Chapter 4: Mutation - Tamhidi Centre Universiti Sains Islam Malaysia

What is the definition of mutation according to the lecture notes?

A change in the genetic material.

What is Progeria and what causes it according to the case study of Sam Berns ($1996-2014$)?

A mutation which causes deformed nuclei.

What characterizes Tetra-amelia and which gene/chromosome is involved?

It is an autosomal recessive disorder caused by mutations in the $WNT3$ gene in chromosome $17$, resulting in birth without fully formed limbs.

What are the two ways mutation can occur?

1. Spontaneous mutation 2. Induced mutation.

At what specific times or conditions can mutation happen during cell processes?

1. During replication of the chromosome 2. During crossing over and movement of chromosome during anaphase 3. Because of the environment.

What is a mutagen?

Substances that can cause mutation; they can be physical (UV light, X-rays, gamma rays) or chemical (mustard gas, colchicine, drugs, food preservatives, pesticides).

What is the difference between somatic and germ cell mutations regarding inheritance?

Somatic mutations occur in body cells and are not transmitted to the next generation, whereas germ cell mutations occur in reproductive tissues and may be passed on to offspring.

What is a gene (or point) mutation?

A change in the sequence of the DNA in a gene.

What are the four types of gene mutation mentioned in the notes?

Base Substitution, Base Insertion, Base Deletion, and Base Inversion.

What is base substitution?

A type of mutation where one nucleotide replaces another in the DNA, resulting in the change of only one amino acid in the polypeptide sequence.

Describe the mutation that causes Sickle Cell Anaemia and its physical result.

The triplet code $CTT$ is substituted with $CAT$, producing mutant Hb. This results in red blood cells becoming sickle-shaped, which can block capillaries and burst easily.

What is the effect of base insertion or base deletion on the polypeptide sequence?

They result in a frameshift mutation, which is the change of all amino acids at and after the point of insertion or deletion.

What is base inversion?

A mutation where a small region of DNA containing two or more nucleotides breaks off and rotates $1800$ before rejoining the DNA.

What is the difference between a missense mutation and a nonsense mutation?

A missense mutation codes for a different amino acid, while a nonsense mutation codes for a stop codon.

What are the two main categories of chromosome mutation?

a) Changes in the structure of the chromosome (chromosome aberration) b) Changes in the number of chromosome (chromosome number alteration).

What are the four types of changes in chromosome structure?

Translocation, Duplication, Inversion, and Deletion.

Define translocation in chromosome structure.

A segment of the chromosome breaks and is reattached to a non-homologous chromosome.

Define duplication in chromosome structure.

A segment of the chromosome breaks and rejoins its homologous partner.

What are the symptoms and cause of Cri du chat syndrome?

It is caused by the deletion of part of chromosome no. 5. Patients suffer from mental and physical abnormalities, a small head, and crying sounds like a cat meowing.

Define Aneuploidy and its notation.

A condition where an organism loses or gains one or more individual chromosomes ($2n+1, 2n-1$).

What is the primary cause of Aneuploidy?

Non-disjunction, which is the failure of a pair or pairs of homologous chromosomes to separate during Anaphase I or Anaphase II of meiosis.

What are the symptoms of Down syndrome, also known as trisomy $21$?