scientists published a paper describing three unusual human families where some individuals ex- hibited biparental inheritance of mitochondria. The researchers made this discovery by determining the base-pair sequences of the mtDNAs of many individ- uals in each family, and the results are shown in the three pedigree diagrams that follow. The

scientists published a paper describing three unusual human families where some individuals ex- hibited biparental inheritance of mitochondria. The researchers made this discovery by determining the base-pair sequences of the mtDNAs of many individ- uals in each family, and the results are shown in the three pedigree diagrams that follow. The

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Description: In 2018, scientists published a paper describing three unusual human families where some individuals ex- hibited biparental inheritance of mitochondria. The researchers made this discovery by determining the base-pair sequences of the mtDNAs of many

Biology 2e

2nd Edition

ISBN:9781947172517

Author:Matthew Douglas, Jung Choi, Mary Ann Clark

Publisher:Matthew Douglas, Jung Choi, Mary Ann Clark

Chapter12: Mendel's Experiments And Heredity

Section: Chapter Questions

Problem 26CTQ: The gene for flower position in pea plants exists as axial or terminal alleles. Given that axial is...

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2. Null mutations are valuable genetic resources becausethey allow a researcher to determine what happens to anorganism in the complete absence of a particular protein. However, it is often not a trivial matter to determinewhether a mutation represents the null state of the gene.a. Geneticists sometimes use the following test forthe nullness of an allele in a diploid organism: If theabnormal phenotype seen in a homozygote for theallele is identical to that seen in a heterozygote(where one chromosome carries the allele in question and the homologous chromosome is known tobe completely deleted for the gene) then the alleleis null. What is the underlying rationale for thistest? What limitations might there be in interpreting such a result?
17) There is a hypothetical gene in mice that produces a substance that induces twitchiness in leg muscles. A female mouse of a true-breeding twitchy strain is mated with a male of a true-breeding non-twitchy strain. All progeny are twitchy. Twitchiness may simply be a dominant trait caused by a nuclear allele, or it could be due to mtDNA. How would you distinguish between these two possibilities? Include possible results and how you would interpret them?
17) There is a hypothetical gene in mice that produces a substance that induces twitchiness in hind leg muscles. A female mouse of a true-breeding twitchy strain is mated with a male of a true-breeding non-twitchy strain. All progeny are twitchy. Twitchiness may simply be a dominant trait caused by a nuclear allele, or it could be due to mtDNA. How would you distinguish between these two possibilities? Include possible results and how you would interpret them.
8. Using recombinant DNA techniques (which willbe described in Chapter 9), it is possible to take theDNA of a gene from any source and place it on achromosome in the nucleus of a yeast cell. Whenyou take the DNA for a human gene and put it into ayeast cell chromosome, the altered yeast cell canmake the human protein. But when you remove theDNA for a gene normally present on yeast mitochondrial chromosomes and put it on a yeast chromosome inthe nucleus, the yeast cell cannot synthesize the correctprotein, even though the gene comes from the sameorganism. Explain. What would you need to do to ensurethat such a yeast cell could make the correct protein?
6. Albinism, which is caused by a mutational disruption in melanin (skin pigment) production, has been observed in many animal species. In 1991, the only documented observation of an albino humpback whale (named “Migaloo”) was observed near New South Wales, Australia. a) Do you think that Migaloo’s albinism is more likely caused by a dominant or recessive mutation? Why?b) Would knowing the sex of the only albino humpback whale ever observed help answer whether the albino gene is sex-linked or autosomal? Explain your reasoning.c) Assuming that Migaloo’s albinism is caused by a rare recessive gene, what is the likelihood of the establishment of a natural robust subpopulation of albino white humpback whales in this population?d) Assuming that Migaloo’s albinism is caused by a rare dominant gene, what is the likelihood of the establishment of a natural robust subpopulation of albino white humpback whales in this population?
2. Uniparental disomy is a rare phenomenon in whichonly one of the parents of a child with a recessivedisorder is a carrier for that trait; the other parent ishomozygous normal. By analyzing DNA polymorphisms, it is clear that the child received both mutantalleles from the carrier parent but did not receive anycopy of the gene from the other parent.a. Diagram at least two ways in which uniparentaldisomy could arise. (Hint: These mechanismsall require more than one error in cell division,explaining why uniparental disomy is so rare.)Is there any way to distinguish between thesemechanisms to explain any particular case ofuniparental disomy?
2. Uniparental disomy is a rare phenomenon in whichonly one of the parents of a child with a recessivedisorder is a carrier for that trait; the other parent ishomozygous normal. By analyzing DNA polymorphisms, it is clear that the child received both mutantalleles from the carrier parent but did not receive anycopy of the gene from the other parent.a. Diagram at least two ways in which uniparentaldisomy could arise. (Hint: These mechanismsall require more than one error in cell division,explaining why uniparental disomy is so rare.)Is there any way to distinguish between thesemechanisms to explain any particular case ofuniparental disomy?b. How might the phenomenon of uniparental disomyexplain rare cases in which girls are affected withrare X-linked recessive disorders but have unaffectedfathers, or other cases in which an X-linked recessive disorder is transmitted from father to son?c. If you were a human geneticist and believed oneof your patients had a disease syndrome caused…
6. A research group has selected three independent Trp−haploid strains of Neurospora, each of which cannotgrow in the absence of the amino acid tryptophan.They first mated these three strains with a wild-typestrain of opposite mating type, and then they analyzedthe resultant octads. For all three matings, two of thefour spore pairs in every octad could grow on minimalmedium (that is, in the absence of tryptophan), whilethe other two spore pairs were unable to grow on thisminimal medium.a. What can you conclude from this result?In the matings of mutant strains 1 and 2 with wild type,one of the two topmost pairs in some octads had sporesthat could grow on minimal medium while the other ofthe two topmost pairs in the same octads had spores thatcould not grow on minimal medium. In the mating ofmutant strain 3 with wild type, either all the spores inthe two topmost pairs could grow on minimal mediumor all could not grow on minimal medium.b. What can you conclude from this result?The…
8. As explained in the text, the cause of many geneticdiseases cannot yet be discerned by analyzing wholeexome/genome sequences. But in some of theseseemingly intractable cases, important clues can beobtained by looking at mRNAs or proteins, ratherthan at the DNA.a. As you will see in more detail in later chapters, it ispossible to use single-molecule methods to sequence cDNA copies of millions of mRNA molecules from any particular tissue cheaply. Howcould you sometimes use such information to finda disease gene? When would this information benoninformative?b. A technique called Western blotting allows you toexamine any protein for which you have an antibody; it is possible to see differences in size oramount of that protein. How could you sometimesuse such information to find a disease gene? Whenwould this information be noninformative?
The gene for flower position in pea plants exists as axial or terminal alleles. Given that axial is dominant to terminal, list all of the possible F1 and F2 genotypes and phenotypes from a cross involving parents that are homozygous for each trait. Express genotypes with conventional genetic abbreviations.
1. a. Assume that two transcription factors are required for expression of the blue pigmentationgenes in pansies. (Without the pigment, theflowers are white.) What phenotypic ratioswould you expect from crossing strains heterozygous for wild-type and recessive amorphicalleles for each of the genes encoding thesetranscription factors?b. Now assume that either transcription factor issufficient to get blue color. What phenotypicratios would you expect from crossing the sametwo heterozygous strains?
I. In humans, chromosome 16 sometimes has a heavilystained area in the long arm near the centromere. Thisfeature can be seen through the microscope but has noeffect on the phenotype of the person carrying it.When such a “blob” exists on a particular copy ofchromosome 16, it is a constant feature of that chromosome and is inherited.A couple conceived a child, but the fetus hadmultiple abnormalities and was miscarried. When thechromosomes of the fetus were studied, it was discovered that it had three copies of chromosome 16 (it wastrisomic for chromosome 16), and that two of thethree chromosome 16s had large blobs. Bothchromosome 16 homologs in the mother lacked blobs,but the father was heterozygous for blobs. Which parent experienced nondisjunction, and in which meioticdivision did it occur?