Download Chromosome Mutation - Hicksville Public Schools

AIM: What causes genetic disorders?
Do Now: What are genetic disorders?
Explain how a genetic disorder is
“passed on” to an individual.
There are two causes of genetic disorders:
1. Chromosome mutations
2. Gene mutations
Chromosome Mutation:
Causes a change
in chromosome
number.
Nondisjunction- occurs when homologous
chromosomes or sister chromatids fail to
separate during meiosis.
Trisomy Vs Monosomy:
Trisomy 21
3 Copies of a
Chromosome
Down Syndrome
Monosomy X
1 copy of a
homologous pair
Turner Syndrome
What causes nondisjunction to
occur?
Trisomy 21
No one really knows
for sure, but the older
the age of the
mother the greater
the likelihood of
having a child with
Down Syndrome.
Gene Mutations
Mutations (changes in the genetic code)
that can lead to changes in the amino
acid sequence and ultimately to the
overall shape of the protein. Why?
Gene Mutations:
Is due to a change in the nucleotide
sequence of DNA. They can involve large
regions of a chromosome or just a single
nucleotide pair.
What causes mutations
errors in DNA replication?
• Chemicals
• UV Radiation
• X-Ray radiation
Types of Mutation
• Substitution
Original
DNA Strand
• Deletion
• Insertion
• Inversion
Substitution and Deletion
Mutations
• Substitution – One nitrogenous base is
substituted for another.
DNA
CCC CAA GAT GCG
mRNA
GGG GUU CUA CGC
• Deletion – One nitrogenous base is deleted
(removed).
DNA
CTC AAG ATG CG
mRNA
GAG UUC UAC GC
•
Insertion and Inversion
Mutations
Insertion – Extra nitrogenous bases are
added to the genetic code.
DNA
CCT CTA AGA TGC G
mRNA
GGA GAU UCU ACG C
• Inversion – The genetic code is inverted or
reversed.
DNA
CCT CAA TAG GCG
mRNA
GGA GUU AUC CGC
Point and Frame Shift
Mutations
Point mutation
A change in ONE nitrogenous base, the overall number of bases stays the same
(Substitution or Inversion)
Frame shift mutation
A change in the number of overall nitrogenous bases in the genetic code
(Addition or Deletion)
Recessive v Dominant genetic
disorders:
REMEMBER: YOU
HAVE TWO
COPIES OF EACH
CHROMOSOME
• One from mom
• One from dad
Recessive
• You need two mutated copies of the gene
to show symptoms of the disorder
• Mom and Dad were both carriers- each of
them passed down a mutated gene to you
What is a carrier?
• You have one mutated copy of the gene
• You will not show symptoms but you could
pass that mutated copy to your offspring
Dominant
• You only need one mutated copy of the
gene to show symptoms of the disorder
1. Achondroplasia - most common genetic cause of dwarfism
2. Albinism - little or no production of melanin in hair, skin, and iris of the eyes
3. Bloom Syndrome - high frequency of breaks and rearrangements in the chromosomes
4. Cystic Fibrosis - autosomal recessive disorder secreting mucus and sweat
5. Down Syndrome - abnormal cell division of chromosome 21
6. Duchenne Muscular Dystrophy - rapidly gradual muscle weakness and damaged muscular
tissue in the pelvis and legs
7. Fragile X Syndrome - inherited form of mental retardation
8. Galactosemia - body’s inability to break down galactose
9. Hemophilia - body’s inability to control bleeding (interior or exterior, or both)
10. Klinefelter Syndrome - abnormal testicular evolution and decreased fertility
11. Lesch-Nyhan Syndrome - deficiency of the enzyme hypoxanthine-guanine
phosphoribosyltransferase (HPRT)
12. Neurofibromatosis - development of tumors along the different nerves and evolution of nonnervous tissues, like skin and bones
13. Noonan Syndrome - heart malformations, short stature, characteristic facial features, impaired
blood clotting, and indentation of the chest
14. Osteogenesis Imperfecta - weakened muscles, brittle bones, curved spine, and impaired
hearing
15. Phenylketonuria - mental retardation, seizures, or brain damage
16. Porphyria - accumulation of porphyrin or its precursors in the body
17. Sickle Cell Anemia - blood disorder causing sickling of the red blood cells
18. Tay-Sachs Disease - damage of the nerve cells in brain and spinal cord
19. Turner Syndrome - lack of either one whole or a part of an X chromosome
20. Wilson’s Disease - body’s inability to get rid of excess copper in the body