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Flashcards in DNA Deck (87)
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1

who discovered dna

watson and crick in 1953
but rosalind franklin worked out the structure

2

what does DNA stand for

deoxyribose nucleic acid

3

DNA is a polymer, what is a polymer

long chain of molecules made of the same units

4

what are the individual units of DNA

nucleotides

5

what is a single nucleotide made up of in DNA

phosphate, deoxyribose (pentose) sugar and a nitrogenous base

6

how are nucleotides joined together

in a condensation reaction

7

what bonds do sugar and phosphate form when nucleotides join together

phosphodiester bond

8

what are the 4 bases (complimentary pairs)

adenine and thymine
guanine and cytosine

9

what are the bases made up of

rings of carbon and nitrogen

10

what is a purine and which bases are purines

double rings
guanine and adenine

11

what is a pyrimidine and which bases are pyrimidines

single rings
cytosine and thymine

12

a purine always pairs......

with a pyrimidine

13

what is synthesis

making something

14

what is replicating

copying somethig

15

what do nitrogen bases act like

oxygen in what making the bases polar which allows hydrogen bonds to form

16

are the hydrogen bonds formed weak or strong and why

weak
essential for replication

17

what is DNA replication

chromosomes must make copies of themselves so that when cells divide each daughter cell receives an exact copy

18

what is protein synthesis

the sequence of bases represents the information carried in DNA and determines the sequence of amino acids in a protein

19

what are the 3 theories of DNA replication

conservative
semi conservative
dispersive

20

what is conservative theory

the original DNA is completely conserved and a whole new copy is created

21

what is semi conservative theory

one strand of the original goes to each daughter strand and one copy strand

22

what is dispersive theory

the original is fragmented and is split between the copies

23

what is the DNA replication process

1) helicase enzyme breaks the hydrogen bonds and the DNA unzips
2) free nucleotides bond to both DNA strands by complimentary base pairing
3) DNA polymerase enzymes joins the nucleotides between the sugar and phosphate groups
4) this results in two identical double stranded molecules

24

what did meselson and stahl do

devised an experiment to deduce which was the correct theory

25

how did meselson and stahl conduct their experiment

1 - e coli were grown for several generations in a medium with N-15 present
2 - the n 15 e coli were transferred to a n14 medium to allow the e coli to divide
3- dna was extracted periodically and compared to the density of a pure sample of n14 and n15, they used a centrifuge to compare densities

26

what is the correct DNA replication theory

semi conservative

27

what is the function of DNA

contains the instructions for protein synthesis

28

what are codons

the section of a molecule that codes for one amino acid (in mRNA)

29

what did NIRENBERG discover

that there was 4 bases and 20 possible amino acids
so said that there codons must be at least 3 bases long

30

what is the triplet code

three bases code for one amino acid
there are at least 64 possible codons
but only 20 amino acids
3 of the codons are stop codons which ends protein synthesis