Chapter 14 Flashcards
Define mutation
- any heritable change in the genetic material
- Sometimes spontaneous and random mistakes occur during DNA replication
- Most are eliminated but some persist and are passed on to daughter cells when the cell divides (somatic mutations).
- Mutations can be harmful, beneficial, or neutral
- Mutations that occur in the germ line (eggs and sperm) are heritable and passed down to the next generation
what is polymorphism?
refers to any genetic difference among individuals that is present in multiple individuals in a population.
define alleles
The different forms of the gene
define homozygous
An individual with two of the same alleles
define heterozygous
An individual with one allele from each parent
Polymorphisms can be harmful, beneficial, or have neutral effect on an individual’s phenotype.
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If the average number of new mutations for an entire genome in one generation is so high for humans, how is it tolerated?
Only 2.5% of the human genome actually codes for protein.
Most mutations occur in noncoding DNA and their effects are neutral.
Mutations account for the genetic diversity of populations and the genetic uniqueness of every individual.
what’s somatic mutation?
A somatic mutation in the Japanese morning
glory results in sectors of pigmentation.
The mutation affects the ability to make
purple/pink pigment.
A mutation occurred in the flower-colour gene
in one cell
can the descendants of that mutated
cell carry the mutation
yes when cell replicates it can be passed on
how are cancer and somatic mutation related
Most cancers result from mutations in somatic
cells
what are the 2 major types of mutations?
- Small scale (nucleotide substitution or point
mutation) - Large scale (chromosomal mutations)
Examples for small scale mutation
- Synonymous (silent) mutations
- Nonsynonymous (missense) mutations
- Nonsense mutations
- Frameshift mutations
Examples for large scale/ chromosomal mutations
- Insertion
- Deletion
What does a silent mutation/ aka synonymous look like?
A sense codon is changed to a different sense codon but that codon specifies the same amino acid as in the normal polypeptide
Is the function of the polypeptide changed in silent/synonymous mutation
no, the function remains unchanged
What is Missense mutation (aka nonsynonymous)?
changes sense codon to a sense codon for a different amino acid
what is nonsense mutation?
Translation of an mRNA containing a nonsense mutation results in a shorter-than-normal polypeptide—in many cases, this polypeptide will be only partially functional
What is frameshift mutation
•A single base-pair deletion or insertion in the coding region of a gene alters the reading frame of the resulting mRNA
•After the point of mutation, the ribosome reads codons that are not the same as for the normal mRNA, producing a different amino acid sequence
in the polypeptide
•Resulting polypeptide typically is nonfunctional because of the significantly altered amino acid sequence
In insertion/ deletion mutations multiples of 3 may not drastically affect the protein
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what faulty protein causes cystic fibrosis?
CFTR (cystic fibrosis transmembrane conductance regulator)
in-frame deletion of three nucleotides that code
for PHE at amino acid 508.
The resulting protein does not fold properly.
Copy number variation
Inversions
Reciprocal translocation image
How does DNA repair
- Base excision repair
- Nucleotide excision repair
How does Nucleotide excision repair works?
