Ch. 10 Molecular Biology of the Gene Flashcards
Bacteriophage (Phage)
A virus that infects bacteria
Molecular Biology
The study of the molecular basis of genes and gene expression; molecular genetics.
Nucleotide
An organic monomer consisting of a 5-carbon sugar covalently bonded to a nitrogenous base and a phosphate group; building blocks of nucleic acid
Polynucleotide
A polymer made up of many nucleotides covalently bonded together
Sugar-phosphate backbone
Repeating pattern of sugar phosphate
What are pyrimidines?
Single ring of nitrogen and carbon
- Thymine and Cytosine
What are purines?
Large double ring
- Adenine and Guanine
What does RNA have that DNA doesn’t?
Uracil
Double Helix
2 DNA strands with 2 nm diameter
What are 3 major things learned?
1) How DNA is hereditary material of life
2) DNA stores information and replicates self
3) DNA controls cells by directing DNA synthesis
Virus
Infective substance, packaged genes
- 1000x smaller than bacterium
- DNA or RNA
What are the lifelike aspects of a virus?
1) Highly organized
2) Contain nucleic acids (RNA or DNA)
3) Experiences reproduction
What are non lifelike aspects of a virus?
1) Not cellular (not made of cells)
2) Cannot reproduce on its own (Inert)
Nucleic Acids
Polymer/monomers of DNA and RNA
- made of nucleotides
What are the 3 parts of a nucleotide?
1) Phosphate group
2) 5 Carbon Sugar (Deoxyribose or ribose)
3) Nitrogen Base
What is a nitrogen base?
Rings of nitrogen and carbons with various functional groups attached
What is encoded in the nucleotide sequence?
Genetic information in chromosomes
- how to make proteins
- makes each organism unique
- understand/explains life’s process
DNA Replication
Process in which genetic instructions are copied before the cell divides
What are the 3 steps of DNA Replication?
1) Two parent strands separate to serve as a template for complimentary strand
2) Free nucleotides line along template and connect to corresponding nucleotide according to base pairing
3) Enzymes link nucleotides together to form new DNA strand
Why is DNA replication biochemically complicated?
1) DNA must unravel and copy simultaneously
2) Speed! Occurs very rapidly!!
Origin of Replication
Site where proteins attach to DNA molecule and separate strands
Replication Bubble
Areas where origin of replication are; several exist to reduce time; eventually combine for daughter strands
DNA Polymerase
Enzyme that links DNA nucleotides to growing strand (proper location)
- only adding on 3’ (5’ -> 3’)
- Adds nucleotides in continuous pieces for one and in discontinuous pieces for another
- proofreads the sequence and fixes it (repairs DNA damage)
DNA Ligase
Enzyme that ties all the pieces intro one strand
- 12 altogether
What does DNA replication ensure?
Ensures all somatic cells have same genetic instructions for continuity between generations
What is the 3’ end of a DNA strand?
3’ with -OH
What is the 5’ end of DNA strand?
5’ with phosphate group
What is the connection between genotype and proteins of phenotype?
DNA specifies the synthesis of proteins.
DNA -> RNA -> Proteins
Transcription
Transfer of info from DNA to RNA
- occurs in nucleus
- uses only 1 DNA strand and hydrogen bonds
Translation
Transfer of info from RNA into protein synthesis
- nucleotide -> amino acid (converts language)
- occurs in cytoplasm/ribosome
What did Archibald Garrod hypothesize?
Genes dictate phenotypes thru enzymes, the proteins that catalyze chemical processes in the cell
What did Beadle and Tatum hypothesize?
“One-Gene One-Polypeptide”
- each polypeptide is specified to its own genre
Triplet Code
Set of rules giving the correspondence between nucleotide triplets (codons) in mRNA and amino acid in protein
Codons
A 3 nucleotide sequence in mRNA that specifies a particular amino acid or polypeptide termination sequence; basic unit of the genetic code
What is the code for the start of a polypeptide chain?
AUG
What is the stop/end code for a polypeptide chain?
UAA, UAG, UGA
RNA Polymerase
An enzyme that links together the growing chains of RNA nucleotides during transcription, using a DNA strand as a template
Promoter
A specific nucleotide sequence in DNA, located at the start of a gene, that is the binding site for RNA Polymerase and the place where transcription begins
What are the 3 steps for transcription?
1) Initiation = attachment of RNA polymerase to promoter and start of synthesis
2) Elongation = RNA strand increases in length, copies DNA sequence
3) Termination = RNA polymerase reaches terminator sequence (Transcription stops, RNA polymerase detaches from RNA molecule & gene, RNA strand is prepared for exportation into cytoplasm)
Messenger RNA (mRNA)
Transcribes genetic instructions on DNA in the nucleus to ribosomes
- has codons
What are the four things that translation requires?
1) mRNA, tRNA, rRNA
2) Enzymes
4) Chemical energy in ATP
Transfer RNA (tRNA)
Interpreter of translation
- 3 letter words -> amino acids
- has anticodons
What are the functions of tRNA?
1) Picking up the appropriate amino acids
2) Recognizing the appropriate codons in the mRNA
Anticodon
On a tRNA molecule, a specific sequence of 3 nucleotides that is complimentary to a codon triplet on mRNA
What does a ribosome consist of?
2 subunits, proteins, and rRNA.
ribosomal RNA (rRNA)
Type of ribonucleic acid that together with proteins make up ribosomes
- most abundant type of RNA
What are the differences between the two units? Small and large?
Small unit is for binding site of mRNA.
Large unit is for binding site of tRNA.
What is the differences between P and A site?
P site holds tRNA carrying the growing polypeptide chain.
A site holds tRNA carrying the next amino acid.
What is the role of initiation?
Determined exactly where translation will begin. It brings together mRNA, first amino acid, tRNA, and 2 subunits.
Start codon
Specific 3 nucleotide sequences AUG to which an initiator tRNA molecule binds, starting translation of genetic info
What are the 3 steps of elongation? (Translation)
1) Codon Recognition
- anticodon of incoming tRNA pairs w/ mRNA codon of Site A
2) Polypeptide bond formation
- polypeptide separates from its blinded tRNA and attaches to amino acid carried by tRNA in A site
3) Translocation
- during protein synthesis, the movement of a tRNA molecule carrying a growing polypeptide chain from the A site to P site on ribosome
Stop codon
in mRNA, one of 3 triplets (UAG, UAA, UGA) that signal gene translation to stop
Mutation
A change in the nucleotide sequence of RNA; the ultimate source of genetic variety
- base substitution and base insertion/deletion
What base substitution?
Replacement of 1 nucleotide for another.
- no, little, or significant change (usually negative)
- mal alter amino acid w/ little change to function
- improved proteins/capabilities possible
What is base inception/deletion?
May alter the reading frame (how nucleotides read 3 nucleotides at a time)
- disastrous effects
Mutagenesis
Creation of a mutation
- results from errors during DNA replication/recombination
- causes… 1) Spontaneous 2) Mutagen
Mutagen
A chemical or physical agent that interacts with DNA and causes a mutation
- pH, chemical, radiation, etc
Lytic cycle
A type of viral replication cycle resulting in the release of new viruses by lysis (breaking open) of the host cell
Lysogenic cycle
A type of bacteriophage replication cycle in which the viral genome is incorporated into the bacterial host chromosome as a prophage
- new phages are not produced, and the host cell is not killed or lysed unless the viral genome leaves the host chromosome
Prophage
Phage DNA that has inserted by genetic recombination into the DNA of a prokaryotic chromosome
How does the virus’s reproductive cycle function?
1) RNA enters cytoplasm
2) Enzymes then remove the protein coat
3) Enzymes of virus enters cell to make complementary strands of RNA
4) New coat proteins assemble around the new viral RNA
5) Viruses leave the cell by cloaking themselves in plasma membrane
Retrovirus
An RNA virus that reproduces by means of a DNA molecule. IT reverse transcribes its RNA into DNA, inserts the DNA into a cellular chromosome, and then transcribes more copies of the RNA from the viral DNA
Reverse Transciptase
An enzyme that catalyzes the synthesis of DNA on an RNA template
AIDS
Acquired immune deficiency syndrome; the late stages of HIV infection; characterized by a reduced # of T cells; usually results in death caused by other diseases
HIV
Human immunodeficiency virus, the retrovirus that attacks the human immune system causes AIDS
What is the flow of genetic info?
DNA -> RNA -> proteins
What does “In genetic code, there is redundancy, by no ambiguity” means what?
Some codons code for same amino acid but no codon codes for more amino acids
What are introns?
Genetic garbage that fills gaps
- majority of strand thought to be used for evolution
What are extrons?
Sequence that codes for particular protein
Primary Transcript
First copy of the template
What is protein synthesis comprised of?
1) Transcription
2) Translation
What are the 3 stages of translation?
1) Initiation
- When translation begins, binds to smaller subunit
2) Elongation
- Amino acids added to chain, peptide bonds form
3) Termination
- Stop codon reaches A site
Tobacco Mosaic
Rod Shaped plant virus
