Transcript AP Biology - Cloudfront.net

Mutations
https://www.youtube.com/watch?
v=HEyCmXL_IM0
Being Brenden
Mutations

Point mutations
single base change
 base-pair
substitution


silent mutation
 no amino acid change
 redundancy in code

missense
 change amino acid

nonsense
 change to stop codon
When do mutations affect the
next generation?
Point mutation leads to Sickle cell anemia
What kind of mutation?
Sickle cell anemia
Mutations

Frameshift

shift in the reading
frame


insertions


changes everything
“downstream”
adding base(s)
deletions

losing base(s)
What’s the
value of
mutations?
Errors of Meiosis
Chromosomal Abnormalities
AP Biology
2006-2007
Chromosomal abnormalities
 Incorrect number of chromosomes

nondisjunction
 chromosomes don’t separate properly
during meiosis
 parts of chromosomes are broken off and/or
lost during meiosis.
 or may break and rejoin incorrectly
AP Biology
Chromosomal abnormalities
breakage of chromosomes
 Deletion: piece of chromosome breaks off and is

AP Biology
lost.
Duplication: chromatid breaks off and attaches
to its sister chromatid
Chromosomal abnormalities

breakage of chromosomes
 Inversion: chromosome breaks off and is
reinserted backwards-or not in the right
order
 Translocation: chromosome breaks off and
is added to a nonhomologous
chrosomosome
AP Biology
replication
error of
Changes in chromosome structure
 deletion

 duplication
crossing over

error of
loss of a chromosomal segment
repeat a segment
 inversion

reverses a segment
 translocation

AP Biology
move segment from one chromosome
to another
Nondisjunction
 Baby has wrong chromosome number

trisomy
 cells have 3 copies of a chromosome

n+1
AP Biology
monosomy
 cells have only 1 copy of a chromosome
n-1
n
n
trisomy
monosomy
2n+1
2n-1
Karyotype
 A karyotype is a standardized
arrangement of all the chromosomes of
a cell
Homologous
chromosomes are
paired up, then they
are put in order from
the LARGEST
chromosome pair to
the smallest.
AP Biology
Karyotypes
AP Biology
Karyotypes
AP Biology
2 different sized sex chromosomes = male
Down syndrome
 Trisomy 21
3 copies of chromosome 21
 1 in 700 children born in U.S.

 Chromosome 21 is the
smallest human chromosome

but still severe effects
 Frequency of Down
syndrome correlates
with the age of the mother
AP Biology
Down’s syndrome
•decreased muscle tone at birth
•asymmetrical or odd-shaped skull
•round head with flat area at the back of the head
•slanting eyes
•small mouth with protruding tongue
•single crease on the palm
•slowed growth and development
•delayed mental and social skills
AP Biology