Genes and Triplet Code

Question 1

What is a gene?

Answer 1

A gene is a section of DNA that contains the coded information for making polypeptides and functional RNA

Question 2

What is the coded information in genes present as?

Answer 2

• The coded information is in the form of a specific sequence of bases along the DNA molecule

Question 3

What do genes determine?

Answer 3

• Polypeptides make up proteins

* Genes determine the proteins of an organisms.

Question 4

What is the purpose of enzymes?

Answer 4

• Enzymes control chemical reactions, they are responsible for an organisms development andactivities

Question 5

What determines the nature and development of all organisms?

Answer 5

• Genes along with environmental factors determine:

Nature and development of all organisms.

Question 6

What is a locus?

Answer 6

Section of DNA located at a particular position, on a DNA molecule.

Question 7

What is the purpose of a gene?

Answer 7

Codes for:
• Amino acid sequence of a polypeptide
• or Functional RNA including ribosomal RNA and transfer RNA
One DNA molecule carries many genes

Question 8

How many bases are required for each amino acid?

Answer 8

3 Bases are required for each amino acid

Question 9

Why are three bases required for each amino acid?

Answer 9

• Only 20 different amino acids occur in proteins
• Each amino acid must have its own code of bases on the DNA
• Only four different bases are present in DNA
• If each base coded for a different amino acid, only four different amino acids could be coded for
• Using a pair of bases, 16 ( 4 ^ 2 ) different codes are possible, which is still inadequate
• Three bases produce 64 ( 4^3 ) different codes, more than enough to satisfy the requirements of 20 amino acids

Question 10

What is a triplet?

Answer 10

Code that has three bases for each amino acid, each one is called a triplet.

Question 11

What is degenerate code?

Answer 11

Called degenerate code because a single amino acid may be programmed for by more than one codon

Question 12

What does it mean for code to be overlapping?

Answer 12

Each base in the sequence is read only once

Question 13

How are amino acids evidence for evolution?

Answer 13

• Code is universal, with a few minor exceptions each triplet codes for the same amino acid in all organisms, this is evidence for evolution.

Question 14

What is the start of the DNA sequence that codes for polypeptide?

Answer 14

• Start of a DNA sequence that codes for a polypeptide is always the same triplet.

Question 15

What are some features of genetic code?

Answer 15

• A few amino acids are coded for by only a single triplet
• Remaining amino acids are coded for by between two and six triplets each
• The code is known as degenerate code because most acids are coded for by more than one triplet
• A triplet is always read in one particular direction along the DNA strand
• The start of a DNA sequence that codes for a polypeptide is always the same triplet
• Three triplets do not code for any amino acid, these are called stop codes and mark the end of a polypeptide chain
• Code is non overlapping, each base in a sequence is read only once
• Code is universal, with a few minor exceptions each triplet codes for the same amino acid in all organisms.

Question 16

What are exons?

Answer 16

Exons are sequences which code for amino acids.

Question 17

What are introns?

Answer 17

• parts which separate coding sequences

* These are non coding sequences

Question 18

What is a cells genome?

Answer 18

Complete cell set of genes in the cell

Question 19

What is a cell proteome?

Answer 19

Full range of proteins that the cell is able to produce