Transcript Human_Heredity

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 Chromosomes
On 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
X
X
X
XX
XX
y
Xy
Xy
Dad determines sex of the baby.
SO ____
If dad gives X with mom’s X = girl
If dad give y with mom’s X = boy
Human
GENETIC DISORDERS
CHROMOSOMAL MUTATIONS
____________________________:
structure
Change in the ______________
or
number
____________
of chromosomes
Homologous chromosomes
fail to separate
________________
during MEIOSIS
NONDISJUNCTION
= _________________________
One cell gets 2 copies of
the chromosome the
other cell gets none.
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
Sex Linked
GENETIC DISORDERS
SEX CHROMOSOMES CAN
CARRY OTHER GENES TOO
SEX LINKED TRAITS
= ___________________
These traits show up in different
_______________
percentages in males and females
because they move with the sex
chromosomes
Y-LINKED GENES:
carried on Y chromosome
Genes ______________
EXAMPLE:
Hairy pinna
Y linked
ONLY show up in males
_________genes
_____
X-LINKED GENES:
____________
are carried on the X chromosome
X-linked recessive disorders
MORE frequently
show up _____________
MALES than females
in ______
because males only have
ONE X chromosome.
______
HEMOPHILIA
CAUSE:
Blood clotting proteins carried
Mutation in genes for __________________
on X chromosome
______
Blood clotting proteins are missing so person with this
disorder can’t stop bleeding when injured; can
bleed to death
________________
from minor cuts or suffer internal
bleeding from bruises or bumps.
Muscular Dystrophy
CAUSE:
deletion in gene
that codes for a
muscle
protein
_______________
On X Chromosome
Results in
weakening
____________________
and loss of
skeletal
muscle
___________________
1
out of 3000 males in US
http://www.cadenhead.org/workbench/gems/jerry-lewis-telethon.jpg
http://www.tokyo-med.ac.jp/genet/chm/dei.gif
COLORBLINDNESS
CAUSE:
Color vision
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
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/23
41727/2/istockphoto_2341727_cute_cartoon_couple_drinki
ng_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/23
41727/2/istockphoto_2341727_cute_cartoon_couple_drinki
ng_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