Pedigrees are typically used to track disease history Diseases can be… Normal inheritance Recessive Dominant Sex-linked

Autosomal vs. Sex-Linked Autosomal traits are caused by genes on autosomes (chromosomes #1- #22) Sex-linked traits are caused by genes on the sex chromosomes (X or Y)

Today we are learning sex-linked pedigrees The sex-linked traits. You can find them here!

Just a reminder… XY = MALE XX = FEMALE

Key Point #4: For sex-linked diseases Males are either sick or healthy Females can be sick, carrier, or healthy INM

Let’s make a sex-linked pedigree for a family with some hemophiliacs INM

XHY XHXh Hemophilia XHXh XHY The female offspring will ALL be carriers of the trait. The males will all be normal. Hemophilia in humans is due to an X- chromosome mutation. What will be the results of mating between a normal (non- carrier) female and a hemophiliac male? Xh Y XHXh XHY XH XHXh XHY XH

Normal female (not a carrier) and sick man Can you label their genotypes?

Normal female (not a carrier) and sick man Can you label all their genotypes? XhY XHXH Can you label their genotypes? XHY XHY XHY XHXh

Okay, lets do one like this one more time…

XhY XhXh Color Blindness XHXh XHY Xh Y XH Xh The female offspring will either be carriers of the trait or color blind The males will either be normal or colorblind Color blindness in humans is due to an X-chromosome mutation. What will be the results of mating between a carrier female and a color blind male? Xh Y XHXh XHY XH XhXh XhY Xh

Pedigree: Carrier female and a color blind male with 3 female & 1 male offspring Based on what you know about the white-eyed female and red-eyed male fly. Can you create a Pedigree?

REAL PROBLEM TIME… What if I only give you a pedigree and no parent genotypes to make a Punnett Square?

STEP ONE: REMEMBER THE KEY! Sick boy: Healthy boy: Healthy girl: Carrier girl: Sick girl:

Phenotype Genotype Healthy female XHXH Carrier female XHXh Sick female H=healthy h=sick Phenotype Genotype Healthy female XHXH Carrier female XHXh Sick female XhXh Healthy boy XHY Sick boy XhY

Step 2: Find the sick males and label their genotypes

Sex-linked recessive

Sex-linked recessive XhY XhY

Step 3: Find the healthy males and label their genotypes

Sex-linked recessive XhY XhY

XHY Sex-linked recessive XhY XhY

Step 4: Find the sick girls and label their genotypes

XHY Sex-linked recessive XhY XHY XhY

Step 5: Find the healthy girls and decide if they are totally healthy or carriers! Make 2 punnett squares Look at the resulting offspring Circle the kids! Decide which mother genotype creates the correct offspring genotypes

XHY Sex-linked recessive XhY XHY XhY

Let’s start with the mom! What do we know about her?

Mom LET’S MAKE TWO PUNNETT SQUARES, LOOK AT THE BABIES She’s a girl She’s either healthy or a healthy carrier She had babies with a healthy man She had 2 sick boys, 1 healthy boy, and a healthy or carrier girl LET’S MAKE TWO PUNNETT SQUARES, LOOK AT THE BABIES DETERMINE THE MOM’S GENOTYPE!

Dad is def healthy! Mom is either healthy or a carrier! XH Y XH Y XHXH XHY XHXH XHY XH XH Carrier Healthy XHXh XhY XHXH XHY Xh XH

Let’s see if mom’s kids make sense if shes a carrier XH Y HEALTHY GIRL, SICK BOY, HEALTHY BOY – OH MY!!!!! MAKES SENSE!!!!! XHXH XHY XH Carrier XHXh XhY Xh

Let’s see if mom’s kids make sense if she’s healthy not carrier XH Y HEALTHY GIRL, HEALTHY BOY – EEK!!! NO SICK BOY!!!!!! DOES NOT MAKE SENSE!!!!! NOT THE MOMMA XHXH XHY XH Healthy XHXH XHY XH

HEALTHY GIRL, SICK BOY, HEALTHY BOY – OH MY!!!!! XH Y HEALTHY GIRL, SICK BOY, HEALTHY BOY – OH MY!!!!! MAKES SENSE!!!!! XHXH XHY XH Carrier XHXh XhY Xh

Mom, you are a carrier. XHY XHXh Sex-linked recessive XhY XHY XhY

Only remaining mystery… The daughter! Let’s look in the Punnett Square

Daughter XHY XHXh XhY XH Y XHXH XH Xh She could be healthy OR A carrier SHES SO MYSTERIOUS… XHXH XHY XH XHXh XhY Xh

This is a sex linked trait. What can you conclude about daughter? XHY XHXh Sex-linked recessive XhY XHY XhY XHXH or XHXh

Whew! That was a lot of work for one problem… That’s okay… they are difficult and YOU GOT IT RIGHT! Yay! Go you!

Try this one…. (Remember you can use the reference sheet!)

Rules for Sex Linked 1. More of one gender affected than the other , usually males 2. Females are usually carriers*, no male carriers for sex linked