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Genetics

UWORLD Genetics review

QuestionAnswer
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