Mutations that happen during Transcription and Translation

What happens if there is a mistake (mutation) in the DNA code? Possibly proteins won’t be made or are made improperly. If the mutations occur in the gametes, the offspring’s DNA will be affected positively, negatively, or neutrally. What can cause a mutation? Replication error Transcription/translation error Cell division error Chemical agents (mutagens) Spontaneous changes

Point mutation A point mutation is a change in a single base pair in DNA. A change in a single nitrogenous base can change the entire structure of a protein because a change in a single amino acid can affect the shape of the protein.

Point mutations May change the amino acid code if the mutations occurs in the right place in the code. mRNA Normal Protein Stop Replace G with A Point mutation mRNA Protein Stop

Frameshift mutations Losing or gaining a single nucleotide base This mutation would cause nearly every amino acid in the protein after the deletion to be changed Deletion of U mRNA Protein

Chromosomal mutations When a part of a chromosome is left out, a deletion occurs When part of a chromatid breaks off and attaches to its sister chromatid, an insertion occurs. A B C D E F G H A B C E F G H Deletion A B C D E F G H A B C B C D E F G H Insertion

Changes to the chromosome When part of a chromosome breaks off and reattaches backwards, an inversion occurs. When part of one chromosome breaks off and is added to a different chromosome, a translocation occurs. A B C D E F G H A D C B E F G H Inversion A B C D E F G H W X A B C D E F G H W X Y Z Y Z Translocation

nondisjunction failure either of two homologous chromosomes to pass to separate cells during the first meiotic division

Repairing DNA Enzymes proofread the DNA and replace incorrect nucleotides with correct nucleotides. The greater the exposure to a mutagen such as UV light, the more likely is the chance that a mistake will not be corrected.