Transcript Chromosomal Mutations and Nondisjunctions

Chromosomal Mutations and
Nondisjunctions
Mistakes of Meiosis
CHROMOSOMAL
________________
Abnormalities
• 1 infant in 200 newborns has a
chromosomal abnormality
• 28% of first trimester miscarriages have
a chromosomal abnormality
• Abnormalities in larger
chromosomes don’t usually survive
Chromosomal Mutations
Change in the structure of a chromosome due to the deletion, replication, or
changing position, of a gene or set of genes
Deletion
Replication
Inversion
Translocation
NONDISJUNCTION
Homologous chromosomes
fail to separate
___________________
during MEIOSIS
One cell gets 2 copies (an
extra) chromosome the
other is missing a
chromosome .
Normal
Meiosis
Nondisjunctio
n
http://web.udl.es/usuaris/e4650869/docencia/gen_etica/meioferti2.html
http://www.tokyo-med.ac.jp/genet/anm/domov.gif
How Does Nondisjunction Affect Fertilization?
Since it happens to a
sperm or egg, the new
baby can end up
3 copies of a
with _____________
chromosome
TRISOMY
= __________________
OR
only one
___________
copy of a
chromosome
= ___________________
MONOSOMY
Body cells have 2 of each chromosome
except one pair has 3 copies
= Trisomy (2n+1)
How many chromosomes?
47
Body cells have 2 of each chromosome
except one pair
= Monosomy (2n-1)
How many chromosomes?
45
How are Abnormalities Detected?
A __________
KARYOTYPE is a picture of an organism’s
(need cells from baby)
chromosomes
What Does a Karyotype Show You?
MISSING/EXTRA chromosomes and also
Can tell __________________
the GENDER
DELETIONS/INSERTIONS
______________________ of a sequence of genes
single gene
Can’t see _______________
mutations
How is Gender Determined?
Chromosomes that
determine
the sex of an organism =
Sex chromosomes
_________________
All other chromosomes =
_________________
autosomes
X
Humans have two sex chromosomes
44 autosomes
and _____
y
SEX DETERMINATION
XX = female
Xy = male
Which of these is a Male?
Who determines the gender?
X
Mom can give X
Dad can give
X or y
X XX
y
Xy
X
XX
Xy
If dad gives X with mom’s X = girl
If dad give y with mom’s X = boy
Human Abnormalities
caused by NonDisjunction
Down syndrome
__________________
Klinefelter syndrome
__________________
Turner syndrome
__________________
Down syndrome (Trisomy
21)
• 1 in 800 births
• Similar facial
features
• Slanted eyes
• Protruding tongue
Down syndrome (Trisomy 21)
Simian line on palm
TRISOMY 21
Down syndrome (= ___________)
Nondisjunction of Autosomal
Chromosomes
Male with
trisomy 21
(Downs
syndrome)
Down syndrome (Trisomy 21)
• Most common
chromosomal
abnormality
• 50% have heart defects
that need surgery to
repair
• Mild to severe mental
retardation
• Increases susceptibility
to many diseases
• Risk of having a child
with Down syndrome
increases with age of
mom
Sex Chromosomal Nondisjunction
• Failure of
chromosomes to
separate
properly during
meiosis
• Can lead to cells
with extra
genetic material
(chromosomes)
• Can lead to cells
without any
chromosomes
(bar bodies)
1. What would be the gender make-up of a zygote if a sperm with two XX
chromosomes fertilized a normal egg?
2. What would be the gender make-up of a zygote if a sperm with an X and a Y
chromosomes fertilized a normal egg?
3. What would be the gender make-up of a zygote if a sperm without a gender
chromosome fertilized a normal egg?
Turner syndrome
Turner syndrome
XO
____
•
•
•
•
•
•
•
•
•
1 in 5000 births
Females have only one X chromosome
Small size
Slightly decreased intelligence
35% have heart abnormalities
Hearing loss common
Broad chest
Reproductive organs don’t develop at puberty
Can’t have children
http://medgen.genetics.utah.edu/photographs/diseases/high/611.gif
Klinefelter syndrome XXy
Klinefelter syndrome
• 1 in 1000 births
• Males have extra X chromosomes
(Can be XXy, XXXy, or XXXXy)
• Average to slight decrease in
intelligence
• Small testes/can’t have children
• Usually not discovered until puberty
when don’t mature like peers