nucleotides and nucleic acids

Question 1

What is a nucleotide?

Answer 1

A molecule that is the basic building block of the nucleic acids DNA and RNA

Question 2

What is a phosphodiester bond?

Answer 2

A bond that forms between the phosphate group of one nucleotide and the pentose sugar of the next nucleotide in a condensation reaction

Question 3

Complementary base pairing

Answer 3

Arrangement of nitrogenous bases.
Adenine and Thymine are held together by 2 hydrogen bonds. Guanine and Cytosine are held together by 3 hydrogen bonds

Question 4

What is a purine and give examples.

Answer 4

A large, double ring structure
Adenine and Guanine

Question 5

What is a pyrimidine and give examples.

Answer 5

They are smaller and have a single ring structure
Thymine, Cytosine and Uracil

Question 6

What does DNA stand for?

Answer 6

Deoxyribonucleic acid

Question 7

What is the function of DNA?

Answer 7

DNA contains the instructions needed to make proteins

Question 8

DNA

Answer 8

DNA must be able to replicate itself

DNA must be able to store genetic information in a stable form, providing the instructions on how to make proteins

DNA must be capable of mutation

Question 9

What is DNA made up of?

Answer 9

DNA is a polymer, made up of millions of monomers called nucleotides

Question 10

What is the structure of DNA?

Answer 10

•A pentose sugar (deoxyribose), a phosphate group and a nitrogenous base (A, G, T, C)

•2 polynucleotide strands that are antiparallel to each other to form a double helix

Question 11

What is a polynucleotide chain?

Answer 11

A chain of nucleotides joined together by phosphodiester bonds made as a result of condensation reactions

Question 12

How does a condensation reaction occur?

Answer 12

The reaction occurs between the OH of the phosphate group of one nucleotide and the OH group on the pentose sugar of another nucleotide

Question 13

What is a sugar-phosphate backbone and what does it do?

Answer 13

A chain of phosphates and sugars that protects coding bases on the inside of the helix

Question 14

What bases bind together in complementary base pairing?

Answer 14

•A smaller pyrimidine one base always binds to a larger purine base

•This arrangement maintains a constant distance between the two sugar-phosphate backbones

Question 15

What does RNA stand for?

Answer 15

Ribonucleic acid

Question 16

What does RNA do?

Answer 16

Transfers genetic information from the DNA to proteins (ribosomes) that make enzymes and tissues in the body

Question 17

What is the structure of RNA?

Answer 17

A phosphate group, a pentose sugar (ribose) and a nitrogenous base (Adenine, Uracil, Guanine or Cytosine)

Question 18

How many strands does RNA have?

Answer 18

RNA is single stranded, this strand is much shorter than DNA strands

Question 19

What is the mnemonic for nitrogenous bases?

Answer 19

Apples (Adenine) in the Trees (Thymine).
Cars (Cytosine) in the Garage (Guanine)

Question 20

What is a gene?

Answer 20

A gene is a small section of DNA that contains the complete sequence of bases to code for a protein

Question 21

How many strands does DNA have?

Answer 21

DNA is double stranded, one strand is called the TEMPLATE strand and the other strand is called the CODING strand

Question 22

What is a DNA triplet?

Answer 22

Each DNA triplet codes for a specific amino acid

Question 23

What is an allele?

Answer 23

An allele is a version of a gene

Question 24

Why is the genetic code needed?

Answer 24

DNA molecules are incredibly long and must be tightly packed so they are unable to leave the nuclear pore

Question 25

What does a chromatin do?

Answer 25

A chromatin helps pack the DNA into chromosomes. Each chromosome contains just a single molecule of DNA

Question 26

What is a histone?

Answer 26

A protein that packages DNA

Question 27

How is the genetic code read?

Answer 27

The genetic code is read from the first codon until a stop codon is reached

Question 28

What is always at the start of every genetic code?

Answer 28

Methionine

Question 29

When does a genetic code end?

Answer 29

When a stop codon is reached

Question 30

What does the sequence of bases determine?

Answer 30

The sequence of bases on one of the strands determines the sequence of amino acids in a polypeptide chain

Question 31

What happens in transcription?

Answer 31

DNA is unable to leave the nucleus so to make a protein, the gene that codes for it must be copied which is the process called transcription

Question 32

What is a product of transcription?

Answer 32

mRNA

Question 33

What enzymes are used in transcription?

Answer 33

DNA helicase and RNA polymerase

Question 34

What is translation?

Answer 34

To decode/translate the mRNA using tRNA

Question 35

What is tRNA?

Answer 35

Transfer RNA in translation

Question 36

What is the structure of tRNA?

Answer 36

•tRNA is a single strand, folded into a clover shape (all similar lengths). •tRNA has a specific amino acid attached with an anticodon on the opposite end

Question 37

What does translation produce?

Answer 37

A polypeptide chain

Question 38

Transcription

Answer 38

• DNA can’t leave the nucleus and so the DNA unwinds in the region of the gene and hydrogen bonds are broken • RNA nucleotides line up by complementary base pairing opposite the exposed bases on the template strand of the DNA • RNA polymerase joins nucleotides together by a condensation reaction to form a phosphodiester bond. A molecule of mRNA is made. • The mRNA leaves the nucleus via a nuclear pore and becomes attached to a ribosome • The ribosome exposes the first two codons on the mRNA • tRNA molecules bring a specific amino acid to the ribosome • The codon on the mRNA the anticodon on the tRNA join up by complementary base pairing • There is a condensation reaction and a peptide bond forms between the first two amino acids (catalysed by the enzyme peptidyl transferase) • The first tRNA molecules detaches and the mRNA moves through the ribosome, exposing the next codon • The process continues as more tRNA molecules bring specific amino acids to be added to the growing polypeptide chain • Thus, it is the sequence of bases in the DNA that determines the sequence of amino acids in the primary structure of a protein

Question 39

Why is DNA replication semi-conservative?

Answer 39

It is semi- conservative as one strand is an old strand (the template strand) and the other is a new strand

Question 40

DNA replication

Answer 40

• DNA helicase unzips DNA (separates 2 strands) by breaking the hydrogen bonds between complimentary base pairs • Free DNA nucleotides are attracted to exposed bases by complementary base pairs • Free nucleotides are joined together through phosphodiester bonds by DNA polymerase - form sugar- phosphate backbone of new DNA strand • A new strand and old strand form a replication in a semi-conservative process