lec 21 Flashcards
What are the two main kinds of mutations?
Chromosomal mutation and Point mutation
Chromosomal mutations involve large segments of chromosomes, while point mutations involve changes in a single nucleotide.
What is a point mutation?
A change in a single nucleotide within a gene
This may change the protein produced by the gene.
What happens during a deletion mutation?
Loss of a chromosome segment
This can lead to significant changes in the genetic information.
What occurs during a duplication mutation?
A segment of a chromosome is repeated
This can increase the dosage of genes present in that segment.
What is an inversion mutation?
A segment is ‘flipped’
This can affect the regulation of genes within the inverted segment.
Define translocation mutation.
Segments break and join the ‘wrong’ chromosome
This can cause gene fusion and disrupt normal gene function.
What are chromosomal mutations?
Large-scale mutations affecting entire segments of DNA
These result from errors during mitosis or meiosis.
What causes changes to the DNA sequence?
Mistakes during DNA replication and DNA damage
Damage can be caused by radiation, UV, chemicals, etc.
What is a heritable mutation?
A mutation occurring in germ line cells
Only mutations in these cells can be passed to offspring.
What are germ cells?
Cells that produce eggs or sperm
These are the cells involved in reproduction.
What are somatic cells?
All other body cells
These cells do not contribute to the next generation.
What are spontaneous errors?
Errors due to ‘natural’ alterations to DNA
These occur without external influence.
What are the three repair mechanisms for DNA errors?
- Proofreading
- Mismatch repair
- Excision repair
These mechanisms help correct errors in the DNA sequence.
What is DNA proofreading?
DNA polymerase III recognizes mismatched pairs during replication
The next bond isn’t formed until the correct match is present.
What happens during mismatch repair?
Newly replicated DNA is scanned for mistakes and corrected
Mismatch repair proteins cut out mismatched nucleotides, and DNA polymerase replaces them.
What is excision repair?
Repair mechanism for induced mutations caused by mutagens
Enzymes scan for damaged bases, cut them out, and replace them.
True or False: All mutations are harmful.
False
While many mutations can lead to genetic disorders, some provide genetic diversity.
How do mutations contribute to evolution?
They provide genetic diversity
This diversity is essential for evolution by natural selection.
What is the maximum number of nucleotide substitutions in a human gamete?
Up to 30 nucleotide substitutions
This highlights the variability in genetic information passed to offspring.
What is the significance of redundancy in the genetic code?
It can lead to no change in protein function despite mutations
This means that some mutations may not affect the protein at all.
What is a ‘reading frame’?
The sequential sets of codons – non-overlapping triplets
Changes in the reading frame can lead to significant alterations in protein structure.
