SEX LINKED INHERITANCE & PEDIGREES

A DAY: 5/17

B DAY: 5/18

ONLY 2 MORE CLASSES WITH NEW CONTENT

RETEACH AND RETAKE

• DURING FRESHMEN SEMINAR TODAY I

WILL RETEACH THE MATERIAL ON THE

QUIZ FROM LAST CLASS

• IF YOU WANT TO RETAKE THE QUIZ, YOU

NEED TO COME TO F.S. AND GET

RETAUGHT THE INFORMATION

• YOU WILL HAVE TIME DURING F.S. TO

RETAKE THE QUIZ AFTER BEING

RETAUGHT THE INFORMATION

QUICK REVIEW

• HOW MANY COPIES OF EACH CHROMOSOME DO WE HAVE?

• TWO: ONE FROM MOM & ONE FROM DAD

• HOW MANY PAIRS OF CHROMOSOMES DO WE HAVE?

• WE HAVE 23 PAIRS OF CHROMOSOMES

• WHAT DO WE CALL CHROMOSOMES 1-22?

• AUTOSOMES

• WHAT ABOUT THE 23RD PAIR OF CHROMOSOMES?

• SEX CHROMOSOMES

SEX CHROMOSOMES• THE EXPRESSION OF GENES ON THE SEX CHROMOSOMES DIFFERS FROM

THE EXPRESSION OF AUTOSOMAL GENES

• GENES THAT ARE LOCATED ON THE SEX CHROMOSOMES ARE CALLED

“SEX-LINKED GENES”

• IN HUMANS, WHAT IS THE GENOTYPE FOR A FEMALE?

• XX

• IN HUMANS, WHAT IS THE GENOTYPE FOR A MALE?

• XY

• MAKE A PUNNETT SQUARE TO SHOW WHAT PERCENTAGE OF BABIES

SHOULD BE MALE VERSUS FEMALE

• ACCORDING TO PUNNETT SQUARES, 50% OF BABIES SHOULD BE

MALE AND 50% OF BABIES SHOULD BE FEMALE

SEX CHROMOSOMES• IF WOMEN HAVE A GENOTYPE OF XX, WHERE DO THEIR

BABY BOYS GET THEIR Y CHROMOSOME FROM?

• DAD

• WHAT IS THE ONLY POSSIBLE SEX CHROMOSOME THAT

MOM CAN GIVE TO A BABY?

• X BECAUSE SHE ONLY HAS X CHROMOSOMES

• IN HUMANS, THE FATHER DETERMINES THE SEX OF THE

BABY

• BRITISH KINGS ARE RUMORED TO HAVE THEIR WIVES

BEHEADED IF THEY DIDN’T “PRODUCE” SONS. WHAT IS

IRONIC ABOUT THIS BEHAVIOR.

SEX LINKED TRAITS• HOW MANY COPIES OF EACH GENE DO

WE HAVE?

• 2 COPIES OF EACH AUTOSOMAL GENE

• MALES ONLY HAVE 1 COPY OF THE X

CHROMOSOME

• MALES EXPRESS ALL OF THEIR GENES ON

THEIR X CHROMOSOME, EVEN IF THEY

ARE RECESSIVE

• FEMALES HAVE TWO COPIES OF THEIR X

CHROMOSOME

ME-WOW!

• IN SOME CATS, COAT COLOR IS A SEX LINKED TRAIT

• GENES ON THE X CHROMOSOME DETERMINE IF THEY

ARE ORANGE AND WHITE, OR BLACK AND WHITE,

OR ALL THREE (CALICO)

• LET’S USE “O” TO REPRESENT ORANGE FUR AND

“B” TO REPRESENT BLACK FUR

• XOXO = WHAT IS THE PHENOTYPE OF THIS CAT,

INCLUDING SEX?

• XBY = WHAT IS THE PHENOTYPE OF THIS CAT,

INCLUDING SEX?

• WHICH OF THESE CATS ARE FOR SURE FEMALE?

SEX LINKED TRAITS• IN HUMANS, THE FOLLOWING TRAITS ARE FOUND ON

THE X CHROMOSOME:

• RED-GREEN COLORBLINDNESS – RED AND GREEN

APPEAR THE SAME

• BALDNESS – LOSS OF HAIR ON THE HEAD

• DUCHENNE MUSCULAR DYSTROPHY – ABNORMAL

SKELETAL AND MUSCULAR DEVELOPMENT

• HEMOPHILIA – CANNOT STOP BLEEDING FROM

INJURY; SPONTANEOUS BLEEDING

• ARE MEN OR WOMEN MORE AFFECTED BY THESE

TRAITS?

• MEN, BUT WHY?

PEDIGREE SHOWING HEMOPHILIA INHERITANCE FOR A ROYAL FAMILY

PEDIGREES• A PEDIGREE IS A CHART THAT TRACKS PHENOTYPES AND GENOTYPES

IN A FAMILY

• PEDIGREES CAN SHOW WHO HAS THE TRAIT AND WHO IS A CARRIER

FOR THE TRAIT

• BUILDING A PEDIGREE IS LIKE SOLVING A PUZZLE

• USE A SQUARE TO REPRESENT MALES & USE A CIRCLE TO REPRESENT

FEMALES

• WHEN A SHAPE IS COLORED IN, THAT INDIVIDUAL HAS THE TRAIT

• WHEN A SHAPE IS NOT COLORED IN, THAT INDIVIDUAL DOES NOT HAVE THE

TRAIT

• WHAT DOES IT REPRESENT WHEN A SHAPE IS PARTIALLY COLORED IN?

PEDIGREES

• A HORIZONTAL LINE BETWEEN TWO PEOPLE SHOW THEY ARE A COUPLE (I.E.

MARRIED)

• A VERTICAL LINE BETWEEN TWO PEOPLE SHOW THEY HAVE REPRODUCED

• A HORIZONTAL ABOVE TWO PEOPLE SHOW THEY ARE SIBLINGS

PEDIGREES

BOOK NOTES

• TURN TO PAGE 214 AND READ THROUGH

THE TWO PEDIGREES ON 215

•WHY ARE ALL OF THE CARRIERS OF COLOR

BLINDNESS FEMALES?

•WHY ARE ONLY MALES AFFECTED IN THIS

PEDIGREE?

•WHY CAN WE NOT BE SURE OF THE

GENOTYPE FOR PERSON NUMBER 5?

PEDIGREES – QUICK QUIZ

• WHAT IS THE PHENOTYPE OF INDIVIDUAL #1? WHAT IS THE GENOTYPE OF

INDIVIDUAL #1?

• PHENOTYPE = HAVE THE TRAIT & GENOTYPE =

• WHAT IS THE PHENOTYPE OF INDIVIDUAL #2? WHAT IS THE GENOTYPE OF

INDIVIDUAL #2?

• PHENOTYPE = CARRIER & GENOTYPE =

#1 #2

ARE MALES OR FEMALES MORE AFFECTED BY HEMOPHILIA? WHY?

PEDIGREE OVERVIEW

• ARE CARRIERS OF A DISEASE HOMOZYGOUS OR

HETEROZYGOUS?

• CAN MEN BE CARRIERS OF AUTOSOMAL DISEASES?

WHAT ABOUT SEX-LINKED DISEASES?

• BALDNESS IS SEX-LINKED (X-CHROMOSOME)

RECESSIVE DISORDER. IF A MAN’S FATHER HAS A

FULL HEAD OF HAIR INTO OLD AGE, DOES THAT

MEAN THE MAN CAN EXPECT TO ALSO KEEP HIS

HAIR INTO OLD AGE? WHY OR WHY NOT?

IN CLASS ASSIGNMENTS

• FIRST, YOU WILL MAKE A BABY…A MARTIAN BABY

• SECOND, YOU WILL NEED TO COMPLETE A PEDIGREE

WORKSHEET

• THIRD, COME AND GET A PASS FOR FRESHMAN

SEMINAR IF YOU NEED TO RETAKE THE QUIZ