| A | B |
|---|
| What is a gene? | It's a sequence of DNA that codes for a protein & thus determines a trait. |
| What's the composition of a nucleotide? (review) | It's made of a 5-carbon sugar, a phosphate group, and a nitrogenous base. |
| Give the 3 main differences between RNA and DNA. | 1) the sugar in RNA = ribose; in DNA, it's deoxyribose; 2) RNA is usually single-stranded; DNA is double; 3) RNA contains uracil; DNA has thymine. |
| What is the main function of most RNA molecules? | They're involved in protein synthesis. |
| What types of RNA are most common? | 1) messenger RNA; 2) ribosomal RNA; 3) transfer RNA. |
| What does messenger RNA do (mRNA)? | It carries copies of instructions for the assembly of amino acids into proteins from DNA to the rest of the cell. |
| What is the function of ribosomal RNA (rRNA)? | It's the type of RNA that makes up the major part of ribosomes. |
| What does transfer RNA (tRNA) do? | It's the type of RNA molecule that transfers amino acids to ribosomes during protein synthesis. |
| What is transcription? | It's the process in which part of the nucleotide sequence of DNA is copied into a complementary sequence in DNA. |
| What is an RNA polymerase? | It's an enzyme similar to DNA polymerase that binds to DNA and separates the DNA strands during transcription. RNA polymerase then uses 1 strand on DNA as a template from which nucleotides are asembled into a strand of RNA. |
| What are promoters? | They're the regions of DNA that indicate to an enzyme where to bind to make RNA. They have specific base sequences. So, they're signals in DNA that tell the enzyme where to bind to make RNA. (Similar signals in DNA stop transcription when the new RNA molecule is completed.) |
| What are introns? | They are intervening sequences of DNA and do NOT code for a protein. They are edited out of RNA molecules before the RNA becomes functional. |
| What are exons? | They're expressed sequences of DNA; they code for a protein. After introns are edited out of the pre-mRNA molecule, the remaining pieces (the exons) are spliced together, and a cap and tail are added to form the RNA molecule. |
| How are proteins made? | They are made by joining amino acids into long chains called polypeptides. |
| What are the four different bases for RNA? | A, U, C, and G. (see 302-303) |
| What is a codon? | It's a 3-nucleotide sequence on mRNA that codes for a single amino acid. |
| What is a codon that serves as a start codon. | AUG starts protein synthesis OR it can also specify methionine. |
| What are 3 STOP codons? | UAG, UGA, UAA. |
| What is translation? | It's the decoding of a mRNA message into a polypeptide chain. (see 304) |
| When does translation begin? | It starts when an mRNA molecule in the cytoplasm attaches to a ribosome. As each codon of the mRNA molecule moves through the ribosome, the proper amino acid is brought into the ribosome by tRNA. |
| How many kinds of amino acids does each tRNA molecule carry? | A tRNA molecule carries ONLY ONE kind of amino acid. |
| What's an anticodon? | An anticodon is a group of 3 bases on a tRNA molecule that are complementary to an mRNA codon (see 304-305 for example). |
| Describe the steps in translation. | See the picture on page 304-305: the mRNA, the tRNA, the polypeptide "assembly line", and the completion of the polypeptide. |
