Study Unit 5 Flashcards

Mutation and genetic variation

1
Q

Neurofibromatosis type 1 is caused by various mutations, including point mutations, deletions, and insertions in the NF1 gene. These mutations lead to the loss of function of neurofibromin, a tumor suppressor, causing the formation of benign and malignant tumors along nerves.

A

Genotype is the genetic makeup of an individual, while phenotype is the expression of the genotype.

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2
Q

What are the different types of mutations and their effects?

A

Mutations can be neutral, beneficial, or harmful. They include point mutations, insertions, deletions, and movement of transposable elements.

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3
Q

What are point mutations and their types?

A

Point mutations are changes in a single nucleotide. Types include synonymous (silent), nonsynonymous (missense), and nonsense mutations.

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4
Q

What is a synonymous (silent) mutation?

A

A mutation where there is no change in the amino acid in the protein, thus having no effect on the phenotype.

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5
Q

What is a nonsynonymous (missense) mutation?

A

A mutation that changes the amino acid sequence of a protein, potentially altering its function.

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6
Q

What is a nonsense mutation?

A

mutation that introduces a premature stop codon in the mRNA, resulting in a truncated, nonfunctional or unstable protein.

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7
Q

What are frameshift mutations?

A

Mutations caused by the insertion or deletion of one or two base pairs, shifting the reading frame and altering the entire downstream amino acid sequence.

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8
Q

What is the difference between frameshift and in-frame insertions/deletions?

A

In-frame insertions or deletions involve multiples of three bases and do not alter the reading frame, only adding or removing amino acids.

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9
Q

Give an example of a harmful mutation.

A

A mutation in the HTT gene increases glutamines, leading to Huntington’s disease.

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10
Q

Give an example of a beneficial mutation.

A

Lactase persistence in some adults allows continued digestion of lactose, improving survival and reproduction.

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11
Q

What is the difference between somatic and germ-line mutations?

A

Somatic mutations occur in nonreproductive cells and are not passed to offspring, while germ-line mutations occur in reproductive cells and are heritable.

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12
Q

What are the two classifications of mutations?

A

Small-scale mutations include single base-pair changes and frameshift mutations. Large-scale mutations include chromosome-level changes.

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13
Q

What are transposable elements?

A

DNA sequences that can change positions within the genome, potentially causing or reversing mutations and altering the cell’s genome size.

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14
Q

Who discovered transposable elements and how?

A

Barbara McClintock discovered transposable elements by studying the mutation in corn that resulted in yellow kernels due to the insertion of these elements.

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15
Q

What are some examples of chromosomal level mutations?

A

Examples include deletions, duplications, inversions, and reciprocal translocations.

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16
Q

What are the different DNA repair mechanisms?

A

DNA repair mechanisms include postreplication mismatch repair, base excision repair, and nucleotide excision repair.

17
Q

How does postreplication mismatch repair work?

A

Mismatch repair involves recognizing and removing mismatched bases that alter the DNA double helix shape, followed by replacement with the correct bases.

18
Q

How does base excision repair differ from nucleotide excision repair?

A

Base excision repair removes specific chemically modified bases, while nucleotide excision repair removes larger sections of mismatched or damaged DNA.

19
Q

What types of damage does nucleotide excision repair address?

A

It removes multiple mismatched bases or bulky lesions, such as thymine dimers caused by UV damage.

20
Q

What are some key concepts related to mutation and genetic variation?

A

Key concepts include the role of mutations in genetic variation, types of mutations, and DNA repair mechanisms.