Human Heredity

Chapter 14

Human Chromosomes• Chromosomes are only visible during cell division

(mitosis/meiosis).• To analyze chromosomes, biologist photograph

cells during mitosis and align the chromosomes in homologous pairs.

• This picture is known as a karyotype

Types of ChromosomesOn a human karyotype:

• Chromosome pairs 1-22 are known as autosomes.– They code for traits that are not related to sex.– Both males and females have the same type

• Chromosome pair 23 contains the sex chromosomes.– Males have XY and females have XX.

Boy or Girl?

Boy or Girl?

Did you know???

• Sex is determined by the father of a child.

• You have a 50% chance of having a boy or a girl

?

Who decides?

Mom can give X

Dad can give X or y

SO ____ determines sex of the baby.

If dad gives X with mom’s X = girlIf dad give y with mom’s X = boy

X X

X

y

X X X X

X y X y

Dad

GENETIC DISORDERS Human

____________________________:Change in the ______________ or ____________ of chromosomes

CHROMOSOMAL MUTATIONS structure

number

Homologous chromosomes ________________ during MEIOSIS

= _________________________

One cell gets 2 copies of the chromosome the other cell gets none.

NONDISJUNCTION

fail to separate

Down syndrome = TRISOMY 21

Down syndrome (Trisomy 21)• Most common chromosomal

abnormality

• Mild to severe mental retardation

• Risk of having a child with Down syndrome increases with age of mom

GENETIC DISORDERS Sex Linked

SEX CHROMOSOMES CAN CARRY OTHER GENES TOO= ___________________SEX LINKED TRAITS

These traits show up in different _______________ in males and females because they move with the sex chromosomes

percentages

Y-LINKED GENES: Genes ______________ chromosome

EXAMPLE:Hairy pinna

_________genes _____ show up in males Y linked

carried on Y

ONLY

____________ GENES: are carried on the X chromosome

X-linked recessive disorders show up _____________in ______ than femalesbecause males only have______ X chromosome.

MALES

X-LINKED

ONE

MORE frequently

HEMOPHILIA CAUSE:

Mutation in genes for __________________ carried ______ chromosome

Blood clotting proteins are missing so person with this disorder can’t stop bleeding when injured; can ________________ from minor cuts or suffer internal bleeding from bruises or bumps. bleed to death

Blood clotting proteins

on X

Muscular DystrophyCAUSE: deletion in genethat codes for a_______________On X ChromosomeResults in ____________________and loss of

___________________

http://www.cadenhead.org/workbench/gems/jerry-lewis-telethon.jpghttp://www.tokyo-med.ac.jp/genet/chm/dei.gif

muscle protein

weakening

skeletal muscle

1 out of 3000 males in US

COLORBLINDNESS CAUSE:

Mutation in one of three genes for _______________ carried on X chromosome

Persons with this disorder have trouble distinguishing colors.

Seen in 1 in 10 males

1 in 100 females

Color vision

http://gizmodo.com/gadgets/peripherals/samsung-develops-lcd-for-colorblind-036306.php

When Harry Met Sally…• Harry and Sally are two normal vision adults who

have a color blind son.

–B – normal vision b – color blind–What are the genotypes of Harry and Sally?• XBY, XBXb

• Show the cross between Harry and Sally.

http://www1.istockphoto.com/file_thumbview_approve/2341727/2/istockphoto_2341727_cute_cartoon_couple_drinking_vector.jpg

When Harry Met Sally…Give all of the possible genotypes and phenotypes

of their offspring.

• _________ – normal vision daughter• ________ – normal vision daughter (carrier)• ________ – normal vision son• ________– color blind son

• Sally’s dad has normal vision. Is Sally’s Mom colorblind?• She could be colorblind, or she could be a carrier

for the colorblindness trait.

http://www1.istockphoto.com/file_thumbview_approve/2341727/2/istockphoto_2341727_cute_cartoon_couple_drinking_vector.jpg

PEDIGREE CHARTS• Show the relationships within a family to study

one particular observable trait/phenotype.• Refer to page 342 in text.• Circle=female• Square=male• Horizontal line=marriage• Vertical line and bracket=children• Shaded=person expresses trait• Unshaded=person does not express trait.

Pedigree Chart for Color Blindness