1.5 DNA and RNA Flashcards
What is the monomer that makes up DNA and RNA?
A nucleotide
What is a nucleotide made up of?
A pentose sugar
A phosphate group
A nitrogenous base
What sugar makes up DNA?
Deoxyribose
What does DNA stand for?
Deoxyribonucleic acid
What is the general structure of DNA?
Made up of two polynucleotide strands
They run in opposite directions (anti parallel)
They twist round each other called a double helix
How are nucleotides bonded together?
In a condensation reaction
Held together by phosphodiester bonds
What is the function of DNA?
It codes for manufacture of particular proteins or RNA
The hereditary material which carries information of genetic code to pass on from cell to cell and generation to generation
What is the deoxyribose and phosphate group also called?
The sugar phosphate backbone
What are the complementary base pairs?
Adenine - Thymine
Cytosine - Guanine
What are the pyrimidines?
Thymine and Cytosine
They have a single ring therefore are smaller
What are the purines?
Adenine and Guanine
They have a double ring structure and are therefore bigger
What are the hydrogen connections between the bases?
A=T 2 hydrogen bonds Spikey letters (easier to grab)
G ≡ C
3 hydrogen bonds
Curley letters (harder to hold onto)
What are some features of DNA?
Long coiling molecule Sugar phosphate backbone Bases in sequence Complementary pairs Hydrogen bonds Helical structure
How does DNA having the property of a long coiling molecule help?
Makes it very compact
You can store a lot of genetic material in a small space
How does DNA having the property of a sugar phosphate backbone help?
It is a very strong molecule
Denatured at 86 degrees
Very stable
How does DNA having the property of bases in sequence help?
It allows a lot of variation
They form triplet codes to relate to one amino acid
Therefore 64 variations of the triplet
How does DNA having the property of a complementary base pairing help?
The replications are a lot more accurate
Mutations are rare
How does DNA having the property of a many hydrogen bonds help?
Weak hydrogen bonds are easily overcome
DNA can separate easily meaning replication is much simpler
Adds stability as there are many
How does DNA having the property of a helical structure help?
Protects more chemically reactive base pairs from physical and chemical forces
This allows genetic information not to be corrupted
What did Griffiths conclude about DNA in 1928?
That if a virile strain was heated and put with a non-virile then the DNA in the virile strain can survive the heating and be taken in by the non-virile strain making it now virile
Therefore DNA was important
What did Avery conclude about DNA in 1944?
That it was in fact DNA that contained the transformation for the virile strain
What was the first Hershey-Chase experiment involving?
A bacteriophage with a sulfur (S35) labeled protein capsule i.e radioactively labelled
When the cell became infected the labelled capsule remained on the outside
What was the second Hershey-Chase experiment involving?
A bacteriophage with a phosphorus labelled DNA
When the cell became infected we could see the phosphorus labelled DNA on the inside of the cell
What did Hammerling use to do his experiment on the part of the cell controlling characteristics? Why?
Acetabularia
It is a single cell organism
Has distinguishable parts (cap, stalk, foot)
Quick regenerative properties
Nucleus in the foot
What did Hammerlings conclude from his first experiment?
He cut the cap of and it regenerated
He cut the foot of and it didn’t regenerate
Therefore genetic information for regeneration must be in the foot
What does RNA stand for?
Ribonucleic acid
What is RNA made up of?
Nucleotide monomers containing
A pentose sugar
A phosphate group
A nitrogenous base
What is the pentose sugar in RNA?
Ribose
What are the bases in RNA?
Adenine
Cytosine
Guanine
Uracil
What are the main differences between DNA and RNA?
Uracil instead of Thymine
RNA is single stranded
Ribose instead of deoxyribose
RNA can’t self replicate
RNA can leave the nucleus
What are the three types of RNA?
Messenger RNA - mRNA
Transfer RNA - tRNA
Ribosomal RNA - rRNA
What does mRNA do?
Transfers genetic information from DNA in the nucleus to the ribosomes in the cytoplasm
What are the key features of mRNA?
Single stranded polynucleotide Made by the transcription of the DNA (can form hydrogen bonds with DNA) Much shorter than DNA (length of gene) Leaves the nucleus Unstable so easily broken down
What does tRNA do?
Binds with amino acids to allow for protein synthesis
What are the key features of tRNA?
Relatively small (no nucleotides) Single stranded folded into a clover shape Amino acids attach to the extended end
What does rRNA do?
Forms ribosomes
When rRNA combines with proteins
What is the structure of rRNA?
60S and 40S subunits
S = svedbergs
Measures how fast molecules move in a centrifuge
What is DNA replication?
When a cell divides a perfect copy of the information in the DNA needs to be reproduced
What happens in DNA replication?
DNA helicase separates the two strands breaking the hydrogen bonds between nitrogenous bases
Free nucleotides are attracted to their complementary base pairs on the template strands
Then DNA polymerase joins the nucleotides together when they have lined up
Two identical strands are formed each one contains half the original DNA material
Why does semi-conservative describe DNA replication?
One original parental strand remains in the new DNA molecule whilst one new strand coils around the original
What does DNA polymerase do?
Joins the nucleotides together to form the new strand through the sugar phosphate backbone
It uses the template strand and the complementary base pairings to achieve this
What does DNA helicase do?
It separates or unwinds the strands by breaking the hydrogen bonds between the nitrogenous bases
What is significant about DNA polymerase?
It can only replicate a bit at a time in short sections
It can only travel in one direction
3’ - 5’
3 to 5 refers to the carbons on the deoxyribose
In THE experiment to prove semi conservative replication where do the ticks go?
1
5
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