Wednesday 31 July 2024

New Video Posted: Understanding Mendelian Genetics: Dominance, Codominance, and Incomplete Dominance

In this video, I explain some of the key terms in Mendelian genetics:

  • dominant
  • recessive
  • codominance
  • incomplete (partial) dominance

 

Blog Bonus: Free information sheet summarising the video and defining the key terms - download.

 

Introduction to Mendelian Genetics

Mendelian genetics is named after Gregor Mendel, who studied inheritance patterns in pea plants and published his findings in 1866. His experiments with pea plants, including traits like seed shape and flower colour, laid the foundation for understanding how traits are inherited. By cross-breeding plants with different traits, Mendel observed how traits reappear in subsequent generations, leading to the formulation of key genetic principles.

Dominant and Recessive Traits

Mendel discovered that certain traits, like round seeds, are dominant, while others, like wrinkled seeds, are recessive. Through cross-breeding experiments, he noted that in the first generation (F1) of true-bred plants that produced round or wrinkled seeds, the offspring all exhibited the dominant trait. However, when these F1 plants were self-pollinated, the second generation (F2) showed a 3:1 ratio of dominant to recessive traits (see Figure 1).

Using modern terminology, this can be explained with uppercase and lowercase letters representing dominant and recessive alleles, respectively. For instance, the round seed trait is represented by "R" and the wrinkled seed by "r." The F1 generation consists of heterozygous plants (Rr), which exhibit the dominant trait. The F2 generation reveals a combination of homozygous dominant (RR), heterozygous (Rr), and homozygous recessive (rr) plants, demonstrating Mendel's observed ratios (see Figure 1).

Figure 1: Crossing round and wrinkled pea plants
Figure 1: Crossing round and wrinkled pea plants

Codominance and Incomplete Dominance

Moving beyond simple dominance, we come to codominance and incomplete (partial) dominance.

In codominance, neither allele masks the other; both traits are fully expressed (see Figure 2). For example, in a hypothetical scenario with cows, crossing a blue cow (BB) and a yellow cow (bb) would result in offspring with both blue and yellow spots (Bb).

Figure 2: Codominance

Figure 2: Codominance

In incomplete dominance (sometimes called partial dominance), the traits blend rather than mask one another (see Figure 3). Using the same example of cows, crossing a blue cow and a yellow cow would produce green offspring (Bb), illustrating a blend of the two parent traits.

Figure 3: Incomplete Dominance - also called partial dominance
Figure 3: Incomplete Dominance - also called partial dominance

Key Takeaways

  1. Dominant and Recessive Traits: Dominant alleles mask recessive ones in heterozygous pairings.
  2. Codominance: Both alleles are fully expressed in the phenotype.
  3. Incomplete (Partial) Dominance: The traits blend, creating an intermediate phenotype.

Additional Resources

For further assistance, a Bioscience Glossary with over 2000 terms, chemical structures, and supporting videos is available. This glossary can help clarify additional terms and concepts in biosciences.

If you would like to say thanks for the video, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Blog Bonus: Free information sheet summarising the video and defining the key terms - download.
 

Additional Reading

The video was produced with help from the following resources:

Tuesday 30 July 2024

New Video Posted: How to Calculate the Gradient (m) and Intercept (c) in y = mx + c | Gel Analysis Tutorial

This video is in response to a question I have received on YouTube:

“Thanks it is very helpful but can you present how to calculate slope and intercept in this curve”

The question often gets asked about two of my other videos:

In the How to Calculate the Gradient (m) and Intercept (c) in y = mx + c | Gel Analysis Tutorial, I explain how to calculate the gradient (m) and intercept (c) in the linear equation y = mx + c. I explain three methods that can be used:

  1. Graph-based calculation
  2. Solving simultaneous equations
  3. Using Excel or Apple Numbers.
In the video, I use DNA gel data to illustrate these calculations.

If you would like to say thanks for the video, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Blog Bonus: Free information sheet summarising the video and defining the key terms - download.

Additional Resources

Monday 29 July 2024

New Video Posted: Understanding Mitochondrial DNA: Structure, Function, and Disease

In this video - Understanding Mitochondrial DNA: Structure, Function, and Disease - I look at the mitochondria's circular DNA that contains 37 genes. I discuss how mitochondrial DNA (mtDNA) differs from nuclear DNA and can exhibit either homoplasmy or heteroplasmy. I then discuss how mitochondrial DNA is maternally inherited and not synchronised with cell division, leading to unique genetic traits and potential mitochondrial diseases that predominantly affect high-energy tissues. I wrap up by introducing the idea of how mitochondrial diseases can be treated using "three-parent babies" by replacing the nucleus of a donor egg with one from a mother with mitochondrial disease, effectively substituting the mutated mitochondria.

If you would like to say thanks for the video, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Blog Bonus: A free guide giving step-by-step instructions on calculating m and c is available at: - download.
 

Additional Reading

The video was produced with help from the following resources:

Friday 26 July 2024

New Video Posted: Understanding the Function of Mitochondria | Dr. Peter Mitchell's Nobel Prize-Winning Work

 In this video - Understanding the Function of Mitochondria | Dr. Peter Mitchell's Nobel Prize-Winning Work - I discuss the function of mitochondria, highlighting Dr. Peter Mitchell's Nobel Prize-winning chemiosmotic theory, which explains how mitochondria generate ATP using an electrochemical gradient across their inner membrane.  

I finish up by highlighting that while the mitochondria can give the cell the energy it needs for life, they also play a role in cell death by releasing factors that trigger apoptosis.

If you would like to say thanks for the video, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Blog Bonus: Free information sheet summarising the video and defining the key terms - download.
 

Additional Reading

The video was produced with help from the following resources:

Thursday 25 July 2024

New Video Posted: How to Determine Protein Size on an SDS-PAGE Gel | Step-by-Step Tutorial

retention factorThis video - How to Determine Protein Size on an SDS-PAGE Gel | Step-by-Step Tutorial - is in response to questions I have had about a video in which I show how to calculate the size in base pairs of bands on a DNA gel.

In the video, I explain how to determine the molecular weight (kilodaltons; kDa) of a protein on an SDS-PAGE gel. The method involves constructing a table with the known molecular weights of protein markers, calculating their logarithmic values, measuring the distance each band travels and determining their retention factor (Rf) values.

I then show how to plot the graph and determine the size in kilodaltons (kDa) for the protein under investigation.

If you would like to say thanks for the video, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Blog Bonus: A free step-by-step guide is available for this video - download.
 

Additional Reading

The video was produced with help from the following resources: