Mutations Flashcards
Gene expression 2 steps
Transcription
Translation
- the process of DNA being copied to generate a single-strand RNA
Transcription
- the process of the RNA nucleotide sequence being converted into the amino acid sequence of a protein.
Translation
Transcription occurs in the____; translation occurs in the______.
nucleus
cytoplasm
Sense vs Antisense strans
Sense - coding; non tenplate
Antisense - non coding; template
THE GENETIC CODE
Each “______” is composed of_____ three-letter codes,____ in all.
______codons are recognized by_____ for the incorporation of the____ common amino acids.
codon box; four; 64
Sixty-one; tRNAs; 20
“________” proposed by_____
The hypothesis states that the pairing between codon and anticodon at the first two codon positions always follows the usual rule for complementary base pairing, but that exceptional “wobbles” (non-Watson-Crick base pairing) can occur at the third position.
Wobble Hypothesis; Francis Crick
• Some sites on chromosomes are “_______” where mutations arise at a higher frequency than other regions of the DNA.
hotspots
are those that occur as a result of interaction of DNA with an outside agent or mutagen that causes DNA damage.
• Induced mutations
is one that occurs as a result of natural processes in cells, for example DNA replication errors.
spontaneous mutation
• result from changes in the nucleotide sequence of DNA or from deletions, insertions, or rearrangements of DNA sequences in the genome.
Mutations
Mutations are of fundamental importance in molecular biology for several reasons:
Mutations are important as the major source of genetic variation that drives evolutionary change.
Mutations may have deleterious or (rarely) advantageous consequences to an organism or its descendants.
Mutations in germ cells can lead to heritable genetic disorders, while mutations in somatic cells may lead to acquired diseases such as cancer or neurodegenerative disorders.
Mutant organisms are important tools for molecular biologists in characterizing the genes involved in cellular processes.
Mutations are important as the major source of ______that drives evolutionary change.
genetic variation
______may have deleterious or (rarely) advantageous consequences to an organism or its descendants.
Mutations
Mutations in_____ cells can lead to heritable genetic disorders, while mutations in_____ cells may lead to acquired diseases such as cancer or neurodegenerative disorders.
germ
somatic
Mutant organisms are important tools for _____in characterizing the genes involved in cellular processes.
molecular biologists
TYPES OF MUTATION
Gene Mutation
Chromosome Mutation
Genome Mutation
Mechanism of Gene Mutations
Substitution
Deletion
Insertion
Insertion-
addition of a base
Deletion
- removal of a base
Substitution
Nucleotide Substitution or Point Mutations-
The most common nucleotide mutations are those that affect a single base pair, in which one base is replaced by another.
(Insertions/Deletions
Base INDELS
3 types of gene mutation
Point
Frameshift
Point
Silent
Missense
Nonsense
Frameshift
Deletion
Insertion
- usually due to a substitution in the third base of a codon, known as the _______, which often represents the same amino acid as the original codon.
Silent Mutations (Synonymous)
Wobble position
- Mutations that change the nucleotide sequence without changing the amino acid sequence
Silent Mutations (Synonymous)
- Nucleotide substitutions in protein-coding regions that do result in changed amino acids
Missense mutations (Nonsynonymous)
- cause premature chain termination during protein synthesis, the remaining polypeptide fragment is nearly always nonfunctional
Nonsense mutations-
- A nucleotide substitution that creates a new stop codon
Nonsense mutations-
Nonsense mutations-
cause premature chain termination during protein synthesis, the remaining polypeptide fragment is nearly always______
nonfunctional
Sickle Cell Anemia
• Mutation in a_____ codon of______ gene which results in the substitution of _____ with _____
• Formation of abnormal hemoglobin molecules cause sickle-shaped RBCs.
6th
beta-globin
glutamic acid with valine
- Results in abnormal protein products with an incorrect
amino acid sequence that could lead to severe genetic diseases
Frameshift Mutations
- shifting the reading frame of the codons due to deletion or insertion of one nucleotide.
Thus, altering the subsequent sequence of amino acids.
Frameshift Mutations
• Genetic disorder caused by mutations in the HEXA gene.
• Deletion of cytosine in the coding sequence which causes premature termination.
Tay-Sachs Disease:
Tay-Sachs Disease:
• Genetic disorder caused by mutations in the____
• Deletion of_____ in the coding sequence which causes premature termination.
HEXA gene
cytosine
: the altered codon codes for the same amino acid.
Silent mutation
: the altered codon codes for a different amino acid and the protein is often nonfunctional.
Missense mutation
the new codon is a termination codon.
Protein synthesis stops and the protein is nonfunctional.
Nonsense mutation:
the addition or deletion of one or more base pairs results in a shift in the reading frame of the resulting mRNA, and leads to production of a nonfunctional protein.
Frameshift mutation
Change in a single nucleotide
No shift in the reading frame
May be silent, missense, or nonsense
Often mild or neutral
Point mutation
Shifts the reading frame
Usually results in a nonfunctional protein
Usually severe and damaging
Insertion or deletion of nucleotides
Chromosome Mutation (4)
Deletion
Duplication
Inversion
Translocation
Chromosme Segment Lost
Deletions
A segment from chromosome is
transferred to another
Translocation
A segment from one chromosme is transferred to its homologous chromosme, giving it a duplicate of some genes
Duplication
A segment of a chromosme arm is inverted
Inversion
Genome Mutation
Aneuploidy
Polyploidy
Changes in whole sets of chromosomes
Having more or less than normal number of sets
Monoploid and Polyploids
Aberrant Euploidy
Other Types of Mutations
• Expansions of trinucleotide repeats
• Extensive insertions and deletions
• Major chromosomal rearrangements
