MCB 2000 Midterm: Exam 2 Study Guide

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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 productsusually 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 DNA1 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 expressiononly 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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