1. Where would a mutation be introduced during replication?
Mutations during DNA replication can be introduced at several points, particularly when the DNA polymerase enzyme incorporates incorrect nucleotide bases into the newly synthesized strand. Mutations can occur due to:
- Misincorporation of bases: The wrong nucleotide may be added because of a mistake in matching the nucleotide to the template strand.
- Slippage: During replication, the DNA polymerase might either skip a nucleotide or add extra nucleotides through copying errors, particularly in regions with repeat sequences (insertion or deletion mutations).
- Chemical changes: Environmental factors, such as chemicals or radiation, can cause modifications to bases, leading to mistakes during the replication process.
2. What nucleotide bases pair together to create new strands of DNA?
In DNA, nucleotide bases pair together through complementary base pairing. The specific pairs are:
- Adenine (A) pairs with Thymine (T) through two hydrogen bonds.
- Cytosine (C) pairs with Guanine (G) through three hydrogen bonds.
This pairing ensures the double-stranded structure of DNA is maintained, with A-T and C-G pairs forming the rungs of the DNA ladder.
3. Where do environmental factors impact DNA?
Environmental factors can impact DNA in several ways, including:
- Chemical exposure: Certain chemicals can cause DNA mutations or damage. For example, carcinogens can lead to changes in nucleotides.
- Radiation: UV light or ionizing radiation can result in DNA breaks or the formation of pyrimidine dimers, which disrupt normal base pairing.
- Biological agents: Some viruses can integrate their genetic material into the host DNA, leading to mutations or dysregulation of normal cellular processes.
- Temperature and pH changes: Extreme conditions may affect the stability of DNA and increase the likelihood of replication errors.
4. How does crossing-over and independent assortment contribute to genetic variation?
Crossing-over and independent assortment are two crucial mechanisms during meiosis that contribute to genetic variation:
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Crossing-over: This occurs during prophase I of meiosis when homologous chromosomes exchange segments of genetic material. This process creates new combinations of alleles on each chromosome, resulting in gametes that carry different genetic information than either parent.
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Independent assortment: During metaphase I of meiosis, the orientation of each homologous chromosome pair is random. This means that the distribution of maternal and paternal chromosomes into gametes occurs independently for each pair. As a result, gametes receive a mix of chromosomes from both parents, leading to a vast number of possible combinations.
Together, these processes ensure that offspring have unique combinations of genetic traits, contributing to the diversity and adaptability of populations.