Мутация себептері. Биология, 10 сынып, дидактикалық материал.

Name:__________________________________ Date:_________________ Period:_______

• What can result when a mutation to DNA occurs?

Cancer (mutation affecting body cell/somatic cell),

Decreased functioning,

Birth defects (mutation affecting sex cell), or

No observable problem within the cell.

• Explain the following types of gene mutations:
• Insertion – addition of an extra nucleotide – results in a frameshift mutation
• Deletion - removal of an original nucleotide – results in a frameshift mutation
• Substitution – change of a nucleotide to another – results in a point mutation
• Point mutation – mutation affecting one or a few nucleotides
• Frame-shift mutation – mutation causing a change in the reading frame of codons which in turn can change the amino acid sequence after the mutation.
• A DNA segment is changed from-AAGTAG- to -AAATAG-. This is a point substation mutation because a G was replaced with a A.
• A DNA segment is changed from -AATTAGAAATAG- to -ATTAGAAATAG-. This is a(n) frameshift mutation due to the deletion of adenine from the beginning of the sequence.
• A DNA segment is changed from-GCTAGC- to -GCTATGC-. This is a frameshift insertion mutation because a T was added between the A and G.
• A DNA segment is changed from -AGTTGAAATAG- to -AGTTGAATAG-. This is a(n) frameshift mutation due to the deletion of adenine from the middle of the sequence.
• A DNA segment is changed from -CCGTAAGAG- to - CCGGAAGAG -. This is a(n) point substitution mutation due to the change of thymine to guanine.
• A DNA segment is changed from -AATTAGAAATAG- to -ATTAGAAATAG-. This is a(n) frameshift mutation due to the deletion of adenine from the beginning of the sequence.
• Here are two related mRNA sequences: 5'UUUAGCGAGCAU3' and 5'UUUAGCCAUAAAAAAAA3'. How was the second sequence formed? Intron (GAG) removed and a poly A tail was added to form the second sequence.

• A bacterium that was once able survive in a tryptophan-free environment is now unable to synthesize its own tryptophan. The bacterium is otherwise unaffected. Where is the most likely location for the mutation causing the change?

The trp promoter is the most likely location for the mutation because if it cannot operate, transcription of the tryptophan-synthesizing enzymes does not take place.

• What is a promoter? Binding site for RNA polymerase.

• What type of mutation has occurred in the figure?

Deletion of the nucleotide U caused a frameshift mutation since the codons following the deletion will code for a different amino acid.

• What will be the result of the mutation in the figure?

Nearly every amino acid in the protein will change.

• Using DNA sequencing, you discover that a bacterium has experienced a deletion mutation that removed three nucleotides. The bacterium appears completely unaffected in all its functions. Where is the mostly likely location for the mutation?

Introns, or intervening sequences, which get processed out of the mRNA before it leaves the nucleus, so removal of an intron would probably have little effect on bacterial functions such as enzyme synthesis.

Gene Regulation – can Hide Mutations Under certain condition

• An expressed gene is turned on.
• Proteins that bind to Regulatory Sites on DNA determine whether a gene is expressed.
• If a specific kind of protein is not continually used by a cell, the gene for that protein is turned on and off at different times.