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What is a phenotype determined by?

A phenotype is determined by proteins produced as a result of gene expression.

Only a fraction…

Only a fraction of the genes present in a cell are expressed.

What also influences phenotype?

Environmental factors also influence phenotype.

What does gene expression involve?

Gene expression involves transcription and translation of DNA sequences.

Describe the general structure of RNA.

RNA is made up of a single strand of nucleotides containing a ribose sugar, phosphate, and the bases adenine, cytosine, guanine, and uracil.

Describe the role of mRNA

Messenger RNA (mRNA) carries a copy of the DNA code from the nucleus to the ribosome.

Describe the role of rRNA

Ribosomal RNA (rRNA) and proteins form the ribosome

Describe the role of tRNA

Transfer RNA (tRNA) folds due to complementary base pairing and each tRNA molecule carries its specific amino acid to the ribosome.

What is the process of transcription?

RNA polymerase unwinds the DNA double helix and breaks the hydrogen bonds to expose the bases. Free RNA nucleotides are attracted to the exposed bases, and complementary base pairing takes place. Adjacent RNA nucleotides are joined by sugar-phosphate bonds to form a primary mRNA transcript.

How does RNA polymerase synthesise a primary transcript?

RNA polymerase moves along the DNA unwinding the double helix, breaking the hydrogen bonds between the bases and synthesising a primary transcript of RNA by complementary base pairing.

What is the meaning of the terms intron and exon?

Introns are non-coding regions of the primary transcript that are removed, while exons are coding regions that are joined together to form the mature transcript.

What is the process of RNA splicing?

RNA splicing forms a mature mRNA transcript by removing the introns and joining the exons together.

What is the structure of a tRNA molecule including anticodon site and an attachment site for a specific amino acid?

tRNA has three bases exposed called the anticodon and an amino acid attachment site.

What is the process of translation including the role of tRNA and ribosomes?

During the process of translation, mRNA attaches to a ribosome. A tRNA molecule carrying a specific amino acid arrives and aligns its anticodon to the mRNA codon using complementary base pairing. Peptide bonds form between amino acids to produce a polypeptide chain until a stop codon is reached.

Where are codons and anticodons found?

Codons are found on mRNA and anticodons are found on tRNA.

What are the bonds which hold amino acids together in a protein?

Amino acids are linked by peptide bonds.

What are the roles of start and stop codons?

Translation begins at a start codon and ends at a stop codon.

How can different proteins be expressed from one gene?

Different proteins can be expressed from one gene as a result of alternative RNA splicing.

What is the process of alternative splicing?

Different mature mRNA transcripts are produced from the same primary transcript depending on which exons are retained.

How are amino acids linked to form polypeptides?

Amino acids are linked by peptide bonds to form polypeptides.

Why do proteins have a wide range of functions?

Proteins have a large variety of structures and shapes resulting in a wide range of functions.

What gives a protein its final structure?

Polypeptide chains fold to give the final structure of the protein.

How are proteins held in a three-dimensional shape?

Proteins are held in a three-dimensional shape by peptide bonds, hydrogen bonds, and interactions between individual amino acids.

What is the meaning of the term mutation?

Mutations are changes in DNA.

What is the result of a mutation being expressed?

Mutations result in no protein or a faulty (altered) protein being expressed.

What are single gene mutations?

Single gene mutations involve the alteration of a DNA nucleotide sequence as a result of the substitution, insertion, or deletion of nucleotides.

What are the effects of single-nucleotide substitutions?

Substitutions include missense (replacing one amino acid codon with another), nonsense (replacing an amino acid with a premature stop codon), and splice-site mutations (which can alter the mature mRNA)

What are the effects of frame-shift mutations?

Nucleotide insertions or deletions result in frame-shift mutations where every amino acid on the protein after the point of mutations is altered.

What are the types of chromosome structure mutations?

Chromosome structure mutations include duplication (adding a section from a homologous partner), deletion (removing a section), inversion (reversing a section), and translocation (adding a section to a chromosome that is not its homologous partner)

Why are substantial changes in chromosome mutations often lethal?

Substantial changes in chromosome mutations often make them lethal.

How are genetic disorders caused?

Genetic disorders are caused by changes to genes or chromosomes that result in the proteins not being expressed or the proteins expressed not functioning correctly.