simplify this please

Hemoglobin, heterotetramer $[$$-$globin$2,$ $-$globin$2]$

person with $2$ copies $[$homozygous$]$ of allele with GTA can suffer from sickle cell anemia.

$-$under oxygen stress, hemoglobin in red blood cells $[$rbcs$]$ aggregate

$-$form rigid rod$-$like structures $-$rbcs change cell shape

$-$from dumbbell shape in XS to RIGID sickle shape

Sickle Cell Anemia $[$cont$.]$

Sickled rbcs clog capillaries

$-$restricts blood flow downstream of blockage

$-$results in $$localized anoxia$[$oxygen deprivation$]-$results in cell death, tissue damage, organ damage $-$in some cases causes death

But condition called $$sickle cell anemia$-$ WHY?

$-$sickled cells $$turned over$[$destroyed$]$ more rapidly

$-$body cannot generate new rbcs fast enough to replenish$/$replace lost rbcs

$-$result is low rbc count or anemia.

Sickle Cell Anemia $[$cont$.]$

Person with one $$sickle cell allele$-$generally rbcs have $$normal$$ shape

$-$under extreme oxygen deprivation, cells may sickle

$-$person is more resistant to malaria

$-$parasite has difficulty infecting rbc $[$explanation$?]$

$-$allele more prevalent$/$common in human populations where malaria is prevalent. $[$Selective advantage$]$