DNA and RNA (p1)

Question 1

benefits of DNA being double stranded

Answer 1

allows strands to act as templates in DNA replication

Question 2

sugar phosphate backbone role in DNA

Answer 2

protects the coding bases on the inside of the helix

Question 3

Complementary base pairing in DNA

Answer 3

• A and T (two hydrogen bonds between)
  -C and G (3 hydrogen bond between)
  -a smaller pyrimidine base always binds to the larger purine base
  -this arrangement maintains constant distance between 2=the 2 sugar phosphate back bones.

Question 4

Polynucleotides

Answer 4

1) is a polymer of nucleotides
2)Nucleotides join via a condensation reaction between the phosphate group of one nucleotide and the sugar of another
3)Forms a phosphodiester bond
4) the chain of sugars and phosphate is known as the sugar phosphate backbone

Question 5

A DNA molecule is a _______ helix with two anti-parallel polynucleotide chains
held together by _________ bonds between specific complementary
base pairs.

Answer 5

A DNA molecule is a double helix with two polynucleotide chains
held together by hydrogen bonds between specific complementary
base pairs.

Question 6

There are to categories of DNA bases:

Answer 6

purines-larger bases that contain two carbon ring stuctures (A and G)
Pyrimidines- smaller bases that contain one carbon ring (C and T)

Question 7

The components of an RNA nucleotide are ______, a
phosphate group and one of the organic base adenine,cytosine,guanine or ______.

Answer 7

The components of an RNA nucleotide are ribose, a
phosphate group and one of the organic bases adenine,
cytosine, guanine or uracil.

Question 8

A nucleotide are formed from a phosphate group, a ________ sugar and a ___________ containing organic base

Answer 8

A nucleotide are formed from a phosphate group, a pentose sugar and a Nitrogen containing organic base

Question 9

DNA and RNA are polymers of _______.

Answer 9

Nucleotides.

Question 10

Ribosomes are made of _______ and proteins.

Answer 10

Ribosomes are made of RNA and proteins.

Question 11

RNA __________ genetic information
from DNA to the ribosomes

Answer 11

RNA transfers genetic information
from DNA to the ribosomes.
Ribosomes synthesise proteins , they read the RNA to make poly peptides (translation).

Question 12

In all living cells, DNA
holds ______ information- all the instructions an organism need to grow and develop .

Answer 12

In all living cells, DNA
holds genetic information- all the instructions an organism need to grow and develop .

Question 13

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are
important ______—carrying molecules.

Answer 13

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are
important information-carrying molecules.

Question 14

why is DNA a large molecule?

Answer 14

Contains lots of information

Question 15

benefits of DNA’s double helix structure?

Answer 15

Makes it compact

Question 16

what does complementary base pairing allow?

Answer 16

accurate DNA replication (ensures accurate transcription of genes for protein synthesis).

Question 17

benefits of weak hydrogen bonds between complementary bases in DNA?

Answer 17

allows strands to separate in DNA replication- so transcription can occur.

Question 18

RNA is a single stranded molecule made up just one _________________ strand. It is ______ than DNA.

Answer 18

RNA is a single stranded molecule made up just one polynucleotide strand. It is shorter than DNA.

Question 19

RNA is a single stranded molecule,made up of just one ______________ strand.

Answer 19

RNA is a single stranded molecule,made up of just one poly nucleotide strand

Question 20

who were the scientist who determined the double-helix structure which helps DNA carry out its function?

Answer 20

Watson and Crick

Question 21

The semi-conservative replication of DNA ensures genetic___________ between generations of cells.

Answer 21

The semi-conservative replication of DNA ensures genetic continuity between generations of cells.

Question 22

why is DNA replication called semi conservative replication?

Answer 22

Because 1 of the strands in each new DNA molecule is from the original DNA molecule (one is new)-this means there is genetic continuity between the generations of cells.

Question 23

The step of semi-conservative DNA replication?

Answer 23

1) the enzyme DNA helicase breaks the hydrogen bonds between bases on the two polynucleotide DNA strands.
2)Each original single strand acts as a template for a new strand, Complementary base pairing mean that-free floating DNA nucleotides attract to their complementary exposed bases on the originaltemplate strand.
3)Condenstaion reactions join the nucleotides of new strands together-catalysed by the enzyme DNA polymerase. Hydrogen bonds form between the new strands .
4)Each new DNA molecule contains one strand from the original DNA molecule and one new strand.

Question 24

who were the scientists that determined the double Helix structure that helps DNA to carry out it’s function?

Answer 24

Watson and Crick

Question 25

DNA was observed in the 1800s but lots of scientists doubted that it could carry genetic code because of its relatively _________ chemical composition. Some argued that genetic information must be carried on ____________.

Answer 25

DNA was observed in the 1800s but lots of scientists doubted that it could carry genetic code because of its relatively simple chemical composition. Some argued that genetic information must be carried on proteins.

Question 26

Why is DNA replication called semi-conservative replication?

Answer 26

One of the strands in each new DNA molecule is from the original DNA molecule (and one new strand).

Question 27

Benefits of DNA being a semi-conservative process?

Answer 27

Means there is genetic continuity between generation.

Question 28

Steps involved in semi-conservative DNA replication?

Answer 28

1) enzyme DNA helicase breaks hydrogen bonds between the two polynucleotide strands-causing double helix to unwind forming 2 single strands. 2)Each original single strand acts as a template for a new strand. complementary base paring means that free-floating DNA nucleotides are attracted to complementary exposed bases on the template strands. 3)condensation reaction joins the nucleotides of the new strands together-catalysed by the enzyme DNA polymerase. Hydrogen bonds form between the bases. 4)each new DNA molecule contains one original strand and one new strand.

Question 29

In a DNA helix DNA strands run in opposite directions, they are ____________.

Answer 29

antiparallel

Question 30

Each end of a DNA strand is slightly different in its structure. One end is called the _____ end and one end is called the ______ end.

Answer 30

Each end of a DNA strand is slightly different in its structure. One end is called the 3' end and one end is called the 5' end.

Question 31

Why does DNA polymerase move in opposite ways along the antiparallel DNA strands?

Answer 31

-The active site of DNA polymerase is only complemtary to the 3' end of the newly forming DNA strand. - so it can only add nucleotides to the new strand at this end. -so new strand is made in a 5' to 3' direction -it moves down the template strand in a 3' to 5' direction- because the strands are antiparallel. -The DNA polymerase working on one template strand moves in the opposit direction the the DNA polymerase working on the other.

Question 32

Meselson and Stahl's experiemnt provided evidence for semi-conservative replication, a theory suggested by ______________.

Answer 32

Meselson and Stahl's experiemnt provided evidence for semi-conservative replication, a theory suggested by Watson and Crick

Question 33

summary of meselson and stahls experiment

Answer 33

1)showed that DNA replicated through semi-conservative process using 2 isotopes of nitgorgen (Heavy and light) 2)2 sample bacteria one grown in nutreint broth containing light nitrogen one in a broth containing heavy nitrogen. as bacteria reproduced took up nitorgen to make nucleotides for DNA. 3)sample DNA taken from each and spun in centrifuge.DNA from heavy nitrogen bacteria settled lower down than DNA from light. 4)bacteria grown in heavy nitrogen broth put in light nitrogen broth. And left for one round of DNA replication, DNA sample taken and spun in centrifuge. 5)if replication=conservative heavy DNA would be at top and new light DNA be at bottom. 6) if semi-conservative new DNA contain one light strand and one heavy so would settle between. 7) Findings=DNA settled in middle showing DNA contained a micture of heavy and light = semi conservative replication.