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MED GEN EXAM 1 SP26
Lectures 1-7
| Question | Answer |
|---|---|
| Locus | Location in genome |
| Allele | Genetic Variant.... typically two alleles for each gene |
| Autosomes | Chromosomes 1-22 |
| Sex Chromosomes | X and Y chromosomes |
| Somatic Cells | Body/tissue cells |
| Gametes | Reproductive cells |
| Homozygous | same sequence on both alleles |
| complete dominance | one allele masks another |
| incomplete dominance | blending of phenotypes from both alleles (Red + White = Pink) |
| codominance | representation of both alleles |
| multiple alleles | multiple genes that regulate a phenotype/trait (like eye color) |
| Consanguinity | when close relatives mate |
| Allelic heterogeneity | different mutations in the same gene |
| Locus heterogeneity | mutations in different genes that have similar functions |
| Modifier loci | mutations in a gene where the product influences the disease related gene product |
| Compound heterozygote | having two different mutations in different alleles.... both alleles have a mutation, but its a different one |
| 1/5000 occurence | Mutation |
| 1/50 occurence | Polymorphism |
| Autosomal dominant | Dominant chromosome 1-22, no skipping |
| Autosomal recessive | Recessive chromosome 1-22, |
| X-Linked recessive | recessive gene comes from a male X chromosome |
| X linked dominant | Males pass to only daughters and females pass to sons and daughters |
| Y linked | Females cannot get this genetic variation |
| Skipping | Recessive |
| No skipping | Dominant |
| X linked dominant most severe phenotype is in | males |
| X linked dominant moderate phenotype is in | female homozygous |
| X linked dominant least severe is | female heterozygous |
| Recurrence risk is calculated using a | Punnett square |
| cystic fibrosis is | autosomal recessive |
| Aa x aa how many affected? | 50% |
| XX x X*Y how many affected? | Females are 100% carriers and Males are 100% WT |
| X inactivation | epigenetic process to silence majority of one X chromosome in somatic cells that have more than one X chromosome |
| Dosage compensation | Keeping expression of X linked genes similar in males and females |
| Manifesting heterozygote | Female who presents with a recessive X-linked disorder due to X inactivation skewing |
| Lyon hypothesis | X- inactivation occurs randomly in somatic cells in females during embryogenesis resulting in mosaicism |
| Mosaicism | differences between cells |
| Barr body | Condensed X-chromosome, normal females have one Barr body per cell |
| a trisomy X would have | 2 Barr bodies |
| a monosomy X would have | NO Barr bodies |
| Affect disorder phenotype | the physical symptoms that manifest from genetic mutations |
| Imprinting | epigenetic silencing of a subset of genes due to being methylated on the autosomes on either maternal or paternal chromosome |
| Define X-inactivation | epigenetic silencing of genes on the X chromosome |
| Which genes are typically affected by imprinting? | growth and metabolism genes |
| Loss of imprinting | we lose epigenetic patterns and both alleles are expressed.... bad because they either need to be expressed from mom OR dad |
| Deletion of imprinted region | deletion of portion of chromosome where imprinted genes are found... can result in either lack or extra expression depending on which allele is deleted |
| Prader Willi Syndrome | Loss of function on chromosome 15, causes issues with metabolism, growth, and behavior |
| Angelman syndrome | Loss of function in the UBE3A gene from mother, that is critical in nervous system development |
| Uniparental disomy | results from chromosome nondisjunction during meiosis (eggs), usually happens in mother |
| What is the rescue pattern for uniparental disomy? | rescue process that results in two chromosomes having the same imprinting pattern |
| Short arm is | p |
| Long arm is | q |
| Metacentric | centromere is in the middle |
| Submetacentric | centromere is off center |
| Acrocentric | the centromere is at one end |
| We count away from the centromere, true or false? | true |
| Stalk satellite phenomenon | consists of very large arrays of repeating, non-coding DNA, the main component of functional centromeres, and form the main structural constituent of heterochromatin |
| main chromosomal disorder features | distinct facial features, developmental delays, growth delays, and congenital defects (heart) |
| main metabolic disorder features | variable presentation, usually no phenotype until 24 hours after child is born, may result in death |
| True or false, we take blood samples for metabolic disorder testing | True |
| why don't metabolic disorders show up until the baby is born? | because the mother's nutrients keep the baby alive and healthy and filter out toxins |
| Sickle cell anemia | missense mutation (GLU to VAL) in beta subunit of hemoglobin, the HBB gene. |
| Huntington disease | 100% of carriers will display the disease at an advanced age |
| Hemophilia | X-Linked recessive disorder that affects blood clotting, more frequent in males |
| Marfan syndrome | Autosomal dominant disorder that results from mutations in fibrillin, a component of connective tissue. |
| Rett Syndrome | X-linked dominant disorder caused by a mutation in the MECP2 gene which controls DNA methylation |
| Cystic fibrosis | Autosomal recessive disorder caused by a mutation of the CFTR gene that affects Na and Cl transport |
| Pleiotropy | when a mutation in a single gene results in multiple seemingly disconnected phenotypes (marfan syndrome) |
| Penetrance | what percentage of people who have the mutation(s) will exhibit the disorder |
| Heteroplasmy | multiple copies of mitochondrial DNA in mitochondria (ratio of mutant to WT) and mitochondria in a cell and need of that cell for ATP |
| Anticipation | more recent generations having worse and earlier symptoms (usually associated with repeat expansion) |
| Euploidy | chr sets of 23 |
| Aneuploidy | chr sets not of 23 (monosomy and trisomy) |
| Polyploidy | extra sets of chromosomes (whole sets of 23) |
| Monosomy | having 1 of a set of chr |
| What is partial monosomy | when part of a chromosome is deleted, but not all |
| Trisomy | having 3 of a set of chr |
| Multifactorial disorders | combination of multiple genes and environment that are affecting disease presentation |
| FISH stands for | Fluorescence In Situ Hybridization |
| SKY stands for | spectral karytotyping |
| When would we use FISH? | genetic chromosomal test - for a known genetic alteration |
| When would we use SKY? | genetic chr test - painting the whole genome - for an unknown genetic alteration |
| Principle of Independent assortment | traits are inherited separately (crossing over allows for this when traits (genes) are on the same chromosome) |
| Principle of Segregation | pass on either maternal or paternal chr to offspring - we inherit one set of chr from mom and one from dad |
| New Mutation | a single gamete that acquires a mutation that is then used for reproduction |
| Germline Mosaicism | germ cells acquire mutation during embryogenesis leading to a portion of gametes having the same mutation |
| Point mutation | - Missense - 1 base change resulting in different amino acid |
| Nonsense | 1 base change to a stop codon |
| Insertion | addition of nucleotides |
| Deletion | removal of nucleotides |
| Frameshift | in/del of a number of nucleotides not equally divisible by 3 |
| Repeat expansion | insertion of excess short repeats (2-3 BP long) leading to additional repeats over generations (due to polymerase slippage) |
| Reciprocal translocation | flip flopping of chr regions between two chr - balanced |
| Loss of function | lack of production of a functional gene product |
| Haplosufficient | recessive, gene products are enough to not express mutant phenotypes |
| Haploinsufficient | dominant, gene products are not enough to prevent expression |
| Gain of function | excessive or new function - dominant |
| Dominant negative | mutant protein disrupts function of normal protein (usually in complexes) - dominant |
| Polymorphism | genetic change >/=1% of a population |
| Mutation | genetic change < 1% of a population |
| Trisomy 21 | almost always an inheritance of maternal nondisjunction, risk increases with maternal age, almost always the result of a new mutation |
| Hypercholesteremia | autosomal dominant, mutations in genes that affect the metabolism of cholesterol |
| People who are heterozygous for sickle cell anemia have immunity to | Malaria |
| Sickle cell anemia is most common in | Africa, Mediterranean, India, and Middle East |
| In males, there is a reoccurrence rate of 0.000025 of the hemophilia A genotype. Is this a mutation or a polymorphism? | Mutation |
| Blood type A has a 40% incidence, is this a mutation or a polymorphism? | Polymorphism |
| Marfan syndrome is a great example of the concept | Pleiotropy |
| What is the purpose of translation? | to produce protein at the ribosome |
| Mitosis results in | diploid cells |
| Meiosis results in | haploid cells |
| diploid means | 2N |
| haploid means | 1N |
| True or false? A change in DNA sequence can be considered a mutation in one population and a polymorphism in another population. | True |
| What best defines autosomal dominant inheritance? | Displayed in all those that have at least one copy of the dominant allele |
| True or false, there is skipping of generations in X-linked dominant | False |
| Based on the Genetic Conflict Hypothesis, paternal imprinting favors | larger offspring |
| A chromosome with the centromere at the middle is called? | metacentric |
| Oncogene | mutated forms of genes that are normally involved in preventing cell proliferation and are usually a result of loss of function types of mutations. |
| Blending of phenotypes | Incomplete dominance |
| aneuploid | missing or duplicate chromosomes |
| epigenetic silencing of a subset of genes from either the maternal or paternal autosomes | Imprinting |
| amniocentesis | It is a prenatal test performed at 15-17 weeks gestation that isolates fetal cells from the amniotic fluid to test for genetic abnormalities. |
| Loci that are > 50 centiMorgans apart are considered unlinked, true or false? | true |
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gpopop
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