2.1- STRUCTURE OF RNA AND DNA Flashcards
What are nucleic acids?
group of most important molecules of which best known are RNA and DNA
What does RNA stand for?
ribonucleic acid
What does DNA stand for?
deoxyribonucleic acid
What structure of DNA makes it immediately recognisable?
double helix structure
What does DNA do?
carries genetic information
What is DNA made up of?
nucleotides that have just three basic components
How many components does each nucleotide have?
three components
What are the three components of a nucleotide?
pentose sugar
phosphate group
nitrogen-containing organic base
Why is a pentose sugar called a pentose sugar?
it has 5 carbon atoms
What are the nitrogen-containing organic bases?
cytosine C, thymine T, uracil U, adenine A and guanine G
What is the pentose sugar, phosphate group and organic base joined as a result of?
condensation reactions
When the pentose sugar, phosphate group and organic base are joined by condensation reactions what does it form?
mononucleotide
How can two mononucleotides be joined?
through a condensation reaction
Where does the condensation reaction happen between two mononucleotides?
between the deoxyribose sugar and the phosphate group of another
What is the bond called that is formed between two mononucleotides?
phosphodiester bond
What is the new structure called when two mononucleotides are bonded?
dinucleotide
What does the continued linking of mononucleotides form?
a long chain known as a polynucleotide
What is ribonucleic acid?
polymer made up of nucleotides
Two characteristics of ribonucleic acid?
single, relatively short
What is always the pentose sugar of a ribonucleic acid?
always ribose
What are the organic bases of RNA?
adenine, guanine, cytosine and uracil
What does one type of RNA do?
transfers genetic information from DNA to the ribosomes
What are the ribosomes themselves made up of?
made up of proteins and other types of RNA
What is the third type of RNA involved in?
protein synthesis
What did James Watson and Francis Crick do in 1953?
worked out the structure of DNA
What did Rosalind Franklin do?
pioneering work on the X-ray diffraction patterns of DNA
What is always the pentose sugar in DNA?
deoxyribose
What are the organic bases on DNA?
adenine, guanine, thymine and cytosine
How many strands of nucleotides is DNA made up of?
two
What is the length like of each of the strands on DNA?
extremely long
How are the two strands on DNA joined?
by hydrogen bonds formed between certain bases
What is the base pairing for adenine?
adenine and thymine
What is the base pairing for guanine?
guanine and cytosine
What is adenine said to be to thymine, and guanine to cytosine?
complementary
What are the quantities of thymine and adenine like?
same
What are the quantities of cytosine and guanine like?
same
How is the two polynucleotide strands of DNA twisted?
uprights of phosphate and deoxyribose wind around one another
What is formed when the uprights of phosphate and deoxyribose wind around each other?
double helix
What importance does the phosphate and deoxyribose have?
form structural backbone of DNA molecule
How is DNA a stable molecule? (2)
phosphodiester backbone protects more chemically reactive organic bases inside double helix
hydrogen bonds link organic base pairs forming bridges between phosphodiester uprights.
How many hydrogen bonds are there between cytosine and guanine?
three hydrogen bonds
What would a higher proportion of C-G pairings mean?
more stable the DNA molecule
What else is there between the base pairs holding the molecule together?
other interactive forces
What is the function of DNA?
hereditary material responsible for passing genetic information from cell to cell and generation to generation
In the DNA of a typical mammalian cell, what is approximately the total number of base pairs?
3.2 billion pairs
What does the vast number of base pairs in a typical mammalian cell mean?
there’s an almost infinite variety of sequences of bases along the length of a DNA molecule
What does the variety of sequences of bases along the length of a DNA molecule provide?
genetic diversity within living organisms
How is the DNA molecule adapted to carry out its functions? (5)
very stable
two separate strands only joined with hydrogen bonds
extremely long molecule
base pairs within helical cylinder of deoxyribose-phosphate backbone
base pairings leads to DNA being able to replicate + transfer information as mRNA
Why is DNA being very stable good?
normally passes from generation to generation without change- rarely mutates
Why is the two strands of DNA being joined by hydrogen bonds only good?
allows them to separate during DNA replication and protein synthesis
Why is DNA being an extremely long molecule good?
means it carries an immense amount of genetic information
Why is the base pairs within the helical cylinder of the deoxyribose-phosphate backbone good?
genetic information is to some extent protected from being corrupted by outside chemical and physical forces
What does the function of DNA depend on?
sequence of base pairs that is possesses
Why is the sequences of base pairs the DNA possesses important?
sequence is important to everything it does and to life itself