c5- Mutations Flashcards
What is a mutation
A mutation is a change in the DNA sequence of an organism, which can be caused by errors during DNA replication, exposure to mutagens, or viral infections. These changes can be harmful, beneficial, or neutral, and they are the raw material for evolution.
Point mutations/ substitution
A point mutation is a genetic alteration where a single nucleotide base is changed, inserted, or deleted in a DNA or RNA sequence. There are 3 types:
1.Substitution:
2.Insertion:
3.Deletion:
and 3 examples of this:
1. Silent Mutations
2. Missense mutation
3. Nonsense mutation
PM- Silent
A silent mutation, also known as a synonymous mutation, is a change in the DNA sequence that doesn’t alter the resulting amino acid sequence of the protein, effectively having no observable effect on the organism’s phenotype.
PM- Missense
A missense mutation is a type of point mutation where a single nucleotide change in DNA results in a different amino acid being incorporated into the protein, potentially altering its structure and function.
PM- Nonsense
a mutation in which a sense codon that corresponds to one of the twenty amino acids specified by the genetic code is changed to a premature chain-terminating codon. (truncating the protein)
Insertion Mutations
An insertion mutation occurs when an extra nucleotide is added to the DNA sequence. This can have drastic effects due to frameshift mutations.
IM- Frame shift
Because the genetic code is read in triplets (codons), adding a single nucleotide shifts the reading frame, changing every subsequent codon. This usually results in a completely different and often non-functional protein.
Deletion Mutations
A deletion mutation occurs when a nucleotide is removed from the sequence. Like insertions, deletions can also cause frameshift mutations.
DM- Small Deletions
if one or two nucleotides are deleted, it shifts the reading frame, resulting in a completely altered protein sequence and potentially severe functional loss.
DM- Large Deletions
If multiple nucleotides or entire genes are deleted, it can eliminate protein function entirely, leading to genetic disorders.
Block Mutations
Block mutations (also known as chromosomal mutations) involve changes to large segments of a chromosome rather than single nucleotides. These mutations can have significant effects on gene expression and an organism’s development, often leading to genetic disorders or evolutionary changes.
BM- Duplication
//- A section of a chromosome is copied and inserted into the genome.
//- Can increase gene expression if the duplicated gene produces extra proteins.
BM- Deletion
//- A section of a chromosome is lost.
//- Leads to missing genes, potentially causing developmental or metabolic issues.
BM- Inversions
//- A chromosome segment breaks off, flips around, and reattaches in the reverse order.
//- Often has no major effect if genes remain intact, but can disrupt regulation or meiosis.
BM- Translocation
//- A segment of one chromosome breaks off and attaches to a different chromosome.
//- Can disrupt gene function if it occurs within a critical region.
What is a Gene
A gene is a fundamental unit of heredity, a specific sequence of DNA (deoxyribonucleic acid) that contains the instructions for building proteins, which in turn determine traits and functions within an organism
What is meiosis
Meiosis is a type of cell division that produces gametes (sperm and egg cells) in sexually reproducing organisms. It reduces the chromosome number by half, ensuring that offspring receive the correct number of chromosomes from each parent.
Features of Meiosis
Produces four genetically unique daughter cells.
Each cell has half the original number of chromosomes (haploid, n).
Involves two rounds of division: Meiosis I and Meiosis II.
Introduces genetic variation through crossing over and independent assortment.
Why Is Meiosis Important?
Ensures genetic diversity in populations.
Maintains a stable chromosome number across generations.
Allows for evolution and adaptation through variation.
Mitosis
mitosis, a process of cell duplication, or reproduction, during which one cell gives rise to two genetically identical daughter cells.
Features of Meiosis
Why Is Meiosis Important?
Factors affecting Mutations- Chemicals (mutagens):
Certain Chemicals, like cigarette smoke, industrial pollutants, or some drugs, can damage DNA and increase mutation rates. Examples include alkylating agents, base analogues, and intercalating agents.
Factors affecting Mutations- Loss of DNA repair Mechanisms:
DNA repair mechanism help to correct errors that arise during DNA replication. IF these mechanisms are impaired or absent, such as in certain genetic disorders, mutation rates can increase significantly
