DNA Replication/Transcription/Regulation PT.1 Flashcards
Chapter 16 & 17
Chapter 16
Who are Watson & Crick?
- Introduce double helic model of the structure of DNA
- Discovered nitrogenous bases: A, T, C, G
- Figured out through Rosalind Franklin that DNA formed a double helix
Chapter 16
What is transformation?
- Phenomenon discovred by Fredrick Griffith
- Change in genotype and phenotype due to assimilation of foreign DNA
Chapter 16
What are the parts of a nucleotide (monomer of DNA)
- 5C Sugar (5’ end starts where phosphate group sticks out)
- Phosphate group
- Nitrogenous Bases - held with hydrogen bonds
* Antiparallel - 2 strands run in opposite directions (5’ to 3’ & 3’ to 5’)
Chapter 16
What is Chargaff’s Rule?
- Base composition of DNA varies between species
- # of A & T are equal and # of C &G are equal
Chapter 16
What are Purines & Pyrimidines?
Purines: A & G
Pyrimidines: T & C
* Purine + Purine = too wide
* Pyrimidine + Pyrimidine = too narrow
Chapter 16
What is the difference between the pairing of A & T and C & G?
C & G bind with 3 hydrogen bonds while A & T bind with 2 hydrogen bonds
Chapter 16
What is Watson’s and Crick’s semiconservative model?
Every replicated double helix has one old strand from parent molecule and one newly made strand
Chapter 16
Steps to DNA replication
- Origins of Replication: two DNA strands are separated
- Replication bubble is opened
- Primase: adds RNA primer to start new strand
- DNA polymerase: adds more nucleotides (in 5’ to 3’ direction)
- New DNA strands are elongated at the replication fork
- Helicases: enzymes that seprate the double helix at the replication forks
- Single-strand binding proteins bind and stabalize single stranded DNA
- Topoisomerase prevents supercoiling. Breakes and rejoins DNA strands
Chapter 16
Lagging strand vs leading strand
- Leading strand replicates continuously while lagging strand replicates discontinuosly forming Ozaki Fragments
- Leading strand is in same direction as replication fork and lagging strand is in opp
- Leading strand is 5’ to 3’ direction and lagging strand is 3’ to 5’ direction
Chapter 16
What is ligase?
Binds Ozaki Fragments
Chapter 16
What is a mismatch repair and nucleotide excision repair?
- Mismatch repair: correct errors in base pairing
- Nucleotide excision repair: nuclease cuts out and replaces damaged stretches of DNA
Chapter 16
What is the role of telomeres?
- Junk DNA at the end of a chromosome that sets the max number of replication
- Shortens as one ages; protects cells from cancerous growth
- Telomerase: creates the lengthening of telomeres in germ cells
Chapter 16
What are histones?
Proteins responsible for packing and organizaing chromatin (unwounded chromosome)
* Nucleosome: basic unit of DNA packaging - involved in regulation of gene expression
* Happens during interphase
Chapter 16
What is the difference between euchromatin and heterochromatin?
- Euchromatin: loosely packed chromatin that is unclumped
- Heterochromatin: highly condensed chromatin that is clumped
Chapter 17
What is gene expression?
- Process where DNA directs protein synthesis
- Two stages: Transcription and Translation
Chapter 17
What is the relationship between a gene and a protein?
- The function of the gene is to dictate specific production of a protein
- Proteins are composed of polypeptides that have their own gene
Chapter 17
What is the difference between Transcription and Translation?
- Transcription: produces mRNA using infro from DNA
- Translation: produces polypeptides using info mRNA
Chapter 17
What are ribosomes?
- Where translation occurs
Chapter 17
What is the difference between translation/transcription in prokaryotes and eukaryotes?
- Prokaryotes: have no cell membrane: translation can happen before transcription finishes
- Eukaryotes: nuclear envelope separates transcription from translation; rna processsing occurs before translation
Chapter 17
What is the general process of protein making through genes?
- Template strand of DNA provides nucleotides for RNA transcript
- RNA (nontemplate) strand is read in codons; each codon specfies for one amino acid
- Codon is read in the correct reading frame (correct grouping)
- Polypetides are produced to form a protein
Chapter 17
What is RNA polymerase in transcription?
- Splits DNA strands apart and joins together RNA nucleotides
- Doesn’t need a primer
- Uracils replaces thymines
Chapter 17
What is the promoter, terminator, and transciption unit?
- Promoter: DNA seqeunce where RNA polymerase attaches
- Terminator: seqeunce signaling end of transcription
- Transciption unit: stretch of DNA that has been transcibed
Chapter 17
What are the three stages of transcription?
- Initiation: transcription factos mediate binding of RNA polymerase
- Transcription initiation complex: assembly of tranciption factors and RNA polymerase
- TATA box: creates initiation complex - Elongation: nucleotides added to the 3’ end of growing RNA molecule
- Termination
Chapter 17
What happens during RNA processing after transcription?
Pre-mRNA is modified; they help export mRNA to cytoplasm, protect mRNA, and help ribosems attach to 5’ end
* 5’ end receives a modified 5’ cap
* 3’ end gets a poly-A tail
Chapter 17
What is the relationship between introns/exons and RNA splicing?
- Introns: noncoding regions
- exons: coding regions, eventually translated
- RNA splicing: splicesomes remove introns and joins exons - creates continuous coding sequence
Chapter 17
What is alternative RNA splicing?
Genes that encode more than one kind of polypeptide depending on which segments are treated as exons
Chapter 17
What is the role of tRNA?
- Helps cell translate an mRNA message into protein
- Transfer and attach amino acids to growing polypeptide
- Carries specfic amino acid on one end (3’ to 5’ end) and anticodon on the other end
- Roughly L shaped
Chapter 17
What are the two steps for accurate translation?
- Aminoactyl-tRNA synthetase helps correctly match tRNA and amino acid
- Correct macth between tRNA anticodon and mRNA codon
Chapter 17
What is wobble?
Allows flexible pairing of third base of a codon
Chapter 17
What are the two ribosomal subunits made out of?
Proteins and ribosmal RNA (rRNA)
Chapter 17
What are the three binding sites for tRNA?
- A site: holds tRNA that next amino acid to be added to the chain
- P site: holds tRNA that carries the growing polypeptide chain
- E site: exit site; discharged tRNAs leave the ribosome
Chapter 17
What is a polyribosome/polysone?
- When multiple ribosomes can translate a single mRNA simultaneously
- Enable cells to make many copies of a polypeptide really quickly
Chapter 17
What are types of substitution mutations?
- Point mutation: changes in just one nucleotide pair of a gene
-Nucleotide pair substiution: self - explanatory
-Silent Mutations: codes for same amino acid even with wrong sequence
-Missence Mutations: codes for wrong amino acid
-Nonsense Mutations: code for STOP codon
Chapter 17
What are types of insetion/deletion mutations?
- Insertion: additions of nucleotide pairs in a gene
- Deletion: losses of nucleotide paits in a gene
- Frameshift mutations: altering of reading frame that changes many amino acids
Chapter 17
What is a mutagen?
A Physical or chemical agent that can cause mutations
