DNA and RNA (p1) Flashcards
benefits of DNA being double stranded
allows strands to act as templates in DNA replication
sugar phosphate backbone role in DNA
protects the coding bases on the inside of the helix
Complementary base pairing in DNA
- A and T (two hydrogen bonds between)
-C and G (3 hydrogen bond between)
-a smaller pyrimidine base always binds to the larger purine base
-this arrangement maintains constant distance between 2=the 2 sugar phosphate back bones.
Polynucleotides
1) is a polymer of nucleotides
2)Nucleotides join via a condensation reaction between the phosphate group of one nucleotide and the sugar of another
3)Forms a phosphodiester bond
4) the chain of sugars and phosphate is known as the sugar phosphate backbone
A DNA molecule is a _______ helix with two anti-parallel polynucleotide chains
held together by _________ bonds between specific complementary
base pairs.
A DNA molecule is a double helix with two polynucleotide chains
held together by hydrogen bonds between specific complementary
base pairs.
There are to categories of DNA bases:
purines-larger bases that contain two carbon ring stuctures (A and G)
Pyrimidines- smaller bases that contain one carbon ring (C and T)
The components of an RNA nucleotide are ______, a
phosphate group and one of the organic base adenine,cytosine,guanine or ______.
The components of an RNA nucleotide are ribose, a
phosphate group and one of the organic bases adenine,
cytosine, guanine or uracil.
A nucleotide are formed from a phosphate group, a ________ sugar and a ___________ containing organic base
A nucleotide are formed from a phosphate group, a pentose sugar and a Nitrogen containing organic base
DNA and RNA are polymers of _______.
Nucleotides.
Ribosomes are made of _______ and proteins.
Ribosomes are made of RNA and proteins.
RNA __________ genetic information
from DNA to the ribosomes
RNA transfers genetic information
from DNA to the ribosomes.
Ribosomes synthesise proteins , they read the RNA to make poly peptides (translation).
In all living cells, DNA
holds ______ information- all the instructions an organism need to grow and develop .
In all living cells, DNA
holds genetic information- all the instructions an organism need to grow and develop .
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are
important ______—carrying molecules.
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are
important information-carrying molecules.
why is DNA a large molecule?
Contains lots of information
benefits of DNA’s double helix structure?
Makes it compact
what does complementary base pairing allow?
accurate DNA replication (ensures accurate transcription of genes for protein synthesis).
benefits of weak hydrogen bonds between complementary bases in DNA?
allows strands to separate in DNA replication- so transcription can occur.
RNA is a single stranded molecule made up just one _________________ strand. It is ______ than DNA.
RNA is a single stranded molecule made up just one polynucleotide strand. It is shorter than DNA.
RNA is a single stranded molecule,made up of just one ______________ strand.
RNA is a single stranded molecule,made up of just one poly nucleotide strand
who were the scientist who determined the double-helix structure which helps DNA carry out its function?
Watson and Crick
The semi-conservative replication of DNA ensures genetic___________ between generations of cells.
The semi-conservative replication of DNA ensures genetic continuity between generations of cells.
why is DNA replication called semi conservative replication?
Because 1 of the strands in each new DNA molecule is from the original DNA molecule (one is new)-this means there is genetic continuity between the generations of cells.
The step of semi-conservative DNA replication?
1) the enzyme DNA helicase breaks the hydrogen bonds between bases on the two polynucleotide DNA strands.
2)Each original single strand acts as a template for a new strand, Complementary base pairing mean that-free floating DNA nucleotides attract to their complementary exposed bases on the originaltemplate strand.
3)Condenstaion reactions join the nucleotides of new strands together-catalysed by the enzyme DNA polymerase. Hydrogen bonds form between the new strands .
4)Each new DNA molecule contains one strand from the original DNA molecule and one new strand.
who were the scientists that determined the double Helix structure that helps DNA to carry out it’s function?
Watson and Crick
DNA was observed in the 1800s but lots of scientists doubted that it could carry genetic code because of its relatively _________ chemical composition. Some argued that genetic information must be carried on ____________.
DNA was observed in the 1800s but lots of scientists doubted that it could carry genetic code because of its relatively simple chemical composition. Some argued that genetic information must be carried on proteins.
Why is DNA replication called semi-conservative replication?
One of the strands in each new DNA molecule is from the original DNA molecule (and one new strand).
Benefits of DNA being a semi-conservative process?
Means there is genetic continuity between generation.
Steps involved in semi-conservative DNA replication?
1) enzyme DNA helicase breaks hydrogen bonds between the two polynucleotide strands-causing double helix to unwind forming 2 single strands.
2)Each original single strand acts as a template for a new strand. complementary base paring means that free-floating DNA nucleotides are attracted to complementary exposed bases on the template strands.
3)condensation reaction joins the nucleotides of the new strands together-catalysed by the enzyme DNA polymerase. Hydrogen bonds form between the bases.
4)each new DNA molecule contains one original strand and one new strand.
In a DNA helix DNA strands run in opposite directions, they are ____________.
antiparallel
Each end of a DNA strand is slightly different in its structure. One end is called the _____ end and one end is called the ______ end.
Each end of a DNA strand is slightly different in its structure. One end is called the 3’ end and one end is called the 5’ end.
Why does DNA polymerase move in opposite ways along the antiparallel DNA strands?
-The active site of DNA polymerase is only complemtary to the 3’ end of the newly forming DNA strand.
- so it can only add nucleotides to the new strand at this end.
-so new strand is made in a 5’ to 3’ direction
-it moves down the template strand in a 3’ to 5’ direction- because the strands are antiparallel.
-The DNA polymerase working on one template strand moves in the opposit direction the the DNA polymerase working on the other.
Meselson and Stahl’s experiemnt provided evidence for semi-conservative replication, a theory suggested by ______________.
Meselson and Stahl’s experiemnt provided evidence for semi-conservative replication, a theory suggested by Watson and Crick
summary of meselson and stahls experiment
1)showed that DNA replicated through semi-conservative process using 2 isotopes of nitgorgen (Heavy and light)
2)2 sample bacteria one grown in nutreint broth containing light nitrogen one in a broth containing heavy nitrogen. as bacteria reproduced took up nitorgen to make nucleotides for DNA.
3)sample DNA taken from each and spun in centrifuge.DNA from heavy nitrogen bacteria settled lower down than DNA from light.
4)bacteria grown in heavy nitrogen broth put in light nitrogen broth. And left for one round of DNA replication, DNA sample taken and spun in centrifuge.
5)if replication=conservative heavy DNA would be at top and new light DNA be at bottom.
6) if semi-conservative new DNA contain one light strand and one heavy so would settle between.
7) Findings=DNA settled in middle showing DNA contained a micture of heavy and light = semi conservative replication.
