BIO130H1 Lecture Notes - Lecture 18: Lafora Disease, Laforin, Missense Mutation

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9 Apr 2016

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Document Summary

Gene: epm2a: the geneic disease associated with the mutaion in the nucleoide sequence is lafora. Myoclonus epilepsy: the gene which causes lafora disease is usually found on chromosome 6 (cytogeneic. Lafora disease is an autosomal recessive disease caused by a missense mutaion in the. Since lafora disease is an autosomal recessive disease it can be passed down through families. An autosomal recessive disease means that two copies of an abnormal gene, in this case epm2a must be present in order for the disease to develop and be passed on. The epm2a gene was exposed to a missense mutaion. A missense mutaion is a point mutaion in which a single nucleoide is changed. This results in a codon change, which now codes for a diferent amino acid: as menioned above, lafora disease is an autosomal recessive disease caused by a missense mutaion in the epm2a gene.

Related Questions

1. An occurrence of a gene made larger by trinucleotide repeats is:

Allelic expansion

Nucleotide expansion

Translocation mutation

Transformation

2. a chemical that can damage and/or change DNA is called a/an:

Allele

Endonuclease

Vector

Mutagen

3. An occurrence when a section of a chromosome relocates itself to an entirely different (non-homologous) chromosome is called a/an:

Inversion mutation

Translocation mutation

Transformation mutation

Duplication mutation

4. The tandem repeat in the sequence GGGAAGGGAAGGGAAGGGAAGGGAAG is:

GGA

GGGAA

GGAAG

GGAAGGG

A disease characterized by abnormally shaped hemoglobin is called:

Cystic Fibrosis

Sickle Cell Anemia

Marfan Syndrome

Leukemia

5. A point mutation that causes a substitution of a stop codon with an amino acid and leads to the formation of a longer protein is a:

Nonsense mutation

Missense mutation

Sense mutation

Frameshift mutation

6. Addition or deletion of nucleotides in a DNA sequence is known as a:

Nonsense mutation

Missense mutation

Sense mutation

Frameshift mutation

7. The least severe type of chromosomal mutation is:

Point

Frameshift

Inversion

Translocation

8. Chemicals inserting themselves into DNA can cause a:

Missense mutation

Nonsense mutation

Sense mutation

Frameshift mutation

9. A genetic condition caused by allelic expansion is:

Familial hypercholesterolemia

Fragile X syndrome

Alkaptonuria

Galactosemia

10. Which of the following is most likely the original DNA strand if the mutated DNA strand is ATAGUUGATGUA ?

ATAGAAGATGAA

ATAGCCGATGCA

ATAGGGGATGGA

ATAGTTGATGTA

11. An unbalanced chromosomal mutation would include a/an:

duplication (insertion)

inversion

translocation

denaturation

12. Many translocation mutations are found to be involved with:

cancers

sickle cell anemia

Huntington disease

cystic fibrosis

13. A common repeat throughout the human genome that is approximately 300 bases in length is called a/an:

EcoRI repeat

Hind repeat

Exo repeat

Alu repeat

14. A balanced chromosomal mutation includes:

imprintation

denaturation

inversion

deletion

salmondinosaur263

Parent Telomere Length	Child Telomere Length
- 4.7	-6.6 -6.0 -6.1
-3.9	-0.6
-1.4	-2.2
-5.2	-5.4
-2.2	-3.6
-4.4	-2.0
-4.3	-6.6
-5.0	-3.8
-5.3	-6.4
-0.6	-2.5
-1.3	-5.1 -3.9
-4.2	-3.9

The sequence change affecting the TERC gene in each of the families is different. However, consider an example where the disease-associated allele results in the following abnormal sequence of the RNA template: 5â-CGGCAACCCCAA-3â

a. Explain the impact you expect this mutation to have on telomere synthesis.

b. Provide a hypothesis/explanation for why the disease allele is dominant to the non-disease allele.

please explain in detail need real help :( THIS ARE QUESTIONS I NEED THEM ANSWER NOT THE ONE AT THE BOTTOM

If You get confused this second part questions and the background can help.

Dyskeratosis congenita (DKC) is a rare genetic disorder characterized by abnormal fingernails and skin pigmentation, the formation of white patches on the tongue and cheek, and progressive failure of the bone marrow. An autosomal dominant form of DKC results from mutations in the gene that encodes the RNA component of telomerase (the TERC gene). Fifteen families with autosomal dominant DKC are evaluated. The median age of onset of DKC in parents was 37 years, whereas the median age of onset in the children of affected parents was 14.5 years. Thus, DKC in these families arose at progressively younger ages in successive generations. The researchers measured telomere length of members of these families (see table). Telomere length normally shortens with age, so telomere length was adjusted for age of the subject. Note that the age-adjusted telomere length of all members of these families is negative, indicating that their telomeres are shorter than normal. For age-adjusted telomere length, the more negative the number, the shorter the telomere.

a. How do the telomere lengths of parents compare with the telomere lengths of their children?

b. Explain why the telomeres of people with DKC are shorter than normal and why DKC arises at an earlier age in subsequent generations.

Part B

Think about the DNA coding sequence of a gene. If an A were swapped for a T, what kind of mutation could it cause and why?

a) It could cause a frameshift nonsense or frameshift missense mutation because it would change the reading frame of the codon triplet.

b) It could cause a silent, missense, or nonsense mutation because those are the types that can be caused by a nucleotide-pair substitution like this one.

c) It could cause a nonsense mutation because the sequence would no longer be the same, so the protein would be shorter and non-functional.

d) It could cause a silent mutation because A and T are complementary to each other so it is not really a substitution mutation.

Part C

Why is a frameshift missense mutation more likely to have a severe effect on phenotype than a nucleotide-pair substitution missense mutation in the same protein?

a) A substitution missense mutation causes the protein to be shorter and thus non-functional.

b) A frameshift missense will cause the codons to be out of order, but a substitution missense does not change the order of the codons.

c) A frameshift missense mutation will cause an early Stop codon, but a substitution missense might be silent.

d) A substitution missense affects only one codon, but a frameshift missense affects all codons downstream of the frameshift.

Part D

Which of the following sequences shows a frameshift mutation compared to the wild-type mRNA sequence?

a) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUACAGAGUGA-3â

b) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUACGUUGGAGUGA-3â

c) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUACAUCUGGAGUGA-3â

d) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUGUGACAUUGGAGUGA-3â

Part F

Suppose that the triplet of nucleotides indicated in bold (AGC) spans two codons, that is, CTA and GCC. If the triplet AGC were deleted from this DNA coding sequence, what effect would it have on the resulting protein?

5â-ATGCTAGCCTATCGTAAC-3â

a) The two flanking codons would be altered, but the rest of the amino acid sequence would be the same because there would be no frameshift.

b) The entire amino acid sequence would be altered due to the frameshift.

c) All of the amino acids after the deletion would be altered due to the frameshift.

d) All of the amino acids up to the deletion would be altered due to the frameshift.