Lecture 5- Nucleic Acid Structure/DNA Replication Flashcards
What 3 features/substances does the nucleus contain?
-DNA
-Double nuclear membrane that is continuous with endoplasmic reticulum
-Nuclear pores which allow selective transport to out to cytoplasm
What substances can pass freely through nuclear membrane? What substances require regulation?
-Ions and small molecules pass freely
-Proteins and nucleic acids are regulated
Why is DNA tightly packaged?
DNA is much longer than the size of a nucleus. Must be packaged tightly in order to fit
List the DNA organization levels
DNA–>Histones–>Nucleosomes–>Chromatin–>Chromosomes
What are the two main features of euchromatin?
- DNA is loose
- DNA is easily accessible
What are the two main features of heterochromatin?
- DNA is compact
- DNA is inaccessible
Who first identified nucleic acids?
How did they know it wasn’t just a protein?
-Friedrich Miescher
-It was unaffected by pepsin
Which treatment allowed mice to live vs mice to die?
What did this show?
DNAse- mouse lives
Protease- mouse dies
This showed that there was a transformation in the nucleic acids that was affecting mice
What were proteins labeled with in the Hersey-Chase experiment?
What was DNA labeled with?
What did the bacteria show after being labeled?
Proteins- labeled with sulfur
DNA- labeled with phosphorus
Bacteria only showed phosphorus, DNA was being infected
What does a nucleoside consist of?
Only a base and sugar NO phosphate group
What does a nucleotide consist of?
Base, sugar, and phosphate group
What is the difference between a nucleoside and nucleotide?
Nucleosides lack a phosphate group
What do purines consist of?
Adenine and Guanine
Remember Pure Silver (Ag)
What do pyrimidines consist of?
Cytosine, Thymine, and Uracil
Remember CUT the Pie (py)
What replaces Thymine in RNA?
Uracil will bind with Adenine
Where does carbon 1 link to in a sugar?
The base
What does carbon 2 help do?
Identifies the sugar (DNA or RNA)
H group attached to carbon 2 in DNA
OH group attached to carbon 2 in RNA
What do carbons 3 and 5 form?
Sugar-phosphate backbone (phosphodiester bond)
How is the phosphodiester bond formed?
In nucleotide 1, OH on the carbon 3 will interact with the carbon 5 phosphate of nucleotide 2
What do nucleic acids write from?
5’ end to 3’ end
Name the bases starting from the 5’ end
Adenine, Thymine, Guanine
5 apple trees grow
What is Chargaff’s rule?
DNA from any cell of all organisms should have a 1:1 ratio (base Pair Rule) of pyrimidine and purine bases
How do strands run in the DNA double helix?
Opposite ways
Antiparallel orientation
How many hydrogen bonds connect Adenine and Thymines?
How many hydrogen bonds connect Cytosine and Guanine?
A-T: 2 hydrogens
C-G: 3 hydrogens
What must happen for hydrogen bonding to occur between bases?
There must be optimal distance. 2 purines will be too small to fit and 2 pyrimidines will be too far apart
Atoms must be able to match up and form hydrogen bonds
How many copies of DNA does each cell have?
The entire genetic code is copied faithfully into what?
One copy
Two identical daughter cells
What is the role of helicase in DNA replication?
Unwinds DNA strands by breaking hydrogen bonds between base pairs
What is the role of DNA primase in DNA replication?
Creates RNA primer
What is the role of DNA polymerase in DNA replication?
Writes complementary bases from 5’ to 3’
Reads 3’ to 5’
What is the role of DNA ligase in DNA replication?
Joins okazaki fragments
What are the four players in DNA replication
Helicase, DNA primase, DNA polymerase, DNA ligase
Which strand is continuous?
Which strand is made up of pieces (Okazaki fragments) that must be ligated?
Continuous strand- leading
Made up of fragments- lagging
What are the steps in the DNA replication process?
- Helicase unwinds DNA
- DNA polymerase reads and matches template strand
- Creates two identical DNA double helices
- Each new DNA double helix contains 1 original strand and 1 new daughter strand
What way can the DNA polymerase ONLY read?
3’ to 5’
What must happen to DNA before it goes through division?
Replication
Which way does the leading and lagging strands read?
Leading: 3’ to 5’
Lagging: 5’ to 3’
What is the central dogma?
DNA———–>RNA———->Proteins
Transcription Translation
How do nucleotide orientations differ between DNA and RNA?
DNA has a hydrogen on the carbon 2 of the deoxyribose sugar
RNA has a hydroxyl group on the carbon 2 of the ribose sugar
What bases are common to DNA and RNA? What bases differ?
Common- Adenine, Guanine, Cytosine
DNA- Thymine VS RNA- Uracil (no methyl group)
How are nucleotides connected to form DNA and RNA?
Through the phosphodiester bonds
When is DNA replication used?
Just bfore the cell divides
Why is there a leading and lagging strand?
Can only read the strand in one direction and synthesize in the opposite direction
In eukaryotic cells, enzymes that form phosphodiester bonds between nucleotides function in the:
Nucleus
Endoplasmic reticulum
Cytosol
More than one answer is correct
Nucleus
Deoxyribonucleoside contains all of the following except:
Nitrogenous base
Deoxyribose sugar
Phosphate group
None of the above
Phosphate group
During DNA replication, helicase is needed to unwind the double helix and pull apart the two strands of DNA. Helicase functions by breaking the:
-Hydrogen bonds between nitrogenous bases
-Phosphodiester bonds between 5 carbon sugars
-Hydrogen bonds between nucleosides
-Covalent bonds between nitrogenous bases
Hydrogen bonds between nitrogenous bases
The presence of the OH group in ____ carbon makes RNA less stable than DNA
1
2
3
4
2
Is RNA or DNA more stable?
DNA
In what form can DNA be read?
Euchromatin
Chromosome
Heterochromatin
Histone
Euchromatin
What type of bond would occur between the codon and anticodon?
Hydrogen
Ester
Peptide
Phosphodiester
Hydrogen
Hydrogen bonds break during helicase of codons and anticodons
