lecture 11 - genomes

Question 1

what is meant by “purifying selection”?

Answer 1

selection that eliminates individuals carrying mutations that interfere with important genetic functions

Question 2

what does weissmann barrier state?

Answer 2

only mutations in the germline are important as mutations in the somatic cells have no influence on future generations

Question 3

what is one mechanism that provided genetic novelty during evolution?

Answer 3

GENE DUPLICATION: evolution depends on creation of new genes and modifications of those that already exist
mildly deleterious mutations occur quickly in both copies of a duplicated gene
one copy might lose expression in a particular tissue as a result of a regulatory mutation, while the other copy loses expression in a second tissue

Question 4

what is an example of gene duplication?

Answer 4

the evolution of the beta globin gene

they must have all derived from a common ancestral gene
they have unmistakable similarities in aa sequence
this most likely happened with the help of the retroviral element, which produces a DNA strand that can be placed into the genome. This element can become part of a gene or a transcripted and translated at the same time as another gene due to the location where it jumps into the genome
these genes are full of repetitive sequences, which causes mistakes in meiosis as machinery recognizes wrong leading to wrong crossing over leading to mutations.
Therefore, this leads to duplication of DNA seen in the globin gene locus

if patient is homozygous for mutations in the beta globin gene, it results in sickle cell anemia’
if patient is heterozygous for the mutation, they have an increased chance of surviving malaria