1.4 DNA and protein synthesis

Question 1

What is a gene?

Answer 1

A sequence of bases on a DNA molecule that code for a sequence of amino acids in a polypeptide chain

Question 2

What is a gene mutation?

Answer 2

A change to at least one nucleotide base or the arrangement of the bases in DNA

Question 3

Coding DNA

Answer 3

The sections of DNA which code for proteins

Question 4

Non-coding DNA

Answer 4

The sections of DNA which do not code for proteins

Question 5

What are the purines?

Answer 5

A class of nitrogenous bases that are made up of two rings

Question 6

What are the pyrimidines?

Answer 6

A class of nitrogenous bases that are made up of a single ring

Question 7

What 2 bases are purine?

Answer 7

Adenine and guanine

Question 8

What 3 bases are pyrimidines?

Answer 8

Cytosine, thymine and uracil

Question 9

What does the term triplet describe in reference to genetic code?

Answer 9

The way that DNA is grouped into three base long codons that are read together and code for an amino acid

Question 10

What does the term non-overlapping describe in reference to genetic code?

Answer 10

The way that each base is only part of one codon and how each codon is read one at a time in order

Question 11

What does the term degenerate mean in reference to genetic code?

Answer 11

The way that some amino acids can be coded for by multiple different codons

Question 12

What is a deletion mutation?

Answer 12

A type of mutation where a nucleotide or multiple nucleotides are not incorporated into the DNA chain and are lost, resulting in a frameshift mutation

Question 13

What is an insertion mutation?

Answer 13

A type of mutation where an extra nucleotide or multiple extra nucleotides are incorporated into the growing DNA chain, resulting in a frameshift mutation

Question 14

What is a frameshift mutation?

Answer 14

A type of mutation where a nucleotide or multiple nucleotides are lost or added to a DNA chain, displacing all other nuceleotides downstream from the mutation and leading to an incorrect reading of them

Question 15

What is a substitution mutation?

Answer 15

A type of mutation where the incorrect nucleotide is incorporated into the growing DNA chain

Question 16

What is transcription and where does it occur?

Answer 16

It is the process of synthesising a new mRNA strand from a molecule of DNA and it occurs in the nucleus

Question 17

What is translation?

Answer 17

The process of protein synthesis where complementary tRNA strands carrying amino acids are brought to each codon in an mRNA molecule as it moves through a ribosome

Question 18

What is DNA?

Answer 18

A helical double stranded polymer made of deoxyribose monomers joined by phosphodiester bonds which contains genes that code for proteins

Question 19

What is an anti-sense strand?

Answer 19

The strand of DNA which is used as a complementary template and is used for complementary mRNA synthesis

Question 20

What is DNA helicase?

Answer 20

The enzyme that unzips the DNA helix by breaking the hydrogen bonds between the chains during DNA replication and transcription

Question 21

What is DNA polymerase?

Answer 21

The enzyme that catalyses the formation of phosphodiester bonds between nucleotides during the sysnthesis of a new DNA strand

Question 22

What is ligase?

Answer 22

The enzyme that joins Okazaki fragments on the lagging strang together by forming phosphodiester bonds between them

Question 23

What is messenger RNA (mRNA)

Answer 23

A type of single-stranded RNA molecule that carries genetic information from the DNA in the nucleus to the ribosomes for translation

Question 24

What are nucleotides?

Answer 24

The individual monomers that make up polynucleotides which are composed of a phosphate group, a pentose sugar and a nitrogenous base

Question 25

What are ribosomes and where are they found?

Answer 25

They are organelles that catalyse protein synthesis, and are found either free in the cytoplasm or as a part of the rough endoplasmic reticulum

Question 26

What is RNA polymerase?

Answer 26

An enzyme that catalyses the formation of phosphodiester bonds between nucleotides during the synthesis of a new RNA strand

Question 27

What is semi-conservative replication?

Answer 27

A type of DNA replication where each new molecule of DNA produced contains one original strand and one newly synthesised strand

Question 28

What is a sense strand?

Answer 28

The strand of DNA which is complementary to the anti-sense strand and is identical to the transcribed mRNA (with the exception of the sense strand containing thymine in the place of uracil)

Question 29

What is sickle cell anaemia?

Answer 29

A type of genetic disease which produces a faulty 'sickle shaped' haemoglobin due to a point mutation, causing a change in a single amino acid in the polypeptide sequence

Question 30

What is transfer RNA (tRNA)?

Answer 30

A type of RNA that has three hairpin loops, an anticodon for attachment to the mRNA codon and an amino acid binding site that is used to carry amino acids to the ribosome for translation

Question 31

What are the stop and start codons in a DNA strand?

Answer 31

The codons which either stop or start protein synthesis

Question 32

What does the term universal mean in reference to genetic code?

Answer 32

The way that the genetic code is the same in all organisms and species

Question 33

What are the 4 stages of DNA replication?

Answer 33

- DNA helicase catalyses the hydrogen bonds between the complimentary bases to be broken, unravelling the DNA helix - One of the strands is used as a template, where complimentary base pairing occurs between the template strand and free nucleotides - DNA polymerase catalyses adjacent nucleotides to be joined by phosphodiester bonds in condensation reactions - The new DNA molecules then automatically fold into double helices as hydrogen bonds are formed between the strands

Question 34

What are the 4 stages involved in transcription during protein synthesis?

Answer 34

- DNA helicase catalyses the hydrogen bonds between complimentary bases to be broken, unrevalling the DNA helix - One of the strands is used as a template (known as the anti-sense strand), where complimentary base pairing occurs between the template strand and free nucleotides - RNA polymerase catalyses adjacent nucleotides to be joined by phosphodiester bonds in condensation reactions, forming a molecule of mRNA - The newly made mRNA molecule then moves out of the cytoplasm through a nuclear pore and attaches to a ribosome in the cytoplasm ready for the translation stage of protein synthesis

Question 35

What are the stages involved in translation during protein synthesis?

Answer 35

- A tRNA molecule with a specific amino acid attached to its amino acid binding site binds to the mRNA via its anticodon - Hydrogen bonds form between the anticodon of the tRNA and the codon of the mRNA - A second tRNA molecule binds to the next codon of the mRNA and the two amino acids form a peptide bond - A third tRNA molecule joins the ribosome as the first one leaves - This process is repeated until the stop codon on the mRNA is reached, forming a completed polypeptide chain