Genetics - Robbins

Question 1

What is a mutation, and what are its significants in somatic and germ cells?

Answer 1

Permanent change in the DNA

Somatic cell: not transmittet to the progeny but are important in the causation of cancers and some congenital malformation

Germ cells: transmittet to the progeny and may give rise to inherited disease.

Question 2

Point mutation, missense mutation and nonsense mutation

Answer 2

Substitution of a single nucleotide base by a different base

E.g. sickle cell anemia

Missense mutation is a point mutation in which a single nucleotide change results in a codon that codes for a different amino acid

Nonsense mutation is a point mutation in a sequence of DNA that results in a premature stop codon, or a nonsense codon in the transcribed mRNA, and in a truncated, incomplete, and usually nonfunctional protein product

Question 3

Frameshift mutation

Answer 3

Occur when the insertion or deletion of one or two base pairs alters the reading frame of the DNA strand

Question 4

Trinucleotide repeat mutation

Answer 4

Trinucleotide repeat disorders (also known as trinucleotide repeat expansion disorders, triplet repeat expansion disorders or codon reiteration disorders) are a set of genetic disorders caused by trinucleotide repeat expansion, a kind of mutation where trinucleotide repeats in certain genes exceed the normal, stable threshold, which differs per gene. The mutation is a subset of unstable microsatellite repeats that occur throughout all genomic sequences. If the repeat is present in a healthy gene, a dynamic mutation may increase the repeat count and result in a defective gene.

All affect sequences for the nucleotides guanine (G) and cytosine (C). E.g. fragile X syndrome.

Question 5

Single nucleotide polymorphism

Answer 5

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Question 6

What are a Mendelian disorder?

Answer 6

Diseases caused by a single-gene defect