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Biology, Prentice Hall. 2000.
Standard B4: Genetics.
DNA composes the genes that hold specific instructions for life processes and are inherited by the next generation.
What does it mean?
Genes inherited from parents contain specific instruction for the direct production of specific proteins in the form of DNA containing chromosomes. Modifications and random distribution of parental genes provide the genetic variation necessary for evolution.
Michigan Standard for Genetics Instruction
“Students recognize that the specific genetic instructions for any organism are contained within genes composed of DNA molecules located in chromosomes. They explain the mechanism for the direct production of specific proteins based on inherited molecules of DNA. Students diagram how occasional modifications in genes and the random distribution of genes from parent provide genetic variation and become the raw material for evolution.
Michigan Biology Standards
Unpacking Genetics as a Learning Goal
In order to understand DNA and its function, students must first know that living things reproduce either sexually or asexually. They must also know that characteristics are inherited from parents, and can be influenced by heredity and also by the environment. It is also important that they distinguish the difference between inherited and non-inherited mutations for future lessons on Evolution. Students should learn about the structure and purpose of DNA, how it is reproduced and segregated during Mitosis and Meiosis, the causes of genetic variation, and the process of RNA and protein synthesis. They should also understand that though each species has unique DNA, the process of protein synthesis is the same for everyone.
Students should be able to:
• Differentiate sexual and asexual reproduction and their associated advantages and disadvantages
• Understand that characteristics are influenced by heredity and the environment, but only genetic traits are inherited.
• Successfully draw and label a homologous chromosome pair, and highlight a gene location on a heterozygous alleles.
• Understand that each cell has DNA, which is made of genes that code information to synthesize proteins for cellular function, and this information was inherited from parents.
• Understand the differences between dominant, recessive, codominant, polygenic, and sex-linked traits.
• Explain the genetic importance of Mendel’s laws of segregation and independent assortment.
• Determine the genotype and phenotype of monohybrid crosses using a Punnett Square.
• Explain that sex-cell mutations can be passed on to offspring (inherited mutation), but if they occur in other cells only descendant cells of the organism will inherit this trait (non-inherited mutations).
• Understand that each species has its own characteristic DNA sequence.
• Predict the consequences that mutations of specific genes will have on an organism.
• Understand how the genetic information in DNA provides instructions for RNA to assemble proteins.
What do students need to understand?
• DNA is a polymer of nucleotides, which are arranged in a double helix and their arrangement holds the information that makes us unique.
• Traits are inherited from parents, one set of chromosomes from each parent allow for genetic variety.
• Some genes are dominant and some are recessive, I have blonde hair even though both of my parents are brunettes.
• One side of the helix ladder is maternal, one side is paternal.
• When two different traits are inherited, they blend (black hair parent + blond hair parent = brown haired kid)
• DNA for organisms is very different because organisms are very different.
• We get an exact copy of our parent’s chromosomes.
What Project 2061 had to say about this Prentice Hall biology book (one edition prior to the one I used).
2061’s statement “Overall, textbooks do not make many connections (i.e., explain the relationship) among key ideas about cell structure and function” is also true for genetics. There are many steps in mitosis and meiosis that must be linked for true understanding of DNA replication and cellular division. The textbook did a poor job of describing each step, and what organelles were involved in the process. As most textbooks will have the same problem, I plan on using the textbook as a review or study guide for the students, and not the main information source. I want to construct a 3-D cellular model as we learn cellular structure, having each student contribute some part of the cell. This model can then be used to describe DNA replication and protein synthesis providing a visual explanation and more in depth information on how the steps and parts of the cell are related. I have also found a good website with animations of cellular and genetic topics with in-depth information that can aid student understanding.
Because photosynthesis will be covered before genetics, it would be good to start growing pea plants at the beginning of the year. Students could study these plants for photosynthesis, and then observe the F1, F2, and F3 generation crosses (because of time limitation, I would have to grow all three generations at once). The textbook covers Mendelian Genetics first, then moves on to DNA and the explanation of chromosomes. I would do this first, as Mendelian genetics can be intimidating and punnett squares could be confusing and cause students to lose interest.
Providing students with variety and vivid relevant phenomena
Variety of Phenomena
Representing Ideas Effectively
Explain that the information passed from parents to offspring is transmitted by means of genes that are coded in DNA molecules. These genes contain the information for the production of proteins.
Figure 11.2 outlines all the possible traits inherited from parents in a clean easy-to-read table. Figure 11.3 Shows gamete production by parental generations and lists the trait contained in the gamete and what happens when these gametes combine to produce another generation. Figure 11.4 shows homologous chromosomes and distinguishes the loci of different genes.
Practice Problems 11.1 require students to practice determining phenotype for gametes that a Generation can produce. Practice Problems 11.2 require students to think about phenotype expression for various gamete combinations.
Charts and Figures outline the complicated process of crossing different gametes and traits for student ease in understanding the process of inheritance. These aids are placed on the same page as the textual content and aid the student in understanding the concepts discussed in the text. Pictorals provide additional infomation and description for students what are confused by or misunderstand the complicated subject of the text.
Explain the genetic basis for Mendel’s laws of segregation and independent assortment.
Figure 11A goes into detail describing the role Meiosis plays in determining segregation and independent assortment summarized by Mendel's Laws.
Other than reading the text or doing punnett squares, this concept is only discussed in the text and not represented in any activities.
Figure 11A is easy to understand and gives a good pictoral representation of the Mendel's Laws, but the book lacks activities that require the student to actively think about the Laws and their genetic basis.
Determine the genotype and phenotype of monohybrid crosses using a Punnett Square.
Figures 11.6, 11.7, and 11.8 are all examples of punnett squares using different organisms and traits.
Practice Problems 11.4, and 11.5 require students to complete three punnett squares.
The book lacks any outside activities that might enhance the construction of a punnett square. An animation from a CD or a website might help students understand what a punnett square is and how to complete them.
Draw and label a homologous chromosome pair with heterozygous alleles highlighting a particular gene location.
Figrue 11.4 shows a homologous chromosome before and after duplications with loci of multiple alleles labeled.
There are no activities or representations of homologous chromosomes in the text, this is covered in a previous chapter and assumes the students have mastered this concept.
The book only shows homologous chromosomes with alleles labelled in one figure, and chromosomes are only shown in two figures. Students might get caught up in the pictoral representations of phenotypic expression used in the other figures and lose the connection that traits are actually inherited genetically.
Barely Satisfactory. This is a very abstract concept and the ways the book presents them is excellent, though it would be nice to see more depth in descritptions with prior knowledge built upon to enhance understanding of these concepts.
Poor. The book only has practice problems, has no interactive activities for visual, or kinesthetic learners, and does not really stimulate the students to think by connecting concepts to real life.
Satisfactory. The book is very well organized and uses many helpful figures to increase understanding of the textual content and link concepts to visual representations.
I went to hear Dr. Lowry, a professor and researcher from U of C Berkley speak this past weekend. He discussed the three types of learning: Concrete (hands-on), Pictoral (second-hand), and Symbolically (through reading texts). He stressed that the brain carries concepts, not the words in a textbook and that the more interactive students can be, and the more areas of the brain stimulated through learning, increase the likelyhood that the students will remember the concept.
The NES is designing lessons to engage student minds in this order (concrete first, with texts last) and to teach vocabulary in context building upon prior knowldge and using critical competitors (compare a maple and an oak leaf to learn about leaves) to involve students. All current US texts are designed to teach students BACKWARDS and do not enhance the learning process. By first telling the students what they will learn, we encourage passive learning instead of using inquiry activities that make them think and make them participate in their learning of concepts.
Here's a link to the FOSS website.
Activities I would add:
There are many other activities I’d like to add, such as identifying inherited traits like the widow’s peak, earlobe attachment, and tooth shape as ice breakers to start the class.
Cells Alive Activity:
What Will Our Baby Look Like Activity
Subject: inheritance, genotypes, phenotypes, alleles
Class Time: One class period to complete lab, one class period for Q & A
Brief Summary: This laboratory activity involves students working in pairs to simulate the production of a baby with certain facial features. In order to accomplish this, the students take turns flipping coins and from the outcome of each flip, indicate whether they will contribute a dominant or recessive allele to the genotype of their offspring (heads represents a dominant allele; tails represents a recessive allele). Upon matching the resulting genotypes with illustrations provided to represent them, the students concluded the activity by drawing and coloring a baby face encompassing the indicated features.
Student Objective(s): Demonstrate the principle of dominance, the relationship between an individual's genotype and phenotype, the role of probability in genetics, and the effects of incomplete dominance. Distinguish between dominance, co-dominance, and incomplete dominance. Illustrate the principles of segregation and independent assortment, and the concept of polygenic inheritance.
Integration (tying it all together): Students discuss and answer questions concerning genotypes, phenotypes, incomplete dominance, co-dominance, principles of dominance, recessiveness, segregation, independent assortment, and probability, polygenic inheritance, Mendelian ratios, and sex-linked traits. Students also utilize chi-square analysis to compare their results with expected ones.
Description of Activities:
1.) Students pair up in groups of two.
2.) To determine the genotype for each trait listed, each partner flips his/her coin (heads represents dominant allele; tails represents recessive allele).
3.) The "father" flips his coin to determine the sex of the child (heads represents a girl, tails represents a boy).
4.) The "parents" then take turns flipping their coins and recording the alleles they contribute for a variety of facial characteristics.
5.) The students match the genotypes that result to a variety of illustrations representing contrasting dominant and recessive characteristics.
6.) Once all of the features for a particular facial structure (for example, the eye) are determined, the students then draw and color this structure.
7.) This process is continued until a complete baby face of a school-age child is constructed.
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