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![• Autism/ ADHD/ Mental Retardation.
• Strabismus (lazy eye)
• Obsessive-Compulsive Disorder (OCD) [some]
• Speech may be cluttered or nervous.
• Stereotypic movements (e.g., hand-flapping)
and atypical social development, particularly
shyness, limited eye contact, memory
problems, and difficulty with face encoding.
People inflicted by FXS have:
•Fragile X Syndrome](https://image.slidesharecdn.com/genemutation2-130611074825-phpapp01/85/Gene-Mutation-28-320.jpg)
Uploaded byJaycris Agnes
Gene Mutation
1. Gene mutations are alterations in DNA sequences that can change the genetic code and potentially cause genetic diseases. 2. The most common type of gene mutation is point mutations, which change a single DNA nucleotide and can be silent, missense, or nonsense. 3. Examples of diseases caused by gene mutations include sickle cell anemia from a missense mutation, various cancers from oncogene and tumor suppressor gene mutations, cystic fibrosis from a deletion mutation, and myotonic dystrophy and fragile X syndrome from trinucleotide repeat expansions.
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Gene Mutation
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- 2. The genetic codeis the set of rules by which information encoded within genetic material (DNA or mRNA sequences) is translated into proteins (amino acid sequences) by living cells. Genetic Code •Introduction:
- 3. • The Codonsin mRNA are nucleotide bases, “read” in blocks of three. • There are 64 codons, 61 of these base triplets correspond to specific amino acids. Three other serve as signal to stop translation. Codons
- 5. A gene mutationis defined as an alteration in the sequence of nucleotides in DNA a polymer of nucleotides joined together. Gene Mutation
- 6. • During proteinsynthesis, DNA is transcribed into RNA and then translated to produce proteins. • Altering nucleotide sequences most often results in nonfunctioning proteins. • Mutations cause changes in the genetic code that lead to genetic variation and the potential to develop disease.
- 7. Kinds of GeneMutation
- 8. Point mutations arethe most common type of gene mutation. Also called a base-pair substitution, this type of mutation changes a single nucleotide base pair. Point mutations can be categorized into three types: 1. Point Mutation SILENT MISSENSE NONSENSE
- 9. SILENT MUTATION Although achange in the DNA sequence occurs, this type of mutation does not change the protein that is to be produced.
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- 11. TYPES OF MISSENSEMUTATION Conservative Non-conservative Result in an amino acid change. However, the properties of the amino acid remain the same (e.g., hydrophobic, hydrophilic, etc). Result in an amino acid change that has different properties than the wild type. The protein may lose its function, which can result in a disease in the organism.
- 12. DNA sequence Aminoacid sequence Type of mutation ATG CAG GTG ACC TCA GTG M Q V T S V None ATG CAG CTG ACC TCA GTG M Q L T S V Conservative ATG CCG GTG ACC TCA GTG M P V T S V Non- conservative Conservative vs. Non-conservative
- 13. Non-conservative Mutation Diseases • SickleCell Anemia (loss-of-function) Sequence for normal hemoglobin ATG GTG CAC CTG ACT CCT GAG GAG AAG TCT GCC GTT ACT START Val His Leu Thr Pro Glu Glu Lys Ser Ala Val Thr Sequence for Sickle Cell Anemia ATG GTG CAC CTG ACT CCT GTG GAG AAG TCT GCC GTT ACT START Val His Leu Thr Pro Val Glu Lys Ser Ala Val Thr
- 14. • Cancer Valine GlutamicAcid Mutation changing a valine to glutamic acid in the braf gene; this leads to an activation of the RAF protein which causes unlimited proliferative signalling in cancer cells.
- 15. All cancers derivefrom single cells that have acquired the characteristics of continually dividing in an unrestrained manner and invading surrounding tissues. •What is cancer? Human melanoma cell undergoing cell division Credit: Paul Smith & Rachel Errington, Wellcome Images
- 16. • Cancer cellsbehave in this abnormal manner because of changes in the DNA sequence of key genes, which are known as cancer genes. Therefore all cancers are genetic diseases. •What is cancer?
- 17. Oncogene(gain-of-function) Cancer Ras Genes which normallyfunction to PROMOTE cell growth/division in a controlled manner
- 18. Tumour suppressor gene(loss-of-function) TS Cancer These genes normally function to PREVENT cell growth/division
- 19. •Importance of somaticDNA changes in human cancer Somatic Inherited Both Only 5 –10% of cancer cases have a clear hereditary component, e.g. BRCA1 and BRCA2 in breast cancer Even in those cases where susceptibility is clearly inherited, somatic changes are required for cancer to develop
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- 22. 3. Repeat ExpansionMutation
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- 25. 1. Causes thick,sticky mucus and very salty sweat. 2. Bacteria colonize in the mucus causing infections. 3. Eventually fatal. • Cause by Deletion of a base in Phenylalanine in chromosome number 7. X-Linked recessive. •Cystic Fibrosis
- 26. 1. Myotonic dystrophyis a chronic, slowly progressing, highly variable, inherited multisystemic disease. 2. It is characterized by wasting of the muscles (muscular dystrophy), cataracts, heart conduction defects, endocrine ch anges, and myotonia. •Myotonic Dystrophy Caused by trinucleotide repeat of CUG (Leucine). X-linked Dominant.
- 27. • Large, protrudingears (one or both) • Long face (vertical maxillary excess) • High-arched palate (related to the above) • Hyperextensible finger joints • Hyperextensible ('Double-jointed') thumbs • Flat feet • Soft skin • Postpubescent macroorchidism (Lar ge testes in men after puberty) • Hypotonia (low muscle tone) • single palm crease (crease goes across entire palm) •Fragile X Syndrome Caused by trinucleotide repeat of CGG(Arginine) in X- Chromosome. X-linked Dominant.
- 28. • Autism/ ADHD/Mental Retardation. • Strabismus (lazy eye) • Obsessive-Compulsive Disorder (OCD) [some] • Speech may be cluttered or nervous. • Stereotypic movements (e.g., hand-flapping) and atypical social development, particularly shyness, limited eye contact, memory problems, and difficulty with face encoding. People inflicted by FXS have: •Fragile X Syndrome
- 29. • Afflicted personsuffered from severe anemia. Caused by Nonsense mutation of CAG(glutamine) to UAG (STOP). Autosomal Recessive. •B-Thalassemia
Editor's Notes
- #16 All cancers result from changes in the DNA sequence of our genome. These changes occur throughout life because the genome within our cells is exposed to mutagens like UV radiation and accumulates mistakes during replication. These changes result in a progressive, subtle divergence of the DNA sequence from the original copy from the fertilised egg. Occasionally, one of these mutations alters the function of a critical gene, providing a growth advantage to the cell in which it has occurred. This means that this cell and its offspring divide at a faster rate than that of their neighbours. The result is tumour formation, invasion of surrounding tissue and eventually ‘metastasis’, or spread of the cancer to other parts of the body. The image in the slide shows a human melanoma cell undergoing cell division. The chromosomes (blue) have separated and the two daughter cells have almost split apart – only a small bridge of cytoplasm remains. The green staining labels the endoplasmic reticulum and the red labels the mitochondria.
- #18 Proto-oncogenes code for proteins that drive cell division. When these genes acquire mutations that result in continually active proteins they become oncogenes and cause uncontrolled cell growth and division. The “cell as a car” analogy: If you are using the car analogy, oncogenes can be seen as the accelerator. When one healthy copy of the proto-oncogene is altered it is the equivalent of the accelerator pedal being stuck – speeding up cell growth and division. Notice in the case of oncogenes that it only takes one copy of the gene to undergo changes to lead to cancer, rather than both copies as is the case with TSGs.
- #19 Tumour suppressor genes (TSG) code for proteins that slow down cell growth. They can halt the cell growth cycle to stop unnecessary division or promote apoptosis (cell death) if the cell’s DNA is damaged.Different tumour suppressor proteins carry out the following functions: Repression of genes which are essential to the cell cycle, therefore inhibiting cell division. Linking the cell cycle to DNA damage; if there is damage to the cell it will not allow it to divide. Identifying where the DNA damage is irreparable and initiating apoptosis (cell suicide).The animated chromosome diagram illustrates that both copies of the TSG have to be inactivated by mutation or other alteration for there to be a loss of cell cycle control. If one functional copy remains, there is still a “brake” on the cell’s growth. The “cell as a car” analogy: One way to think about TSGs is to see them as the brakes of a car. There is a gene on both chromosomes so in a sense there are two brakes. If one gene is mutated and its protein loses its function, the cell can still halt and prevent unregulated cell growth as the other copy of the gene (or brake) is still functioning. However if that back up copy also changes and no longer codes for a functioning protein, the cell cycle is no longer under control and this can lead to cancer.
- #20 An example of germline cancer mutations inherited from parents are mutations in the BRCA1 and BRCA2 genes. These are breast cancer susceptibility cancer genes. They are rare and the risk of cancer is high.Women who have inherited a mutation in one of these genes from a parent will have a life time risk of breast cancer of approximately 70% , compared to 10% in the rest of the population. However, even in those cases where someone has inherited a susceptibility, additional somatic mutations are required.