Mutation Flashcards
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Permanent change in the DNA
sequence.
Mutation
Result in a change to either a DNA base
pair or a chromosome.
Mutation
Responsible for the huge diversity of
genes found among organisms because
mutations are the ultimate source of
new genes
Mutation
Mutations of one or a few nucleotides can
affect ______ structure and function.
protein
When it occurs in a gamete or in a cell that gives rise to gametes, it may be transmitted to offspring and to future generations.
Point Mutations or Gene Mutations
If the mutation has an adverse effect on the phenotype of a person, mutant condition =
genetic disorder or hereditary disease
Mutations can result from
- errors in the DNA
- replication during cell division
- exposure to viral mutagens, or viral infection
_________________ which occur in eggs or sperms, these mutations can be passed onto offspring while _____________ which occur in body cells are not hereditary.
Germline Mutations; Somatic Mutations
a change in a single DNA base.
Point Mutation
a purine replaces a purine (A to G or G to A) or a pyrimidine replaces a pyrimidine (C to T or T to C).
Transition
a purine replaces a pyrimidine or vice versa (A or G to T or C).
Transversion
TYPES OF SMALL-SCALE MUTATIONS
- Point mutations within a gene:
- Insertions and deletions can involve one or more nucleotide pairs.
(TYPES OF SMALL-SCALE MUTATIONS)
Point mutations within a gene:
- Single nucleotide-pair substitutions
- Nucleotide-pair insertions or deletions.
Replacement of one nucleotide and its partner with another pair of nucleotides.
Nucleotide-pair substitution
Some substitutions have no effect on the encoded protein, owing to the redundancy of the genetic code.
Nucleotide-pair substitution
Example: if 3’-CCG-5’ on the template strand mutated to 3’-CCA-5’. The mRNA codon that used to be GGC would become GGU, but a glycine would still be inserted at the proper location in the protein.
Nucleotide-pair substitution
A change in a nucleotide pair may transform
one codon into another that is translated into
the same amino acid =
silent mutations
has no observable effect on the phenotype (can occur outside genes as well)
Silent mutation
substitutions that change one amino acid to another one
Missense
such a mutation have a little effect on the protein
Missense
Alteration of a single amino acid in a crucial area can significantly alter protein activity
Missense
Substitution mutations are usually_______________ : altered codon still codes for an amino acid
missense mutations
there are abnormalities in the hemoglobin that changes or mutations that replace one amino acid into another. This also now changes the property of the hemoglobin as a whole.
Hemoglobinopathies
can also change a codon for an amino acid into a stop codon:
Point Mutation or Nonsense mutation
the resulting polypeptide will be shorter; it causes translation to be terminated prematurely than the polypeptide encoded by the normal gene.
Nonsense mutation
change in DNA that causes a protein to terminate or end its translation earlier than expected.
Stop mutation
Nearly all nonsense mutations lead to
_________________
nonfunctional proteins
occurs when there is a substitution of a nucleotide making the template mRNA have a different code but still produces the same amino acid
Silent Mutation
occurs when the substitution changes amino acid into a completely different amino acid. And this can have two variable effects: little to no effect or significant changes when it occurs at crucial areas.
Missense Mutation
Leads to a shorter template because of the protein stop codon. And proteins that are produced here are non-functional
Nonsense Mutation
Abnormal Hemoglobins
Hemoglobinopathies
AA substitution in the beta chains-substitution of valine for glutamic acid in the 6th position in the normal beta chain.
Causes sickling RBC under conditions of reduced oxygen concentration.
Hemoglobin S
Substitution of lysine for glutamic acid on the 6th position of the beta chain.
RBC appear as target cells, or, less often, precipitated Hb C crystal may be demonstrated.
Hemoglobin C
replaces GLUTAMIC ACID at 6th position = Hb S (insoluble)
VALINE
replaces GLUTAMIC ACID at 6th position = Hb C (insoluble)
LYSINE
replaces GLUTAMIC ACID at 26th position = Hb E
LYSINE
Additions or losses of nucleotide pairs in a
gene
Insertions and Deletions
Insertion or deletion of nucleotides may alter the reading frame of the genetic message, the triplet grouping of nucleotides on the mRNA that is read during translation =
Frameshift Mutation
occurs whenever the number of nucleotides inserted or deleted is not multiple of three.
Frameshift Mutation
All nucleotides downstream of the deletion of insertion will be improperly grouped into codons.
Frameshift Mutation
The Result will be extensive missense, usually ending sooner or later in nonsense and premature termination.
Frameshift Mutation
Unless the frameshift is very near the
end of the gene, the protein is almost
certain to be __________
nonfunctional
Variations from the normal condition and chromosome structure or chromosome number.
Chromosomal Mutations or Chromosomal Aberrations
Phenotype of an organism can be affected by small-scale changes involving individual genes
Large scale chromosomal changes can also affect an organism’s phenotype.
Alterations of chromosome number and structure
Physical and chemical disturbances, as well as errors during meiosis, can damage chromosomes in major ways or alter their number in a cell.
Alterations of chromosome number and structure
Large scale chromosomal alterations in humans and other mammals often lead to spontaneous abortion or miscarriage of a fetus and individuals born with these types of genetic defects commonly exhibit various developmental disorders
Alterations of chromosome number and structure
Occurs in meiosis 1 and meiosis 2
Members of a pair of homologous chromosomes do not move apart properly during meiosis 1 or sister chromatids fail to separate during meiosis 2
Nondisjunction
One Gamete receives two of the same type of chromosome and other gamete receives no copy
Nondisjunction
If either of the apparent gametes unites with a normal one at fertilization the zygote
will also have an abnormal number of a particular chromosome
aneuploid
