Meiosis Mix-Ups
What process during meiosis leads to genetic variation by exchanging DNA between homologous chromosomes?
Crossover (crossing over)
What enzyme proofreads DNA during replication to reduce mistakes?
DNA polymerase
What type of mutation changes a single base pair?
Point mutation
What is one example of an environmental factor that can cause mutations?
Radiation, chemicals, or viruses
Why is genetic variation important for evolution?
It provides traits for natural selection to act on
Independent assortment during meiosis increases variation by doing what?
Randomly distributing maternal and paternal chromosomes into gametes
What is the general term for an error made during DNA replication?
Mutation
A frameshift mutation happens when what occurs?
Bases are inserted or deleted, shifting the reading frame
What is the term for chemicals that cause mutations?
Mutagens
How does sexual reproduction generate more variation than asexual reproduction?
Combines DNA from two parents (crossing over, independent assortment, random fertilization)
How many possible chromosome combinations can humans produce through independent assortment alone (ignoring crossing over)?
About 8 million
Why are most replication errors harmless?
They occur in noncoding regions or are corrected by repair enzymes
Which type of mutation usually has the most drastic effect on proteins?
Frameshift mutation
How can UV radiation from sunlight affect DNA?
It can damage DNA and increase mutation risk (ex: skin cancer)
Give an example of a real-world environmental factor that increased mutation rates in a population.
Radiation exposure from Chernobyl or Fukushima
Explain why meiosis, but not mitosis, increases genetic variation.
Meiosis includes crossing over and independent assortment; mitosis makes identical cells
Give an example of a beneficial replication error (mutation).
Sickle cell allele provides malaria resistance
What is a silent mutation?
A DNA change that doesn’t alter the amino acid sequence of the protein
How can exposure to radiation (like X-rays) affect DNA?
It can break DNA strands or alter bases → mutations
Explain how genetic variation helps populations adapt to climate change.
Some individuals may have traits that improve survival in new conditions
How could errors in meiosis lead to genetic disorders?
Nondisjunction → gametes with extra/missing chromosomes (ex: Down syndrome)
If a mutation occurs in a somatic (body) cell, will it be inherited? Why or why not?
No — only mutations in gametes (egg/sperm) are passed on
Why can mutations increase biodiversity in a population?
They introduce new genetic variations for natural selection to act on
Explain why environmental factors don’t always cause mutations in every exposed cell.
DNA repair mechanisms fix many mutations before they are permanent
Why are small populations more vulnerable to loss of genetic variation?
Genetic drift reduces diversity, limiting adaptability