Question

Complete each sentence with the appropriate terms of phrases Not all terms or phrases will be used

Even with a complete genome sequence, it can be difficult to pinpoint a disease causing mutation because there is some_____1_____ in determining DNA sequence and there are millions of ____2______in the human genome

Identifying a disease causing allele involves narrowing down the possibilities using clues ______3_______.

Knowing the ________4_____ of the disease can help identify the causal mutation For example the disease is X-linked the mutation must be on ________________5_______.

Mapping the location of a disease causing gene by ____6__________ may now down the search to the area between two _____7___________.

Looking for mutations ________8____can be helpful because many (although not ally disease alleles cause missense, nonsense, or frameshift mutations

Comparison with ___________9_______ tells if a certain polymorphism is rare in the population as would be expected if it causes a rare disease.

Comparison with ________10______ identified amino acids that are conserved across species and may be important for function Mutations that affect ________11_____ are likely to cause disease if altered.

Options to use:

a) between genes

b) rare amino acids

c) polymorphisms

d) from many sources

e) other human genome sequences

f) the genomes of other organisms

g) conserved amino acids

h) the X chromosome

i) in exons

j) positional cloning

k) inheritance pattern

l) error

m) an autosome

n) from only DNA sequencing

Answer 1

1- L: Errors

2 - C: polymorphisms

3 - n: from only DNA sequencing

4 - k: inheritance pattern

5-h: on the X chromosome

6- j: positional cloning

7-g: conserved amino acids

8 -i: in exons

9-e: Other human genome sequences

10:f:the genomes of other organisms

11-m: an autosome

Explanation

DNA sequencing is not error free hence a single mutation data from one gene cannot be linked to a disease in an individual, also this is complicated further by gene polymorphisms, wherein more than one allele can occupy that gene locus within a given population. DNA sequencing however provides the best clues in determining the disease causing alleles. Knowing the inheritance pattern of the disease the alleles can be mapped on to the specific mutations, inheritance is determined in a X-linked or as a Y-linked pattern based on the forms of recessive or dominant alleles that is being carried by each of the parent. An X-linked mutation hence resides in the allele positioned on the X chromosome. Positional cloning reveals the positioning or the alignment of the conserved amino acids in a protein, thus it helps a great deal in identifying the particular gene and codon in depth. Looking for mutations in the exons reduces the search load since the exon is the coding part of a gene, hence any mutation in this region can be easily linked to a particular disease but this might not always serve the purpose because not all alleles carry positional mutations causing frame shifts, missense or nonsense mutations. Although it is of great reduction in data and thereby helps in narrowing down to the mutations. This can be further simplified by comparing gene polymorphism frequency and combination across other humans in a given population which will predict the disease causing tendency of the gene or its allele. In a larger scale comparing the gene mutations and conserved sequences of the disease genes across other organisms and their species will give more information regarding the function. Mutation on the non-sex chromosomes - the autosomes is more likely to cause a disease since the presence of even one dominant allele is enough to cause a disease.