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Genetics
UWORLD Genetics review
| Question | Answer |
|---|---|
| A telomerase is a: | RNA-dependent DNA Polymerase |
| What is the function of telomerase? | Synthesize telomeric DNA sequences to replace the lost chromosomal ends to the telomeres |
| Which cells tend to have increased telomerase activity? | Stem cells and cancer cells |
| VEGF: | signal protein that helps create new vessels after injury |
| Cyclin D: | protein mode during G1 phase; helps promote G1/S-phase transition; |
| What does increased levels of cyclin D provoke? | Unchecked cellular proliferation |
| RNA-dependent DNA polymerase reverse transcriptase | Telomerase |
| What nucleotide sequence is added by telomerases in the 3'end? | TTAGGG |
| TTAGGG | Added sequence by telomerase to 3' end |
| What are two types of stem cells? | Epidermal basal cells, and Stem bone marrow cells |
| What are Stem cells? | Undifferentiated cells that that the potential to differentiate into other cell types |
| Short telomeres | Seen in differentiated cells Condition associated as a signal for programmed cell death |
| Acetylation of Histones: | Weakens DNA - HIstone bond, leading the Transcription factors to ENHANCE transcription of the associated genes |
| Histone deacetylation | Strengthens DNA-Histone bond, which makes it harder for transcription of associated genes |
| Histone deacetylation | Silencing of transcription |
| What condition is associated with the deacetylation of histones? | Huntington's disease |
| Hypermethylation | The promoter region results in transcriptional silencing |
| Hypomethylation | improves gene expression |
| Northern blot identifies ________________, which normally presented as an _____________ ______________. | RNA; mRNA enzyme |
| ELISA | test used to measures the amount of protein in body fluids |
| What is Polygenic Inheritance? | Inheritance pattern that has several modes of passing on the genes (AD + AR + etch) |
| Examples of conditions related to Polygenic inheritance: | 1. Androgenic (male) alopecia 2. Epilepsy 3. Glaucoma 4. Hypertension 5. Schizophrenia 6. DM type 2 7. Ischemic heart disease |
| Polygenic inheritance is often associated with: | Variable expressivity |
| Autosomal Recessive | 25% chance of affected offspring in case both parents are asymptomatic carries (Aa) |
| What is the function of Releasing Factors? | Recognize stop codons (UAA, UAG, UGA) an terminate protein synthesis |
| What proteins facilitate the release of pyhopypenpte chain at the ribosome and disolution of the ribosome-mRNA complex? | Releasing factors |
| Charged tRNA | delivers amino acids to the protein synthesis complex |
| Charged tRNA | The anticodon on the tRNA molecule recognized the corresponding codon on mRNA, assuring proper amino acid sequence |
| Uncharged tRNA | lacking amino acid; does not interact with mRNA and ribosomes |
| Allele frequency = | p + q = 1 |
| p(2) + 2pq + q(2) | Phenotypic frequency |
| Disease prevalence | q(2) |
| What is the calculation for Carrier Frequency in a rare autosomal recessive disorder? | 2q |
| In rare AR disorders the vale of "p" is ? | 1 |
| What are the chances of passing an affected allele if the mother or father is a carries? | 50% or 1/2 |
| So if the vignette mentions that the population is affected 1 in 40,000, thus, what is the q(2) and q? | q(2) = 1/40,000 q = 1/200 |
| Mutant allele frequency is___ | q |
| So, if q =200, what is the Carrier frequency of the affected allele? | 2(q) = 2 x 200 = 400 |
| Kozak Consensus sequence: | (gcc)gccRccAUGG |
| (gcc)gccRccAUGG | Kozak Consensus sequence |
| What is the function of the Kozak consensus sequence? | Helps initiate translation at the methionine start codon (AUG) |
| What is the Methionine start codon? | AUG |
| Kozak consensus sequence is found in __________________ mRNA. | Eukaryotic |
| What is the analogous sequence of Kozak consensus sequence but in prokaryotes? | Shine-Dalgarno sequence |
| What does the "R" represent int h Kozak consensus sequence? | It can be ADENINE or GUANINE |
| What is the Shine-Dalgarno sequence nucleotides? | AGGAGGU |
| What enzyme catalyzes peptide bond formation? | Peptidyl transferase,and mRNA enzyme (Ribozyme) that resides in the large ribosomal unit |
| What enzyme is often found int large ribosomal subunit? | Peptidyl transferase |
| B-Thalassemia | Results in hypochromic, microcytic anemia due to decreased B-globin chain synthesis |
| What occurs to a-globin chains in B-Thalassemia? | Unpaired a-globin chains precipitate within RBCs and cause membrane damage, leading to ineffective erythropoiesis and extravascular hemolysis |
| Nondisjunction is: | Failure of chromosome pairs to separate properly during cell division |
| What are the two most common times or places for nondisjunction errors? | 1. Failure of HOMOLOGOUS chromosomes to separate in MEIOSIS I 2. Failure of sister chromatids to separate during MEIOSIS II |
| What is the most common example of nondisjunction? | Down Syndrome |
| Most of Down syndrome cases are due to: | Maternal Nondisjunction in Meiosis I |
| What is RFLP analysis? | Technique used to identify nondisjunction errors |
| How can RFLP analysis help distinguish between nondisjunction during Meiosis I or Meiosis II? | The "lines" or "band" in Meiosis I will be the same thickness and darkness in the child and the inherited parent chromosome, while in Meiosis II, the affected chromosomes in the child will have a darker and thicker band. |
| GAG ---> GTG | Sickle Cell disease |
| Sickle cell disease | missense mutation, replacing glutamic acid (GLU) with Valine (VAL) in the 6 position of the B-globin chain. |
| Which codon and its position is the one replaced in the Sickle cell disease? | Glutamic acid (GAG) to Valine (GTG) ; 2nd position |
| What is Linkage Disequilibrium? | Two allele loci are in linkage disequilibrium when a pair of alleles are inherited together i the same gamete (haplotype) more tan or letlls tan wu-ld be expected given random pairing. |
| What condition increases the changes of Linkage disequilibrium? | As genes are in close physical proximity o the same chromosome |
| Haplotype frequency = | (frequency of gene 1) x (frequency of gene 2) |
| Pleiotropy: | occurence of multiple phenotypic manifestation, often in different organ system, which result from a mutation in a single gene |
| Law of segregation: | phenomenon which gametogenesis results the separation of paired chromosomes so that the offspring inherit only half of each parent's genetic composition |
| What is a common trinucleotide disease associated with Hypermethylation? | Fragile X syndrome (FXS) |
| What test or technique can be used to assess the degree of methylation? | Southern blot analysis |
| What is the Trinucleotide repeat in FXS? | CGG |
| What direction is the Translation of mRNA? | 5' to 3' |
| What is the direction of tRNA anticodon? | 3' to 5' |
| Which two types of RNA complement each other during translation? | mRNA in the 5'-->3' direction with tRNA anticodon in the 3'--> 5' direction |
| RNA has _____ and DNA has _________________, and both interconvete to or from_______ (___) | RNA -- uses Uracil (U) DNA -- uses Thymine (T) Interchange into or from Adenosine (A) |
| Which histone is not part of the Nucleosome core? | H1 |
| How many and which are the components of the Nucleosome core? | 8 components; 2 of each H2A, H2B, H3, and H4. |
| NF-1 is of autosomas _____________ inheritance | Dominant |
| What are important features of NF-1? | Skin --> cafe-au-lait spots Neurofibromas -- large, sessile, pedunculated lesions in the body Eye --> Lisch nodules and possible vision loss Bone deformities (Sphenoid) |
| Associated NF-1 tumors? | Meningiomas, Neurofibromas, astrocytomas, gliomas, and pheochromocytomas |
| Chromosome 22q11.2 microdeletion causes: | DiGeorge syndrome and Velocardiofacial syndrome |
| What are the features of Di George syndrome? | Cardiac abnormalities, hypoplastic or absent thymus, and HYPOcalcemia |
| Cleft palate, cardiac abnormalities, adn dysmorphic facies | Velocardiofacial syndrome |
| Defected neural crest migration into derivatives of the 3rd and 4th pharyngeal pouches | DiGeorge syndrome |
| What are the cardiac defects most associated with microdeletion of 22q11.2 gene? | Tetralogy of Fallot, Truncus arteriosus, and interrupted aortic arch |
| What are the dysmorphic facies seen in Velocardiofacial Syndrome? | Orbital hypertelorism, short palpebral fissures, and short philtrum, cleft palate, and bifid uvula |
| Gold standard test for Digeorge Syndrome? | Fluorescent in situ hybridization |
| Primary oocytes are arrested in what phase? | Prophase Meiosis I |
| Secondary oocytes are arrested in what phase? | Metaphase Meiosis II |
| Oocyte development | Primary oocytes are fully developed by 5th month of gestation. Normal menstruation, promotes primary oocyte to rescue differentiation. Just prior fertilization secondary oocytes are arrested in metaphase of meiosis II. |
| Cystic fibrosis is due to a ___________________ mutation | Frameshift |
| Frameshift mutations | deletion or addition of a number of bases not divisible by 3 in coding region of a gene |
| What happens in a frameshift mutation? | alter the reading frame of the genetic code, resulting in formation of non-functional proteins |
| Gel electrophoresis | separates proteins by length of base pairs (BP). |
| X-linked recessive pattern | passes a affected "X" chromosome. No male to male transmission. |
| Affected father of a X-linked recessive disease: | - All daughters are carriers - All sons are normal (only inherit the Y chromosome) |
| Affected mother of an X-linked recessive disease: | - Daughters have 50% of being carriers - Sons have 50% of been affected |
| What are the chances of being a carrier of a AR disorder is the patients status is unknown, but has a sibling affected by that disorder? | 2/3 |
| What are the chances of passing an affected allele of an AR disorder in a mother who is 2/3 chances of been a carrier? | 1/3 ( 2/3 x 1/2) |
| What does the Homeobox genes encode? | DNA-binding transcription factors, that play important role in the segmental organization of the embryo along the Craniocaudal axis. |
| Mutations to the Homeobox genes result in? | Skeletal malformation and improperly positioned limbs and appendages. |
| Achondroplasia is an autosomal _______________________ disorder. | Dominant |
| What are the percent chances of been affected of an AD disorder if only one parent is affected? | 50% |
| Two parents with only one allele affected of an AD disorder decide to have children, what are the percent chances of the offspring to be affected? | 75% |
| What is the TATA box? | Promoter region that binds transcription factors and RNA pol II during the initiation of transcription. |
| Where is the location of the TATA box? | 25 bases upstream from the beginning of the coding region. |
Created by:
rakomi
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