SGU Genetics

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Term 2 - Genetics Flashcards for SGU Made by Ryan Ismail

Achondroplasia

Autosomal Dominant, FGFR3 gene, prone to germline mosaicism (gonadal mutation)

Retinoblastoma

Autosomal Dominant, 90% Penetrance

Myotonic Dystrophy

Autosomal Dominant, variable expression, triplet repeat expansion disorder, worse as more expanded (Anticipation). CTG repeats.

Marfan Syndrome

Autosomal Dominant, variable expression, pleiotropy as well

Osteogenesis Imperfecta

Autosomal Dominant, variable expression, (prone to gonadal mosaicism)

Neurofibromatosis Type 1

Autosomal Dominant, mutation in tumor suppressor gene Neurofibromin, small, soft, benign skin growths. 100% penetrance. Some cases of epilepsy and CNS tumors. 50% caused by new mutations.

Acute Intermittent Porphyria

Autosomal Dominant

Tuberous Sclerosis

Autosomal Dominant, Pleiotropy, causing several different problems.

Hemochromatosis

Autosomal Recessive, incomplete penetrance, delayed onset

Thalassemia

Autosomal Recessive, Arab, Medeitteranean, Asian more common. (Plasmodium Falciparum Resistance) a-Thalassemia Can be splice site mutations. A) loss of splice site, intron added to protein. B) NEW splice site, part of exon lost from protein. Both non-functional.

Bloom Syndrome (Congenital Telangiectasia)

Autosomal Recessive, Due to BLM Helicase gene mutation, due to lots of recombination. Growth deficiency, pigmentation, photosensitivity, erythema (skin telanglectasia), cancer suceptible.

Ataxia Telegiectaxia (ATM)

Autosomal Recessive. ATM initiates repair due to DS breaks. Related to ATR, which repsonds to Hypoxia, UV damage, replication damage. Causes increase in cancer susceptibility, due to lack of repair. Lympomas, tumors, sensitive to radiation.

Fragile X Syndrome

X-linked Dominant, Anticipation (repeat expansion in the mother). CGG repeat causes Methylation of the FMR-1 Gene

Hemophelia A/B

X-linked Recessive, FVIII gene, lyonization

Incontinetia Pigmenti

X-linked Dominant, so all sons have it and only mothers pass it. Females will get it

Vitamin D resistent Ricketts

X-linked Dominant

Night Blindness

Heterogenetity, Autosomal Recessivity. Need Both genes, ROM1 and Peripherin degenerate rods to get this.

Down Syndrome (47, XX, +21)

Wide, slanting forehead (brachycephaly), single simeon crease on hands (Clinodactyly), GI abnormalities, Mental Retardation, Brushfield spots on iris, adult cataracts. Trisomy 21, Nondisjunction in Meiosis I or II, OR Robertsonian Reciprocal Translocation, two satellite chromoesomes join together. Translocation can end up with 3 copies of chromosome 21. (47, XX, +21)

Patau Syndrome (47, XX, +13)

Trisomy 13. Cleft Lip, polydactyly, Microthalmia, mental retardation, lethal heart defects, fatal. Can detect Polydactytly on Ultrasound.

Edward's Syndrome (47, XX, +18)

Trisomy 18. Rockerbottom Feet, Clinched hands, Congenital heart defects, Fatal. Can see Rockerbottom feet on ultrasound, clinched hands, also Exomphalos.

Familial Breast/ovarian cancer

Mutations in BRCA1 and BRCA2 cause breast cancer susception, causing faulty HRR. Has delayed onset

Alzheimer's Disease

Can be a Promoter mutation, increaing the amyloid precursor protein synthesis. Causes plaques. Dementia, B-amyloid protein mis folding and aggregation due to insolubility. Familial and Sporadic. Familial is < 10%. ALL are early onset <65years. Dominant inheritance. Sporadic, associates with APOE4 Gene on Chr. 19, 25% population is heterozygoing for mutant gene (4X increased risk, 10X in homozygous (2% pop)). Aluminum exposure supposed increase in likelyhood.

Hemophelia B

clotting factor 9 mutation, promoter mutation, severe deficiency in IX until pubery, when androgens upregulate the synthesis.

Heteroplasmy

Mixed mitochondrial genes, some mutant, some normal. Explains variability in mitochondrial diseases.

Homoplasmy

Either both normal, or both mutated genes.

Aneuploidy

Single genes are altered

Euploidy

Whole chromosomes are altered, added or deleted

Polyploidy

Whole genome altered, (ex. 3 copies of every chromosome).

Digynic Polyploidy

Non-Molar placenta. Two sets of maternal chromosomes. ("Di-gina, two ginas.")

Diandric Polyploidy

Molar. Two sets of Paternal chromosomes. ("Di-andy, two Andy's")

Heterodysomy

Nondysjunction in Meiosis I, causing germline mosaicism. Causes 2 haploid cells with no copies, and 2 with 2 copies of the chromosome.

Homodysomy

Nondysjunction in Meiosis II, causing germline mosaicism. Causes 1 empty haploid cell and one with 2 copies of a chromosome, + 2 normal ones.

Alternate Segregation

Robersonian translocation that results in BALANCED chromosomes, nonviable. Will result in Normal or Downsyndrome in the case of 14/21 R.trans.

Adjacent Segregation

Robersonian translocation that results in UNBALANCED chromosomes, nonviable

G banding

detects 5Mb mutations

FISH

Detects 1.5Mb mutations, understand which mutations will be visible on the karyotype, and which need FISH. Needed for Williams Syndrome, Prader Willi, Angelman, Velocardiofacial Syndrome/Di George's

Amniocentesis

Amnoitic Fluid aspirated guided by Ultrasound, screened for a-fetoprotein. Can increase miscarraige by 1%

Chorionic Villus Sampling

Remove fetal cells by aspiration from inner surface of placenta, increases possibility of misscarraige. Can be done at 11-12 weeks, sooner than amniocen.

short tandem repeats

Very good marker for DNA fingerprinting using PCR, sequencing, restriction enzymes, Southern Blot Probing. Very variable between individuals, used for forensic fingerprinting. IMPORTANT: Can prove NOT the father with one loci better than is the father. Must use multiple loci to do this.

Structural Variants

Deletions, Inversion, dupilications. Most associated with human variability.

Tautaumerism

The incorporation of a wrong base

Oxidative Damage to DNA

Causes transversion, tautaumerism, damaged G's pair with A's, instead of C.

Single Base Excision Repair

ROS, Alkylation, Deamination, Abasic (depurination/pyrimidization), or single strand breaks due to energy. DNA glycosylates remove the wrong base. Example would be MYH Polyposis.

Hereditary Non-Polyposis Colorectal Cancer (HNPCC)

Autosomal Dominant. Mutation in gene's for MLH1 on Chromosome 3, or MSH2 on Chromosome 2. (90%). Genetic Predisposition for cancer. Screen with colonscopy starting at age 25. Look for Microsatellite expansions, which will accumulate in those with this mutation. Mutation in MMR (mismatch repair)

BLM Helicase

Resolves Holiday junctions in Double strand Break, non-homologous end joining repair. (DSB, NHEJ). Also inhibits crossing of of sister chromatids.

Bloom Syndrome (Congenital Telangiectasia)

Autosomal Recessive, DNA Ligase mutation. Due to BLM Helicase gene mutation, due to lots of recombination. Growth deficiency, pigmentation, photosensitivity, erythema (skin telanglectasia), cancer suceptible.

HRR (Homologous Recombination Repair)

BRCA1promotes HR, and BRCA2 stimulates it. BLM helicase resolves the holiday junctions between adjacent chromatids. DNA pol fills in gaps. Uses

Ataxia Telegiectaxia (ATM)

Autosomal Recessive. Mutation in Topoisomerase ATM initiates repair due to DS breaks. Related to ATR, which repsonds to Hypoxia, UV damage, replication damage. Causes increase in cancer susceptibility, due to lack of repair. Lympomas, tumors, sensitive to radiation.

MMR (Mismatch Repair)

HNPCC (colon cancer, MLH1 or MSH2 genes)

NHEJ, HRR (non-homologous end joining, homologous recombination repair)

corrects double strand breaks, like Breast Cancer (BRCA1/2), or Bloom Syndrome (BLM)

BER (Base excision repair)

MYH Polyposis (colon cancer)

NER (Nucleotide excision repair)

Xeroderma Pigmentosum (XPA in japanese, XPC in USA).

Haploinsufficiency

Familiar Hypercholesterolemia, one mutation in LDL receptor, other gene cannot make up for it.

Dominant-negative loss

Osteogenesis Imperfecta, collagen 1A1 or 1A2, affects dimer/multimer protein, or protein interferes with normal proteins

Gain of function

Huntington's disease, overexpression of CNS proteins, neurological degeneration, usually dominant mutations.

Frameshift

insertion or deletion of bases, that arent multiples of 3. Tay Sach's disease caused by insertion of 4 bases.

ASO (Allele specific oligonucleotide Probes)

Used for point mutations or short aberations

Southern Blots

Used for larger aberations. Fragile X is tested with this. You CAN test for CF (3 base deletion). Triplet repeats, like Fragile X and Huntington's needs this.

FISH

NEVER use FISH for CF. Used for chromosomal changes and large insertions, deletions.

Proto-oncogenes

molar. Two sets of Paternal chromosomes. ("Di-andy, two Andy's")

Oncogenes

a mutated proto-oncogene, V-onc is a viral oncogene, causing host cell to become cancerous, and C-onc, a cellular mutation, causing cancer. INCREASE in function genes. DOMINANT mutations.

Myeloid Leukemia

Translocation of ABL oncogene from Ch. 9 to Chr. 22. Causes a fusion of BRC and ABL proteins, which is permanenely active, overexpressive. Inhibits DNA repair and increases cell cycle.

Burkitt Lymphoma

Translocation of c-MYC gene from Chr.8 to Chr. 14. (90% of cases). Codes for Enhancer boxes, and recruiting histone acetyltransferases. (HAT's and E-boxes). MYC genes related to Cancer, as well as Growth Factors.

Familial Adenomatous Polyposis (FAP)

APC gene on Chr. 5, tumor suppressor gene. Inherited Recessive. Requires a second hit mutation/deletion to cause the cancer.

Multifactorial Diseases

Genes at multiple loci, polygenic diseases. Cleft Lip, Diabetes, Autism, Schitzophrenia, Neural tube defects, depression, hypertension, cardiac defects.

Liability Curves for Mutifactorial Disorder

Way of explaining inheritance. Multiple factors, graph has a Threshold. The more factors contributing to possible inheritance (people affected, closeness, environmental, etc), the graph is shifted to the right towards the threshold. Above the threshold, the disease is seen in the dividual. Can be faulty, is predicative, not Absolute.

Parents/Siblings

share 1/2 of genes

Grandparents, half siblings, cousins

share 1/4 of genes

1st cousins, Third degree family

share 1/8 of genes

Heritability

Heritability = (Variance in DZ - Variance in MZ) / Variance in DZ . The proportion of variayion caused by genetic, rather than environmental factors. For a completeley genetic disorder. Should be variance - 1/variance. So, proportion of

Relative Risk (RR)

measures relative risk of getting a disease. The frequency that the individual may contract the disease if the individual has a particular marker for it. Taking in account environment, can predict increase in Risk for particular persons. Percentage of those with a predisposition (allele w/risk /total) : to those without the predisposition (alleles/total). Example was smoker/cancer : non-smoker/cancer = 5.8X more likely.

Odds Ratio (OR)

compares relative odds of occurance. Tells you how much more likely you are of having a disease if you have the allele, vs not having it. Disease w/allele / no disease : disease w/o allele / no disease.

Idiopathic Chronic Pancreatitis

10-40% have 2 mutations in the CFTR gene, but don't have Cystic Fibrosis, however These are modifier genes, since those with CF get a much more severe case because of this.

MSS, a-fetoprotein

16 weeks

Triple Test (a-FP, un-estroil down, Gonadotropin UP

16 weeks

Ultrasound

18weeks

amniocentesis

16 weeks

chorionic villus sampling

10-12 weeks

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