2. All cells arise from pre existing cells(Rudolf Virchow). Cell is the fundamental, structural and functional unit of all organisms(Schleiden and Schwann).
3. All cells have a cell membrane.
All cells have chromosomes present.
All cells have cytoplasm.
4.Eukaryotic cells contain a nuclear membrane but Prokaryotic cells have only pseudo nucleus
Eukaryotic cells contain membrane bound organelles but prokaryotic cells don't.
The mass extinctions that occurred 250 million years ago and 65 million years ago may have been due to gradual process or Catastrophic events.
Hello,
PCR is a useful technique because it is used to amplify small segments of DNA.
Thanks,
Answer:
Answer is C.
Explanation:
For A and B, a base substitution affects one of the three bases that comprise a codon, the DNA/RNA unit that corresponds to a particular amino acid. If one base is substituted, one codon and therefore one amino acid will be affected. Codons have built-in redundancy, so even by changing one base, the new codon sometimes still corresponds to the same amino acid. Therefore, a base substitution at most affects one amino acid, and sometimes doesn't affect it all.
Frameshift mutations cause a lot more trouble. These occur when you have a deletion or insertion that changes the number of bases in your gene. As a result, the "frame" of the codons changes (everything shifts one way or the other by the number of bases added/removed). This affects EVERY codon downstream of the mutation, so you can imagine that such a mutation would have a bigger effect the closer to the start of the gene it occurs. This is why C is correct.
