Heredity and Variation: Genes in Action

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Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the second of three Science Objects in the Heredity and Variation SciPack. It explores sexual reproduction and the process of meiosis.

We now know that structures and functions at the molecular and cellular levels provide the mechanism for reproduction and the continuity of species. Instructions for development are passed from parents to offspring in thousands of discrete genes, each of which is a segment of a molecule of DNA. An organism’s particular genetic information, coded in its DNA (genotype), contains genes that provide the information necessary to assemble proteins. Offspring of asexual organisms inherit all of the parent's genes. In organisms that reproduce sexually, specialized female and male sex cells (gametes) are formed during a process of cell division called meiosis. Each of these sex cells contains a random half of the parent's genetic information.

When a particular male gamete fuses with a particular female gamete during fertilization, they form a cell with one complete set of paired chromosomes, a combination of one half-set from each parent. This random combining of gametes and their chromosomes during fertilization results in millions of different possible combinations of genes, which causes the offspring genotypes to vary from their parents’. Some of the new gene combinations make little difference in the ability of the offspring to reproduce or survive, some can produce organisms with capabilities that enhance their ability to survive and reproduce, and some can be deleterious, resulting in an inability to survive and/or reproduce. Learning Outcomes:

  • Distinguish among the following structures by describing their relationship to one another: DNA, chromosomes, genes, and alleles.
  • Describe the role genes play in the production of proteins and defining the phenotype of an organism.
  • Compare and contrast the DNA in cells produced during asexual reproduction versus the DNA in gametes produced during meiosis.
  • Indentify and describe those steps within the process of meiosis that explain the random distribution of genotypes among offspring resulting from sexual reproduction.
  • Explain how the recombination of the allele pairs for individual genes during sexual reproduction results in phenotypic variation among offspring.

  • Elementary
  • Middle
  • High

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Reviews (6)
  • on Thu Jan 26, 2017 11:15 PM

The investment in time spent was well worth it. I found that I had a good handle on some areas and was guided in areas that needed improvement. Looking for my next topic to study.

Cynthia Thomas
Cynthia Thomas

  • on Sat Oct 24, 2015 9:28 PM

Well explained. I can easily translate this information for my sixth graders.

Amy  (Tiki Island, TX)
Amy (Tiki Island, TX)

  • on Wed Apr 15, 2015 11:45 AM

I wanted to review concepts in genetics before introducing the content to my students, and this was a good refresher course. It would be better suited for someone with less familiarity with the processes of mitosis and meiosis, but it was very clear and easy to follow.

June K  (Chicago, IL)
June K (Chicago, IL)

  • on Tue Mar 17, 2015 8:41 PM

A perfect review for a middle school life science teacher. I thought the interactives and images clearly explained the concepts. I liked the attention and time spent on crossing over. I was a little disappointed in the mitosis and meiosis sections but since there are completely different sci guides on both that go in more detail it was fine. Thanks for the review!

Emily K  (Northbrook, IL)
Emily K (Northbrook, IL)

  • on Wed Oct 29, 2014 6:48 PM

I like that this resource gives you activites about genes. I find genes to be a somewhat difficult topic that having activites you can do with students can help making it less complex. The resource went into detail about reproduction and its connection with genes and heredity. I find this resource helpful for teachers because it provides ample of examples in this topic and how to apply it in class.

Mariana Morales
Mariana Morales

  • on Tue Sep 02, 2014 7:29 AM

I really enjoy Science Objects. In 1-3 hours, the Heredity and Variation: Genes in Action Science Object will help me re-learn, refresh, or learn for the first time some critical science concepts I will have to know to obtain my Science Educator credentials. I appreciate that I can complete them at my own pace, and that, if used as park of a SciPack, I have access to a content expert to go to for help. The NSTA Learning Center Science Objects are very beneficial!

Naomi Beverly  (Marietta, GA)
Naomi Beverly (Marietta, GA)

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