A mutation is a process that creates genetic variation Mutation creates variations in protein-coding portions of genes that can affect the protein Eself More often, & creates variations in the switches that control
when and where a protein is active, and how much protein is made. For example, lactase is an enzyme that helps infants break down lactose, a sugar in mik. Normally the gene that codes for lactase is active in
babies and then turned off at about age four When people who do not make lactase consume milk, they experience discomfort. But some people have a variation in a genetic switch that keeps the lactase gene
active and people who have it can keep milk in their dets even as aduts
Mutations that occur in sex cells or gametes can be passed from one generation to the next. It is possible during gamete formation, meiosis, that there is an exchange of genes between homologous
chromosomes, resulting in a change in the chromosome This type of mutation is called crossing-over Mutations that occur in somatic or body cells, like a mutation causing skin cancer, will not be passed on
Most of the mutations in our DNA are naturally occuring For example, when a cell divides, & makes a copy of Es DNA, and sometimes the copy is not perfect. That small difference from the original ONA
sequence is a mutation Mutations can also be caused by exposure to specific chemicals or radiation, called mutagens
There are many different ways that DNA can be changed, resulting in different types of mutation
Substitution
A substitution is a mutation that exchanges one base for another. A substitution could
change a codon to one that encodes a different amino acid and causes a small change in the protein produced. For example, sickle cell anemia is caused by a substitution in the beta-hemoglobin gene, which
aters a single amino acid in the protein produced
change a codon to one that encodes the same amino acid and causes no change in the protein produced. These are called slent mutations
change an amino-acid-coding codon to a single "stop" codon and cause an incomplete protein. This can have serious effects since the incomplete protein probably won't function
Insertion
insertions are mutations in which extra base pairs are inserted into a new place in the DNA
Deletion
Deletions are mutations in which a section of DNA is lost, or deleted
How do mutations occur in the genetic code? (Choose 3)
A
B
4* C
Mutations can only occur when passed on thorough reproduction
Mutations can be sent and not affect the organism that has them
The majority of mutations are the result of exposure to mutagens
D
A woman who has sickle cell anemia passes this disease on to her offspring. This means that the mutation for sickle cel anemia MUST occur in the woman's gametes
E During DNA replication, the original DNA strand GTC ACA GGC ATC is copied into complementary strand CAG CCG TAG. This is an example of deletion