Genetics Chapter: Mutations and Evolution

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Questions and Answers

What is one potential outcome of a mutation in a somatic cell?

Skin cancer (correct)

Improved survival of the organism

Increased fertility

Hereditary disease

All mutations are harmful to organisms.

False

What type of mutation involves a change in the nucleotide sequence of a gene?

Gene mutation

A mutation that leads to the substitution of a single nucleotide is known as a __________ mutation.

point Signup and view all the answers

Match the following types of mutations with their definitions:

Chromosomal mutation = Change in chromosomal structure or number Gene mutation = Alteration in the nucleotide sequence of a gene Point mutation = Substitution of a single nucleotide Frameshift mutation = Insertion or deletion that shifts the reading frame Signup and view all the answers

What type of mutation results in a premature stop codon?

Nonsense mutation Signup and view all the answers

A substitution mutation can affect multiple codons at once.

False Signup and view all the answers

What is the consequence of a frameshift mutation?

It alters the reading frame of the gene, resulting in a completely different translation from the point of mutation. Signup and view all the answers

A substitution mutation can lead to a __________ mutation if it results in a different amino acid.

missense Signup and view all the answers

Match the type of mutation with its correct description:

Silent mutation = No change in protein function Nonsense mutation = Introduces a premature stop codon Missense mutation = Changes one amino acid in the protein Frameshift mutation = Alters the entire reading frame of the gene Signup and view all the answers

What is a frameshift mutation primarily caused by?

Insertion or deletion of nucleotides Signup and view all the answers

Spontaneous mutations occur without a known cause.

True Signup and view all the answers

Name one disorder associated with frameshift mutations.

Tay-Sachs disease Signup and view all the answers

The mutation frequency in eukaryotes ranges from $10^{}$ to $10^{}$ per nucleotide pair per generation.

7; 9 Signup and view all the answers

Match the following disorders with their associated mutations:

Color blindness = Point mutation Cystic fibrosis = Frameshift mutation Haemophilia = Point/Frame mutation Sickle-cell disease = Point mutation Tay-Sachs disease = Frameshift mutation Signup and view all the answers

Which of the following best describes conditional lethal mutations?

Lethal only under certain conditions Signup and view all the answers

Induced mutations can occur due to natural causes.

False Signup and view all the answers

What is the typical mutation frequency range for bacteria?

10^-8 to 10^-10 Signup and view all the answers

Study Notes

Topics for Second Semester

Different types of mutations
DNA repair mechanisms
Microbial genetics
Hardy-Weinberg principle
Natural selection and random genetic drift
Population genetics

Mutations

Mutations are changes in the nucleotide sequence of genetic material.
Mutations can occur in somatic cells (not passed to offspring) or in gametes (passed to offspring).
Mutations happen randomly.
Most mutations are neutral.
Chemicals and UV radiation can cause mutations.
Many mutations are repaired by enzymes.
Mutations in somatic cells can lead to cancers (e.g., skin cancer, leukemia).
Some mutations can improve an organism's survival (beneficial).
Mutation effects range from no observable change to lethality.

Mutation: Phenotypic Effects

Mutations' effects on phenotypes vary, from no visible change to lethality.

No Observable Effect

Due to the degeneracy of the genetic code, some mutations have no effect on an organism's phenotype.
These are called neutral mutations.

Category of Mutation

Chromosomal mutations:
- Structural mutations (disjunction)
- Numerical mutations (non-disjunction).
Gene mutations

Chromosomal Structural Mutations

Inversion
Duplication
Deletion
Insertion
Translocation

Chromosome Mutation (Numerical)

Nondisjunction: Homologous chromosomes or sister chromatids fail to separate during meiosis.
Causes a change in chromosome number.

Gene Mutation

Changes in the nucleotide sequence of a gene.
Can be caused by copying errors, chemicals, or viruses.
Types: point mutation (substitution), frameshift, insertion, deletion.

Point Mutation (substitution)

Change of a single nucleotide.
One nucleotide is substituted in a gene.
Changes in the third base of a codon often have no effect (degenerate codon).

Point mutation examples

Missense mutation: changes one amino acid.
Nonsense mutation: creates a premature stop codon.
Silent mutation: does not change the amino acid.

Point Mutation Examples (continued)

Sickle cell anemia: missense mutation causing abnormal hemoglobin.

Frameshift Mutation

Insertion or deletion of one or more nucleotides.
Changes the "open reading frame."
Produces incorrect proteins.
Examples: Tay-Sachs disease (four-base insertion in hexosaminidase A gene).

Mutations: Additions

A frame shift mutation, with addition of a nucleotide.

Mutations: Deletions

A frame shift mutation, with a deletion of a nucleotide.

What is Tay-Sachs Disease?

Rare genetic disorder destroying neurons in the brain and spinal cord.
Results from gene defect on chromosome 15.

Common Gene Mutations in Humans

Different disorders are caused due to specific gene mutations.

Mutation: Spontaneous or Induced

Spontaneous mutations occur without an identifiable cause (inherited metabolic errors or unknown environmental factors).
Induced mutations result from exposure to mutagens (physical or chemical agents) causing DNA changes (e.g., ionizing radiation, UV light, chemicals).

Mutation Frequency

Spontaneous mutations are infrequent.
Bacteria and phages: 10^-8 to 10^-10 per nucleotide pair per generation.
Eukaryotes: 10^-7 to 10^-9 per nucleotide pair per generation or 10^-4 to 10^-7 per gene per generation.
Treatment with mutagens can increase mutation frequency to over 1% per gene.

Conditional Lethal Mutations

Lethal in restrictive conditions, but viable in permissive conditions.
Examples: Favism (sex-linked condition due to glucose-6-phosphate dehydrogenase deficiency, avoiding fava beans) and temperature-sensitive mutants (grow at certain temperatures but not others).

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Description

Explore the intricate world of genetic mutations and their impact on organisms. This quiz covers various types of mutations, DNA repair mechanisms, and key principles like Hardy-Weinberg and natural selection. Test your knowledge on how mutations influence phenotypes and contribute to population genetics.