answer the following question down below and respond to 3 posts made by other students.
1) identify a TRAIT that demonstrates ONE of the following inheritance patterns:
- incomplete dominance
- multiple alleles
- lethal alleles
In your posting, state the trait involved and the related gene(s), alleles, inheritance pattern, and three facts associated with that trait.
One resource that may be useful is the Genetics Home Reference (https://ghr.nlm.nih.gov/), but feel free to use and cite other sources as appropriate.
2) Respond to at least THREE of your classmates’ postings and share additional information related to that trait.
Student 1:Incomplete dominance is when instead one dominant allele for a specific trait coming though as the phenotype, the two alleles come together creating its own third type of phenotype. For example, I found an article that explains that sometimes when a person with the homozygous dominant brown-eyed trait mates with someone with the homozygous recessive blue-eyed trait, their offspring can have a phenotype of green or hazel eyes, instead of the expected dominant brown-eyed trait. Although there are about 16 different genes responsible for eye color, HERC2 and OCA2, found on chromosome 15, are the two genes most likely to be involved.
Three facts associated with this trait is that tyrosinase (TYR) is the enzyme responsible for pigment production in the body. Another one is that two people with the phenotype of blue eyes can have a brown-eyed baby. In the article I found, they explained using a Punnett square that one parent with a mutation in the HERC2 intron in both alleles that also has an allele with the coding for brown eyes, while the other parent has a non-mutated HERC2 allele and does not have the coding for brown eyes in the OCA2 gene can have offspring with brown eyes. It is then likely, their offspring will have blue eyes, but there is a 25% chance that the offspring could have brown eyes. One more fact is that heterochromia is a disorder that is characterized by different-colored irises of different colors within the iris that is either caused or inherited by somatic mutations within the cells.
Student 2: The condition I decided to cover was the lethal recessive disease known as cystic fibrosis. This genetic condition causes the secretions from the cells that line the lungs to become viscous and sticky. Rather than lubricating the lungs it impedes the afflicted’s ability to breath properly (Mayo Clinic). The expect life span for many is low and only recently has it improved along with patient’s quality of life through medical advancements. Geneticists have discovered that disease is linked to a mutation on the CFTR gene. This gene is responsible for creating a regulatory protein that prevents cystic fibrosis from happening. The mutation is recessive so only those who carry both mutated alleles (homozygous recessive cfcf) contract the disease. Those who are homozygous dominant (CFCF) or heterozygous (CFcf) don’t have the disease; however heterozygous individuals are carriers and can potentially pass the mutated allele to their children (CF Foundation). This condition is a very clear example of lethal alleles in genetics.
Student 3: An example of the inheritance pattern of lethal alleles is Sickle Cell Anemia. This diagnosis, or trait, is caused by a mutation in the HBB gene. This gene provides instruction for making a protein that is a component of hemoglobin, which is located in red blood cells. Because of this mutation, red blood cells, ultimately, become sickle shaped, which causes a number of complications for the individual. The inheritance pattern for this is Autosomal recessive, which means that both parents were carriers and the individual diagnosed with Sickle Cell Anemia received two copies of this allele.
Sickle Cell Anemia usually presents in early childhood and most commonly affects people of African descent. The distorted, sickle shape, of the cell cause red blood cells to prematurely breakdown. This is what causes the ‘anemia’ in the disease. Other symptoms include repeated infections, shortness of breath, fatigue, delayed growth, jaundice, pulmonary hypertension and episodes of pain. These patients also can experience a ‘Sickle Cell Crisis’, which consists of those episodes of severe pain. During this crisis, organs and tissues are deprived of oxygen and have the potential to cause organ damage.