Biology Help

STUDY GUIDE on DNA, biotechnology, & gene expression

Readings: Ch. 5 (Sections 5.1-5.7; 5.12-5.17)

NOTE: Students are responsible for the following information on the lecture exams: any and all information discussed in class, presented in the PowerPoint slides, and specified in the study guides and handouts.

Key terms to be familiar with for DNA replication & biotechnology

Nucleic acid	Deoxyribonucleic acid (DNA)	Double helix	Phosphate-sugar backbone	Nucleotide
Phosphate	Ribose	Nitrogenous bases	Adenine (A)	Guanine (G)
Cytosine (C)	Thymine (T)	Complementary base-pairing	Genome	Chromosome
Gene	Allele	Nucleotide sequence or base sequence	Hydrogen bonds	DNA replication
Helicase	Single strand binding proteins	DNA polymerase	Topoisomerase	DNA ligase
Nuclease	UVA rays	UVB rays	Melanin	Xeroderma pigmentosum
Biotechnology and genetic engineering	Genetically modified organisms	DNA fingerprinting	Watson and Crick	Rosalind Franklin

Study Qs: Complete questions discussed in class on a weekly basis.

1. Nucleic acids make up the category of biological molecules responsible for storing genetic information. Deoxyribonucleic acid (DNA) is an example of a nucleic acid.

a. A molecule of DNA is constructed by linking together simple building blocks called nucleotides. What are the three components of a nucleotide? Label them in the diagram below.

b. Which two components of the nucleotide form the “back bone” of the DNA double helix? What is the function of this backbone?

c. What single component of the nucleotide is variable (changeable) and has four possibilities: adenine (A), guanine (G), cytosine (C), and thymine (T)? What is the function these variable parts of the DNA double helix?

2. Explain the arrangement of the two DNA strands relative to each other.

3. The DNA double helix consists of two separate DNA molecules that are joined together by chemical bonds between the nitrogenous bases. What types of chemical bonds unite the two strands of the double helix? Describe their properties.

4. In order for one DNA strand to bind to its complementary DNA strand and form a helix, specific base pairing is seen between the nitrogenous bases. Memorize the following complementary base-pairing rules used in DNA replication (note: a different set of rules will be used during transcription).

DNA	DNA
A	T
T	A
C	G
G	C

a. Identify and explain which of the base pairs is stronger. Which bonds (A-T or C-G) would you expect to find at the beginning of a genes that would enable easier access to genetic information?

5. Distinguish among the following terms (use your textbook):

a. Genome:

b. Chromosomes:

c. Gene:

d. Allele:

6. Cell division occurs during the growth and development of our bodies; it also allows us maintain all organs by replacing damaged or worn out cells. Before a cell divides, it must replicate its DNA so that all future cells have their own set of genetic instructions.

a. Outline the steps in DNA replication, including the function of the following:

· Helicase

· Single-strand binding proteins

· DNA polymerase

· Topoisomerase

b. Explain why DNA replication is termed a semi-conservative process.

7. When is DNA mismatch repair used? What enzyme is involved in this repair process?

8. When is DNA excision repair used? What enzymes are involved in this process?

9. As a last resort, what are cells programmed to do when their DNA is damaged beyond any type of repair?

10. Review your notes on the effect of UVA and UVB radiation on skin cells.

11. Xeroderma pigmentosum (XP) is a genetic disease caused by the inability of afflicted individuals to repair DNA damage that is caused by exposure to the sun’s ultraviolet rays.

a. Exposure of ultraviolet radiation alters the shape of our DNA by causing an abnormal bond to form with the DNA molecule itself. Describe the type of bond that forms.

b. In a normal person, what type of DNA repair is used to correct damage that is caused by sunlight?

c. Explain why individuals with XP are unable to use this DNA repair process.

d. What are the symptoms of XP?

e. What are ways to manage this genetic condition?

12. Biotechnology is a branch in science where living systems are modified to create products that somehow benefit the human population. Review your lectures notes and PowerPoint slides when answering the following questions:

a. How is biotechnology in the form of DNA fingerprinting used in crime scenes and paternity tests?

b. How can producing genetically modified foods be beneficial to humans?

c. What are the concerns and side effects of genetically modified foods?

d. How can biotechnology be used to help those with chronic disease? Refer to the insulin example.

e. How can biotechnology be used in early diagnosis of genetic diseases ( NOVA Science video).

Key terms to be familiar with for gene expression (DNA to proteins)

Transcription (noun)	Transcribe (verb)	Translation (noun)	Translate (verb)	Promoter region
Terminator region	Introns	Exons	Codon	Start codon
Stop codon	RNA polymerase	Uracil (U)	Transfer RNA (tRNA)	Ribosome
Amino acids	Proteins	Gene	5’ Methylated cap	3’ Poly-A tail

Study Qs: Complete questions discussed in class on a weekly basis.

13. Define and understand all of the above terms.

14. Write down where each of the following structures is located (i.e., nucleus, cytoplasm, or both):

DNA mRNA Ribosomes tRNA RNA polymerase

15. Describe the purpose and the process of transcription. In your answer, define and explain the function of the following key terms: nucleus, DNA, mRNA, RNA polymerase, promoter region, terminator region, gene of interest, introns, exons, 5’ methylated cap, 3’ Poly-A tail. You should also memorize the following complementary base-pairing rules for transcription (which are different from DNA replication):

DNA	mRNA
A	U
T	A
C	G
G	C

16. Describe the purpose and the process of translation. In your answer, define and explain the function of the following key terms: mRNA, amino acids, proteins, codon, start codon, stop codon, tRNA, ribosomes, cytoplasm.

17. Given a DNA sequence, be able to transcribe it into mRNA, and be able to use the genetic code table to translate it into an amino acid sequence of a protein. Refer to activity in the human and cow gene for insulin.