DNA, Genes and Protein Synthesis

Question 1

What are the components of a nucleotide?

Answer 1

• pentose sugar
• inorganic phosphate ion
• nitrogenous base

Question 2

What is a gene?

Answer 2

A section of DNA/sequence of bases that codes for a specific polypeptide

Question 3

Why do genes determine our development and activity?

Answer 3

The polypeptides coded for by genes forms proteins and enzymes

Question 4

What is the locus of a gene?

Answer 4

The position of a gene on a chromosome

Question 5

What is the sequence of nucleotides to proteins?

Answer 5

Nucleotide -> gene -> amino acid sequence -> polypeptide -> protein

Question 6

What is a nucleotide a monomer of?

Answer 6

A monomer of DNA joined by phosphodiester bonds

Question 7

What are amino acids a monomer of?

Answer 7

Proteins

Question 8

What is the triplet code?

Answer 8

3 bases code for 1 amino acids a

Question 9

What 3 things that are true for all triplet codes?

Answer 9

Degenerate, universal and non-overlapping

Question 10

How is a triplet code degenerate?

Answer 10

Each amino acid may have more than 1 triplet code

Question 11

How is a triplet code universal?

Answer 11

Each triplet codes for the same amino acids in all organisms

Question 12

How are triplet codes non-overlapping?

Answer 12

Each base is read once and part of a singular triplet

Question 13

How does a gene code for the production of a polypeptide?

Answer 13

• specific nucleotide base sequence
• that are in triplets
• determine the sequence of amino acids
• specific sequence of amino acids codes for polypeptide

Question 14

What is the triplet code on mRNA?

Answer 14

A codon

Question 15

What are start codons?

Answer 15

Amino acids with 1 triplet ode and ensure base sequence is read in correct direction

Question 16

What are stop codons?

Answer 16

Amino acids that end the amino acid sequence

Question 17

What are introns?

Answer 17

Non-coding DNA

Question 18

What are exons?

Answer 18

Sequence in gene that codes for amino acids

Question 19

How could a changer in sequence of DNA bases result in a non-functional enzyme?

Answer 19

• change in amino acids sequence
• change in hydrogen/ionic/disulphide bonds which changes tertiary structure
• no E-S complexes formed

Question 20

What are the characteristics of DNA in prokaryotes?

Answer 20

• shorter DNA molecules
• not associated with proteins
• no chromosomes
• only exons

Question 21

What are the characteristics of DNA in eukaryotes?

Answer 21

• longer DNA strands
• linear
• associated with histone proteins
• have introns and exons

Question 22

What are the characteristics of DNA in chloroplasts/mitochondria?

Answer 22

• circular
• short
• no introns
• not associated with proteins

Question 23

What are the similarities between DNA in eukaryotes and prokaryotes?

Answer 23

• both are made of nucleotides
• both’s nucleotides are joined by phosphodiester bonds

Question 24

What are some differences between DNA in eukaryotes and prokaryotes?

Answer 24

• eukaryotic DNA is longer than prokaryotic
• eukaryotic DNA is associated with histone proteins whereas prokaryotic isn’t
• eukaryotic DNA has introns whereas prokaryotic doesn’t
• eukaryotic DNA is linear whereas prokaryotic is circular

Question 25

What is a chromosome?

Answer 25

A strand of DNA

Question 26

When are chromosomes visible?

Answer 26

During cell division

Question 27

What is a pair of homologous chromosomes?

Answer 27

Chromosomes that are identical (have same genes on same loci)

Question 28

What holds DNA in chromosomes together and are highly coiled around?

Answer 28

Histone proteins

Question 29

What is a nucleosome?

Answer 29

A DNA helix wound around 8 histone proteins

Question 30

How is a chromosome formed?

Answer 30

- DNA helix wound around 8 histone proteins making a nucleosome - DNA-histone complex - further looped and coiled into chromatin fibres - condensed further into a chromosome

Question 31

Describe how a mutation of a gene could cause a new allele to arise

Answer 31

- change in nucleotide sequence - different amino acid sequence - different polypeptide chain - different tertiary structure of protein

Question 32

What is a genome?

Answer 32

Complete set of genes in a cell including ones in mitochondria/chloroplast

Question 33

What is a proteome?

Answer 33

Complete set of proteins that is produced in the genome

Question 34

What are the 2 types of RNA?

Answer 34

- mRNA - tRNA

Question 35

What is mRNA?

Answer 35

A relatively short singular strand of nucleotides that form codons that is a copy of DNA

Question 36

Why is mRNA unstable?

Answer 36

It is only a single helix

Question 37

Why is mRNA a copy of DNA?

Answer 37

Acts as a template for protein synthesis

Question 38

What is tRNA?

Answer 38

Small single strand of DNA that is highly folded into a clover shape and forms hydrogen bonds between complementary bases

Question 39

What are the 2 specific site on tRNA?

Answer 39

- amino acid attachment site - anti codon

Question 40

What is the amino acid attachment site specific to?

Answer 40

Amino acids

Question 41

What is the anti codon complementary to?

Answer 41

A codon on the mRNA

Question 42

What are the 2 processes involved in coding for a protein?

Answer 42

Transcription and translation

Question 43

What is transcription?

Answer 43

Using DNA to make pre mRNA which is spliced to produce mRNA

Question 44

How is a strand of pre mRNA made?

Answer 44

- DNA helical hydrolyses hydrogen bonds between 12 base pairs - forming a template and sense strand - RNA polymerase uses complimentary free nucleotides to catalyse formation of pre mRNA strand (A with U/T and C with G) - phosphodiester bonds form between nucleotides

Question 45

What is splicing?

Answer 45

- removing introns - exons joining together

Question 46

Why does splicing only happen in eukaryotes?

Answer 46

Prokaryotes don’t have introns

Question 47

Why is splicing necessary?

Answer 47

To ensure the production of the correct polypeptide

Question 48

How does translation of mRNA occur?

Answer 48

- mRNA attaches to ribosome/RER - tRNA anticodons bind to complementary mRNA codons - tRNA brings a specific amino acid - 2 amino acids fit on tRNA - amino acids joined together by peptide bond using ATP - tRNA is released - the ribosome moves along the mRNA strand forming a polypeptide