20.2 Monogenic inheritance Flashcards
what is monogenic inheritance?
inheritance of a characterstic caused by a single gene
what is codominance?
when 2 different alleles occur for a gene which are both equally dominant
so both alleles are expressed equally in the phenotype
how many pairs of chromosomes in human?
23
how many autosomal chromosomes?
22
how many sex chromosomes?
1 (the 23rd)
what are the chromosomes in females?
X X
what are the chromosomes in males?
X Y
what is sex linkage?
when a characteristic is determined by genes carried on the sex chromosome
what causes sex linkage?
in males, genes on the section of the X chromosome which are not found on the Y chromosome are expressed more frequently
so a recessive allele in a male is more likely to be expressed than a recessive allele in a female (as females have a potential dominant allele)
what is a carrier?
an organism who is heterozygous so can carry a recessive disorder but not suffer from it
why do males suffer from haemophilia more than females?
haemophilia is a recessive sex-linked disorder so it’s alleles are found on the sex chromosomes
if a male inherits the recessive allele for haemophilia on X, it cannot have a dominant allele on Y so haemophilia will be expressed
who are the carriers of haemophilia?
heterozygous females
what is larger the Y or X chromosome?
X
where are sex linked alleles found?
the X chromosomes
X-linked
