Warm-Up. Describe an example of a mutation which is beneficial for the individual but deleterious for the individual s offspring.

Transcription

1 Warm-Up Describe an example of a mutation which is beneficial for the individual but deleterious for the individual s offspring.

2 Yesterday s Picture

3 Aa AA aa

4 Some variations (= mutations) are bad for the individual, good for the population. From our dear friend, Wikipedia: HbS is produced by a point mutation in HBB in which the codon GAG is replaced by GTG. This results in the replacement of hydrophilic amino acid glutamic acid with the hydrophobic amino acid valine at the sixth position (6Glu Val). This substitution creates a hydrophobic spot on the outside of the protein that sticks to the hydrophobic region of an adjacent hemoglobin molecule's beta chain. This further causes clumping of HbS molecules into rigid fibers, causing sickling of the entire red blood cells in the homozygous (HbS/HbS) condition (Thom et al, 2013 CSH Persp Med). The Hemophilia Mutation (HBS) HBB wild-type structure

5 Some variations (= mutations) are bad for the individual, good for the population. The Hemophilia Mutation (HBS) so why hasn t HBS been selected out of the human population? HBS allele Homozygous for HBS = sickle cell anemia HBA (wildtype) allele Red blood cells collected from different individuals Homozygous for HBA = normal

6 Some variations (= mutations) are bad for the individual, good for the population. The Hemophilia Mutation (HBS) The Heterozygote Advantage Homozygous for HBS = sickle cell anemia Heterozygous for HBS and HBA = normal, and malaria resistant Homozygous for HBA = normal

7 Copy-and-paste transposition results in gene duplication. some chromosome Transposition some other chromosome transposon cut and paste mechanism

8 Copy-and-paste transposition results in gene duplication. some chromosome Transposition some other chromosome copy and paste mechanism

9 Copy-and-paste transposition results in gene duplication. More gene copies = more alleles = more variation can be an enzyme inside the cell, or can break up ice outside the cell Duplication of the SAS Gene

10 Copy-and-paste transposition results in gene duplication. More gene copies = more alleles = more variation Duplication of the SAS Gene Enzyme inside the cell, and doesn t need to break up ice outside the cell Enzyme not inside the cell, instead breaks up ice outside the cell

11 Copy-and-paste transposition results in gene duplication. More gene copies = more alleles = more variation Duplication of the SAS Gene Enzyme inside the cell, and doesn t need to break up ice outside the cell Enzyme not inside the cell, instead breaks up ice outside the cell

12 Copy-and-paste transposition results in gene duplication. More gene copies = more alleles = more variation Duplication of the SAS Gene What if the gene duplicated? SAS-B (duplicate)

13 Copy-and-paste transposition results in gene duplication. More gene copies = more alleles = more variation Duplication of the SAS Gene Enzyme inside the cell, and doesn t need to break up ice outside the cell Enzyme inside the cell Breaks up ice outside the cell SAS-B (duplicate)

14 Copy-and-paste transposition results in gene duplication. More gene copies = more alleles = more variation Duplication of the SAS Gene Duplication allows for more variation! Lost ability to break up ice Lost ability to be an enzyme (original) SAS-B (duplicate)

15 Copy-and-paste transposition results in gene duplication. More gene copies = more alleles = more variation Duplication of the SAS Gene Enzyme inside the cell, and doesn t need to break up ice outside the cell Enzyme inside the cell Breaks up ice outside the cell True story. This fish is called the Antarctic Eelpout SAS-B (duplicate)

16 CTQ #1 In a 2012 study published in the journal American Journal of Epidemiology, 171 newborn children not affected by malaria were tested every month for malaria. The proportion that continued to stay malaria-negative is plotted on the graph below over time. The solid line represents children heterozygous for the HBA allele, and the dashed line represents children homozygous for the wild-type allele. Assuming that all children affected by malaria died as a result, explain how the genetic makeup of this population changed over time. (LO 1.4)

17 CTQ #2 The ligand Dll1 promotes formation of vertebrae in the spine: species with high levels of Dll1 activity during development, such as snakes, develop more vertebrae and longer spines. Predict the effects of a duplication of the Dll1 gene on a population of giraffids, an extinct deer-like animal which depended on fruit hanging from trees for survival. Justify your prediction. (LO 3.24)

18 Closure Describe how duplication of the SAS gene resulted in molecular variation of cellular function in eelpout fish. (LO 4.22)