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
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