CHAPTER 9 HOW GENES AND GENOMES EVOLVE 2009 Garland Science Publishing Generating Genetic Variation 9 1 Which of the following statements is false a A mutation that arises in a mother s somatic cell often causes a disease in her daughter b All mutations in an asexually reproducing single celled organism are passed on to progeny c In an evolutionary sense somatic cells exist only to help propagate germline cells d A mutation is passed on to offspring only if it is present in the germ line 9 2 Your friend works in a lab that is studying why a particular mutant strain of Drosophila grows an eye on its wing Your friend discovers that this mutant strain of Drosophila is expressing a transcription factor incorrectly In the mutant Drosophila this transcription factor which is normally expressed in the primordial eye tissue is now misexpressed in the wing primordial wing tissue thus turning on transcription of the set of genes required to produce an eye in the wing primordial tissue If this hypothesis is true which of the following types of genetic change would most likely lead to this situation a a mutation within the transcription factor gene that leads to a premature stop codon after the third amino acid b a mutation within the transcription factor gene that leads to a substitution of a positively charged amino acid for a negatively charged amino acid c a mutation within an upstream enhancer of the gene d a mutation in the TATA box of the gene 9 3 Match the type of phenotypic change below with the type of genetic change most likely to cause it Each type of genetic change may be used more than once or may not be used at all Phenotypic changes 1 A protein normally localized in the nucleus is now localized in the cytoplasm 2 A protein acquires a DNA binding domain 3 Tandem copies of a gene are found in the genome 4 A copy of a bacterial gene is now found integrated on a human chromosome 5 A protein becomes much more unstable 6 A protein normally expressed only in the liver is now expressed in blood cells Types of genetic change A mutation within a gene B gene duplication C mutation in a regulatory region D exon shuffling E horizontal gene transfer 9 4 For each of the following sentences fill in the blanks with the best word or phrase in the list below Not all words or phrases will be used use each word or phrase only once Sexual reproduction in a multicellular organism involves specialized reproductive cells called s which come together to form a that will divide to produce both reproductive and cells A point mutation in the DNA is considered a mutation if it changes a nucleotide that leads to no phenotypic consequence a point mutation is considered if it changes a nucleotide within a gene and causes the protein to be non functional common gamete homologous deleterious unequal somatic neutral intron cellulose zygote 9 5 Transposable elements litter the genomes of primates and a few of them are still capable of moving to new regions of the genome If a transposable element jumped into an important gene in one of your cells when you were a baby and caused a disease is it likely that your child would also have the disease Explain 9 6 What is the most likely explanation of why the overall mutation rates in bacteria and in humans are roughly similar a Cell division needs to be fast b Most mutations are silent c There is a narrow range of mutation rates that offers an optimal balance between keeping the genome stable and generating sufficient diversity in a population d It benefits a multicellular organism to have some variability among its cells 9 7 For each statement below indicate whether it is true or false and explain why A B C D E 9 8 To meet a challenge or develop a new function evolution essentially builds from first principles designing from scratch to find the best possible solution Nearly every instance of DNA duplication leads to a new functional gene A pseudogene is very similar to a functional gene but cannot be expressed because of mutations Most genes in vertebrates are unique and only a few genes are members of multigene families Horizontal transfer is very rare and thus has had little influence on the genomes of bacteria Two individuals are represented in each choice in Figure Q9 8 individual 1 is one of the parents of individual 2 The asterisk seen in each choice indicates the occurrence of a single mutation during the cell division Which of the choices in Figure Q9 8 will lead to a mutation in every cell of the individual in which the original mutation occurred Figure Q9 8 9 9 Two individuals are represented in Figure Q9 9 individual 1 is one of the parents of individual 2 The asterisk indicates the occurrence of a single mutation Figure Q9 9 What is the chance that individual 2 will inherit the mutation in individual 1 a 100 b 50 c 1 in 100 000 d none 9 10 Consider a gene with a particular function Mutation X and mutation Y each cause defects in the function of the encoded protein yet a gene containing both mutations X and Y encodes a protein that works even better than the original protein The odds are exceedingly small that a single mutational event will generate both mutations X and Y Explain a simple way that an organism with a mutant gene containing both mutations X and Y could arise during evolution 9 11 For each of the following sentences fill in the blanks with the best word or phrase in the list below Not all words or phrases will be used use each word or phrase only once Most variation between individual humans is in the form of may arise by recombination within introns and can create proteins with novel combinations of domains Scientists and government regulators must be very careful when introducing herbicide resistant transgenic corn plants into the environment because if resistant weeds arise from then the herbicides could become useless Families of related genes can arise from a single ancestral copy by and subsequent divergence exon shuffling gene duplication horizontal gene transfer 9 12 purifying selection single nucleotide polymorphisms synteny unequal crossing over Figure Q9 12 shows an experiment used to determine the spontaneous mutation rate in E coli If the spontaneous mutation rate in E coli is 1 mistake in every 109 nucleotides copied about how many colonies would you expect to see on the plates lacking histidine if you were to assay 1011 cells from the culture for their ability to form colonies Figure Q9 12 a b c d 9 13 1 2 10 100 The