Sex linked Inheritance

Summary

Red-green color blindness is a sex-linked trait, more common in men due to the way sex chromosomes work. Men have one X chromosome and one Y chromosome, while women have two X chromosomes. The gene for color vision is carried on the X chromosome. A man with color blindness will pass the trait to his daughters, but not to his sons, as sons inherit the Y chromosome from their father. For a woman to be colorblind, both her father and mother must carry the recessive allele. The video explains how these genetic patterns result in color blindness being more prevalent in men.

Takeaways

• 😀 Red-green color blindness is a sex-linked trait, meaning it is connected to the sex chromosomes.
• 😀 People with red-green color blindness cannot distinguish between red and green, seeing both as green.
• 😀 A typical test for color blindness involves identifying a number formed by colored dots, which is invisible to colorblind individuals.
• 😀 Sex-linked traits like color blindness are more common in men than in women due to differences in sex chromosomes.
• 😀 Humans have 23 pairs of chromosomes, 22 pairs are autosomes, and the last pair are sex chromosomes (XX for females, XY for males).
• 😀 The gene for color vision is located on the X chromosome, which is larger and carries more genes than the Y chromosome.
• 😀 Girls inherit two X chromosomes (one from each parent), while boys inherit one X chromosome (from their mother) and one Y chromosome (from their father).
• 😀 Males are more likely to be colorblind because they only have one X chromosome, meaning a single defective gene on the X will cause color blindness.
• 😀 A colorblind man and a woman with normal color vision will have children where none will be colorblind, as the mother passes on a dominant allele.
• 😀 A daughter of a colorblind man and a woman with normal vision will not be colorblind unless the mother is a carrier of the colorblind allele.
• 😀 The only way a girl can be colorblind is if her father is colorblind and her mother is a carrier of the colorblind allele, passing two recessive alleles to her.

Q & A

What is red-green color blindness?

Red-green color blindness is a sex-linked trait that causes individuals to perceive both red and green objects as green. Those with the condition cannot distinguish between red and green hues.

How is red-green color blindness tested?

A typical test for red-green color blindness involves identifying a number made out of colored dots. If a person can see the number, they have normal color vision. If the number is invisible to them, they may have red-green color blindness.

Why are sex-linked traits like color blindness more common in men than women?

Sex-linked traits are more common in men because they only have one X chromosome, while women have two. If a man inherits the X chromosome with a defective gene, he will express the trait. Women, however, need two copies of the defective gene (one from each parent) to express the trait.

What are sex chromosomes, and how do they differ between males and females?

Humans have 23 pairs of chromosomes, 22 of which are autosomes and the same in both males and females. The 23rd pair are sex chromosomes: females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).

How do boys and girls inherit their X chromosomes?

Boys inherit their X chromosome from their mother and their Y chromosome from their father. Girls inherit one X chromosome from each parent.

What does it mean for a trait to be sex-linked?

A sex-linked trait is a characteristic that is controlled by genes located on the sex chromosomes, typically the X chromosome. These traits are more likely to be expressed in males because they have only one X chromosome.

How does the inheritance of red-green color blindness work in a family?

If a colorblind man and a woman with normal color vision have children, their daughters will inherit a normal vision gene from their mother, but their sons will inherit a Y chromosome from their father and may inherit a red-green color blindness gene from their mother. Sons have a 50% chance of being colorblind.

Can a woman be colorblind?

Yes, but it is rare. A woman can only be colorblind if her father is colorblind and her mother is a carrier of the colorblind gene, meaning she has one defective X chromosome. This way, the daughter will inherit two defective X chromosomes and express the condition.

What is the Punnett square, and how is it used to explain inheritance patterns?

A Punnett square is a diagram used to predict the genetic outcome of a cross between two individuals. It shows the possible gene combinations in their offspring, helping to predict the inheritance of traits like color blindness.

How do male and female inheritance patterns differ when it comes to sex-linked traits?

Males inherit only one X chromosome from their mother, so if it carries a recessive trait like color blindness, they will express it. Females inherit two X chromosomes, so they must inherit two copies of the recessive trait to express it. If they inherit only one, they are carriers.