DNA Mutations and Repair Mechanisms

Practice questions covering large-scale DNA mutations (CNV, inversions, translocations) and specific DNA repair pathways (mismatch, base excision, and nucleotide excision repair).

What are the four types of large-scale DNA mutations categorized in Chapter $13.4$?

1) Duplication and deletion, 2) Copy Number Variation (CNV), 3) Inversion, and 4) Reciprocal translocation.

From what two errors do duplication and deletion typically occur?

DNA replication error and DNA repair error.

What is the evolutionary outcome of gene duplication and divergence?

It forms new genes and results in gene families, which are groups of genes with related functions.

What specific gene family evolved through several episodes of duplication and divergence?

The eta ext{-globin} gene family.

What is the definition of Copy-Number Variation (CNV)?

A variation where the size of the duplicated or deleted region can include one or more complete genes, resulting in different numbers of copies of a region (e.g., $0$, $1$, or $2$ copies).

How does the average $ext{AMY1}$ copy number per chromosome $1$ vary between low-starch and high-starch diet societies?

In low-starch diet societies, the average is about $2.5$, whereas in high-starch diet societies, it is about $3.5$.

What technique do criminologists use to create a 'DNA fingerprint' using single tandem repeat (STR) sites?

Gel electrophoresis.

What medical condition is caused by a recurrent inversion of the X chromosome that disrupts the $ext{factor VIII}$ gene?

Hemophilia A.

What occurs during a reciprocal translocation?

Nonhomologous chromosomes break and exchange pieces with each other.

Chronic myeloid leukemia (CML) results from reciprocal translocation between which two chromosomes?

Chromosome $9$ and chromosome $22$, resulting in the $ext{BCR-ABL}$ fusion gene.

What are the three main DNA repair mechanisms mentioned in the notes?

1) Postreplication mismatch repair, 2) Base excision repair, and 3) Nucleotide excision repair.

In Postreplication Mismatch Repair, which protein recognizes mismatched bases to initiate the process?

$ext{MutS}$.

What is the role of $ext{MutH}$ in Postreplication Mismatch Repair?

It is recruited (along with $ext{MutL}$) and breaks the DNA backbone some distance away from the mismatch.

In Base Excision Repair, what enzyme is responsible for cleaving uracil from the deoxyribose sugar?

$ext{DNA uracil glycosylase}$.

What is the function of AP endonuclease in Base Excision Repair?

It cleaves the DNA backbone and removes the sugar after the nitrogenous base has been removed.

How does Nucleotide Excision Repair differ from Base Excision Repair in its initial step?

Nucleotide Excision Repair recognizes one or more damaged bases and uses enzymes to cleave the DNA backbone at sites flanking the damage, removing the entire region rather than just a single base.