Download Chromosomal Abnormalities

Formative Assessment
Transcription and Translation
DNA
TTT
mRNA
aa
UAC
GAA
Trp
Transcription
Translation
Formative Assessment
Mutations
• Write a DNA strand that has an insertion
mutation after the 6th base in the following
strand:
–A A T G C G A A G C C T
• What type of mutation is demonstrated
below? Normal mRNA A U G T T T C G U
mutated mRNA U U G T T T C G U
Chromosomal Abnormalities
Name of abnormality
Example
Notes
Chromosomal Abnormalities
2006-2007
PA Standard
3.1.B.B1
• Explain how crossing over, jumping
genes, deletion and duplication of
genes result in genetic variation.
• Student Friendly Target:
–I can explain 5 chromosomal
abnormalities and give real-life
examples of each.
Chromosomal abnormalities
nondisjunction
• chromosomes don’t separate properly during
meiosis so chromosomes aren’t divided evenly into
sperm or egg cells
OR
Structural abnormalities -shape/structure
is incorrect
•
•
•
•
deletion
duplication
inversion
translocation
Nondisjunction
• Baby has wrong chromosome number
– trisomy
• cells have 3 copies of a chromosome
– monosomy
• cells have only 1 copy of a chromosome
n+1
n
n-1
n
trisomy
monosomy
2n+1
2n-1
Human chromosome disorders
• High frequency in humans
– most embryos are spontaneously aborted
– alterations are too disastrous
– developmental problems result from biochemical imbalance
• imbalance in regulatory molecules?
– hormones?
– transcription factors?
• Certain conditions are tolerated
– upset the balance less = survivable
– but characteristic set of symptoms = syndrome
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
Sex chromosomes abnormalities
• Human development more tolerant of
wrong numbers in sex chromosome
• But produces a variety of distinct
syndromes in humans
–
–
–
–
XXY = Klinefelter’s syndrome male
XXX = Trisomy X female
XYY = Jacob’s syndrome male
XO = Turner syndrome female
replication
crossing over
error of
error of
Changes in chromosome
structure
• deletion
– loss of a chromosomal segment
• duplication
– repeat a segment
• inversion
– reverses a segment
• translocation
– move segment from one chromosome to
another
Cri du Chat Syndrome
“Cat Cry” syndrome
• Deletion of the short end arm of chromosome
5 (usually paternal)
•
•
•
•
Characterized by a high pitched mewing cry
Ears are low on the head, abnormal shape
Syndactyly (webbed fingers/toes)
Heart anomolies
replication
crossing over
error of
error of
Changes in chromosome structure
• deletion
– loss of a chromosomal segment
• duplication
– repeat a segment
• inversion
– reverses a segment
• translocation
– move segment from one chromosome to
another
Charcot- Marie-Tooth Syndrome
•
•
•
•
•
•
Slow degeneration of the muscles in the foot
Abnormal gait
Excessive high arch
Hammertoes
Symptoms begin in adolescence
duplication of a very large region on
chromosome 17p.
replication
crossing over
error of
error of
Changes in chromosome structure
• deletion
– loss of a chromosomal segment
• duplication
– repeat a segment
• inversion
– reverses a segment
• translocation
– move segment from one chromosome to
another
Pick Complex
• Spectrum of frontal lobe dementias
• maybe Parkinson’s?
• Mictrotubules in cells of the frontal lobe do
not work properly
• Inversion of chromosome 17 in Tau gene
region
replication
crossing over
error of
error of
Changes in chromosome structure
• deletion
– loss of a chromosomal segment
• duplication
– repeat a segment
• inversion
– reverses a segment
• translocation
– move segment from one chromosome to
another
Burkitt’s Lymphoma
Translocation of the Myc gene on
chromosome 8
Normal Myc genes control cell
growth and division
•Translocated Myc genes don’t
function properly
•Leads to cancer of the lymph
nodes
Barbara McClintock
Discovered “jumping genes”
(translocation of genes on
chromosomes)
Occurs during meiosis (cell division
forming egg and sperm)
Won Nobel Prize in 1983
Mutations
Point Mutations
Chromosomal