Chapter 6: Protein Synthesis

Question 1

2 types of genetic material

Answer 1

DNA and RNA

Question 2

what are DNA and RNA

Answer 2

macromolecules ie polymers made of repeated monomer nucleotides (polynucleotides)

Question 3

difference between dna and rna

Answer 3

dna is double stranded

rna is single

Question 4

important features of genetic material

Answer 4

it carries genetic info in form of genes that are responsible for characters
it is able to be copied when cell divides into daughter cells

Question 5

components of a nucleotides

Answer 5

phosphate group
pentose sugar (deoxyribose/ribose)
nitrogenous base (A,T/U,G,C)

Question 6

difference between deoxyribose and ribose sugars

Answer 6

at position 2 carbon instead of hydroxyl group in ribose we find hydrogen in deoxyribose

recall structure

Question 7

study structures of phosphate and both sugars and somewhat that of purines and pyramidines bases

Answer 7

okur

Question 8

which of A T/U G C are purines and pyramidines

Answer 8

Purines- A, G

Pyrimidines- T/U, C

Question 9

bonds between bases

Answer 9

hydrogen bonds
A double bond T
G triple bond C

Question 10

why do purines only link with pyramidines and vice versa but not with their alike bases

Answer 10

• purines are bigger molecules than pyramidines
• in a dna double strand there is just enough room between the 2 strands for a purine and pyramidine
• 2 purines will be too big and 2 pyramidines will be too small too fit in between

Question 11

structure of DNA

Answer 11

• double stranded
• antiparallel in orientation (3’ to 5’ and 5’ to 3’)
• 3’-5’ phosphodiester bond backbone
• 2 strands held together by hydrogen bonds (nature) between bases via complementary base pairing

Question 12

gene expression ie from dna to protein

Answer 12

DNA replicated this is catalysed by DNA polymerase
DNA transcripted to RNA this is catalysed by RNA polymerase
RNA is translated into protein

Question 13

state the 3 models of DNA replication

Answer 13

• conservative
• semiconservative
• dispersive

Question 14

describe the 3 models of DNA replication

Answer 14

• conservative: one fully new double helix daughter DNA made from one old parent, which doesnt change
• semiconservative: 2 new molecules each contain one old parental strand and one new complementary daughter strand. H bonds broken
• dispersive: new molecule made of bits of old and new bits randomly scattered

Question 15

experimental evidence for the semiconservative model

Answer 15

• meselson and stahl supplied E.coli bacteria with NH4Cl and N-15 isotope initially
• left in NH4Cl to divide so almost all DNA had N15
• then transferred to N14 medium for 3 gens
• then this was centrifuged in caesium chloride solution
• results of bacteria grown in only N15 had a band of DNA
• then for those grown in N14 1st gen there is one thick band of DNA above then previous one
• then for 2nd gen with N14 there were 2 bands (equal)
• then for 3rd gen grown with N14 there was a thin band below and thick band above

Question 16

explanation for results of the centrifuging of gens.

remember n15 is heavier than n14. use this to explain the bands

Answer 16

• initial dna made to 2 n15 strands daughter
• that replicated again to make 2 new dna each of 1 n15 and 1 n14 strands
• those replicate to 4 dna. 2 are of 1 n15 and 1 n14 strands. other 2 are both n14 strands only
• these 4 again lastly replicated to give 8 dna. 2 are of 1 n15 and 1 n14. 6 are of only n14 .

now relate this to the bands in previous fc

Question 17

mechanism for dna replication

Answer 17

1) dna double helix unwinds and unzips as h bonds break
2) in nucleus, free activated nucleotides with 2 extra phosphates which activate and enable them to take part in reactions
3) bases on act.nucl. pair up with complementary bases on each old strand.
4) enzyme dna polymerase links sugar and phosphate of neighbouring molecules together. (only linked if bases are complementary. so errors are like 1 in ever 10^8)
5) phosphates broken off and released to nucleus
6) enzyme polymerises act.nucl. comp to nucls of comp strand in 5’-3’ orientation

Question 18

mRNA function

Answer 18

carries message from DNA to ribosome for protein synthesis

Question 19

mrna synthesis direction

Answer 19

5’-3’

Question 20

mrna formulation occurs complementary to which dna strand and which enyzyme catalyses this

Answer 20

template/sense strand which is 3’-5’

rna polymerase

Question 21

rRNA is present _ and has _ strands and function is

Answer 21

in ribosomes along with protein
single stranded
helps in protein synthesis

Question 22

ribosome made up of

Answer 22

large and small subunits, made of rRNA and proteins

Question 23

tRNA is found in

Answer 23

cytoplasm

Question 24

structure of tRNA

Answer 24

• single stranded polynucleotide chain thats folded into a clover shape
• runs 5’-3’ where 5’ is start of strand and ends with phosphate, and 3’ is amino acid attachment site and has CCA bases overhang always
• at the bottom there are different anticodons loop ie 3 bases comp to mrna codon bases
• some h bonds create some areas of base pairing within strand

Question 25

function of trna

Answer 25

transfer amino acids from cytoplasm to ribosome for protein synthesis

Question 26

what are polyribosomes

Answer 26

in prokaryotes many ribosomes work on same mrna strand at same time to translate it

Question 27

differences in translation between pro and eu karyotes

Answer 27

1) in pro tc and tl are simultaneous as nucleus is not bounded by membrane, in eu its not due to membrane 2) in pro 70s ribosomes involved, in eu its 80s 3) in pro mrna is in cytoplasm, in eu its in nucleus 4) in pro its fast, eu is slow

Question 28

james watson and crick model of dna as in size of height and width of turns how many bp per turn

Answer 28

width- 2nm height- 0.34nm 10bp

Question 29

what is the chargaff rule

Answer 29

A=T and G=C as in amounts of each so A/T=G/C=1

Question 30

why is rna more reactive than dna

Answer 30

hydroxyl group at position 2 carbon of ribose makes rna more sensitive rna is single stranded while dna is double

Question 31

structure of ATP

Answer 31

adenine base attached to sugar which makes the nucleoside called adenosine when this is attached to 3 phosphate groups it is ATP a nucleotide check structure picture

Question 32

difference between atp and dna

Answer 32

pentose sugar in atp is ribose, dna is deoxyribose atp has 3 phosphates, dna has 1 atp has adenine base, dna has ATGC

Question 33

difference between atp and rna

Answer 33

atp has 3 phosphates, dna is has 1 | atp has adenine base, rna has AUGC

Question 34

difference between nucleotide and nucleoside

Answer 34

nt=pentose sugar+base+phosphate | ns+pentose sugar+base

Question 35

what is mutation

Answer 35

alteration in gene sequences where genes code for character, so mutation codes for altered character

Question 36

alternate form of gene called

Answer 36

allele

Question 37

dna and rna are polymers of _ and proteins are polymers of _

Answer 37

nucleotides | amino acids

Question 38

what do proteins do

Answer 38

control cell activities eg enzymes catalyse metabolic reactions

Question 39

sickle cell anaemia is

Answer 39

- autosomal recessive disorder - on chromosome no 11 (an autosome) - due to base substitution mutation in DNA where CTT coding hydrophilic glutamine replaced with CAT coding hydrophobic valine amino acid - hence at position 6 of beta polypeptide chain theres a hydrophobic amino acid which changes circular rbc into a sickle shaped rbc

Question 40

what is translation

Answer 40

conversion of nucleotide sequence of mRNA to amino acid sequence of protein

Question 41

genetic code of amino acid

Answer 41

3 nucleotides ie bases

Question 42

expression used to find total no of amino acids in the world

Answer 42

4^n where 4 is no. of known nucleotides and n is no. of nucleotides coding for an amino acid ie 3 so 4^3=64 but only 20 aa in the world. this is because different base combinations can code for the same amino acid