SEX SEX DETERMINATION DETERMINATION

& SEX-LINKED & SEX-LINKED INHERITANCEINHERITANCE

SEX SEX DETERMINATION DETERMINATION

& SEX-LINKED & SEX-LINKED INHERITANCEINHERITANCE

SEX DETERMINATIONSEX DETERMINATIONSEX DETERMINATIONSEX DETERMINATION

The greatest difference between individual members of the same species is their sex.

IDENTIFY THIS IDENTIFY THIS KARYOTYPEKARYOTYPE

IDENTIFY THIS IDENTIFY THIS KARYOTYPEKARYOTYPE

SEX DETERMINATIONSEX DETERMINATIONSEX DETERMINATIONSEX DETERMINATION

In humans, females have two “X” chromosomes in the 23rd pair.

SEX DETERMINATIONSEX DETERMINATIONSEX DETERMINATIONSEX DETERMINATION

In humans, males have an “X” and a “Y” chromosome on the 23rd pair.

HOW IS SEX HOW IS SEX DETERMINED?DETERMINED?

HOW IS SEX HOW IS SEX DETERMINED?DETERMINED?

If females have the XX combination, then all eggs will contain an X chromosome.

XX

X

X

HOW IS SEX HOW IS SEX DETERMINED?DETERMINED?

HOW IS SEX HOW IS SEX DETERMINED?DETERMINED?

If males contain the XY combination then the sperm can contain either the X or the Y chromosome.

XYX

Y

THEREFORE,THEREFORE,THEREFORE,THEREFORE,

The male always determines the sex of the offspring--if he passes the X chromosome the result is a female offspring.

If he passes the Y chromosome the result is a male offspring.

SEX-LINKED SEX-LINKED INHERITANCEINHERITANCE

SEX-LINKED SEX-LINKED INHERITANCEINHERITANCE

THE DISCOVERY OF SEX THE DISCOVERY OF SEX LINKAGELINKAGE

THE DISCOVERY OF SEX THE DISCOVERY OF SEX LINKAGELINKAGE

The study of the fruit fly by Thomas Hunt Morgan led to the discovery of sex determination and sex linkage.

MORGAN’S MORGAN’S EXPERIMENTEXPERIMENT

MORGAN’S MORGAN’S EXPERIMENTEXPERIMENT

Most flies had red eyes.

Morgan noticed a male with white eyes.

He performed an experimental cross.

RED EYEDFEMALE

WHITE EYEDMALEP1

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ALL OFFSPRING HAD ALL OFFSPRING HAD RED EYES AND THE RED EYES AND THE MALE TO FEMALE MALE TO FEMALE RATIO WAS 50:50RATIO WAS 50:50

ALL OFFSPRING HAD ALL OFFSPRING HAD RED EYES AND THE RED EYES AND THE MALE TO FEMALE MALE TO FEMALE RATIO WAS 50:50RATIO WAS 50:50

WHAT WOULD YOU WHAT WOULD YOU PREDICT IF TWO OF THE PREDICT IF TWO OF THE

FF11 FLIES WERE FLIES WERE

CROSSED?CROSSED?

WHAT WOULD YOU WHAT WOULD YOU PREDICT IF TWO OF THE PREDICT IF TWO OF THE

FF11 FLIES WERE FLIES WERE

CROSSED?CROSSED?

A red eyed female crossed with a red eyed male?

MORGAN FOUND:MORGAN FOUND:MORGAN FOUND:MORGAN FOUND:75% had red eyes, 25% had white

eyes.

50% were male, 50% were female

All of the white eyed flies were MALE.

SEX-LINKED TRAITSEX-LINKED TRAITSEX-LINKED TRAITSEX-LINKED TRAIT

A trait that is carried on the X chromosome.

Almost always expressed in males.

SEX-LINKED TRAITS IN SEX-LINKED TRAITS IN HUMANSHUMANS

SEX-LINKED TRAITS IN SEX-LINKED TRAITS IN HUMANSHUMANS

Hemophilia

Duchenne Muscular Dystrophy

Red/Green Color Blindness

ARE YOU COLOR BLIND?ARE YOU COLOR BLIND?ARE YOU COLOR BLIND?ARE YOU COLOR BLIND?