nucleic acids

Question 1

what is the structure of DNA?

Answer 1

two polynucleotide strands in a double helix
made of nucleotide monomers

Question 2

what is in a nucleotide from DNA?

Answer 2

phosphate group
organic nitrogenous base
deoxyribose sugar

Question 3

what are the bases in DNA?

Answer 3

adenine
thymine
cytosine
guanine

Question 4

what are the two base groups?

Answer 4

pyramidines
purines

Question 5

what bases are in the pyramidines groups?

Answer 5

thymine
cytosine
uracil

Question 6

what bases are in the purines group?

Answer 6

adenine
guanine

Question 7

how many rings do bases in the pyramidines group have?

Answer 7

1 ring

Question 8

how many rings do bases in the purines group have?

Answer 8

2 rings

Question 9

how many bonds are between adenine and thymine?

Answer 9

2 bonds

Question 10

how many bonds are between cytosine and guanine?

Answer 10

3 bonds

Question 11

what is in a nucleotide from RNA?

Answer 11

phosphate group
ribose sugar
organic nitrogenous bases

Question 12

what are the bases in RNA?

Answer 12

adenine
cytosine
guanine
uracil

Question 13

what are the three types of RNA?

Answer 13

mRNA
rRNA
tRNA

Question 14

what is mRNA (structure)?

Answer 14

copy of one strand of DNA
helix shape

Question 15

what does mRNA do?

Answer 15

carries genetic code from DNA in nucleus to ribosomes during protein synthesis

Question 16

what does rRNA do?

Answer 16

component of ribosomes

Question 17

what is rRNA (structure)?

Answer 17

large complex molecule made from both single and double helices

Question 18

what is tRNA (structure)?

Answer 18

single stranded molecule
forms a clover leaf shape

Question 19

what does tRNA do?

Answer 19

brings amino acids to the ribosome so that proteins can be synthesised

Question 20

what is the first stage of DNA replication?

Answer 20

enzyme DNA helicase unwinds double strand of DNA
breaks hydrogen bonds between bases
creates two template strands for new strands

Question 21

what is the second stage of DNA replication?

Answer 21

free DNA nucleotides bind to template strands and form hydrogen bonds with their complementary bases by the enzyme DNA polymerase

Question 22

what is the third stage of DNA replication?

Answer 22

new DNA strands rewind to form a double helix
DNA ligase joins the two fragments of DNA together

Question 23

what type of replication is DNA replication?

Answer 23

semi-conservative

Question 24

what happens in the practical that shows evidence for DNA replication?

Answer 24

bacterium E.coli in cultured medium
15N incorporated into E.coli nucleotides
bacteria washed and transferred to medium containing 14N
bacteria divided once then twice

Question 25

what are the 3 control variables in the DNA replication pratical?

Answer 25

temp volume of DNA time

Question 26

what part of the DNA molecule contains 15N?

Answer 26

nitrogenous bases

Question 27

how do tubes 1 and 2 support semiconservative replication?

Answer 27

tube 1 is all heavy 15N isotope tube 2 is a mixture of heavy 15N and light 14N isotope DNA in tube 2 must be made from one strand of heavy and one strand of light DNA

Question 28

explain how the results in generation 0 and 1 support the theory of semi-conservation.

Answer 28

generation 0 band/peak is all heavy isotope generation 1 band/peak is a mix of heavy and light isotope because each molecule retains one strand of heavy and one strand of newly formed light isotope

Question 29

explain the height of the peaks in the scans for generation 2 and 3.

Answer 29

only 14N isotopes are available for replication generation 2 has equal peaks because one strand of heavy and one strand of light isotope have been used as templates for the formation of new DNA molecules generation 3 has a higher peak of 14N because more light strands are used as templates

Question 30

what is conservative replication?

Answer 30

replication produces one helix made entirely of old DNA and one helix made of entirely new DNA

Question 31

what is dispersive replication?

Answer 31

results in two helices that are mixtures of parental (old) and daughter (new) DNA

Question 32

what is a gene?

Answer 32

sequence of nucleotide bases found in DNA that code for one or more polypeptide

Question 33

what are the 4 different nucleotide bases found in DNA?

Answer 33

adenine thymine cytosine guanine

Question 34

what are the characteristics of the genetic code?

Answer 34

triplet code degenerate/redundant code 3 triplet codes code for STOP universal codons non-overlapping

Question 35

what can a triplet code also be called?

Answer 35

a codon

Question 36

how is the genetic code a triplet code?

Answer 36

3 bases code for 1 amino acid (4 cubed = 64)

Question 37

how is the genetic code a degenerate/redundant code?

Answer 37

all amino acids have more than 1 triplet code that can code for them (except methionine)

Question 38

how does the genetic code code for STOP?

Answer 38

3 codons indicate stop

Question 39

how is the genetic code universal?

Answer 39

codons are the exact same for all living organisms

Question 40

how is the genetic code non-overlapping?

Answer 40

each triplet is read separately each base occurs only once in one triplet

Question 41

what are the 3 stages of protein synthesis?

Answer 41

transcription activation translation

Question 42

what happens in the first stage of transcription?

Answer 42

DNA helicase breaks hydrogen bonds between complementary bases a gene to be transcribed unwinds

Question 43

what happens in the second stage of transcription?

Answer 43

RNA polymerase binds to the template strand RNA polymerase reads nucleotides and allows free RNA nucleotides to bind to their complementary bases stops transcribing mRNA when it reaches stop codon

Question 44

what happens in the last stage of transcription?

Answer 44

mRNA has been synthesised RNA polymerase detaches

Question 45

what happens to the mRNA after transcription in eukaryotes?

Answer 45

has to be processed before made into polypeptide

Question 46

what happens to pre-mRNA to make it into mRNA in eukaryotes?

Answer 46

has introns and exons SPLICING occurs to removes introns so exons can join together (by ligase)

Question 47

what is the first stage of translation?

Answer 47

mRNA transfers nucleotides through nuclear pores to cytoplasm mRNA attaches to ribosome

Question 48

what is the second stage of translation (tRNA)?

Answer 48

amino acid is activated by ATP and attaches to specific tRNA molecule

Question 49

what is the third stage of translation (start codon)?

Answer 49

ribosome binds to start codon on mRNA tRNA with complementary anticodon to first codon binds the the first attachment site on mRNA and releases amino acid occurs a second time

Question 50

what is the fourth stage of translation (two amino acids now)?

Answer 50

peptide bond forms between two amino acids continues until stop codon is reached

Question 51

what is post-transcriptional modification?

Answer 51

where protein can be further modified in order to become functional e.g. to become a glycoprotein or lipoprotein