Genetic Code + DNA

Question 1

What is a gene?

Answer 1

A sequence of mononucleotide bases on a DNA molecule coding for a sequence of amino acids in a polypeptide chain which produces a protein that results in a characteristic

Question 2

What is the genome?

Answer 2

All the genes in an organism/species

Question 3

What is the proteome?

Answer 3

Full range of proteins that a cell can make

Question 4

What do chromosomes in cells carry? 2

Answer 4

• A large amount of DNA

- Numerous genes

Question 5

What is genetic code?

Answer 5

The sequence of base triplets [codes] in DNA/mRNA coding for specific amino acids

Question 6

What is a codon?

Answer 6

A base triplet coding for an amino acid

Question 7

4 words to describe genetic code

Answer 7

• Universal
• Degenerate
• Non overlapping
• Triplet code

Question 8

Why is genetic code non overlapping?

Answer 8

Each triplet code is adjacent and seperate, doesn’t share bases

Question 9

Why is genetic code degenerate?

Answer 9

• More possible combinations of triplets than amino acids

- Some amino acids code for more than 1 triplet

Question 10

Why is genetic code universal?

Answer 10

• It is the same genetic code in all living organisms, codes for the same proteins

Question 11

What are start and stop codons?

Answer 11

Codons telling cell when to start and stop gene production

Question 12

Where are start and stop codons found?

Answer 12

At the beginning and the end of the gene

Question 13

What is a mononucleotide?

Answer 13

A monomer that makes up polynucleotides e.g DNA and RNA

Question 14

What bonds to what in DNA?

Answer 14

Phosphate to pentose to nitrogen containing base

Question 15

What are mononucleotides made up of?

Answer 15

• Phosphate group
• Pentose sugar
• Nitrogen containing base

Question 16

What are mononucleotides joined by?

Answer 16

Condensation reactions

Question 17

What is the full name of DNA?

Answer 17

Deoxyribosenucleic Acid

Question 18

What is the function of DNA?

Answer 18

To store genetic code which contains instructions for coding for the characteristics of an organism

Question 19

What does DNA control?

Answer 19

Manufacture of proteins

Question 20

What bases does DNA have?

Answer 20

• Adenine
• Thymine
• Cytosine
• Guanine

Question 21

What type of sugar is in RNA nucleotides?

Answer 21

Ribose

Question 22

What is DNA made up of?

Answer 22

Long polynucleotides

Question 23

What is RNA made up of?

Answer 23

Short polynucleotides

Question 24

What is different about RNA bases compared to DNA bases?

Answer 24

Uracil replaces thymine as a base

Question 25

What is the full name of RNA?

Answer 25

Ribonucleic acid

Question 26

What is the main function of RNA?

Answer 26

To transfer genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm

Question 27

Where do polynucleotides bond?

Answer 27

Between the phosphate group of 1 mononucleotide and the sugar group of another

Question 28

What is the by product of condensation reactions?

Answer 28

Water

Question 29

What type of bond forms between mononucleotides?

Answer 29

Phosphodiester

Question 30

How many polynucleotide strands make up DNA?

Answer 30

2 - double stranded

Question 31

How many polynucleotide strands make up RNA?

Answer 31

1 - single stranded

Question 32

How are the 2 polynucleotide strands in DNA joined?

Answer 32

Hydrogen bonds between bases

Question 33

Why are the 2 strands of DNA described as "antiparallel"?

Answer 33

They run in opposite directions

Question 34

Why do 2 DNA strands run in opposite directions? 2

Answer 34

- The hydrophilic phosphate groups are outside the molecule | - The hydrophobic bases lie within the molecule

Question 35

What is complimentary base pairing?

Answer 35

Each base can only join with one specific partner

Question 36

How do DNA bases join up?

Answer 36

Adenine to Thymine | Cytosine to Guanine

Question 37

How many hydrogen bonds form between A and T?

Answer 37

2

Question 38

How many hydrogen bonds form between C and G?

Answer 38

3

Question 39

How do the 2 antiparallel strands form a double helix?

Answer 39

They twist

Question 40

Why did scientists doubt DNA could carry genetic code?

Answer 40

It had a relatively simple chemical composition

Question 41

What did other scientists argue must carry genetic info and why?

Answer 41

Proteins - more chemically varied

Question 42

Define codon

Answer 42

Triplet of bases coding for a specific amino acid

Question 43

Define "gene mutation"

Answer 43

Changes to the base sequence of DNA during DNA replication

Question 44

List the types of gene mutation 5

Answer 44

- Insertion - Deletion - Substitution - Inversion - Duplication

Question 45

What is substitution?

Answer 45

When one base is swapped for another

Question 46

What is deletion and how is it a mutation?

Answer 46

- One base is removed - Causes a frame shift - Changes all following codons

Question 47

What is insertion?

Answer 47

An extra base is added

Question 48

What is duplication?

Answer 48

One/more bases is repeated

Question 49

What is inversion?

Answer 49

Sequence of bases is reversed

Question 50

What are the 3 theories of DNA replication?

Answer 50

- Fragmentation - Semi conservative replication - Conservative replication

Question 51

Explain the theory of fragmentation in DNA replication

Answer 51

Parent DNA breaks into segments and new nucleotides fill the gaps randomly

Question 52

Explain the theory of semi conservative DNA replication 3

Answer 52

- Parent DNA molecule separated into 2 strands - Each strand becomes a template for formation of complementary strand - 2 new daughter DNA molecules: 1/2 parent DNA 1/2 new DNA from nucleotides

Question 53

Explain the theory of conservative DNA replication 2

Answer 53

- Parent DNA molecule acts as template for new daughter molecule assembled from free nucleotides - Parent DNA is unchanged

Question 54

Explain how Meselson and Stahl proved semi conservative replication - 7

Answer 54

- Bacteria [E.coli] grown in medium of heavy 15n isotope - All bacterial DNA contains heavy nitrogen - Then fed on medium containing light 14n isotope - Allowed to replicate a few times - Bacterial DNA is extracted and centrifuged - Shows up in centrifuge tube as a band in the middle of the tube as DNA is half heavy and half light - After replicating twice, one intermediate band in the middle and one light band at the top - Some of the DNA is 1/2 heavy, 1/2 light and some is all light

Question 55

Explain DNA replication - 7

Answer 55

- DNA helicase unwinds DNA - By breaking hydrogen bonds between complementary bases - Forms 2 single strands - each original strand acts as template strand - New DNA nucleotides pair with complementary bases on template strand - DNA polymerase joins nucleotides together in condensation reaction by forming hydrogen bonds between the bases - There are now 4 DNA strands which wind back up to form 4 DNA helixes

Question 56

How is DNA antiparallel and why?

Answer 56

- Nucleotides arranged oppositely | - DNA polyermase is an enzyme whose active site only binds to nucleotides at 1 end

Question 57

How is DNA replication semi conservative?

Answer 57

Each new DNA molecule has one strand of original DNA and one stand of new nucleotides