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Galaydick Biology 1

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases? DO NOW: NEW TERM 1.  AUTOSOMES- All chromosomes #1-22 in

humans. 2.  Sex chromosomes- #23 (XX or XY in

humans)

Karyotypes

l Karyotype: a photograph of chromosomes arranged in homologous pairs, placed in order of descending size, with sex chromosomes at the end.

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

Sex chromosomes

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Galaydick Biology 2

Normal Human Male Karyotype: 46,XY

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

Normal Human Female Karyotype: 46,XX

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

What are abnormalities?

l The most common error in meiosis is nondisjunction, which means “not coming apart”.

l Nondisjunction occurs= abnormal numbers of chromosomes in gametes.

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

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Galaydick Biology 3

Autosomal Chromosome Disorders l Example

l Two copies of an autosomal chromosome fail to separate during meiosis, an individual may be born with THREE copies of a chromosome.

l This is known as a “Trisomy” l Trisomy 13, Trisomy 18, Trisomy 21.

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

Male: 47, XY, +21 Female: 47, XX, +21

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

DOWN SYNDROME

l Turner’s Syndrome (nondisjunction) ¡ Female inherits only one X chromosome ¡ Karyotype: 45, X ¡ Women are sterile, sex organs do not develop

at puberty. l Klinefelter’s syndrome (nondisjunction)

¡ Males receive an extra X chromosome ¡ Karyotype: 47, XXY ¡ The extra X chromosome interferes with

meiosis and prevents ind. from reproducing.

Klinefelter’s Syndrome, 47 XXY

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

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Galaydick Biology 4

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

Sex-linked traits (X chromosome) u Hemophilia

u blood doesn’t clot u Duchenne muscular dystrophy

u loss of muscle control u red-green color blindness

l see green & red as shades of grey

X Y

X X

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

objective: How do pedigrees and karyotypes enable scientists to study diseases?

How can we track genetic abnormalities? How can a chart show a family’s

medical history be used to assist a couple that is thinking about having children?

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Galaydick Biology 5

Pedigree

l A pedigree shows the relationships within a family and it helps to chart how one gene can be passed on from generation to generation.

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

l On a pedigree: § A circle represents a female § A square represents a male § A horizontal line connecting a male and

female represents a marriage § A vertical line and a bracket connect the

parents to their children § A circle/square that is shaded means the

person HAS the trait. § A circle/square that is not shaded means

the person does not have the trait. §  Children are placed from oldest to

youngest. § A key is given to explain what the trait is.

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

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Galaydick Biology 6

Male-DAD Female-MOM

Female-daughter Female-daughter Male- Son Male-Son

Oldest to youngest

Marriage

Has the trait

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

Steps: • Identify all people who have the trait.

• In this example, all those who have the trait are homozygous recessive. (autosomal)

• Can you correctly identify all genotypes of this family?

• F- Normal • f- cystic fibrosis

ff

ff ff

Ff

Ff Ff

Key: affected male affected female unaffected male unaffected female

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

l PKU ¡ P- Unaffected ¡ p- phenylketonuria

Key: affected male affected female unaffected male unaffected female

pp

pp

pp

Pp Pp

Pp PP or Pp

Pp Pp

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Galaydick Biology 7

Key: affected male affected female unaffected male unaffected female

l H-huntington’s disease

l h-Unaffected

Hh

Hh

Hh

Hh

hh

hh

hh hh

hh

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

Sex-Linked Inheritance l  Colorblindness

Key: affected male affected female unaffected male unaffected female

cc Cc

cc cc cc Cc Cc

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?

As the genetic investigator, you need to map the hairy feet trait in the Walhberg family using a pedigree. Make sure to use the correct symbols for each person. Try and figure out the genotype under their symbol. Finally, make a pedigree on the paper provided to show the type of inheritance pattern for the Walhberg Family’s hairy feet. (HAIRY FEET CAN EITHER BE A DOMINANT OR RECESSIVE TRAIT= BOTH WORK!)

l  The Walhberg family has a rare genetic inheritance that causes the infected person to have a large amount of hair on their feet. Grandma Walhberg has hairless feet, but Grandpa Walhberg has the hairy feet trait. Grandma and Grandpa Walhberg, in their long loving marriage had five children. Danny, Donny, Mark, and Elaine all have hairy feet while Monica has the only hairless feet of all the children. Danny got married to Rachel and two of the three children (the two boys) have hairy feet while their daughter has hairless feet. Donny and his wife have four children, two boys and two girls, all with hairless feet. Mark is still single, while Elaine and her husband have two children, one girl with hairy feet and one boy without hair on his feet. Monica doesn’t have hairy feet as we said earlier, but wonders what types of children she will have since her husband has hairy feet. They already have one daughter, but she doesn’t have hairy feet.

OBJECTIVE: How do pedigrees and karyotypes enable scientists to study diseases?