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Molecular Medicine Flashcards

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1
Q

What does molecular medicine examine ?

A

The origin and course of illness and disease and how they can be prevented and treated at the cellular or molecular level

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2
Q

What are the types of genetic disorders?

A

Single gene disorders
-Autosomal recessive

  • autosomal dominant
  • sex linked

Multifactorial or complex disorders

Chromosome imbalances

Mitochondrial disorders

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3
Q

What 3 factors contribute to disease?

A

Genetic- inherited failure in one or more components

Behavioral- exercise, diet, smoking,alcohol consumption

Environmental-infections, toxic substances, physical forces

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4
Q

What are the frequency and symptoms of cystic fibrosis ?

A

1 in 2000 (N. European)

Symptoms- recurrent lung infections, pancreatic exocrine deficiency, male sterility

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5
Q

What are the frequency and symptoms of phenylketonuria ?

A

1 in 2000 to 1 in 5000 (Europeans)

Symptoms: mental retardation

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6
Q

What are the frequency and symptoms of Tay-Sachs?

A

Frequency- 1 in 3000(Ashkenazi Jews)

Symptoms- neurological degeneration, blindness and paralysis

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7
Q

What are the frequency and symptoms of thalassemia?

A

1-2 in 100 (Mediterranean and Asia in malaria endemic regions)

Symptoms- anemia

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8
Q

What are the frequency and symptoms of sickle cell anemia ?

A

1-2 in 100 (parts of Africa where malaria is endemic). Also in India, the Caribbean, the Middle East, and the Mediterranean

Symptom: anemia

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9
Q

What are the frequency and symptoms of galactosemia?

A

Frequency:1 in every 55,000 newborns

Sympt9ms: kidney failure, an enlarged liver, cataracts(clouding of the eye lens), poor growth, and mental retardation

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10
Q

Describe sickle cell anemia

A

Autosomal recessive disorder

Sickle cell anemia- alpha and beta thalassemias caused by an inherited structural abnormality of globin

Aff3cts the formation of the protein hemoglobin

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11
Q

What is hemoglobin?

A

Two a-subunits

Two b-subunits

Each subunits complexed with one hememolecule

In vertebrates, hemoglobin transports oxygen from lungs to the rest of the body (e.g. muscles) where it releases the oxygen load

Decrease of heamoglobin, with or without an absolute decrease of red blood cells, leads t9 symptoms of anemia

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12
Q

What causes sickle cell anemia?

A

Caused by point mutations (single base) mutation in B-globin gene

Protein= defined amino acid sequence

Mutation changes a single protein(amino acid build8ng block in B-hemoglobin)

-amino acid glutamic acid (GAG) is replaced with the amino acid valine (GTG) at position 6 in B-heamoglobin-Glu-6Val

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13
Q

Explain the pathophysiology of Sickle cell anemia

A

Sickle cell anemia hemoglobin forms long inflexible chains -this causes red blood cells to become stiff and angular, causing them to become stuck in small capillaries

Sickle shaped RBCs die prematurely, leading to shortage of RBCs (anemia)

-Sickled RBC can also block small blood vessels, causing pain and organ damage

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14
Q

What are the molecular diagnostics of SCA?

A

Targeted mutation analysis

-ASO

RFLP: mutation be identified directly in DNA by use of either of 2 restriction endonucleases -Ddel or Mstll. The nucleotide substitution alters a specific cleavage site recognized by each of the 2 enzymes

Prenatal diagnosis: FISH

Preimplamentation genetic analysis :

PCR, FISH

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15
Q

Describe management and treatment of SCA

A

Management:
-prevent tissue deoxygenation

  • promote proper hydration
  • avoid sources of infection
  • Prompt medical attention when sick

Treatment:
-medication

  • transfusion
  • bone marrow transplantation
  • gene therapy
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16
Q

How can sickle cell disease be corrected in human models using stem cell-based gene therapy?

A

Combined RNA interference with globin gene transfer to create a therapeutic transgene

The new gene had two functions

  • produce normal hemoglobin
  • and suppress the generation of sickle shaped hemoglobin S.

The therapeutic gene was engineered into a lentivirwl vector and introduced into hematopoietic stem cells to produce normal hemoglobin

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17
Q

How can sickle cell be treated with CRISPR/Cas9 gene editing technology ?

A

By using CRISPR/Cas9 gene editing technology, it is possible to activate gene expression, gene repression, histone modification, Epigenetic alterations and paint genomic sequences or tag sequence regions with a fluorescent protein or protein tag

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18
Q

What are the frequency and symptoms of Huntington’s disease?

A

Frequency: 1-2 in 10,000

Symptoms: involuntary choreiform movements, dementia, late onset

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19
Q

What is the frequency and symptoms of myotonic dystrophy ?

A

1 in 8,500

Symptoms: myotonia, heart defects, cataracts

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20
Q

What are the frequency and symptoms of familial hypercholesterolaemia?

A

1 in 500

Symptoms: premature heart disease

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21
Q

What are the frequency and symptoms familial breast cancer BRCA1 or BRCA2?

A

1 in 800 (USA) -BRCA1

1 in 100 (askhkenzai) Jews)-BRCA2

High lifetime risk of breast cancer and ovarian cancer. Earlier onset than sporadic cases

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22
Q

What are the frequency and symptoms of familial Ahlzeimer’s disease ?

A

Frequency- 10% lifetime risk at age 80

Symptoms- dementia. Earlier onset than sporadic cases

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23
Q

What causes Huntington disease?

A

Caused by a mutation in a HD gene on chromosome 4

The coding region of this gene contains the DNA sequence “CAG” repeated again and again

The number of times this triplet is repeated varies from person to person, ranging from 10 to 26 persons

People with HD have an abnormally high number of these CAG triplets, approximately 40 or more

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24
Q

Describe the effects of the premature range of Huntington disease

A

Premature range individuals. Are Norma, but their offsprings at risk of developing the disease

As the treated HD gene is passed from one generation to the next, the size of the. CAG repeat expansion can change

It often increases in size, especially when it is inherited from the father

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25
Q

What are the different CAG repeat sizes of Huntington disease?

A

Normal- 10-26

Prematuration- 27-41

Affected- 36-121

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26
Q

Explain Huntington disease as a neurodehenerative disease

A

Neurodegenerative disease

Huntington disease aff3cts the part of the brain that controls thinking, emotion, and movement

Inability to recognize disgust in others appears in carriers of the Huntington gene before symptoms are manifest

Uncontrollable movements, jerky, random, uncontrollable, rapid movement, although some exhibit very slow movement and stiffness, speech like slurring of words

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27
Q

Explain the basics of Huntington’s disease

A

The CAG repeat expansion leads to the production of Huntington protein that contains an abnormal number of glutamines at the N-terminal

  • This likely disrupts the function of the gene’s protein product, Huntington
  • the job of its protein product, Huntington, is to direct the delivery of small packages (vesicles containing important molecules) to the outside of the cell
  • Cellular enzymes cut this elongated protein into fragments that have sticky ends
  • The protein fragments from abnormal clumps inside nerve cells and may attract other, normal proteins into the clumps

These nerve cells don’t function properly

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28
Q

Summarize the age of onset versus number of CAG repeats

A

The greater the number of CAG repeats, the earlier the onset of symptoms

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29
Q

Comeback to HD electrophoresis

A

Electrophoresis

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30
Q

Describe management and treatment of HD

A

Medications ease feelings of depression and anxiety; others control involuntary movements

Physical or speech therapy helps HD patients lead more normal lives

Gene silencing or RNA interference is a promising technique to treat HD

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31
Q

What are X-linked disorders?

A
  • Affects genes located on the X-chromosome
  • males are much more likely to be affected because they have only one copy of X-chromosome
  • Can affect male children of unaffected parents
  • females are mostly carriers and are unaffected
  • Sometimes females may show some symptoms of the disease because of X-chromosome inactivation
32
Q

What are the frequency and symptoms of heamophilia A and B(X-linked)?

A

Frequency- 1 in 10,000

Symptoms: abnormally prolonged bleeding after trauma

33
Q

What are frequency and symptoms of Duchenne muscular dystrophy(x-linked)?

A

1 in 3,000 to 1 in 4,000

Symptoms: muscle wastage in teenage years

34
Q

What is the frequency and symptoms of fragile-X syndrome ?

A

Frequency- 1 in 1000

Symptoms- mental retardation

35
Q

What are the frequency and symptoms of X-linked severe combined immunodeficiency ?

A

1 in 50,000 to 100,000 births

Symptoms,s- recurrent and persistent infections

36
Q

Summarize severe combined immunodeficiency (X-SCID)

A
  • caused by a mutation in the SCIDX1 gene located on the X chromosome
  • This gene encodes a protein that is used to construct a receptor called interleukin-2 receptor, subunit gamma(IL2RG) also called cytokine receptor common gamma chain
  • Cytokine receptor common gamma chain is found on the surface of immune cells (T cells, natural killer, and B cells) and allow these cells to communicate
37
Q

What happens when the SCIDX1 gene is mutated?

A

The IL2RG receptors cannot form properly or are absent from immune cells

As a result, the immune cells can’t communicate with one another about invaders in the environment

-Insufficient T and B cells are produced to fight off the infection, and the body is left defenseless

38
Q

What mutations lead to X-SCID?

A

Mutation in IL2RG-receptor gene may be caused by:

  • missense
  • nonsense
  • insertion
  • deletions, mutations and,
  • splice defects
39
Q

What molecular diagnostic testing can be done for X-SCID?

A

Sequence analysis- sequence analysis of the IL2RG coding region

Targeted mutation analysis- Southern blot analysis for the detection of large deletions and complex mutations for individuals in whom mutations are not detected by sequence analysis

40
Q

What are the types of genetic heterogeneity ?

A

Alleluia heterogeneity- different mutations within a single gene locus (I.e. multiple alleles of a gene) result in same phenotypic expression. E.g. over 1000 known mutant alleles of the CTFR gene cause cystic fibrosis

Locus heterogeneity: variations in completely unrelated gene loci cause a single disorder. E.g. retinis Pigmentosa can have autosomal recessive or X-linked origin

41
Q

What is penetrance?

A

The frequency with which a particular genotype manifests itself in the phenotype- complete or incomplete

42
Q

What is expressivity?

A

Same disease alleles but differences in severity

43
Q

What is Mosaicism?

A

All body cells aren’t genetically identical

44
Q

What is a phenocopy?

A

Same symptoms(e.g. deafness) may be caused by an environmental factors (e.g. rubella virus infection) or by an inherited disorder

45
Q

What are environmental effects?

A

E.g. phenylketonuria

46
Q

What is anticipation?

A

Severity of disease increases with succeeding generations, e.g. muscular dystrophy

47
Q

What is genomic imprinting ?

A

Expression of disease depends on the parent from which it was inherited. E.g. deletion of some genes from chromosome 15: father-Prader-Willi syndrome, mother-Angelman syndrome

48
Q

Explain genetic and complex disorders

A

Diseases caused by combined effects of multiple genetic and environmental (e.g. age, gender, infection, or nutrition) risk factors)

There is no dominance or recessivity at each of these genes

  • The genes act in concert in an additive fashion, each adding or detracting a small amount from the phenotype
  • most risk factors probably of small effect individually and with complex interaction
49
Q

How does the environment play a role in complex disorders?

A

The environment interacts with the genotype to produce the final phenotype

Members of the same family are likely to suffer from the same disease

  • they are likely to share the same environment
  • They are likely to share the same genes

Often not easy to differentiate the relative contribution of genetic and environmental factors in some diseases

Genetic tests for predisposition may allow at-risk individuals to change their lifestyle to avoid the disease

50
Q

Summarize multifactorial/comped disease

A
  • Affected children may have normal parents
  • Recurrence risk increases with the number of aff3cted children in family
  • A more severely affected parent is more likely to produce an affected child
  • Consaguity slightly increases the risk for an affected child
51
Q

Give an example of complex psychiatric complex disorders

A

Manic depression

Alcoholism

Schizophrenia

Tourette’s

Dyslexia

Ahlzeimer’s

52
Q

Give examples of comped diseases in common diseases of later life

A

Rheumatoid arthritis

Various cancers

Epilepsy

Multiple sclerosis

Insulin-dependent diabetes mellitus

Non-insulin dependent DM

peptic ulcer

Ischaemic heart disease

Hyperthyroidism

Gallstones

Migraine

Asthma

53
Q

Give examples of congenital disorders that are complex disorders

A

Neural tube

  • spina bifida
  • anencephaly

Congenital heart disease

Cleft heart disease

Mental retardation

54
Q

What are the types of chromosomal mutations ?

A

Entire chromosomes, or large segments of them, are missing, duplicated, or altered

Trisomy

Monosomy

Translocation: chromosomes break and the fragments rejoin to other chromosomes

55
Q

What is the frequency of turners?

A

45X: turners- 1 in 5000

56
Q

What ‘s the frequency of kleinfelters?

A

47XXY :1 in 1000

57
Q

What is the frequency of trisomy 21/Down syndrome ?

A

1 in 800 (maternal age dependent)

58
Q

What is the frequency of trisomy 18/edwards syndrome?

A

1 in 10,000

59
Q

What do mitochondrial mutations cause?

A

A number of disorders where there is a decline in energy availability and other clinical abnormalities

Mitochondria are maternally inherited, therefore mitochondrial disorders can only be inherited from an individuals mother

Different factors lead to great complexity in the age of onset and severity of symptoms

Mitochondrial disorders affect many different organs simultaneously, including the central nervous system

60
Q

Describe mitochondria

A

The number of mitochondria in a cell depend on the metabolic requirement of that cell

Each mitochondria has 2-10 copies of a 16.6 kB circular DNA genome (mtDNA).

90% of cellular energy is generated in the mitochondria by the respiratory chain

Mitochondria diseases comprise those disorders that in one way or another affect the function of the mitochondria and/or are due to mitochondrial DNA mutations

61
Q

What diseases are caused by in part due to mit9chondria dysfunction ?

A

Diabetes

Some forms of cancer

Cardiovascular disease

Lactic acidosis

Specific forms of myopathy

Osteoporosis

Ahlzeimer’s

Parkinson’s

Stroke

mtDNA mutations are believed to play a role in aging

62
Q

What are the symptoms and affected genes of Chromic Progressive external ophthalomoplegia?

A

CPEO- myopathy and paralysis of eye muscles

Affected gene -multiple gene loss because of deletion (results from mitochondria mutation loss)

63
Q

What are the symptoms and affected gene of Pearson’s syndrome ?

A

Symptom- childhood bone marrow dysfunction giving rise to multiple blood disorders and pancreatic failure

Affected gene- multiple gene loss because of deletion

Mitochondrial mutations

64
Q

What are the neurogenic muscle weakness, ataxia, and rein is Pigmentosa?

A

NARP- muscle weakness ataxia and blindness

Affected gene- subunits of ATP synthase

Mitochondrial mutations

65
Q

Who was Alec Jeffreys be found?

A

He coined the term DNA fingerprinting: a technique used by scientists to distinguish between individuals of the same species using only samples of their DNA

66
Q

Describe classic fingerprinting

A

Subject to interpretation and
-valuable samples can be difficult to obtain

Uniform nature of DNA in a single individual and the genetic variability between individuals make DNA fingerprinting possible

When properly conducted, DNA-based testing not only provides exclusionary evidence, it can provide positive evidence of a person’s identity without bias

Forensic scientists scan DNA regions that vary from person to person (VNTR, STR) and use the data to create a DNA profile (DNA fingerprint) of that individual

67
Q

What are the protocol for DNA fingerprinting?

A
  1. Isolate chromosomal DNA from a sample of cells
  2. Cut the DNA with a restriction enzyme
  3. Separate the DNA fragments by gel electrophoresis
  4. Transfer bands to nitrocellulose
  5. Denature the DNA and add probe. Allow probe to hybridize and wash away excess probe
  6. Expose the filter to photographic film and compare the results
68
Q

What is looked for in DNA typing?

A

You look for matches (based on sequence or on numbers of small repeating units of DNA sequence) at a number of different locations on the person’s genome

Several matches must be identified to be confident (“beyond a reasonable doubt”) that the right person is identified

There is an extremely small chance that another person has the same DNA profile for a particular set of regions

69
Q

What are the uses of DNA in forensic identification?

A
  • identify potential suspects whose DNA may match evidence left at crime scenes
  • exonerate persons wrongly accused of crimes like rape or murder
  • identify crime and disaster victims
  • establish paternity and other family relationships
    • humans, animals, plants (e.g. Cabernet Sauvignon grapes= Cabernet Franc + Sauvignon blanc)

Inheritance cas3s

Immigration cases

Identify endangered and protected species as an aid to wildlife offic8als(could be used for prosecuting poachers)

  • detect bacteria and other organisms that may pollute air, water, soil, and food
  • match organ donors with recipients in transplant pr9grams
  • determine pedigree for plants, seeds, or livestock breeds- e.g. herbal product ginseng
  • authenticate consumables such as wine
70
Q

What were the first practical tests of DNA Fingerprinting?

A

1983-1985: a two year struggle by Chrostiana Sarbah and her son, Andrew, to prove to the home office in England that they were, indeed, mother and son

1986: the Pitchfork murder case- the origins of DNA profiling

71
Q

What is Y-chromosome analysis ?

A

The Y-chromosome passed directly from father to son valuable in analysis of:
-genetic markers on the Y chromosome is specifically useful for tracing relationships among males

-biological evidence involving multiple male contributors

72
Q

What is mitochondrial DNA analysis ?

A
  • in the investigation of cases that have not been solved for many years, mtDNA is extremely valuable
  • Comparing the mtDNA profile of unidentified remains with the profile of a potential maternal relative can be an important technique in missing person investigations

Short down 1972 in Vietnam

Remains of unknown laid to rest, 1984

Identified and buried 1998

73
Q

Describe U.K. DNA Data banking

A

National DNA Dayabase

Suspect profiling

Database contains DNA profiles of individuals:

  • suspected of
  • charged with or
  • about to be reported for a recordable offense
74
Q

Describe DNA Databanking in the USA

A

National DNA indexing system

Convicted offender profiling

The Combined DNA Index System (CODIS) -uses two indexes:

  • The Convicted Offender Index contains DNA profiles of individuals convicted of felony sex offenses (and other violent crimes)
  • the forensic imdex contains DNA profiles developed from crime scene evidence
75
Q

What are the potential benefits of DNA Databanks Arrestees?

A

-many major crimes involves people who also have committed minor offenses

  • innocent people are often incarcerated for crimes they did not commit
    • if samples had been taken at the time of arrest, these individuals may have been excluded early in the investigative process
  • Ability to compare other cases against the arrested person’s DNA profile, just as with fingerprints
  • Savings in investigation, prosecution, and incarceration. E.g. John Mark Karr/Jon Berret Ramsey case

Molecular Biology (24 decks)

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