the dominant allele is present (usually represented by a lower case letter)
  • homozygous: having two alleles that are the same
  • heterozygous: having two alleles that are different
  • probability: the likelihood of an even

We then applied the vocabulary to an example Punnett Square about eye color inheritance patterns.  Students were provided with the following set of notes to reinforce concepts learned yesterday and provide context for our work today:

We then applied these concepts to a Single-Trait Punnett Square Gizmo in which students worked together in pairs to complete a work packet which included a review and application of the vocabulary learned thus far.

Students looking for additional practice are invited to complete the Punnett Square worksheet.

Structure and Function of Genes

For day one of our two-day lesson on the structure and function of genes, students were tasked with modeling the four types of DNA mutations described in yesterday’s case study on cystic fibrosis.  Students were given a wild-type DNA sequence and then had to solve the RNA and resulting amino acid sequences (see Structure and Function of Genes – Day 1 Power Point).  After a review of the types of mutations, students then introduced each type of mutation into the DNA sequence, solving both the RNA and amino acid sequences and connecting the vocabulary with the actual process of mutating DNA in specific ways to effect a specific outcome on the amino acid sequence.

Update: January 19

For day 2 of this lesson, we took notes on the structure of genes, including a review of how chromosomes are found in the nucleus of cells, how chromosomes consist of DNA coiled around histone proteins, and how genes consist of regulatory regions, exons, and introns.  At the end of the lesson, we previewed single-trait Punnett Squares to prime students for next week.

Structure and Function of Genes
Punnett Square Preview

Case Study of Cystic Fibrosis

In today’s lesson, we used a case study about cystic fibrosis as the mechanism to:

  • review the stop codon;
  • connect the concepts of protein structure and function;
  • review how R groups differentiate amino acids;
  • review how R group interactions result in protein folding;
  • discuss “structure equals function”;
  • bring a human face to a genetic disease;
  • and help students recall the mechanism of genetic inheritance.

For the entry task, students were challenged to consider how genes begin and end.  We discussed how mRNA sequences always begin with AUG (which codes for methionine, and amino acid which may also occur elsewhere in a protein).  Students were then reminded of the three “stop codons” and we reviewed how those work to release a protein from the ribosome.  We reviewed the structure of amino acids, focusing on the 20 different R groups and how those R groups each have different properties.  The interactions between R groups determine protein shape, and shape determines protein function.  When the sequence changes, the shape changes, thus changing the function of a protein.  We then moved into the cystic fibrosis case study, first watching the video below and then working through the lesson PowerPoint.

Class concluded with a few additional notes, pictured below:

Mirror-Image Isomers

We began with the Lesson 47 PowerPoint ChemCatalyst to help get students thinking about mirror images.  We then watched a short video about chirality (below):

Students then received the Lesson 47 Worksheet, working in pairs to model the compounds using the class set of molecular modeling kits.  The worksheet concluded with students hypothesizing whether L-carvone will smell like D-carvone, and then testing their hypothesis.  For homework, students were assigned textbook questions 5-8.

Update: January 18

Given the challenging nature of the subject matter in Lesson 47, we used most of the class period to review the homework, build molecules, and discuss the relationship between isomers and chirality.  Notes from the overhead are shown below:

Want more?  Check out the blog post Perhaps looking-glass milk isn’t good to drink for an overview of Lewis Carroll, looking-glass milk, and L- and D-carvone.  Want more?  Joanna Shawn Brigid O’Leary from Rice University published an even more extensive investigation of how Lewis Carroll (author of Alice in Wonderland and Through the Looking Glass) weaved biochemistry into his fiction.  Her paper (available as a PDF), WHERE ‘THINGS GO THE OTHER WAY’: THE STEREOCHEMISTRY OF LEWIS CARROLL’S LOOKING-GLASS WORLD is well worth the read.  Perhaps it will even inspire students to read the book before the movie is released in theaters on May 27!

Nature vs Nurture

Unit 5 was introduced with the following entry task:

In your lab notebook, list at least 5 traits that best describe who you are.

After responding to the entry task, students were assembled into groups of 2-3 students and together they debated whether a list of traits provided on a worksheet are inherited via nature, nurture, or both.  We came back together as a class so students could share their thinking and hear each others ideas.

Class concluded with the following assignment, due tomorrow:

Using your list of traits from the entry task, write an explanation about which of your traits are nature, which are nurture, and which are both.  Explain your thinking!