FR Chap 11 DNA and Language of Life Flashcards
Three parts make up a single nucleotide
1) A ring-shaped sugar called deoxyribose
2) A phosphate group (a phosphorus atom surrounded by 4 oxygen atoms).
3) A nitrogenous base: a single or double ring of carbon & nitrogen atoms with functional groups (nitrogenous means “nitrogen-containing”).
What are the four Nitrogen bases? How do they pair up?
The bases thymine (T) and cytosine (C) are single-ring structures called pyrimidines. Adenine (A) & guanine (G) are larger, double-ring structures called purines. The one-letter abbreviations stand for both the bases alone & for the nucleotides containing them. Nucleotides are joined to one another by covalent bonds that connect the sugar of one nucleotide to the phosphate group of the next.
What are three differences between DNA and RNA?
RNA is any nucleic acid whose sugar is ribose rather than the deoxyribose of DNA. Another difference between RNA & DNA is that RNA contains a nitrogenous base called uracil (U) instead of thymine of DNA. RNA typically forms a single, sometimes twisted strand, not a double helix like DNA.
Explain DNA Replication. Where does it take place?
During DNA copying, the two strands of the double helix separate. Each single strand acts as a “negative” for producing a new, complementary strand. Nucleotides line up one at a time across from the existing strand as predicted by the base-pairing rules. Enzymes link the nucleotides together to form the two new DNA strands, called daughter strands. This process of copying the DNA molecule is called DNA replication. DNA replication begins at specific sites called origins of replication.
What is transcription? Where does it take place?
Several RNA molecules play a part in the intermediate steps from gene to protein. In the first step, DNA’s nucleotide sequence is converted to the form of a single-stranded RNA molecule in a process called transcription. This “transcribed” message leaves the nucleus & directs the making of the proteins in the cytoplasm, while the DNA remains in the nucleus.
What is translation? Where does it take place?
After transcription, the RNA travels to the cytoplasm where it is translated into the specific amino acid sequence of a polypeptide. Genetic translation converts nucleic acid language into amino acid language. The flow of information from gene to protein is based on codons. Several codons form a “sentence” that translates into a polypeptide.
Codon?
in RNA, a three-base “word” that codes for one amino acid.
Anticodon?
in tRNA, a triplet of nitrogenous bases that is complementary to a specific codon in mRNA.
