Unit 2 Overview and Outcomes
Welcome to the study of heredity — the inheritance of traits. In this unit, you will begin the study of heredity by examining how chromosomes are transmitted from one cell to the next. Each of us started from a single fertilized egg that had 46 chromosomes — 23 from your mother and the other 23 from your father. As adults, we are made of approximately 50 trillion cells, and each of those cells still has 46 chromosomes. How is this possible? And how is it that each parent only contributes half of her/his chromosomes to each offspring?
In this unit, you will also examine the mechanisms of chromosome segregation in cell division and the relationship between DNA and chromosomes.
After completing this unit, you should be able to:
- Define the molecular structure of chromosomes.
- Compare and contrast mitosis and meiosis.
Course Outcome(s) practiced in this unit:
SC435-2: Explain the chromosomal basis of inheritance.
Discussion Topic
When Cell Division Goes Wrong – Aneuploidies
Organisms vary widely in the number of chromosomes per cell. The ant, Myrmeciapilosula, has only two chromosomes (one pair) per cell. By contrast, the fern, Ophioglossum, has up to 1260 chromosomes (630 pairs) per cell. This variation among organisms seems to be unrelated to how complex those species are. Instead, the precise chromosome number seems to be an important characteristic. So, an ant with one pair of chromosomes must have just one pair of chromosomes, and a fern with 1260 chromosomes must have 1260 chromosomes. Any different number results in changes in characteristics that are often so dramatic that the organisms cannot survive.
Humans typically have 46 chromosomes (23 pairs) per cell. Human aneuploidies are conditions where the chromosome number is not 46.
- Select a human aneuploidy.
- Describe the symptoms of this human aneuploidy.
- Explain the cellular processes that lead to this condition.
- Is it possible to treat aneuploidies in utero? Why or why not?
- In your opinion, if aneuploidies could be treated in utero, should it be done? Why or why not?
Be sure to answer all Discussion topics in an original, well-thought-out manner. Main posts should be at least 200 words and include a reference in APA and make frequent, informed references to this unit’s material. Engage in on-going, productive conversation by responding to a minimum of two classmates per thread. Responses to classmates should consist of approximately 50 words. Remember you will learn more by sharing ideas.
