1.5 Flashcards
State the role of DNA in living cells
-base sequence of genes codes for functional RNA & amino acid sequence of polypeptides
-Genetic information determines inherited characteristics = influences structure & function of organisms
State the role of RNA in living cells
mRNA: Complementary sequence to 1 gene from DNA with introns (non-coding regions) spliced out. Codons can be translated into a polypeptide by ribosomes
rRNA: component of ribosomes (along with proteins)
tRNA: supplies complementary amino acid to mRNA codons during translation
How do polynucleotides form?
-Condensation reactions between nucleotides form strong phosphodiester bonds (sugar-phosphate backbone)
Describe the structure of DNA
-double helix of 2 polynucleotide strands (deoxyribose)
-H-bonds between complementary purine & pyrimidine base pairs on opposite strands:
adenine + thymine
guanine + cytosine
which bases are purine and which are pyrimidine?
A & G = 2-ring purine bases
T & C = 1-ring pyrimidine bases
Name the complementary base pairs in DNA and the number of H-bonds
2 H-bonds between adenine and thymine
3 H-bonds between guanine + cytosine
Name the complementary base pairs in RNA and the number of H-bonds
2 H-bonds between adenine + uracil
3 H-bonds between guanine + cytosine
Relate the structure of DNA to its functions
-sugar-phosphate backbone and many H-bonds provide stability
-long molecule stores lots of information
-helix is compact for storage in nucleus
-base sequence of triplets codes for amino acids
-double-stranded for semi-conservative replication
-complementary base pairing for accurate replication
-weak H-bonds break so strands separate for replication
name the pentose sugars in DNA and RNA
DNA: deoxyribose
RNA: ribose
Describe the structure of messenger RNA (mRNA)
-Long ribose polynucleotide (shorter than DNA
-contains uracil instead of thymine
-single stranded and linear (no complementary base pairing)
-Codon sequence is complementary to exons of 1 gene from 1 DNA strand
