Sickle Cell + Down Syndrome

Question 1

Sickle cell anemia

Answer 1

Is a disease that affects hemoglobin molecule for red color and oxygen transport in RBC. People have a type of hemoglobin s which makes the RBC have a sickle shape instead of the regular bi concave disc shape.

Persons with sickle cell have mutations in their HBB gene which codes for the Beta globin subunits that make up hemoglobin. Ppl with sickle cell have abnormal beta globin subunits and therefore abnormal hemoglobin.

The change in the DNA sequence causes a valine amino acid to be incorporated into the protein instead of a glutamic acid residue. This is an example of a non-conservative missense mutation. This is significant as valine is hydrophobic while glutamic acid is hydrophilic.

DNA=GAG/CTC to GTG/CAC
RNA=GAG to GUG
PROTEIN=Glutamic acid to Valine

Question 2

Sickle cell anemia and Malaria

Answer 2

SCA has a protective function against malaria. In malaria infested areas SCA ppl have an advantage. Their sickled shaped RBC prevent the malaria virus from successfully reproducing within the organism. As a result they are less affected by malaria than persons who have normal RBC

Question 3

Phenylketonuria

Answer 3

Is a disorder where the amino acid phenylalanine builds up in the body due to a defect in the gene responsible for making the enzyme that is breaking it down

Question 4

Down Syndrome

Answer 4

Occurs when a person is born with an extra whole/part in the chromosome 21. This is mainly due to an error in meiosis known as non-disjunction(failure to separate) where both copies of a chromosome migrate to the same pole

Example of aneuploidy(having missing or extra chromosomes)

Question 5

Importance of heritable variation to Nat selection

Answer 5

Heritable variation occurs when the variation can be passed onto the next generation. Heritable variations are important to selection. Variation allows some individuals within a population to adapt to the changing environment. Because natural selection acts directly only on phenotypes more genetic variation within a population usually enables more phenotypic variation.

Some new alleles increase an organisms ability to survive and reproduce, which then ensures the survival of the allele in the population. Other new alleles may be immediately detrimental and organisms carrying these will die out. Neutral alleles are neither selected for nor against and usually remain in the population.

Genetic variation is advantageous because it enables some individuals and therefore a population to survive despite a changing environment.