Multifactorial Traits
Some mutations result in small phenotype differences – dimples vs. no dimples. Other mutations, such as those in the SRY gene on the Y chromosome may result in large phenotype differences – male vs. female.
a. The mutation causes a change in a single protein. How can this mutation in the SRY gene result in physical differences involving multiple organ and hormone processes?
A mutation in the SRY gene causes it to detach from the Y-chromosome. Without the SRY gene, ovaries will be produced instead of testes. There are a few different scenarios that can happen involving the SRY gene and the absence or placement of it, these scenarios are listed below.
1: If you are XY without the SRY gene, you produce estrogen and you are externally and internally female.
2: You are XY without the SRY gene attached to the Y gene and it is attached somewhere else, so you would be internally male producing testes, and externally female.
3: If you are XX, but contain the SRY gene attached to the X, you would be internally and externally male, but infertile due to the small size of the testes.
e. Attention Deficit Hyperactivity Disorder (ADHD) affects 5% of children and adolescents and 3% of adults. Individuals with ADHD have difficulty learning in a classroom situation where they must remain still and controlled. Heritability ranges from 60% to 90% in different populations, and the relative risk to someone with an affected sibling ranges from 40-80%. An adopted person is more likely to develop ADHD if a biological parent has the condition. A study in the US identified areas of chromosomes 16 and 17 that might harbor susceptibility genes. A study in the Netherlands, however, pointed to chromosomes 7 and 15. Using the above information, explain how the data indicate that ADHD is a multifactorial trait.
ADHD would be a multifactorial trait because it is found on two different genes on different chromosomes and varies within different countries. ADHD is also influenced by the environment because if your sibling has the condition, you are more likely to develop it, but it can still be inherited because your biological parents can pass it down to you, which would make it an inherited trait.
a. The mutation causes a change in a single protein. How can this mutation in the SRY gene result in physical differences involving multiple organ and hormone processes?
A mutation in the SRY gene causes it to detach from the Y-chromosome. Without the SRY gene, ovaries will be produced instead of testes. There are a few different scenarios that can happen involving the SRY gene and the absence or placement of it, these scenarios are listed below.
1: If you are XY without the SRY gene, you produce estrogen and you are externally and internally female.
2: You are XY without the SRY gene attached to the Y gene and it is attached somewhere else, so you would be internally male producing testes, and externally female.
3: If you are XX, but contain the SRY gene attached to the X, you would be internally and externally male, but infertile due to the small size of the testes.
e. Attention Deficit Hyperactivity Disorder (ADHD) affects 5% of children and adolescents and 3% of adults. Individuals with ADHD have difficulty learning in a classroom situation where they must remain still and controlled. Heritability ranges from 60% to 90% in different populations, and the relative risk to someone with an affected sibling ranges from 40-80%. An adopted person is more likely to develop ADHD if a biological parent has the condition. A study in the US identified areas of chromosomes 16 and 17 that might harbor susceptibility genes. A study in the Netherlands, however, pointed to chromosomes 7 and 15. Using the above information, explain how the data indicate that ADHD is a multifactorial trait.
ADHD would be a multifactorial trait because it is found on two different genes on different chromosomes and varies within different countries. ADHD is also influenced by the environment because if your sibling has the condition, you are more likely to develop it, but it can still be inherited because your biological parents can pass it down to you, which would make it an inherited trait.
Real Life Controversy
b. In 1992, Olympic athletes were screened for the SRY gene for gender verification prior to their participation in female events. If an XY individual can be phenotypically female, how can we accurately determine the gender of an individual?
The SRY gene doesn’t determine gender accurately; you would have to look at the combination of the SRY gene and the internal and external features. However, if you have different internal and external characteristics, you would be a hermaphrodite, which is not a defined gender. However there are certain circumstances that require us to define a gender, such as the case below in the Olympics. When this occurs we would have to look at things such as the level of testosterone or estrogen the individual produces.
c.18-year-old South African runner Caster Semenya had a medal taken away when it was discovered that this female runner was a hermaphrodite – possessing internal testes, but female external genitalia. She makes plenty of testosterone, but the gene that converts the hormone into DHT (required to produce external male genitalia) is not functional. http://sandrarose.com/2009/09/hermaphrodite-runner-may-get-to-keep-gold-medal/
Should this runner be allowed to compete with female athletes in future running competitions? Support your answer using a discussion of gender determination, in addition to your personal opinion.
Hermaphrodite is not a defined ‘gender’; however, there are certain characteristics that could determine whether one should compete with males or females. In the case of Caster who identifies herself as female, she produces a lot of testosterone (about 3 times the normal amount), and should therefore in my opinion be competing with the males. If Caster were to produces low levels of testosterone, or normal levels of estrogen found in females, she could then compete with the females. Testosterone levels give her the features of a male, such as high muscle mass, a deep voice, and even facial hair. The high muscle mass that the testosterone gives her is the trait which would give her an advantage while competing with the females, therefore I believe she could be competing with the males. In the case of Caster who most likely has both chromosome XY, but classifies herself as female because she is externally female should also consider other factors when determining her proper ‘sex’ for competition in the Olympics. Caster has the SRY gene, which tells the body to make testes, however, it must be attached somewhere else because of her external genitalia. Due to the fact that she has testes, she produces extra testosterone, which is found in males, and gives her the advantage over her other competitors. I believe that in Caster’s case, she can be gender classified as female, but compete with the males due to her excess testosterone production.
d. Describe a developmental pathway by which an XY individual can have an external female phenotype.
If you are XY without the SRY gene, one would produce estrogen and one would be externally and internally female, or if one is XY without the SRY gene attached to the Y gene and it is attached somewhere else, so one would be internally male producing testes, and externally female.
The SRY gene doesn’t determine gender accurately; you would have to look at the combination of the SRY gene and the internal and external features. However, if you have different internal and external characteristics, you would be a hermaphrodite, which is not a defined gender. However there are certain circumstances that require us to define a gender, such as the case below in the Olympics. When this occurs we would have to look at things such as the level of testosterone or estrogen the individual produces.
c.18-year-old South African runner Caster Semenya had a medal taken away when it was discovered that this female runner was a hermaphrodite – possessing internal testes, but female external genitalia. She makes plenty of testosterone, but the gene that converts the hormone into DHT (required to produce external male genitalia) is not functional. http://sandrarose.com/2009/09/hermaphrodite-runner-may-get-to-keep-gold-medal/
Should this runner be allowed to compete with female athletes in future running competitions? Support your answer using a discussion of gender determination, in addition to your personal opinion.
Hermaphrodite is not a defined ‘gender’; however, there are certain characteristics that could determine whether one should compete with males or females. In the case of Caster who identifies herself as female, she produces a lot of testosterone (about 3 times the normal amount), and should therefore in my opinion be competing with the males. If Caster were to produces low levels of testosterone, or normal levels of estrogen found in females, she could then compete with the females. Testosterone levels give her the features of a male, such as high muscle mass, a deep voice, and even facial hair. The high muscle mass that the testosterone gives her is the trait which would give her an advantage while competing with the females, therefore I believe she could be competing with the males. In the case of Caster who most likely has both chromosome XY, but classifies herself as female because she is externally female should also consider other factors when determining her proper ‘sex’ for competition in the Olympics. Caster has the SRY gene, which tells the body to make testes, however, it must be attached somewhere else because of her external genitalia. Due to the fact that she has testes, she produces extra testosterone, which is found in males, and gives her the advantage over her other competitors. I believe that in Caster’s case, she can be gender classified as female, but compete with the males due to her excess testosterone production.
d. Describe a developmental pathway by which an XY individual can have an external female phenotype.
If you are XY without the SRY gene, one would produce estrogen and one would be externally and internally female, or if one is XY without the SRY gene attached to the Y gene and it is attached somewhere else, so one would be internally male producing testes, and externally female.