BIO 122 Lecture Notes - Lecture 3: Hbb, Gene Duplication, Teleost

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greenbee40

24 Mar 2017

School

Drexel University

Department

Bioscience & Biotechnology

Course

BIO 122

Professor

Karen Kabnick

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Document Summary

(cid:1005) (cid:1006) (cid:1008) (cid:1007) (cid:1008) (cid:1008) (cid:1009) (cid:1009) (cid:1010) Note: they are not coding for genes: not coding for genes , exons, mutations are random and many have adverse effects on the organism. What can you infer regarding similarity in dna sequences: similar begginings, some similar traits throughout all species, distantly related genes differ more, dna sequences is very similar all across different species. Collectively the set of genes are called a cluster. Tetrapods and teleost fish have multiple clusters compared to the single cluster observed in the other species. Additionally teleost fish have 7-8 clusters, compared to the 4 clusters observed in tetrapods (which include humans btw). Hox genes play an important role in development, as illustrated in the known expression" panel in the figure. What pattern(s) in gene expression can you recognize among the different species: basic and bone structure. To help determine evolutionary relationships among different groups of organisms, scientists compare gene sequences of highly conserved genes.

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On the Edge Selling Personalized Genetics

Several companies on the Internet sell genetic tests directly to consumers including 23andMe, Navigenics, decode Genetics, DNA Tribes, Genelex, ScientificMatch, Consumer Genetics, Salugen, DNAprint Genomics, Genova Diagnostics, Suracell, and many more. The companies ask customers to collect a sample of their genes with a cheek swab and send it to them for testing. Most test by putting the customerâs gene sample on a small flat âDNA microarray chipâ that already contains pieces of DNA matching known genes (or gene mutations). If one of the customerâs genes matches one of the pieces of DNA on the chip, it binds to the DNA fragment which creates a tiny fluorescent glow showing that the gene indicated by the DNA fragment is in the sample. A computer then analyzes the pattern of glowing spots on the chip and prints out a list of the genes (or gene mutations) in the customerâs sample. Scientists have discovered a few genes that are associated with specific diseases or personal characteristics. Studies found, for example, genes that are linked to cystic fibrosis, Tay Sachs disease, and Lou Gehrigâs disease, genes that increase the risk of certain breast, colon, and thyroid cancers, and genes associated with sensation seeking, eye color, obesity, and lactose intolerance. They also found that some genes are more often found in people whose ancestors came from certain regions of the world. The companies say that based on these studies and their own gene tests, they can give customers valuable personalized information (for a price, of course). One company, Sciona, (no longer operating) said on its website: âSciona is a leader in nutrigenomics, the science of personalizing your nutrition and lifestyle choices to match your genesâ; Sciona gave customers âa personalized preventative dietary regimeâ that was supposed to prevent the diseases their genes put them at risk for. Another site promises: âBased upon the . . . [genetic] analysis, Suracell recommends to each client a personalized regimen of nutraceuticals [vitamin supplements].â Another states: âDNA Tribes . . . uses genetic material . . . to measure your genetic connections to individual ethnic groups and major world regions.â Another company claims to do it all: âWith a simple saliva sample weâll help you gain insight into your traits, from baldness to muscle performance. Discover risk factors for 95 diseases. Know your predicted response to drugs, from blood thinners to coffee. And uncover your ancestral origins.â Critics claim, however, that with a few exceptions, most studies have shown only weak connections between genes and specific traits, disease risks, drug responses, nutritional or vitamin needs, or ancestral origins. Many studies that link specific genes to a disease are only preliminary and the full picture has not yet been worked out. Moreover, critics say, it is wrong to tell customers their genes put them at risk of a deadly disease without proper counseling, especially when the scientific studies are weak and many other environmental, demographic, and lifestyle factors determine the actual onset of a disease. Ordinary consumers, they conclude, are being sold a product that they do not have the expertise to interpret. But defenders of the tests say consumers have a right to know what genes they carry and what science has learned about those genes. The companies charge from $140 to test for two or three genes, up to $999 to test for a full suite of genes. Evaluate the ethics of selling gene tests directly to consumers like these companies are doing. What would each of the three theories of a businessâs duties to consumers say about what the companies are doing? Under what conditions do you think selling the tests would be ethically legitimate? Check out the video of GAO interviews of gene-test company salespeople at http://www.gao.gov/products/gao-10-847t .

Based on this issue evaluate the ethics of selling gene tests directly to consumers. Watch the video showing GAO interviews of the gene-test company salespeople and evaluate the ethics of the selling practices shown on the video. Answer the following questions:

1. What would the three theories of business's duties to consumers say about what the companies are doing?

2. Is it ever ethical for direct-to-consumer selling of these tests?

3. Should the government-on its own discretion-be able to use the DNA data in the databases to solve crimes and catch criminals?

http://www.gao.gov/products/GAO-10-847T

Ploidy refers to the number of complete sets of chromosomes (genes) present in a cell. The number of chromosomes in a complete set is a fixed characteristic of a species. Humans are diploid with two sets of 23 chromosomes. Fruit flies are diploid with two sets of 4 chromosomes. Sexually reproducing organisms are diploid, each somatic cell of an organism has two complete sets ("di" is a prefix indicating 2.). To complete a life cycle and reproduce new members of a species, mating is required. Mating brings a donation from a male and a donation from a female together. However, if the male and female cells remain diploid, the fertilization will result in a tetraploid zygote. In general, these are not viable. A mechanism is needed to form special haploid cells, gametes. The diploid set is split precisely into two complete haploid sets. That mechanism is meiosis.

The complete set of chromosomes of a species is also the complete set of genes of a species, the genome. (Yes, there is a minor contribution from mitochondria and chloroplasts. Inheritance of this information is "cytoplasmic".)

Please answer the following questions:

1. How many chromosomes in a brain cell of a fruit fly? How many chromosomes are in a liver cell of a human? Explain both answers.

2. How many chromosomes are in a fruit fly unfertilized egg? How many chromosomes are in a human egg? Explain both answers.

3. Why is meiosis necessary for sexually reproducing organisms? How many chromosomes are in a human zygote? Relate the two answers.

4. What is a gene allele? Suppose there is a gene called "bingo" and it is present once in a complete haploid set. How many alleles of "bingo" does a diploid individual have? How many copies or versions of the gene "bingo" are present in a diploid individual?

5. Modern DNA sequencing clearly identifies alleles by showing the different DNA sequence of each allele. These alleles may be termed structural alleles (I coined the term for this problem.). Classical genetics only dealt with phenotypes or visible traits. As a result, alleles of genes were identified by functionality, usually normal or non-functional. Using your knowledge of gene structure and gene expression, postulate a relationship between structural alleles and functional alleles. (include relative amounts; more, less, or equal).

In this study you will learn about a modification of Mendelian inheritance which is also an important source of genetic variation.

You are about to perform what looks like a classic dihybrid testcross ("A" is the gene for eye color and "B" is the gene for wing color.)

A allele for red eyes

a allele for white eyes

B allele for clear wings

b allele for spotted wings

(AaBb) X (aabb) Note the genotypes and phenotypes.

Question #1: Predict the expected phenotypic ratio of this P X P cross.

Observed results:

500 red eyes clear wings

500 white eyes spotted wings

Question #2: How do the expected results compare with the observed results?

Question #3: Considering Mendel's second law (regarding dihybrid crosses), suggest an explanation for the discrepancy between the observed results and those predicted.

Genes are located at specific positions on a chromosome. The distance between genes is measured in terms of "mapping units". In this exercise the gene for wing phenotype âBâ will be moved from its original position of zero to different positions on the chromosome. You will observe the effect of this gene movement.

First, gene "B" (wing color) is moved from position zero to position 10 on the same chromosome. Gene "A" (eye color) stays at position 0.

Observed Results: (position 10)

450 red eyes clear wings

50 red eyes spotted wings

50 white eyes clear wings

450 white eyes spotted wings

Question #4: How do these results differ from those predicted by Mendel's second law?

Question #5: From those in the first cross?

Question #6: Can you suggest a hypothesis to explain these new results?

Gene "B" (wing color) is now moved to position 20 on the same chromosome. Gene "A" (eye color) stays at position 0.

Observed Results: (position 20)

400 red eyes clear wings

100 red eyes spotted wings

100 white eyes clear wings

400 white eyes spotted wings

Question #7: How do the proportions of the phenotypic classes in this cross differ from the proportions you obtained in the earlier crosses?

The wing color gene "B" is now moved farther away (positions 30, 40, 50, and 60).

Observed Results: (position 30)

350 red eyes clear wings

150 red eyes spotted wings

150 white eyes clear wings

350 white eyes spotted wings

Observed Results: (position 40)

292 red eyes clear wings

220 red eyes spotted wings

195 white eyes clear wings

293 white eyes spotted wings

Observed Results: (position 50)

250 red eyes clear wings

250 red eyes spotted wings

250 white eyes clear wings

250 white eyes spotted wings

Observed Results: (position 60)

250 red eyes clear wings

250 red eyes spotted wings

250 white eyes clear wings

250 white eyes spotted wings

Question #8: Prepare a line graph plotting the % of recombinant offspring (Y-axis) vs. difference in position between the two genes (X-axis). (Hint: your graph should be one line with labeled points at map positions 0, 10, 20, 30, 40, 50, & 60).

Question #9: A genetic definition of "1 map unit" is the distance between 2 genes that gives 1% recombinants out of the total number of progeny. Using this definition, how many map units separate the "A" and "B" genes when the eye color gene "A" is at position 0 and the wing color gene "B" is at position 40? (Show how you determined the results.)

Question #10: How does the distance between two genes on the same chromosome affect the proportion of recombinants? Why?

Question #11: Maximum crossover frequency can be defined as the point at which no more recombination can be detected no matter how far apart the genes are located. Do your results indicate that you are approaching the maximum crossover frequency?

Question #12: Show (using a Punnett Square) the expected phenotypic rations if the two genes were located on different chromosomes.

Question #13: Which of your simulated cross or crosses do the data from the Punnett Square most closely fit? Why?

Question #14: A wild-type fly (heterozygous for gray body color and normal wings - b⁺ vg⁺/b vg) was mated to a black fly with vestigial wings (b vg/b vg). The F1 had the following phenotypic distribution: wild type, 850; black body - vestigial wings, 899; black body - normal wings, 79; gray body - vestigial wings, 85. What is the recombination frequency (RF) between these genes for body color and wing type? (show work)

Question #15: A cross produced 915 offspring with normal pigment and 310 with albinism. Conclusion?

a. One of the parents was homozygous for albinism.

b. Both parents were heterozygous.

c. One parent was homozygous for normal pigmentation.

d. Both parents were albinos. e. 605 albino zygotes must have failed to develop.

NOTE: Please show all work to support your answers.

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BIO 122 Lecture Notes - Lecture 3: Hbb, Gene Duplication, Teleost

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