3.1 Genes

Question 1

what is a gene

Answer 1

a gene is a heritable factor that consists of a length of DNA and influence a specific characteristic

genes are linked in groups and correspond to a particular chromosome

Question 2

do the number of genes relate to the complexity of an organism

Answer 2

no

e.g. protocista - unicellular parasite - trichomonas vaginalis - 60 000 genes

human - 23 000 genes

water flea - daphina pulex - 31 000

but

prokaryotes - E coli - 3 200

Question 3

where are genes located and where are alleles

Answer 3

genes are located in loci

allelles - are different versions due to different nucleotide sequence due to mutation

Question 4

what is sickle cell anemia

Answer 4

caused by a base subsitution mutation which causes a change to teh sequence of a polypeptide in hemoglobin

normal CTT –> GAA –> glutamate (Hb allele)

mutant –> CAT –> GUA –> valine (Ha allele)

most common disease in the world

this causes haemoglobin molecuels to stick together intissues with low o2 concentraion - if they are rigid enough they distort the shape of the RBC

can cause damage by becoming trapped and reduciong blood flood by blocking capallaries

once neough O2 shape returns to normal and the process is repeated

hameoglobin is damaged by this and body ccannot replace RBC fast enough so anemia develops