Genes, traits, and the environment | Inheritance and variation | High school biology | Khan Academy

Summary

The video script delves into the influence of environmental factors on an organism's traits, using the Himalayan rabbit as a prime example. It explains how the C-gene's enzyme activity, crucial for pigment production, is temperature-dependent, with optimal activity between 15 to 25 degrees Celsius. This temperature sensitivity results in the rabbit's distinct color pattern, with cooler areas like the ears, nose, and feet showing pigmentation. The script also touches on how other factors like chemicals, light, food, stress, and hormones can affect gene expression, emphasizing that traits are a complex interplay between genetics and environment.

Takeaways

• 🐰 The traits of an organism are influenced not only by their genes but also by environmental factors.
• 🧬 The C-gene in Himalayan rabbits encodes a protein that acts as an enzyme in pigment production.
• 🌡️ The enzyme from the C-gene is optimally active at temperatures between 15 and 25 degrees Celsius.
• 🐇 The activity of the C-gene enzyme affects the pigmentation pattern on the rabbit, with cooler areas like the ears, nose, and feet being more pigmented.
• 🔥 The body heat of the rabbit, combined with ambient temperature, determines the activity of the enzyme and thus the pigmentation.
• 🌡️ Raising a rabbit in a hotter environment (above 30 degrees Celsius) can lead to a completely white rabbit due to the inactivity of the enzyme.
• 🧪 Environmental manipulations, such as temperature, chemicals, and light, can significantly alter the traits of organisms.
• 🦋 Experiments have shown that light exposure during the caterpillar stage can affect the wing patterns of butterflies.
• 🍽️ Diet and fasting can also activate or inactivate certain genes, influencing an organism's traits.
• 🤯 Stress and hormones are among the many environmental factors that can affect gene expression and, consequently, an organism's traits.

Q & A

What is the main focus of the video script?

The main focus of the script is to illustrate how an organism's traits are influenced not only by its genetic makeup but also by environmental factors, using the example of the Himalayan rabbit and its pigmentation.

What is the role of the C-gene in the Himalayan rabbit?

The C-gene in the Himalayan rabbit encodes a protein that acts as an enzyme in the production of pigment, affecting the coloration pattern of the rabbit.

At what temperature range is the enzyme encoded by the C-gene most active?

The enzyme encoded by the C-gene is most active at temperatures between 15 and 25 degrees Celsius.

Why does the enzyme encoded by the C-gene become inactive on certain parts of the rabbit's body?

The enzyme becomes inactive on parts of the rabbit's body where the temperature is above 35 degrees Celsius, such as the body where it is warmed by the rabbit's own heat production.

How does the rabbit's body temperature affect the activity of the C-gene encoded enzyme?

The rabbit's body temperature, especially in areas closer to the core, is typically above the optimal temperature for the enzyme's activity, causing it to be inactive and resulting in a lack of pigmentation in those areas.

What parts of the rabbit's body are cooler and thus allow the C-gene encoded enzyme to be active?

The ears, nose, and feet of the rabbit are cooler due to less body warmth, allowing the enzyme to be active and produce pigment in these areas.

Can the Himalayan rabbit's pigmentation pattern be altered by environmental temperature?

Yes, raising a Himalayan rabbit in an environment with a temperature consistently above 30 degrees Celsius could result in a completely white rabbit due to the inactivity of the C-gene encoded enzyme.

What was the outcome of the experiment conducted over 100 years ago regarding the Himalayan rabbit's pigmentation and temperature?

The experiment showed that raising a rabbit in a hotter environment led to a completely white rabbit, demonstrating the impact of temperature on the pigmentation pattern controlled by the C-gene.

Besides temperature, what other environmental factors can influence an organism's traits?

Other environmental factors that can influence an organism's traits include chemicals, light exposure, food, fasting, stress, and hormones.

What is the broader implication of the script's discussion on the influence of environmental factors on an organism's traits?

The broader implication is that the traits of an organism are not solely determined by genetics but are also significantly influenced by a range of environmental factors, highlighting the complexity of trait expression.

Can you provide an example of how environmental factors other than temperature can affect an organism's traits?

An example given in the script is the creation of a Cyclops fish through chemicals and rearing conditions, and the impact of light on the wing patterns of butterflies during their caterpillar stage.