MCB 2000 Midterm: Exam 2 Study Guide
MCB 2000 Study guide for EXAM TWO
1. Define Central Dogma of Molecular Biology (list its chain of events).
• Central Dogma of Molecular Biology
o DNA → mRNA → protein → function
2. Define chromosome, gene, genome.
• Chromosome = structures containing DNA that physically carry hereditary information—
chromosomes contain genes
• Gene = segments of DNA that encode functional products—usually proteins
• Genome = all the genetic information in a cell
3. Name different RNA molecules. What is the role of each molecule? Which ones contains codon, anticodon?
• RNA = ribonucleic acid
o Single-stranded nucleotide strand
o 5-carbon sugar = ribose
o Contains uracil (U) instead of thymine (T)
• rRNA = ribosomal RNA
o Part of ribosomes
• tRNA = transfer RNA
o Transports AAs during protein synthesis
o CONTANS ANTICODONS
• mRNA = messenger RNA
o Carries coded information from DNA to ribosomes
o CONTANS CODONS
4. Briefly describe replication, transcription, and translation. What is used as template for each process?
• Replication = one strand of DNA serves as a template for the production of a second strand (each
copy goes to 1 daughter cell)
o DNA is template
o Topotisomerase and gyrase relax the double helix
o Helicase separates the strands
o Replication fork is created
o DNA polymerase adds nucleotides to DNA strand in 5 PRIME TO 3 PRIME direction
o LEADING STRAND = synthesized continuously
o LAGGING STRAND = synthesized in fragments (Okazaki fragments)
▪ Fragments are joined together with ligase
• Transcription
o DNA is template
o RNA polymerase reads the DNA 5 PRIME TO 3 PRIME to make mRNA
o mRNA is able to leave the nucleus and go to ribosomes for translation
▪ mRNA contains CODONS
o Carries coded information from DNA (in nucleus) to ribosomes
• Translation
o mRNA is template
▪ mRNA contains CODONS
o mRNA goes to ribosome, ribosome reads codons
o tRNA comes with matching ANTICODONS attached to AA
5.What are the products of: Replication, Transcription, Translation and Reverse Transcription? What are the
differences between DNA polymerase and RNA polymerase? What is the significance of reverse
transcriptase? What is the source of reverse transcriptase (its origin)? What does it do?
• Replication Products
o 2 new strands of DNA—1 for each daughter cell
• Transcription Products
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o mRNA to go to ribosome for protein synthesis
• Translation Products
o Proteins
o mRNA gets matched with tRNA in the ribosome to put together AAs
• Reverse Transcription Products
o DNA
o DNA is made from RNA
o Reverse Transcriptase
▪ HIV contains only RNA
▪ Reverse transcriptase turns the single stranded RNA into double stranded DNA so
that the virus DNA can be inserted into the host chromosomes
6.Define/Explain/describe: Complementary strands, Anti-parallel, Semiconservative replication, Double helix
7.List the enzymes and their functions involved in DNA replication
• DNA Gyrase = relaxes supercoiling ahead of replication fork
• DNA Ligase = makes covalent bonds to join DNA strands, fragments, and new segments in
excision repair
• DNA polymerase = synthesizes DNA; proofreads and repairs DNA
• Endonucleases = cut DNA backbone into a strand of DNA
• Exonucleases = cut DNA from an exposed end of DNA
• Helicase = unwinds double stranded DNA
• Methylase = adds methyl groups to selected bases in newly made DNA
• Photolyase = uses visible light energy to separate UV induced pyrimidine dimmers
• Primase = an RNA polymerase that makes RNA primers from a DNA template
• Ribozyme = RNA enzyme that removes introns and splices exons together
• RNA polymerase = copies RNA from DNA template
• snRNP = RNA protein complex that removes introns/splices exons together
• Topoisomerase = separates DNA circles at the end of DNA replication; relaxes supercoiling ahead
of replication fork
• Transposase = cuts DNA backbone; leaves single stranded sticky ends
8. What is the genetic material for viruses, DNA or RNA, single stranded or double stranded?
• The genetic material for viruses can be DNA OR RNA and it may be single stranded or double
stranded.
9. Where in eukaryotes and prokaryotes one can find DNA?
• DNA in prokaryotes and eukaryotes is in the chromosomes
o Prokaryotes have 1 chromosome and they may also have a plasmid
o Eukaryotes have many chromosomes in their nucleus
10.Define operons and explain their role in gene expression (transcription) in bacteria. Give examples.
• Operons = things that help regulate gene expression—only express the genes that are needed
o Inducible genes
▪ Lactose operon
• Catabolic processes
• Sugar metabolism
• Will be turned off when the thing they need to break down is not present
o Repressible genes
▪ Tryptophan operon
• Anabolic processes
• Amino acid synthesis
• Usually always turned on
• Only off when the AA comes from outside the body and does not need to be
synthesized
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Document Summary
6. define/explain/describe: complementary strands, anti-parallel, semiconservative replication, double helix. 10. define operons and explain their role in gene expression (transcription) in bacteria. Give examples: operons = things that help regulate gene expression only express the genes that are needed. 11. define catabolic repression: catabolic repression, overrides inducible operons. Inducible operons are turned on during lag time to use up the lactose in the cell: lag time = time it takes to turn on the lactose operon. What is the significance of this difference: ribosomes are made of proteins, prokaryotic ribosomes are much smaller than eukaryotic ribosomes, the smaller ribosomes are easier for antibiotics to target without damaging the larger ribosomes of the eukaryotic cells. Describe the use of recombinant dna in producing. 15. list scientific and agricultural applications of recombinant dna. 16. name the tools used to make a recombinant dna. Example; how you cut dna, how you introduce the. Dna to the host cell, how to track the dna.