Mechanisms of Evolution: Natural Selection and Mutation

Questions and Answers

What is a characteristic of silent mutations?

They do not change the amino acid at all. (correct)

They change the amino acid produced.

They result in a frameshift in the protein sequence.

They prevent the protein from being produced.

What is the primary outcome of a point mutation?

It has no effect on protein production.

It alters multiple genes simultaneously.

It always results in a frameshift.

It changes a single nucleotide. (correct)

What type of mutation occurs when one base is replaced by another?

Insertion

Chromosomal mutation

Substitution (correct)

Deletion

Which of the following mutations will always cause a frameshift?

Insertion or deletion Signup and view all the answers

How do chromosomal mutations primarily affect an organism?

They change all or part of a chromosome. Signup and view all the answers

What is a key difference between germline and somatic mutations?

Germline mutations affect the entire organism. Signup and view all the answers

Which type of mutation is primarily linked to environmental factors?

Induced mutations Signup and view all the answers

What is the most significant effect of chromosomal mutations compared to point mutations?

They can cause changes in multiple genes at once. Signup and view all the answers

What is the main role of natural selection in evolution?

It allows organisms with beneficial traits to reproduce. Signup and view all the answers

What defines a mutation in genetic terms?

It is a random change that can be harmful or beneficial. Signup and view all the answers

What distinguishes gene mutations from chromosomal mutations?

Gene mutations involve changes in a single gene. Signup and view all the answers

Which of the following is an example of a missense mutation?

A change in a nucleotide that results in a different amino acid. Signup and view all the answers

What effect do mutagens have on mutation rates?

They increase the frequency of mutations occurring. Signup and view all the answers

Which of the following statements about nonsense mutations is correct?

They cause the protein synthesis to stop prematurely. Signup and view all the answers

What is the defining characteristic of a mutant organism?

It carries a newly appeared allele due to mutation. Signup and view all the answers

Which statement correctly describes the role of amino acids in proteins?

Most amino acids are represented by multiple coding triplets. Signup and view all the answers

Study Notes

Natural Selection

Mechanism of evolution where individuals with favorable alleles survive and reproduce, passing on their alleles
Also known as "survival of the fittest"

Mutations

Random and permanent change in DNA sequence
Results in variation of a characteristic occurring suddenly and by chance in offspring with no family history of it
Mutant is an organism that possesses a characteristic due to a mutation
Mutation is the only source of a brand new allele appearing in a population
Mutations can be beneficial in some environments, not always harmful

Mutagens

Increase the rate at which mutations occur
Examples include chemicals (e.g. Mustard gas, some antibiotics) and ionizing radiation sources (e.g. UV, X-rays, cosmic rays)

Types of Mutations

Gene Mutations

Changes in a single gene, affecting the traits produced by that gene
Occur during DNA replication before cell division
Copied and passed on during each cell division
Examples include Cystic Fibrosis

Effects of Gene Mutations

Can lead to a change in DNA sequence or base sequence, affecting the protein produced
Missense mutations: change amino acid, affecting protein produced
Nonsense mutations: code to STOP, resulting in shorter protein
Neutral mutations: change amino acid, but not enough to alter protein function
Silent mutations: no change in amino acid, no effect on protein produced

Point Mutation

Change in a single nucleotide (base)
Can alter protein, have no effect, or prevent protein production
Example: Cystic Fibrosis

Other Types of Point Mutations

Substitution: exchanging one base for another
Insertion: adding extra base pairs, resulting in frameshift
Deletion: losing a section of DNA, resulting in frameshift
Insertion or deletion results in a shift in reading frame
Insertion has a bigger effect than substitution

Chromosomal Mutations

Changes to all or part of a chromosome
Affect several genes, as each chromosome contains many genes
5 types: deletions, duplications, inversions, translocations, non-disjunctions
Most cause spontaneous abortion in early pregnancy

Causes of Mutations

Spontaneous mutations: occur randomly due to error in mitosis or meiosis
Induced mutations: caused by mutagens in the environment

Location of Mutations

Hereditability:
- Germline mutations: change in hereditary material in egg or sperm, passed on to offspring
- Somatic mutations: change in non-reproductive cells, not passed on to offspring

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Description

Learn about the mechanisms of evolution, including natural selection and mutation, and how they lead to the survival of the fittest and variation in characteristics.