DNA REPLICATION - PowerPoint PPT Presentation

DNA REPLICATION

• DNA Replicates and Replicates

• Semi-conservative = one of the parent DNA strands is passed to the daugher DNA + one new strand

SNEAK PREVIEW:

DNA REPLICATION PLAYERS(enzyme review)

• Lots of enzymes are needed to start each step

• Topoisomerase Youtube I and II (1:45)
• Topoisomerase Animation (2:16)

Enzyme Helicase:separates(breaking H-bonds) double helix at the replication forkDNA-RNA-Protein (see ani)YOU TUBE DNA replication (1:05)

• The enzyme is unwinding the chain and breaking the H-bonds between the complementary base pairs (A-T, G-C).

• Nucleotides for the starting point for DNA replication
• Short strands of RNA

• Called Replication Bubbles
• They will eventually all meet to form whole

replicated strand

• Stabilize the DNA strands as they are being replicated
• Prevents rejoining of DNA strands

• DNA Polymerase I
• Cuts off RNA primers and fills in with DNA (between Okazaki fragments) –lagging strand
• Can proofread
• DNA Polymerase III
• Elongates the strand by adding DNA nucleotides on leading strand
• Also proofreads and corrects the DNA strand

• Template strand of DNA
• Continuous addition of nitrogenous bases
• in 5’ to 3’ direction
• McGraw-Hill Replication Fork

• Other DNA strand
• Forms short strands of Okazaki fragments (that will be joined later)
• in the 5’ to 3’ direction
• DNA Replication You Tube (1:35)

OKAZAKI FRAGMENTS

• The short strands of newly made DNA fragments on the lagging strand are called Okazaki fragments after the Japanese Biochemist Reiji Okazaki.

DNA LIGASEis the enzyme that joins the Okazaki fragments (sugar -phosphate backbone) with covalent bondsDNA REPLICATION (look for ligase) 2:00

• Summary Youtube of DNA replication (4:11)
• Good explanation of the 5’ to 3’ strands and leading and lagging strands

• Prokaryotic DNA polymerase can work at about 1000 bases per second.
• Eukaryotic DNA polymerase can work at about 50 bases per second.

• DNA makes DNA
• *DNA with enzymes cartoons

McGraw Hill Replication Fork animation

• Card stock papers are original DNA strands
• Colored paper are new DNA strands
• MAKE OWN ENZYMES-construction paper

• At the ends of each chromosome is a protective cap called a telomere.
• Each time a cell divides, the telomeres are snipped shorter,

• enzyme which adds DNA sequence repeats ("TTAGGG" in all vertebrates) to the 3' end of DNA strands (an overhang)
• McGraw Hill Telomeres Animation

• Activity (choose your enzymes and proteins)

• Media Showcase (cool animation)
• Replication Overview Movie

• In this diagram of the process of DNA replication at a replication fork, the strand labeled B is the:
• A template strand
• B lagging strand
• C leading strand
• D Okazaki fragment
• E RNA primer

• In this diagram of the process of DNA replication at a replication fork, the newly synthesized DNA strand labeled C is the: A coding strand
• B parental DNA
• C leading strand
• D lagging strand

• C lagging strand
• The lagging strand is the newly synthesized DNA where addition of nucleotides is on the end opposite or away from the replication fork.

• In this diagram of the process of DNA replication at a replication fork, the black boxes labeled D and E are:
• A RNA primers
• B DNA template strands
• C Okazaki fragments
• D DNA polymerase
• E Newly synthesized DNA strand

• A. RNA primers
• The initiation of replication always starts with a short RNA piece. The DNA replicating enzymes will only add nucleotides to the 3' end of DNA.

• For the DNA strand 5'-TACGATCATAT-3' the correct complementary DNA strand is: A 3'-TACGATCATAT-5
• 'B 3'-ATGCTAGTATA-5‘
• C 3'-AUGCUAGUAUA-5‘
• D 3'-GCATATACGCG-5‘
• E 3'-TATACTAGCAT-5'

• B 3'-ATGCTAGTATA-5'