Exam 2 Flashcards
(53 cards)
amorphic alleles
produces no or very little proteins, usually recessive
Hypomorphic Alleles
Produce Reduced Level or Activity of Otherwise Normal Protein. Usually Recessive.
Hypermorphic Alleles
Produce Higher Level or Activity of Otherwise Normal Protein. Usually Dominant.
Antimorphic Alleles
Produce Proteins That Reduce the Level or Activity of Protein Made by Wild-type Allele. Usually Dominant in Presence of Wild-type Allele. Extremely Rare “Dominant/Negative” Human Alleles.
Spatiotemporal Alleles
Heterochronic (Difference in Timing of Expression) or Ectopic (Difference in Location of Expression) Alleles Could be Hypo/Hyper/Amo/
Neomorphic Alleles
Produce Protein That No Longer Perform the Wild-type Gene Function, but Instead Have a New Function. Jokers Wild, Shows No, Co, or Complete Dominance.
Mullerian Allelomorphy
Mutant Specrtrum Caused by Mutagenesis
A DNA sequence produces a mutant protein in which several amino acids in the middle of the protein differ from the normal protein. What kind of mutation could have occurred?
An addition and a deletion mutation
Shine- Dalgaro sequence
AGGAGG, a sequence which preceded the AUG start codon, facilitating initiation
initiation complex
small ribosomal subunit + initiation factors + mRNA at codon AUG
Translation of mRNA: 3 steps
Initiation: binding of ribosome to mRNA
Elongation: Sequential addition of amino acid to COOH end by many charged tRNA
Termination: Release factors bind when stop codon are found at the ribosome A site. Ribosome, Polypeptide and mRNA disassociate.
Sickle- cell anemia
recessive genetic disease in which afflicted individuals are homozygous for the HbS hemoglobin allele
(Heterozygotes are carriers of the affected gene but are largely unaffected)
an example of “Hypomorphy”
Sickle- cell anemia is caused by:
The difference of a single peptide. Glu #6 becomes Val #6.
Hypomorphy (Partial Loss
of Function)
Point Mutation
Changes Identity of One or
a Few Amino Acids, Resulting
in a Damaged Protein that
Still Retains Some Wild-type
Function.
Amorphic (Null or
Complete Loss of Function)
Allele Produces Little
Or No Wild-type Gene
Function
Neomorphic
(Gain of Function)
Allele Produces a Novel Protein
That May Have Little or No
Function in Common With
the Wild-type Allele
one gene encodes:
one polypeptide
Alkaptonuria and phenylketonuria(2 genetic diseases) are the result of:
mutations that lead to metabolic blocks
phenylketonuria
results when phenylalanine is not converted to tyrosine
Stop Codons:
No Normal tRNA Will Bind to Stop Codons.
peptidyl transferase
catalyzes peptide bond formation between the amino acid on the tRNA at the A site and the growing peptide chain bound to the tRNA in the P site
a peptide bond is formed by:
a dehydration reaction between the carboxyl group of one amino acid and the amino group of another
Initiation of translation(3 steps):
- mRNA binds to small ribosomal subunit along with initiation factors(IF 1 2 3)
- Initiatior tRNA binds to mRNA codon in P site, IF 3 is released
- Large ribosomal subunit binds to complex, IF 2 and 3 are released, EF- Tu binds to tRNA, facilitating entry into A site.
Elongation during translation(6 steps):
- 2nd charged tRNA enters A site, facilitated by EF- Tu, first elongation step commences
- Peptide bond forms, uncharged tRNA moves to the E site and subsequently out of the ribosome, the mRNA has been translocated three bases to the left, causing the tRNA bearing the dipeptide to shift to the left in to the P site.
- the first elongation step in complete, facilitated by EF-G. The third charged tRNA is ready to enter the A site.
- Third charged tRNA has entered A site facilitated by the EF- Tu, 2nd elongation step begins.
- Tripeptide formed, 2nd elongation step completed, uncharged tRNA moves to E site.
MORE ELONGATION
- Polypeptide chain synthesized and exiting ribosome
