Which of the following represents the correct order of enzymes that replicate the lagging strand of DNA? A. Primase, helicase, DNA Polymerase III, DNA Polymerase I, ligase B. DNA Polymerase I, DNA Polymerase III, helicase, primase, ligase C. Helicase, primase, DNA Polymerase III, DNA Polymerase I, ligase D. Ligase, primase, helicase, DNA Polymerase III, DNA Plymerase IBacterial)Replica,on)origin:))h2p://highered.mcgraw8hill.com/classware/ala.do?isbn=0072464631&alaid=ala_661234&showSelfStudyTree=true)Each new DNA strand can be synthesized only in 5’-3’ direction synthesis)of)this)strand)must)con,nue)in)the)direc,on)opposite)to)the)direc,on)of)the)replica,on)fork)Each replication fork consists of a strand that is replicating continuously (leading strand) and a strand that is replicating discontinuously (lagging strand)In eukaryotic chromosomes, replication starts at multiple replication forks are expanding in both directions Replicating fly DNA Pictures)1,2,)and)3)show)how)the)same)por,on)of)DNA)would)appear)at)different)stages)of)replica,on)Fig. 16-21a DNA double helix (2 nm in diameter) Nucleosome (10 nm in diameter) Histones Histone tail H1 DNA, the double helix Histones Nucleosomes, or “beads on a string” (10-nm fiber) In#Eukaryotes,#DNA#exists#in#complex#with#proteins.#This#complex#is#called#Chroma>n)Histones#are)proteins)that)are)responsible)for)the)first)level)of)DNA)packing)in)chroma,n)Clicker question At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork: 3' C C T A G G C T G C A A T C C 5' An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence? A) 5' G C C T A G G 3' B) 3' G C C T A G G 5' C) 5' A C G T T A G G 3' D) 5' A C G U U A G G 3’• Reminder: homework, due Wednesday, 12PM (based in part on independent reading) • No class or sections or OH on Monday, check the website/Announcements for days/times of make-up sections and OH • Today: explaining ideas to your nearest neighborsProkaryotes Eukaryotes Figure#17.3a#TRANSLATION#TRANSCRIPTION#DNA)mRNA)Ribosome)Polypep,de)The Central Dogma: DNA RNA Protein Without)nucleus,)simultaneous)transcrip,on)and)transla,on))TRANSCRIPTION#RNA#PROCESSING)TRANSLATION#mRNA)DNA)Pre8mRNA)Polypep,de)Ribosome)Nuclear)envelope)With)nucleus,)tran scrip,on)and)transla,on)separated) and)requires)RNA)processing)transcription translationFigure#17.4#DNA)molecule)Gene)1)Gene)2)Gene)3)DNA#strand#(template)#TRANSCRIPTION#mRNA)Protei n)TRANSLATION)Amino)acid)A# C# C#A# A# A# C# C# G# A# G#T#U# G# G#U#U# U#G#G# C#U# C#A#Trp#Phe#Gly#Ser#Codon)3’) 5’)3’)5’)Gene expression: DNA RNA ProteinEvolution of the Genetic Code The genetic code is nearly universal, from bacteria to animals Genes can be transcribed and translated after being transferred from one species into another Human insulin protein can be produced in bacteria by introducing insulin DNA into bacterial cells A)firefly)gene)expressed)in)a)plant!)Molecular Components of RNA Transcription RNA polymerase II - Catalyzes mRNA synthesis 5’ to 3’ (just like DNA Pol!) - Pries the DNA strands apart - Phosphodiester bonds RNA nucleotides Uses same base-pairing rules as DNA, except uracil substitutes for thymine If)DNA)template)strand)is: )A)C)G)T)A)C)G)T)Then)mRNA)will)look)like: )U)G)C)A)U)G)C)A)Synthesis of an RNA Transcript 1. Initiation RNA Pol binds promoter, unwinds strands 2. Elongation RNA Pol moves downstream 5’ to 3’, with addition of new nucleotides 3. Termination single-stranded RNA transcript released Figure#17.7#Promoter)Transcrip,on)unit)RNA)polymerase)Start)point)5’)3’)3’)5’)3’)5’)5’)3’)5’)3’)3’)5’)5’)3’)3’)5’)5’)5’)Rewound)RNA)RNA)transcript)3’)3’)Completed)RNA)transcript)Unwound)DNA)RNA)transcript)Template)strand)of)DNA)DNA)Initiation of Transcription Promoters: DNA sequences that signal initiation site for RNA synthesis Transcription factors: proteins that help RNA Pol recognize promoters TATA)box)Start)point)Template)DNA)strand)Transcrip,on)factors)5’)3’)3’)5’)Promoter#Figure#17.8#Start)point)Template)DNA)strand)Transcrip,on)factors)5’)3’)3’)5’)Promoter#RNA)Pol)Transcript#Elonga>on#&#Termina>on#RNA)polymerase)Non8template)strand)of)DNA)RNA)nucleo,des)3’)end)C)A)E ))G)C)A)A)U)T)A)G)G)T)T)A)C)G)U)C)A)T)C) C) A)A)T)3’)5’)5’)Newly)made)RNA)Direc,on)of)transcrip,on)(“downstream”))Template)strand)of)DNA) RNA polymerase moves along DNA, untwisting the double helix, exposing ~15 bases at a time for pairing with RNA, on one strand mRNA)is)single)stranded)DNA)is)double)stranded)Terminator)sequence)signals)release)of)single8stranded)RNA)Discuss with your nearest neighbor. Write answers on a separate sheet of paper + your neighbor’s name 1. What is a primase and what is its function? - Primase is ________ (a class of molecules) that participates in the process of __________. Its role in this process is to __________________. 2. What is a promoter and what is its function? - Promoter is ________ (a class of molecules) that participates in the process of __________. Its role in this process is to __________________.Discuss with your nearest neighbor. Write answers on a separate sheet of paper + your neighbor’s name 1. Explain how replication differs from transcription. 2. List two components that are different between replication and transcription reactions (template, enzymes, product, etc). List two aspects that are