Nucleic Acids and Proteins

1. Test your vocabulary by matching each term to its correct definition, as identified by its preceding letter code.

anticodon

base-pairing rule

coding strand

DNA

gene expression

genetic code

hydrogen bond

nucleic acids

nucleotides

RNA

template strand A Single stranded nucleic acid that consists of nucleotides containing ribose sugar.

B A set of rules by which information encoded in DNA or mRNA is translated into proteins.

C The rule governing the pairing of complementary bases in DNA.

D The structural units of nucleic acids, DNA and RNA.

E Intermolecular bond between hydrogen and an electronegative atom such as oxygen.

F The process by which genetic information is used to produce a functional gene product.

G The sequence of DNA that is read during the synthesis of mRNA.

H Universally found macromolecules composed of chains of nucleotides. These molecules carry genetic information within cells.

I The DNA strand with the same base sequence as the RNA transcript produced (although with thymine replaced by uracil in mRNA).

J Macromolecule consisting of many millions of units containing a phosphate group, sugar and a base (A,T, C or G). Stores the genetic information of the cell.

K The region of a transfer RNA with a sequence of three bases that is complementary to a codon in the messenger RNA.

2. A grasshopper has the following percentages of nucleotides in its DNA: A = 29.3, G = 20.5, C = 20.7, T = 29.3, %GC = 41.2, %AT = 58.6. For a rat, the percentages are A = 28.6, G = 21.4, C = 20.5, T = 28.4, %GC = 42.9, %AT = 57.0.

Use the base pairing rule to explain this data:

3. For the following DNA sequence on the template strand, give the mRNA sequence and then Identify the amino acids that are encoded. For this question you may consult the mRNA-amino acid table earlier in the chapter.

DNA (template strand): G A A AC C C T TAC ATAT C G T G C T

mRNA:

Amino acids:

4. Complete the following paragraph by deleting one of the words in the bracketed () pairs below:

In eukaryotes, gene expression begins with (transcription/translation) which occurs in the (cytoplasm/nucleus). (Transcription/Translation) is the copying of the DNA code into (mRNA/tRNA). The (mRNA/tRNA) is then transported to the (cytoplasm/nucleus) where (transcription/translation) occurs. Ribosomes attach to the (mRNA/tRNA) and help match the codons on (mRNA/tRNA) with the anticodons on (mRNA/tRNA). The (mRNA/tRNA) transports the animo acids to the ribosome where they are added to the growing (polypeptide/carbohydrate) chain.

5. Decide if the nucleotide shown right is from DNA or RNA. Explain your choice:

OH H

OH P O

O CH2

O

H H H H

OH H N N

N NH2

N

H