Nucleic Acids

Question 1

What is a nucleotide?

Answer 1

A molecule consisting of 5 carbon sugar and, a phosphate group and a nitrogenous base which form monomers of DNA and RNA

Question 2

What is the difference between RNA and DNA?

Answer 2

RNA has ribose sugar and DNA has deoxyribose sugar.

Question 3

What is a polynucleotide?

Answer 3

Large molecule containing lots of nucleotides.

Question 4

What are the 4 nitrogenous bases?

Answer 4

Adenine, Cytosine, Guanine and Thymine

Question 5

Explain the conservative replication theory.

Answer 5

A completely new double stranded copy of DNA is made so one daughter DNA molecule is new and has one parent strand.

Question 6

Is the conservative replication theory correct?

Answer 6

No.

Question 7

What is the semi conservative theory?

Answer 7

The DNA strands separate and each strand acts as a template so that both daughter DNA molecules have one new strand and one parent strand.

Question 8

Which nitrogenous bases pair together?

Answer 8

Adenine and Thymine

Cytosine and Guanine

Question 9

How many hydrogen bonds are between adenine and thymine?

Answer 9

2

Question 10

How many hydrogen bonds are between cytosine and guanine?

Answer 10

3

Question 11

Which of the nitrogenous bases are purines?

Answer 11

Adenine and Guanine.

Question 12

Which of the nitrogenous bases are pyrimidines?

Answer 12

Cytosine and Thymine.

Question 13

What is the difference between a pyrimidine and a purine?

Answer 13

Purine has 2 rings and pyrimidine has 1.

Question 14

Describe the structure of DNA.

Answer 14

Antiparallel strands

Phosphodiester bond between sugar and phosphate group

Question 15

What do hydrogen bonds allow?

Answer 15

The DNA to unzip

Question 16

Describe DNA in eukaryotic cells.

Answer 16

In nucleus

A loop of DNA in mitochondria

Question 17

Describe DNA in prokaryotic cells.

Answer 17

DNA is in a loop add in cytoplasm.

Question 18

What is DNA polymerase?

Answer 18

Joins new nucleotides on each of the new strands.

Question 19

What is DNA helicase?

Answer 19

Breaks hydrogen bonds to split the strands apart.

Question 20

What is DNA ligase?

Answer 20

Adds phosphate groups into any gaps on the sugar phosphate backbone on the DNA molecule.

Question 21

What are the steps of DNA replication?

Answer 21

1. DNA helicase breaks down hydrogen bonds which unzips the strands.
2. Free nucleotides are attracted to their complementary base pairs.
3. Each chain acts as a template.
4. Once in place the nucleotides are joined together by DNA polymerase making strong covalent bonds forming a backbone.

Question 22

What direction does DNA polymerase work in?

Answer 22

Only one.

Question 23

Describe ATP.

Answer 23

High energy bonds between phosphate groups.

Made in respiration and used as an energy currency within cell.

Question 24

Describe RNA.

Answer 24

3 forms: mRNA, tRNA and rRNA

Question 25

What does tRNA do?

Answer 25

Transfer, brings amino acids to ribosome.

Question 26

What does mRNA do?

Answer 26

Messenger, takes genetic code from the nucleus to ribosome.

Question 27

What does rRNA do?

Answer 27

Ribosomes are made of rRNA.

Question 28

What is Meselson and Stahl's evidence?

Answer 28

E. Coli grown on medium containing the heavy isotope of Nitrogen N15 for many generations, so all DNA contained heavy N. The bacteria was transferred to a medium containing the lighter isotope n14 for 1 or 2 or 3 generations. After 1,2,3 generations, the cells were killed, the DNA extracted and centrifuged. 15N DNA will sink further than 14N. The samples are visualized under UV light.

Question 29

What does universal mean?

Answer 29

That every known organism has DNA.

Question 30

What does non overlapping mean?

Answer 30

Same letter is not used in more than one different codon.

Question 31

What does degenerate mean?

Answer 31

Each amino acid can be coded for by more than one amino acid.

Question 32

How many possible codes are there?

Answer 32

64

Question 33

What is transcription?

Answer 33

A gene unzips and hydrogen bonds between bases break. mRNA passes out through nuclear envelope and attaches to ribosome.

Question 34

What is translation?

Answer 34

tRNA from the nucleus pass out into the cytoplasm. tRNA brings amino acids to find their place. A ribosome moves along mRNA which reads the code . mRNA breaks down.

Question 35

What does every protein start with?

Answer 35

Methionine.

Question 36

Uracil replaces what?

Answer 36

Thymine.

Question 37

What bases don't code (stop)?

Answer 37

UAA UAG UGA