DNA Unit Test

Question 1

What does DNA stand for?

Answer 1

Deoxyribonucleic acid

Question 2

Who was credited for the discovery of the structure of DNA?

Answer 2

Francis Crick and James Watson (largely work of Rosalind Franklin)

Question 3

What did Rosalind Franklin use to discover what DNA was made of?

Answer 3

X-Ray photograph of DNA crystal

Question 4

What are the basic units that are make up DNA?

Answer 4

Nucleotides (phosphate group, nitrogenous base and the carbon sugar (deoxyribose)

Question 5

What are the 4 different nitrogenous bases?

Answer 5

Adenine, Guanine, Thymine and Cytosine

Question 6

What are purines?

Answer 6

Double ringed structures; adenine and guanine

Question 7

What are pyrimidines?

Answer 7

Single ringed structures; thymine and cytosine

Question 8

What is Chargaffs Rule?

Answer 8

Thymine pairs with adenine

Cytosine pairs with guanine

Question 9

What holds together DNA?

Answer 9

Held by hydrogen bonds

Question 10

How many hydrogen bonds is between A-T

Answer 10

2 (less complex bc count letters)

Question 11

How many hydrogen bonds is between cytosine and guanine?

Answer 11

3 hydrogen bonds

Question 12

What does 5’ to 3’ mean?

Answer 12

Fifth carbon in deoxyribose point upward in one strand and downward in the other

Question 12

What does 5’ to 3’ mean?

Answer 12

Fifth carbon in deoxyribose point upward in one strand and downward in the other

Question 13

How many base pairs are in DNA approx?

Answer 13

6 billion base pairs long

Question 14

How does DNA fit the massive info in each cell?

Answer 14

DNA is coiled upon itself to form chromosomes

Question 15

How does DNA coil upon itself?

Answer 15

Histones (+ charged proteins) act as “spools” on which DNA molecule coils

Question 16

What is a chromatin fibre?

Answer 16

Nucleosomes coil upon themselves

Question 17

How does DNA replicate?

Answer 17

Free-floating nucleotides in nucleus are assembled into a copy of parental DNA

Question 18

What are the 2 models of DNA replication?

Answer 18

• conservative replication
• semi-conservative replication

Question 19

What is conservative replication?

Answer 19

• one daughter DNA molecule is constructed entirely from free floating nucleotides
• parental DNA molecule remains unchanged (conserved)

Question 20

What is semi-conservative replication?

Answer 20

• each daughter dna molecule has one strand of parental nucleotides and one stand made from free-floating nucleotides
• half the parental material is conserved in each daughter DNA molecule (semi-conserved)

Question 21

How did they prove semi-conservative?

Answer 21

Matthew Meselson and Franklin Stahl performed an experiment
- they used cultures of e. Coli that we’re given nutrients containing either “heavy” nitrogen 15N or a more common isotope 14N

Question 22

What are the steps of the Meselson-Stahl Experiment?

Answer 22

1. Grow e.coli in presence of 15N only (parental)
2. Take parental bacteria and allow then to reproduce in presence of 14N (gen 1)
   3 Take gen 1 bacteria and allow them to reproduce in presence of 14N only (gen 2)

Shows that DNA is semi conservative takes half from parent and half from free floating nucleotides

Question 23

What is the correct version of DNA replication?

Answer 23

Semi conservative

Question 24

What needs to happen before DNA replication?

Answer 24

-b4 it can occur highly coiled and condensed DNA molecule must be “straightened” into linear sequence of nucleotides - enzymes serve this function

Question 25

Go over DNA replication

Answer 25

Look at test or notes

Question 26

What way does DNA build?

Answer 26

5’ to 3’

Question 27

What is the central dogma of genetics?

Answer 27

DNA stored genetic code necessary for synthesizing all the different proteins in our body

Question 28

What are genes?

Answer 28

Each protein coded for by specific segment of DNA (coded info)

Question 29

Where is DNA found and where does it go?

Answer 29

DNA is found in nucleus and proteins are constructed by ribosomes in cytoplasm

Question 30

How do instructions get from nucleus to ribosomes?

Answer 30

Make mRNA which moves out of nucleus into cytoplasm to make copies

Question 31

What is the code of DNA made into

Answer 31

mRNA (messenger RNA) - Ribosomes can translate the code into a protein - mRNA moves into cytoplasm (takes the code) and delivers it to meet ribosome

Question 32

What 2 steps does protein synthesis occur in?

Answer 32

- Transcription - Translation

Question 33

How do you read DNA?

Answer 33

3’ to 5’ build from 5’ to 3’

Question 34

What 3 steps does transcription occur in?

Answer 34

Step 1: Initiation - begins “upstream” of gene, at a promoter region Step 2: Elongation - DNA is unwound, exposing template strand at beginning of gene - RNA polymerase synthesizes mRNA molecule in 5’ to 3’ direction, through complimentary base pairing with DNA template Step 3: - RNA polymerase reaches end of gene and encounters termination sequence - RNA synthesis stops - mRNA and RNA polymerase

Question 35

What is a promoter?

Answer 35

Is a specific sequence of DNA nucleotide that RNA polymerase can recognize and bind to

Question 36

What is post-transcriptional modification?

Answer 36

mRNA is modified in 3 ways before it leaves the nucleus 1. 5’ cap (seven methyl guanosine ribonucleotide is added to 5’ end of mRNA- helped mRNA attach to the ribosome during translation) and helps to protect 2. Poly-A-Tail: string of about 50-259 adenine ribonucleotides are added to 3’ end of mRNA- protects the mRNA from RNA digesting enzymes in the cytoplasm 3. Introns are removed: mRNA strand made of sections that code for specific protein (exons) and those that don’t (introns) Proteins called spliceosomes “cut out” introns, leaving on ur one

Question 37

What are spliceosomes?

Answer 37

Proteins that count out introns as they are not important

Question 38

How many and what types of RNA does translation require?

Answer 38

mRNA: copy of instructions for constructing a specific protein tRNA: delivers individual amino acids to ribosome for construction of protein rRNA: ribosomes consist of 2 subunits: each is a combo of rRNA and protein

Question 39

What is the structure of tRNA?

Answer 39

- single stranded and double stranded sections - unique anticodon Anticodon: 3 nucleotide segment that corresponds to codon on mRNA - Carries a specific amino acid

Question 40

Do all codons make amino acids?

Answer 40

No, 61/64 codons specify an amino acid 3 are stop codons

Question 41

What is the wobble hypothesis?

Answer 41

Pairing of the anticodon with first two nucleotides of the codon is always precise, but there is flexibility in pairing with the third nucleotide of the codon

Question 42

What are the 3 steps of Translation?

Answer 42

Step 1: Initiation - tRNA with anticodon that corresponds to AUG brings met and forms a complex with small ribosomal subunit - complex binds to 5’ end of mRNA and scans along until it reaches AUG start codon - Large ribosomal subunit binds to complete ribosomes Step 2: Elongation - Ribosomes move along mRNA reading codons - tRNA continues to deleiver amino acids to ribosome - Peptide bonds form between amino acids - Empty tRNA released - Polypeptide chain folds into specific 3D shape Step 3: Termination - Occurs when a stop codon is read by a ribosome - Ribosomal subunits seperate, tRNA and polypeptide chain released