LP4: Chromosomal Theory of Inheritance + Sex Determination

what determines sex in drosophila?

the # of X chromosomes. 2 means female, 1 means male, regardless of Y chromosome presence.

hemizygous

only has one copy when there’s normally 2 (males are hemizygous for x-linked traits as they only have one X chromosome).

what are the symptoms/signs of kleinfelt’s syndrome? genotype?

XXY. long arms and legs, can’t produce sperm

what are the symptoms/signs of turners syndrome? genotype?

X. short, skin flaps

how do XX males exist?

SRY gene gets trasnfered to X chromosome in inappropraite corssover, SRY gets expressed

what is doasge compensation?

females have two X chromosomes, have potential to produce twice as much product compared to males. enter dosage compensation to balance dose.

barr bodies

method of dosage compensation where all but one X chromosome gets rnadomly inactivated during early development

outside of barr bodies and X-inactivation, what other method of dosage compensation?

twice as much transcription in M drisophala

do all X-linked genes on a barr body get inactivated?

no. this is how syndromes exist. furthermore, some are destined to be gonadal cells before x-inactivation.