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Questions and Answers
What is the role of the IA allele in the ABO blood group system?
What is the role of the IA allele in the ABO blood group system?
Which blood type individual can only accept blood from A or O type donors?
Which blood type individual can only accept blood from A or O type donors?
What genetic characteristic describes individuals with O blood type?
What genetic characteristic describes individuals with O blood type?
What does the enzyme produced by the IB allele do?
What does the enzyme produced by the IB allele do?
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Which blood type individual is more susceptible to Helicobacter pylori infection?
Which blood type individual is more susceptible to Helicobacter pylori infection?
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Which term best describes the expression of both A and B antigens in individuals with genotype IA IB?
Which term best describes the expression of both A and B antigens in individuals with genotype IA IB?
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What type of mutation resulted in the formation of the IB allele from the ancestral IA allele?
What type of mutation resulted in the formation of the IB allele from the ancestral IA allele?
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What is the terminal monosaccharide added by the gene product of the I allele?
What is the terminal monosaccharide added by the gene product of the I allele?
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What initiates the transcription process in eukaryotic cells?
What initiates the transcription process in eukaryotic cells?
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What signal marks the end of transcription in eukaryotic pre-mRNA?
What signal marks the end of transcription in eukaryotic pre-mRNA?
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Which component aids in the stability and processing of mRNA during splicing?
Which component aids in the stability and processing of mRNA during splicing?
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What is the role of the 7-methyl-G cap added to mRNA?
What is the role of the 7-methyl-G cap added to mRNA?
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During translation elongation, which factor is responsible for proofreading aminoacyl-tRNAs?
During translation elongation, which factor is responsible for proofreading aminoacyl-tRNAs?
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How does the 3' Poly-A tail contribute to mRNA functionality?
How does the 3' Poly-A tail contribute to mRNA functionality?
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What is the function of the release factor (RF) during translation termination?
What is the function of the release factor (RF) during translation termination?
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In which phase is the stability of histone mRNA specifically increased?
In which phase is the stability of histone mRNA specifically increased?
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What is the role of the PolyA binding protein (PABP) in mRNA translation?
What is the role of the PolyA binding protein (PABP) in mRNA translation?
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What does the large ribosomal subunit 28S rRNA do during translation?
What does the large ribosomal subunit 28S rRNA do during translation?
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Which protein halts the cell cycle to allow for DNA repair?
Which protein halts the cell cycle to allow for DNA repair?
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What role does ATM kinase play in DNA repair?
What role does ATM kinase play in DNA repair?
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What does Bax do when present in excess?
What does Bax do when present in excess?
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Which component of the apoptosome is responsible for activating procaspase-3?
Which component of the apoptosome is responsible for activating procaspase-3?
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What is the function of the Bromo domain in CBP?
What is the function of the Bromo domain in CBP?
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Which type of protease is a caspase categorized as?
Which type of protease is a caspase categorized as?
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Which type of mutation does NOT change the amino acid sequence of a protein?
Which type of mutation does NOT change the amino acid sequence of a protein?
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What phenomenon is demonstrated when a red and a white flower plant produce pink offspring?
What phenomenon is demonstrated when a red and a white flower plant produce pink offspring?
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What event in meiosis can lead to aneuploidy?
What event in meiosis can lead to aneuploidy?
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What happens to X chromosomes in individuals with more than one X chromosome?
What happens to X chromosomes in individuals with more than one X chromosome?
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Which mutation creates an incomplete gene product?
Which mutation creates an incomplete gene product?
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What phenotype is related to the extra chromosome 21 in Down's syndrome?
What phenotype is related to the extra chromosome 21 in Down's syndrome?
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What is the role of chalcone synthase in pea plants?
What is the role of chalcone synthase in pea plants?
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How does ICAD contribute to the process of apoptosis?
How does ICAD contribute to the process of apoptosis?
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In a cross between a pure-breeding purple-flowered pea plant and a white-flowered pea plant, what is the expected F1 generation ratio?
In a cross between a pure-breeding purple-flowered pea plant and a white-flowered pea plant, what is the expected F1 generation ratio?
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Which trait exemplifies a sex-linked inheritance pattern?
Which trait exemplifies a sex-linked inheritance pattern?
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What is the primary role of ubiquitin in cellular processes?
What is the primary role of ubiquitin in cellular processes?
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Which protein is tasked with delivering tyrosinase to melanosomes in pigmentation?
Which protein is tasked with delivering tyrosinase to melanosomes in pigmentation?
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What is the phenotypic ratio of offspring when crossing two heterozygous pea plants (Pp) for a single trait?
What is the phenotypic ratio of offspring when crossing two heterozygous pea plants (Pp) for a single trait?
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What stabilizes p53 and prevents its proteolysis?
What stabilizes p53 and prevents its proteolysis?
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What is the function of the Y locus protein in pea plants?
What is the function of the Y locus protein in pea plants?
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The ratio of phenotypes in a dihybrid cross of pea plants is typically what?
The ratio of phenotypes in a dihybrid cross of pea plants is typically what?
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Which type of mutation results in the substitution of one amino acid for another?
Which type of mutation results in the substitution of one amino acid for another?
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What does the p53 protein do during DNA damage response?
What does the p53 protein do during DNA damage response?
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Which of the following phenotypes indicates an individual is an unaffected carrier of hemophilia?
Which of the following phenotypes indicates an individual is an unaffected carrier of hemophilia?
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Which pigment is associated with the OCA1 locus enzyme?
Which pigment is associated with the OCA1 locus enzyme?
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What effect does Mdm2 have on p53 protein concentrations?
What effect does Mdm2 have on p53 protein concentrations?
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What is the primary purpose of pigmentation in humans?
What is the primary purpose of pigmentation in humans?
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Which molecule is rapidly destroyed by UV light in hypopigmented individuals?
Which molecule is rapidly destroyed by UV light in hypopigmented individuals?
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What is a consequence of hypopigmentation near the equator?
What is a consequence of hypopigmentation near the equator?
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What role does 7-dehydrocholesterol play under UV exposure?
What role does 7-dehydrocholesterol play under UV exposure?
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Which enzyme is involved in the transport of tyrosinase to melanosomes?
Which enzyme is involved in the transport of tyrosinase to melanosomes?
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What is the main damaging agent produced during ethanol oxidation that affects DNA?
What is the main damaging agent produced during ethanol oxidation that affects DNA?
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What type of DNA damage is primarily caused by UV light irradiation?
What type of DNA damage is primarily caused by UV light irradiation?
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Which enzyme is responsible for removing uracil from DNA?
Which enzyme is responsible for removing uracil from DNA?
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What is the consequence of depleted folate levels during DNA replication?
What is the consequence of depleted folate levels during DNA replication?
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Which compound formed during ethanol metabolism disrupts normal base pairing in DNA?
Which compound formed during ethanol metabolism disrupts normal base pairing in DNA?
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What is the function of ligase in DNA repair mechanisms?
What is the function of ligase in DNA repair mechanisms?
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Which genetic pattern results in bell-shaped distributions for traits like skin pigmentation?
Which genetic pattern results in bell-shaped distributions for traits like skin pigmentation?
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What critical nutrient is required for the absorption of dietary calcium?
What critical nutrient is required for the absorption of dietary calcium?
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What is the role of PCNA in DNA repair processes?
What is the role of PCNA in DNA repair processes?
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Study Notes
ABO Blood Group System
- ABO locus encodes enzymes adding the final monosaccharide to the H antigen.
- IA allele adds N-acetylgalactosamine, forming the A antigen.
- IB allele adds galactose, forming the B antigen.
- i allele produces a nonfunctional enzyme, leaving the H antigen unmodified.
Enzyme Functionality
- IA allele expresses N-acetylgalactosaminyl transferase.
- IB allele expresses galactosyl transferase.
- i allele expresses a nonfunctional transferase.
Blood Type Phenotypes and Compatibility
- A blood type individuals have anti-B antibodies, accepting A or O, but not B or AB.
- O blood type individuals lack A and B antigens, making them universal donors. They may be more susceptible to certain pathogens like Helicobacter pylori.
Genetic Characterization
- O blood type results from the homozygous recessive genotype (ii).
- IA IB genotype exhibits codominance, expressing both A and B antigens.
Mutations and Their Effects
- Missense mutations change one amino acid to another, like the creation of IB from IA.
- Silent mutations do not change the amino acid sequence.
- Nonsense mutations introduce premature stop codons, creating incomplete proteins.
Genetic Patterns of Inheritance
- Incomplete dominance: Illustrated by flower color in four-o'clocks (e.g., red, white, pink).
- Simple Mendelian traits: Observed in pea flower color (purple, white).
- Sex-linked traits: Exampled by hemophilia.
- Multifactorial inheritance: A characteristic of skin/hair pigmentation.
Biochemical Pathways and Pigments
- Anthocyanin: Pigment produced via the P locus pathway.
- Carotene: Pigment produced using the Y locus pathway
- Dopaquinone: A molecule involved in melanin production, with an orange-red dye.
Enzymes and Gene Products
- Chalcone synthase: P locus protein in pea plants.
- Phytoene synthase: Y locus protein in pea plants.
- Tyrosinase: OCA1 locus protein.
- Starch synthase: R locus protein in pea plants.
- Factor IX: Protein at the Hemophilia B locus.
- Fibrin: A product of the Factor IX pathway.
Ratios in Crosses
- Monohybrid cross (purple vs. white): 1:0 (F1) and 3:1 (F2) ratios.
- Incomplete dominance cross (red vs. white): 1:2:1 ratio (F2).
- Dihybrid cross (pea traits): 9:3:3:1 ratio.
Phenotypes
- Red flower (four-o’clock): Genotype CR/CR.
- Pink flower (four-o'clock): Genotype CR/Cr.
- White flower (four-o'clock): Genotype Cr/Cr.
- Albino: OCA1-/OCA1- genotype.
- Red hair: mc1r-/mc1r- genotype.
- Unaffected carrier (hemophilia): XH/Xh genotype.
- Hemophilia: Xh/Y genotype.
Transcription Regulation and p53 Pathway
- p53: Transcription factor for DNA repair and apoptosis.
- p53 response element: DNA site for p21 and Bax regulation.
- ATM phosphorylates p53 at serine 15.
- Chk2 phosphorylates p53 at serine 20.
- Mdm2 modifies p53 to keep its concentration low.
- p21: strongly regulated by p53.
- Bax: weakly regulated by p53.
DNA Repair Mechanisms
- ATM kinase activates Chk2.
- ATM phosphorylates p53 to allow CBP binding for DNA repair
- Repair endonucleases create nicks to replace damaged DNA.
- PCNA loads DNA polymerase delta at repair sites.
Apoptosis Pathway
- Apoptosome: Activates procaspase-9 via a rosette structure.
- Apaf1: Main component of the apoptosome.
- Caspase-9 activates caspase-3.
- Caspase-3 activates CAD for DNA fragmentation.
- CAD generates enveloped nuclear DNA during apoptosis.
- Bax forms pores in the mitochondrial membrane.
- Bcl2 inhibits Bax, preventing apoptosis.
Histones and Chromatin Regulation
- Histone: Octameric core of nucleosomes.
- Lysine: Target of histone acetylase's modification.
- Phosphate: Part of DNA wrapped around adjacent nucleosomes interacting with lysines.
- Bromo domain: Binds to acetylated histone lysines.
Caspase and Protease Activity
- Aspartate: Recognition site for caspases.
- Cysteine: Catalytic part of caspases.
- Serine: Catalytic part of clotting factors.
Cellular Processes and Miscellaneous
- CBP Kix: Binds to phosphorylated transcription factors.
- Ubiquitin: Targets proteins for degradation.
- ICAD: Cleaved by caspase-3 to initiate DNA cleavage.
- Stratum granulosum: Layer of apoptotic cells due to reduced Bcl2 expression in keratinocytes.
- Heterozygote: Repeated exposure to mutagens can lead to mutated p53 that fails to fix problems in subsequent exposures = cancer.
Aneuploidy and Chromosomal Disorders
- Nondisjunction: Error in chromosome segregation, causing aneuploidy.
- Turner's syndrome (XO): Female with one X chromosome.
- Klinefelter's syndrome (XXY): Male with an additional X chromosome.
- Trisomy 21 (Down syndrome): Extra chromosome 21.
- Barr body: Inactivation of extra X chromosomes.
Pigmentation and Its Role
- OCA2: Pumps tyrosine into melanosomes.
- MATP: Transports tyrosinase and TyRP1 to melanosomes.
- Primary purpose of pigmentation: UV light absorption.
- Folate: Destroyed by UV light in hypopigmented individuals.
- 7-Dehydrocholesterol: UV precursor to vitamin D.
Risks Associated with Pigmentation Variations
- Hypopigmentation at the equator: Risk of neural tube defects.
- Hyperpigmentation at high latitudes: Risk of rickets.
- Vitamin D: Necessary for calcium absorption.
Biochemical Pathways and Essential Molecules
- Methyl-tetrahydrofolate: Essential for thymine production.
- Vitamin D: Essential for calcium absorption.
- Folate: Rapidly destroyed by UV light in hypopigmented individuals.
Inheritance Patterns
- Multifactorial inheritance: Traits resulting in bell-shaped curves.
DNA Damage and Oxidative Stress
- Uracil: Oxidized form of cytosine due to ROS.
- Hydrogen peroxide: DNA-damaging agent from SOD.
- Superoxide: Primary ROS from semiquinone interactions.
- Acetaldehyde: DNA damaging agent from ethanol oxidation.
- N2-ethyl-guanine: Result of ethanol oxidation in damaging guanine.
- Benzo(a)pyrene: Smoke component damaging guanine.
- Dopaquinone: DNA damage in redheads after UV exposure.
UV-Induced DNA Damage
- Cyclobutane thymine dimer: Usual damage from UV radiation.
- Folate depletion: Increases uracil incorporation in rapidly replicating cells.
DNA Repair Mechanisms
- Repair endonucleases: Create nicks for removal of damaged DNA.
- Uracil-DNA glycosylase: Removes oxidized cytosines.
- Helicase: Unwinds damaged DNA.
- PCNA: Positions DNA polymerase delta.
- Ligase: Seals repaired DNA.
Summary of Key Concepts
- DNA damage sources: ROS, metabolic byproducts, and UV light.
- Consequences of damage: Base oxidation, adducts, strand distortion.
- Repair mechanisms: Enzymes remove & replace damaged DNA.
Transcription Initiation and Termination
- TATA box: Initiates DNA denaturation for transcription.
- AAUAAA: Signals transcription termination.
Pre-mRNA Processing
- 7-methyl-G cap: Aids splicing and translation initiation.
- Poly-A tail: Stabilises mRNA and aids translation.
- Intron/Exon: Splicing removes introns & joins exons.
Translation Initiation
- AUG: Initiation codon.
- eIF-4E: Binds 5' cap for ribosome recruitment.
- PABP: Binds poly-A tail, circularizing for enhanced translation.
Translation Elongation and Proofreading
- EF-Tu: Proofreads tRNA binding.
- EF-G: Moves ribosome for translocation.
- GTP: Energy source for both processes.
- 28S rRNA: Catalyzes peptide bond formation.
Translation Termination
- Release factor: Recognizes stop codons and releases protein.
Histone-Specific mRNA Regulation
- Histone mRNA: Increased lifetime and translation during S phase.
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Description
Test your knowledge on the ABO blood group system, including the genetic basis, enzyme functionalities, blood type phenotypes, and compatibility. Discover how alleles interact to determine blood types and their implications for transfusions and health.
