Independent Assortment & Crossing Over: Genetic Recombination

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SUMMARY

The discussion centers on the concepts of independent assortment and crossing over in genetic recombination. It confirms that independent assortment of homologous chromosomes can yield four combinations when no crossing over occurs, but emphasizes that the actual number of combinations is significantly higher due to the arrangement of 23 tetrads during Metaphase I of meiosis. Crossing over enhances genetic recombination, leading to increased genetic variation among offspring. The distinction between "identical" chromosomes and homologous chromosomes is clarified, noting that while they share similar traits, they are not genetically identical.

PREREQUISITES
  • Understanding of meiosis and its stages, particularly Metaphase I
  • Knowledge of homologous chromosomes and their role in genetic variation
  • Familiarity with genetic terminology, including alleles and tetrads
  • Basic principles of genetic recombination and inheritance
NEXT STEPS
  • Explore the mechanisms of genetic recombination in detail
  • Study the process of meiosis and its stages, focusing on Metaphase I
  • Learn about the significance of crossing over in genetic diversity
  • Investigate the role of alleles in determining phenotypic traits
USEFUL FOR

Students of genetics, biology educators, and researchers interested in genetic variation and inheritance patterns will benefit from this discussion.

tica86
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1. When crossing over does not occur, how many possible chromosome combination can result from independent assortment of the homologous chromosomes?
I believe it is 4, because we have 4 identical chromosomes. Is this correct?

2. How does this change when crossing over occurs? It increases or decreases the genetic recombination? I believe it increases the genetic recombination but I'm not sure.

I would appreciate any help, thanks!
 
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tica86 said:
2. How does this change when crossing over occurs? It increases or decreases the genetic recombination? I believe it increases the genetic recombination but I'm not sure.

You're correct on that. Crossing over yields an enormous possibility for genetic recombination and therefore variation.With regard for question #1, I'm a bit confused as to what exactly it is asking. Even without crossing over, there is still a great number of ways homologous chromosomes can line up. In the human gamete during meiosis, there are 23 tetrads lining the metaphase plate during Metaphase 1. These can line up in any order, and the one on each pole of the plate being different from the other order creates a huge possibility even without crossing over. I'm not sure what the question is looking for, though watch your vocabulary when discussing "identical" chromosomes. Since one of the two alleles for a specific trait is from each parent, they are not always identical. They have the same size and code for similar proteins, though their genetic nucleic acid makeup differs slightly (i.e. blue eyes vs brown eyes, etc.).

I hope that helps!
 

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