1.  sugar        2. 4             3.  4             4.  DNA             5.  RNA         6. DNA

7. nucleotide    8. 4         9. 2 ; 1             10. thymine; cytosine         11. hydrogen

12. One of the strands can serve as a template for the formation of a complementary strand.

13. The order of the base pairs.

14. A and T are always present in equal amounts also G and C are present in equal amounts.

15. 4

16. RNA is a single stranded molecule. RNA nucleotides contain the sugar ribose (rather than deoxyribose) and the base uracil (rather than thymine).

The correct sequencee is C, B, D, A

1. TCG-GAT-CAG-ATT (The line between each group of 3 bases is inserted just so the order can be more easily read.)
2. This is because of the principle of complementary pairing, i.e., A always pairs with T and C always pairs with G.

Objective 4:

1. Transcription is the formation of mRNA from DNA.

2. AUG UGU AUU CUG GUC UAA

3. 6

4. This question is an error - doesn't belong here!!

5.  AUG—start codon (notice that this also codes for the amino acid, methionine). UAA,UAG, and UGA—stop codons.

6. In the nucleus in a eukaryotic cell.

7.  Three types of RNA: messenger RNA or mRNA (takes the genetic instructions from DNA to ribosomes where it directs the synthesis of a specific protein in the cell); transfer RNA or tRNA (type of RNA needed for the translation of mRNA); and ribosomal RNA or rRNA (RNA type found in ribosomes).

8. Translation is the conversion of the information in mRNA into a specific sequence of amino acids (a polypeptide chain). In eukaryotic cells this takes place on ribosomes in the cytoplasm.

9.  Use the codon chart on page 194 in your text to answer this question.
     Met- Phe- Leu- Pro- Tyr- Lys (stop)  Note that the last codon does not code for a specific amino acid; it acts as punctuation.

10.          UAC AAA GAA GGA AUA UUU AUU   
Seven separate tRNA molecules would be inviolved in this translation.  For example, the tRNA molecule that is complementary to the first codon triplet in mRNA is a tRNA molecule with the anticodon UAC.  This particular tRNA molecule would carry the amino acid met (methionine) to mRNA. Note that the amino acid sequence is read from the chart using the codons rather than the anticodons of tRNA.

11.  It acts to stop transcription.

12.  ribosome

13.  d, b, e, a, f, g, c

Objective 5:

1. 64

2. 3 : CAA, ACA, AAC

3. a. both    b. RNA  (since this contains the base U, it must be RNA)    c. both    d. RNA     e. DNA    f. both

4. all except e

5. all except b and d

6. If it contains T (thymine) it must be DNA, and if it contains U (uracil) it must be RNA. If it contains only A, G, and C bases it could be either DNA or RNA if you did not know the sugar.

7. They serve as start or termination codons.

DNA: TAC AAA GCG TTC ATT

m-RNA: AUG UUU CGC AAG UAA

AA:  Met(the start codon)- Phe- Arg- Lys- (terminator-no amino acid)

1. AUG

2. 3

3. UAA

4. This makes the first codon GUG resulting in val (Valine) as the first amino acid—This is not a start codon.

5. A mutagen is an agent (chemical or physical) that interacts with DNA causing a change in the sequence of bases in DNA and hence a mutation.  Chemicals that either react with the bases of DNA or are very similiar to DNA bases may be mutagenic agents. Also, high energy radiation such as X-rays or UV light act as mutagenic agents.

6.  Mutations are the basic source of genetic variation.  One may think of mutations as the raw material on which natural selection acts.

Objective 7:

Glutamic acid (glu) is coded for by either GAA or GAG.  Valine (val) is coded for by either GUA or GUG.  Thus, the A is replaced with a U.  This is caused by a change in one base in the DNA molecule that mRNA was transcribed from - the base thymine of DNA was replaced with the base adenine.  Look at figure 10.16A on page 201 of your text.

Objective 8:

For the conditions in the chart on page Unit 6-9, see page 165 in your text.  Each of these conditions is due to a particular inborn error of metabolism. You do not need to know the specific defect (it isn't in your book).  You do need to know what an inborn error of metabolism is and that these conditions are examples of inborn errors of metabolism.

Objective 9:

1.  Protein and nucleic acid (it can be either DNA or RNA - not both).

2.  Nucleic acid

3.  They use the machinery of a cell.  Viruses can only reproduce inside a cell.

4.  You are not responsible for this. It is discussed on pages 202-205 in your text.

5.  Reverse transcriptase is the enzyme found in RNA viruses. This enzyme allows RNA viruses to use their  RNA as the template for the synthesis of DNA (the opposite of the usual direction!).  The virus that causes AIDS is such a retrovirus.   This is discussed on page 205 of the text.

Objective 11:

1.  The genotype determines (or sets the basic parameters) for the phenotype. Actually, the phenotype is the expression of the genotype in a particular environment. The characteristics of the environment may influence the expression of the genotype.

2.  Selective gene expression refers to the fact that only a small fraction of the genes in a cell are expressed. Although all the cells in an organisms body are genetically identical (except for sex cells),  the genes that are expressed (that is, that result in the formation of specific kinds of proteins in the cell) are different in different in different cell types. Thus, some types of pancreatic cells may produce insulin whereas epithelial cells do not produce insulin (although the gene for insulin production is in their cells).

3.  a) allows division of labor - cells can specialize in the production of specific kinds of proteins  2) cells don't waste energy manufacturing proteins that are not needed. For example, cells produce certain enzymes only when the specific substrate for the enzyme is present.

Objective 12:

1.  An operon consists of a promoter, an operator, and one or more structural genes.  Study the diagram of the lac operon on page 211 in your text.

2.  The operator determines whether mRNA can be transcribed from the structural genes.  If the repressor protein is attached to the operator, mRNA polymerase is blocked and transcription of the structural genes can not occur.  The regulatory gene (not part of the operon) has the genetic information for repressor protein.  The promoter is the region of the operon where the enzyme needed for transcription, RNA polymerase, attaches.

3.  No

4.  It is a waste of energy for the cell to manufacture enzymes if the substrate that the enzyme works on is not available. Also, a reaction may not be needed if there is a product (the result of the reaction) already present in the cell.

Only do situation A.

4. lactose

5. structural genes

6. inducible enzyme

Objective 13:

A.
1.  2 alpha

2.  gamma

B.
The young blood cells then had the genetic information necessary for transcribing the proteins necessary for blood cell production.

Objective 14:

1. An exon is a protein coding region of a eukaryotic gene.

2. An intron is a non-protein coding region of a eukaryotic gene.

3.  It is thought that introns play a role in regulating gene expression.

Objective 15:

1. This is illustrated on page 234 of your text.

2 and 3.  If a copy of a "good" gene for the production of a valuable protein such as insulin or human growth hormone is inserted into a bacterial cell, the bacteria can then produce the valuable protein that can then be given to persons unable to make this protein. A list of some of these valuable pharmaceutical products is found on page 246 of your text.