2.3.3 sex determination Flashcards
what is the sex of birds, mammals and some insects determined by?
the presence of sex chromosomes
what does the presence of sex chromosomes determine
the sex of birds, mammals and some insects
what determines the development of male characteristics in most mammals
the SRY gene on the Y chromosome
what does the SRY gene on the Y chromosome determine
the development of male characteristics in most mammals
what do heterogametic males lack most of
the corresponding homologous alleles on the shorter Y chromosome
heterogametic males
XY
which chromosome is shorter, X or Y
Y
what can the lack of corresponding homologous alleles on the shorter Y chromosomes in heterogametic males result in
sex linked patterns of inheritance as seen with carrier females and affected males
homogametic females
XX
in homogametic females, one of the two X chromosomes present in each cell is…
randomly inactivated at an early stage of development
what does X chromosome inactivation prevent
a double dose of gene products which could be harmful to cells
what is X chromosome inactivation
a process by which most of one X chromosome is inactivated
are carriers less likely to be affected by any deleterious mutations
yes
why do half the cells in any tissue have a working copy of the gene in question
because the x chromosome inactivated in each cell is random
what are hermaphrodites
species that have functioning male and female reproductive organs in each individual. they produce both male and female gametes and usually have a partner with which to exchange gametes
