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DNA Mutations/Hemoglobinopathies
Cole
31
Biochemistry
Professional
10/13/2011

Additional Biochemistry Flashcards

 


 

Cards

Term

 

 

 

 

oxidative deamination

Definition

 

 

 

removes amino group, converting C to U

 

if this strand is used as a template, uracil is base-paired with A, resulting in overall change of C-->T

Term

 

 

 

Apurination/apyrimidination

Definition

 

 

 

loss of a purine or pyrimidine base

Term

 

 

 

 

 

O6-methyl guanosine

Definition

 

 

 

highly mutagenic species

Term

 

 

 

T-T dimerization

Definition

 

 

blocks DNA polymerase, prevents replication

Term

 

 

 

Nitrous acid deamination

Definition

 

 

A--> hypoxanthine

 

G-->xanthine

Term

 

 

 

conservative mutation

Definition

 

 

aa is changed to another aa of similar size and chemical nature

 

generally does not change protein structure

Term

 

 

non-conservative mutation

Definition

 

 

 

when an aa is changed to another aa of different size or chemical nature

 

usually-->change in protein structure

Term

 

 

 

invariant amino acids

Definition

 

 

aa at functionally active site whose change can result in loss of function

Term

 

 

 

missense mutation

Definition

 

 

 

base change causes coding for different aa

Term

 

 

 

 

nonsense (termination) mutation

Definition

 

 

 

 

codon that codes for aa is mutated to form termination codon

Term

 

 

 

Who discovered the molecular basis/heritability of SCD and in what year?

Definition

 

 

 

Linus Pauling 1945

Term

 

 

 

read-through mutation

Definition

 

 

 

mutation of a termination codon that results in larger than normal protein

Term

 

 

 

 

framshift mutation

Definition

 

 

 

insertion/deletion of a single nucleotide

 

causes shift in 3-base codon reading frame

 

very bad

Term

 

 

 

 

transition mutation

Definition

 

 

purine-pyrimidine pair substituted for another

 

ex: A-T --> G-C

Term

 

 

transversion mutation

Definition

 

 

 

purine-pyrimidine pair subbed for a pyrimidine-purine pair

 

ex: A-T --> T-A

Term

 

 

 

 

peptide mapping or fingerprinting

Definition

 

 

protein can be sequenced to det. primary structure and compared to a normal protein

 

cleaved into small frags by digestion w trypsin/pepsin/another enz, then sep by gel electrophoresis

 

spots compared

can separate abnormal spots and sequence protein

Term

 

 

 

hemoglobinopathies most frequently arise from mutations in the __ gene

Definition

 

 

beta

Term

 

 

Heinz bodies

Definition

 

 

aa mutations can result in unstable Hb (ex: proline subbed in alpha helix sequence) that easily denature and precipitate as Heinz bodies

Term

 

 

 

unstable Hb

Definition

 

 

caused by mutation, results in precipitation/denaturation (Heinz bodies)

 

may cause reticulocytosis, anemia, splenomegaly, urobilinuria

Term

 

 

 

Hb mutation that results in changed o2 affinity

Definition

 

 

ex: due to substitution of aa that bind BPG or release Bohr protons

 

Heinz body formation, hemolytic anemia

Term

 

 

 

 

HbCowtownBeta-His-->Leu

Definition

 

 

 

Loss of His that dissociates 50% of Bohr protons

 

leads to destabilization of T conformation-->inc oxygen affinity

 

 

Term

 

 

 

Methemoglobin

Definition

 

 

 

HbM

oxidation of ferrous ion to ferric state (mut in heme binding cavity of distal/prox His)

 

>10% HbM-->cyanosis

>35%-->clinical symptoms

>80%=incompatible w life

Term

 

 

 

 

diaphorase deficiency

Definition

 

 

 

diaphorase reduces ferric back to ferrous state

 

deficiency-->too much ferric-->methemoglobinemia

Term

 

 

 

 

Thalassemia

Definition

 

 

imbalance in production of alpha and beta Hb chains

 

 

RBCs are microcytic and hypochromic

Term

 

 

 

 

β-thalassemias

Definition

 

synth of beta-globin gene is decreased or absent

 

alpha globin chains for tetramers-->precipitation-->cell death

 

HbF and HbBart (gamma tetramer) accumulation is typical

Term

 

 

 

 

β-thal major and minor

Definition

 

minor/trait: heterozygous, make some adult Hb, don't require tx

 

major aka Cooley's disease: homozygous, babies in 1st yr of life = very sick and require transfusions, results in iron overload and death 15-25.  Tx also includes bone marrow transplantation

Term

 

 

 

HbBart's

Definition

 

 

gamma globin tetramer found in pts w thalassemia

Term

 

 

 

alpha thalassemia

Definition

 

2 copies of alpha globin gene on each copy of chrom 16

(4 total)

 

1 defective=silent carrier, no sx

2=alpha thal trait w mild anemia

3=hemoglobin H disease, mild-sever hemolytic anemia

4=hydrops fetalis, fetal death (alpha chain necessary for HbF)

Term

 

 

oxygen binding of HbBart's and HbH (gamma4 and beta4)

Definition

 

 

no cooperativity, therefore high oxygen affinity, useless for carrying oxygen to tissues

Term

 

 

HbC and HbS

Definition

 

 

HbS: 6th beta chain aa, Glutamate, is mutated to Valine

 

HbC: same Glutamate is mutated to Lysine

Term

 

 

 

acquired hemoglobinemia

Definition

 

 

CO poisoning

 

 

CO binds ferrous ion stronger than O2 does

Tx: 100% O2

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