nucleotides and nucleic acids

Question 1

making DNA nucleotide

Answer 1

• 1phosphate
• 5 carbon sugar (pentose)
• organic (contains carbon) nitrogenous (contains nitrogen) base

Question 2

making polynucleotides

Answer 2

• phosphate group at the 5’ carbon of pentose sugar of one nucleotide forms a covalent bond with the OH group at the 3’ pentose sugar of an adjacent nucleotide
• called a phosphodiester bond
• the sugars and the phosphates for a sugar phosphate backbone

Question 3

what is DNA

Answer 3

• double stranded molecule coil to be a double helix
• strands run anti parallel (caused by size of purines an pyrmidines)
• each strand has a phosphate group 5’ and a hydroxyl group 3’
• polynucleotide strands attached by hydrogen bonds
  G=C
  A=T

Question 4

purines

Answer 4

adenine and guanine bigger

Question 5

pYrimidines

Answer 5

thYmine and cYtosine smaller

Question 6

number on H = bonds between bases

Answer 6

G=C 3 H bonds
A=T 2 H bonds

Question 7

charagaff’s rule

Answer 7

equal amounts of adenine and thymine
equal amounts of guanine and cytosine

Question 8

RNA

Answer 8

single stranded
uracil (not thymine)
ribose pentose sugar
3 types of molecule (rRNA tRNA mRNA)

Question 9

number of nucleotides

Answer 9

DNA = long molecule 1,000,000s
RNA = short molecule 100s

Question 10

DNA —–> RNA why?

Answer 10

DNA too big to leave nucleus
short sections of DNA (genes) transcribed to mRNA shorter and single stranded
can leave nucleus and go to ribosome for protein synthesis

Question 11

DNA precipitation/extraction

Answer 11

why are peas mashed up?
breaks down cell walls
why is the sample mixed with detergent?
break down cell surface membrane
why is salt added?
breaks hydrogen bonds
why add protease enzymes?
break down proteins associated with DNA nuclei
why does DNA precipitate out of solution when ethanol added?
DNA doesnt dissolve in ethanol
why keep a lower temp?
prevent DNA from breaking down

Question 12

DNA replication as semi-conservative (6)

Answer 12

1. DNA unwinds by action of gyrase enzyme
2. Strands of separate by action helicase enzyme which breaks the hydrogen bonds between complementary base pairs
3. Free DNA nucleotides are attracted to and pair up with their complementary bases to for a pair
4. Hydrogen bonds form between complementary base pairs
5. DNA polymerase forms the sugar phosphate backbone by forming phosphodiester bonds between nucleotides
6. Two identical copies of DNA. Called semi-conservative replication because each new DNA molecule has one old strand and one new strand. Each original strand acts as a template

Question 13

replication errors

Answer 13

spontaneous and random
incorrect sequence is called a mutation
daughters cells wont receive identical genetic information
- proteins dont function/ arent made
- new cell dont fuction/ arent made

Question 14

DNA replication models

Answer 14

• conservative model
• semi-conservative model
• dispersive model

Question 15

explain how meselson and stahl proved the semi-conservative model

Answer 15

• grew E.coil bacteria in a medium with heavy nitrogen (15N)
• transferred the bacteria into a medium with lighter nitrogen (14N)
• took DNA samples at intervals after the transfer
• separated the DNA sample using a centrifuge
• after one generation found DNA containing both heavy and light nitrogen
• after two generations observed both hybrid and light DNA

Question 16

DNA synthesis

Answer 16

making proteins in the nucleus and ribosomes

Question 17

RNA polymerase

Answer 17

forms phosphodiester bonds between RNA nucleotides to make mRNA
form sugar phosphate backbone

Question 18

protein synthesis p1 TRANSCRIPTION

Answer 18

• DNA copied by being transcribed into mRNA
• free RNA nucleotides line up with template DNA strand (antisense strand)
• using rules of complementary base pairing
  DNA A= RNA U
  DNA T= RNA A
  G=C

Question 19

protein synthesis p2 TRANSLATION

Answer 19

• mRNA moves to ribosomes
• tRNA molecules to mRNA
• anticodons on tRNA base pair with codons on mRNA
• a specific amino acid attaches to tRNA so amino acids are brought to ribosome in a specific order
• formation of peptide bonds between amino acids

Question 20

transfer RNA

Answer 20

a strand of RNA folded
one end of molecule = 3 bases (anti codon) complementary to codon on mRNA
shorter than mRNA
has amino acid binding site
brings correct amino acid to ribosome

Question 21

ribosomal RNA

Answer 21

hold mRNA in position while it is translated into specific sequence of amino acids

Question 22

genetic code TRIPLET CODE

Answer 22

3 bases (codon) code for an amino acid

Question 23

genetic code NON OVERLAPPING CODE

Answer 23

the sequence is read so that each base is only part of one triplet of bases

Question 24

genetic code DEGENERATE CODE

Answer 24

20 different amino acids that occur in biological proteins
many amino acids can be coded by more than one codon
not all mutations will lead to wrong amino acid being put into the polypeptide chain

Question 25

genetic code UNIVERSAL CODE

Answer 25

same base triplets/ codons code for same amino code in nearly all living organisms

Question 26

ATP properties

Answer 26

SMALL moves easily in and out of cells WATER SOLUABLE energy requiring process takes place in aqueous solution RELEASES ENERGY IN SMALL QUANTITIES ATP EASILY REGENERATED by condensation energy contained in bonds between phosphates is large for cell reactions- not too large (energy lost as heat)

Question 27

Exhalation

Answer 27

Diaphragm and external intercostal muscles relax Volume of thorax decreases Pressure of thorax increases above atmospheric levels Air moves out of lungs PASSIVE - muscles are relaxed - elastic tissues recoiled