2 Flashcards
(27 cards)
What is DNA?
DNA is the control molecule of life
What does dna control?
DNA controls cellular activities, including reproduction
What does dna make
DNA makes exact copies of itself to pass onto other cells
What does dna carry
DNA Carrie’s a code. Genetic instructions are encoded in the sequence of bases strung together in DNA.
What is the source of the unity of life
DNA
What are the sources of life’s variation?
Mutations and recombinations in the structure and number of DNA molecules are the source of life’s variation.
How did life most likely begin?
Life most likely began as a nucleic acid. The first form of life on this planet is thought by many biologists to be a self-replicating strand of RNA
What are the two types of nucleic acids
DNA / RNA
Who was DNA first isolated by?
By Swiss biochemist Johann Friedrich Miescher in 1869. Because DNA molecules are acidic and are found in the nucleus Miescher called them nucleic acids.
Who determined the mechanism for DNA replication
Meselson and Stahl determined it in 1958. In the genetic code of 3 dna nucleotides for 1 amino acid was worked out by Crick and his coworkers
During the 1950s a fierce competition to determine the three dimensional structure of dna took place. Who was the race won by in 1953?
James Watson, an American biologist and Francis Crick, a British physicist. Solved the puzzle using scale modes of nucleotides at Cambridge university in England. Their success depended to a great extent on evidence collected by other biologists especially x ray data from British biochemists Rosalind Franklin and Maurice Wilkins
What is the monomer of a nucleic acid
Nucleotide
What is a nucleotide composed of
A pentose sugar, a phosphate group, a nitrogenous base
What are the two types of bases
Purine and pyrimidine
Purines
Have a double ring structure (adenine and guanine)
Pyrimidines
Have a single ring structure ( thymine, cytosine, uracil - in rna only)
What does the DNA strand consist of
A sequence of nucleotides linked together to form a double helix that can be visualized as an immensely long twisted ladder
What is each strand or one side of the DNA ladder made of
It’s composed of alternating molecules of deoxyribose and phosphate with a nitrogenous base attached to each deoxyribose unit.
What is the complementary base pairing between strands
Adenine bonds with thymine or uracil in rna. Guanine bonds with cytosine. The number of purine bases equals the number of pyrimidine bases
How are bases linked
The bases stick out the side of the sugar molecules and are linked to the bases of the other strand by hydrogen bonds in a very strict pattern. Always a purine with a pyrimidine. Pairs of joined bases project crosswise forming the rungs of the ladder.
How long are DNA strands
DNA strands are extremely long, each one containing millions of atoms. Every human cell contains about one meter of these twisted strands. (This amounts to about 4 billion pairs of bases)
What are genes
The units of inheritance that control particular characteristics or capabilities of an organism.
Where are genes located
On the chromosomes of the cell nucleus and consist of segments of dna molecules
What are chromosomes composed of
Made of nucleic acids and a protein structure called histones
