Biology Chapter 12.4

What is a mutation? A change (mistake) in the replication of genetic material. The daughter cell is different from the parent

Gene Mutation Most replication errors are corrected by the cell’s built in spell check system. However, some do escape detection

Gene Mutation Deletion – Leaving out one nucleotide in the sequence, shifts the reading of the sequence to the left, creating a totally different set of amino acids

DELETION Normal mRNA reads: AUG AAG UUU GGC GCA UUG UAA Met Lys Phe Gly Ala Leu Stop. Mutated mRNA reads: AUG AAG UUG GCG CAU UGU AA… Met Lys Leu Ala His Cys …

Gene Mutation Insertion – Mutation in which an extra nucleotide is added to the chain during replication, shifts reading to the right, creating a totally different set of amino acids

INSERTION Normal mRNA reads: AUG AAG UUU GGC GCA UUG UAA Met Lys Phe Gly Ala Leu Stop. Mutated mRNA reads: AUG AAG UUU GUG CGC AUU GUA A Met Lys Phe Val Arg Ile Val

Gene Mutation Point Mutation – A base substitution occurs. One nucleotide is replaced with a different one

POINT MUTATION Normal mRNA reads: AUG AAG UUU GGC GCA UUG UAA Met Lys Phe Gly Ala Leu Stop. Mutated mRNA reads: AUG AAG UUU AGC GCA UUG UAA Met Lys Phe Ser Ala Leu Stop.

Gene Mutation These mutations arise spontaneously during DNA replication. External agents may cause mutations, called mutagens.

Chromosome Mutations Changes may occur in chromosomes as well as in genes. Chromosome mutations can have serious effects on the distribution of genes to gametes during meiosis.

Chromosome Mutations Deletion: ABCDE---FGH ABCE---FGH

Chromosome Mutations Duplication: ABCDE---FGH ABCBCDE---FGH

Chromosome Mutations Inversion: ABCDE---FGH ADCBE---FGH

Chromosome Mutations Attachment to a different chromosome: ABCDE---FGH WXY---Z WXABCDE---FGH Y---Z

Other causes of genetic variation During meiosis, homologous pairs fail to separate. This would cause the offspring to have an extra chromosome. During meiosis, part of one chromatid breaks of and joins to the other (see pg 264.)

CANCER Abnormal cells, go through cell cycle very fast, creating new cells like it. They reproduce in an uncontrolled way, crowding out healthy cells and destroying tissues and possibly organs. It can spread to other parts of the body

Causes of Cancer Genes that control the cell cycle mutate, called an oncogene. Mutations may be inherited or caused by a carcinogen, a cancer causing agent in the environment. Tobacco smoke, radiation and other chemicals.

Causes of Cancer Viruses may also cause cancer. Their presence disrupts normal cell processes. They can also carry oncogenes into the host cell.

Technology Scientists can transfer a gene artificially from a donor organism to a bacteria. The DNA of the bacterium is called recombinant DNA. The bacteria will transcribe and translate the foreign gene and produce the protein it is coding for.

Technology Small, circular pieces of DNA, called plasmids, are where the foreign DNA is placed.

Technology To obtain a foreign gene, mRNA from a cell is isolated and DNA is produced (called reverse transcription). This single stranded DNA is converted to a double strand and this double strand is the desired gene.

Technology In use today – goats that produce a human blood clot dissolving factor. Plants that are disease resistant. Plants that are larger than normal.