Genetics: From Genes to Genomes
6th Edition
ISBN: 9781259700903
Author: Leland Hartwell Dr., Michael L. Goldberg Professor Dr., Janice Fischer, Leroy Hood Dr.
Publisher: McGraw-Hill Education
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Chapter 22, Problem 19P
Canavan disease, caused by homozygosity for a recessive allele, is a severe neurodegenerative syndrome usually resulting in death by the age of 18 months. The frequency of Canavan disease is particularly high in Jewish populations. In an effort to map the gene causing this condition, researchers looked at 10 SNPs (1–10) spaced at roughly 100 kb distances along chromosome 17 in five affected Jewish patients (Cases) and four unaffected Jewish individuals (Controls). In the accompanying table, each row depicts a single haplotype. (Every individual is diploid and therefore has two haplotypes, although only one is shown in the table.) G, C, A, and T represent the actual
| Case | SNP1 | SNP2 | SNP3 | SNP4 | SNP5 | SNP6 | SNP7 | SNP8 | SNP9 | SNP10 |
| 1 | G | T | G | T | T | T | C | A | G | T |
| 2 | A | T | G | T | T | T | C | A | G | T |
| 3 | G | T | G | T | T | T | C | A | G | C |
| 4 | A | A | G | T | T | T | C | T | C | C |
| 5 | G | A | G | C | C | T | G | A | C | C |
| Control | ||||||||||
| 6 | A | A | G | T | T | T | C | A | G | T |
| 7 | G | T | G | G | C | T | G | A | G | T |
| 8 | A | T | C | T | C | G | C | T | C | C |
| 9 | G | T | C | G | T | G | G | A | C | T |
| a. | Does the disease-causing mutation appear to be in linkage disequilibrium with any of the SNP alleles? If so, which ones? |
| b. | Where is the most likely location for the Canavan disease gene? About how long is the region to which you can ascribe the gene? |
| c. | How many independent mutations of the Canavan gene are suggested by these data? |
| d. | Suppose that individuals 2–9 are Ashkenazic (whose ancestors lived in the Rhine river basin of Germany and France after the Jews were expelled from Judea in 70 A.D.) while individual 1 is Sephardic (a non-Ashkenazic Jew). Would these facts provide any information about the history of the mutations causing Canavan disease? |
| e. | For mapping genes by haplotype association, why is it often helpful to focus on certain subpopulations? Does this strategy have any disadvantages? |
| f. | Human chromosome 17 is an autosome, so each person has two copies of each region along the chromosome. With this in mind, explain the practical difficulty in determining haplotypes. (Hint: Consider heterozygosity.) In light of this difficulty, how could the researchers determine any individual haplotype, such as any of those shown in the table? |
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The DNA of every individual in the pedigree shown
below has been sequenced at the causative locus.
All the non-shaded individuals are wild type apart
from III.1. III.1 has been proven to have the
causative mutation for this autosomal dominant
condition, but they exhibit no symptoms. Based on
this small pedigree, what is the level of penetrance
for the condition? Please give your answer as a
WHOLE percentage, give the number only, no
percentage symbol.
Answer: The level of penetrance for the
condition shown in the pedigree below is Blank 1
percent.
1:1
1:2
Il:1
I1:2
I1:3
Il:4
I1:5
I1:6
II:1 I:2 III:3
III:4
III:3 III:6 III:7
III:8
III:9
III:10 III:11 III12 II:13 III:14
IV:1 | IV:2 IV:3 IV:4 IV:5 IV:6 IV:7 IV:8 IV:9 IV:10 IV:11 IV:12 IV:13 IV:14 IV:15 IV:16 IV:17
IV:18 IV:19
V:1 V:2 V:3 V:4 V:5
V:6
V:7
V:8 V:9
V:10
V:11 V:12
In a particular country in sub-Saharan Africa, a medical study revealed that
0.075% of the country's population are suffering from sickle-cell anemia. Sickle
cell disease is caused by a mutation in the haemoglobin-Beta gene found on
chromosome 11. Sickle cell anemia is controlled by a pair of alleles, H and h,
where the individuals with the illness have the homozygous recessive genotype;
those with normal red blood cells have the alternative genotype.
Using the Hardy-Weinberg's equation, calculate the percentage of the population
of the two genotypes for normal blood cells.
In a few remote areas in that country, the percentage of sickle cell anemia reaches
as high as 5%. Calculate the percentage of homozygous and heterozygous
individuals with the normal blood cells and find the ratio for both phenotypes.
In a family-based genetic study for a mental disorder called marijuana dependence, a total of 50 families, each with a pair of siblings,
were recruited. The result showed that 11 families have the 1st siblings with marijuana dependence and the 2nd siblings without the
disorder, while another 9 families are opposite (i.e. the 1st siblings without the disorder but the 2nd siblings with the disorder). In
contrast, 13 families have both siblings exhibiting the disorder and another 17 families have both siblings without the disorder. What
kind of heritability can you calculate using this family study and what is the heritability value for marijuana dependence?
O A. Broad-sense heritability, approximately 38%
B. Narrow-sense heritability, approximately 38%
O. Narrow-sense heritability, approximately 76%
O D. Broad-sense heritability, approximately 76%
Chapter 22 Solutions
Genetics: From Genes to Genomes
Ch. 22 - Choose the best matching phrase in the right...Ch. 22 - Suppose you grew genetically identical dandelion...Ch. 22 - How can each of the following be used in...Ch. 22 - Two different groups of scientists studying a rare...Ch. 22 - Which of the following statements would be true of...Ch. 22 - Studies have indicated that for pairs of twins...Ch. 22 - Prob. 7PCh. 22 - Prob. 8PCh. 22 - Table 22.2 lists concordance values for MZ and DZ...Ch. 22 - Prob. 10P
Ch. 22 - Prob. 11PCh. 22 - Two alleles at one locus produce three distinct...Ch. 22 - In a certain plant, leaf size is determined by...Ch. 22 - Compare and contrast the use of SNP genotyping: i...Ch. 22 - Explain the similarities and differences between...Ch. 22 - In Fig. 22.14c, the fw2.2 causal gene was...Ch. 22 - Among the most prevalent pathologies that afflict...Ch. 22 - Human geneticists have found the Finnish...Ch. 22 - Canavan disease, caused by homozygosity for a...Ch. 22 - In GWAS analysis, because of the existence of LD...Ch. 22 - In Fig. 22.15: a. Why do some chromosomes in the...Ch. 22 - Consider the triangle diagram shown in Fig. 22.17....Ch. 22 - Prob. 23PCh. 22 - You conduct a Case/Control study comparing the...Ch. 22 - Prob. 25PCh. 22 - ALS amyotrophic lateral sclerosis is a rare, fatal...Ch. 22 - Through GWAS explorations, scientists have...Ch. 22 - In domesticated dogs, size has a high...Ch. 22 - Suppose a GWAS investigation found a particular LD...Ch. 22 - In 2008, Time magazine named as its invention of...
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