B8 - DNA GENES PROTEIN SYNTHESIS

What is a gene

Section of DNA on a chromosome coding for one or more polypeptides

What is a gene locus

Particular position of the gene

What do genes code for

Amino acid sequence of a polypeptide or functional RNA

What do DNA molecules carry many of

Genes

How many amino acids are there

20

How many possible triplets code for 20 amino acids

64

Why is genetic code considered degenerate

Multiple triplets code for the same amino acids

Why is genetic code considered non overlapping

Each base in the sequence is only read once

Why is genetic code considered universal

Each triplet codes for the same amino acids in all organisms

What are stop codons 

Triplets that never code for an amino acid end the chain

What are non coding regions

Repeats of base sequences between genes

What are introns

Non coding regions within genes

What are exons

Coding regions within genes

Structure DNA in eucaryotes

Associated with histone proteins, long and linear

Structure of DNA inprocaryotes

Short, circular and not associated with histone proteins

What are homologous chromosomes

Pair of chromosomes that have the same gene loci and determine the same features 

What happens to chromosomes during meiosis 

Each daughter cell receives one chromosome from each half of the homologous pair

What is an allele

An alternative form of the gene

What is a genome

Complete set of genes in a cell

What is a proteome

Complete set of proteins in a cell

What happens when DNA is confined to the nucleus

Its transcribed onto a single stranded molecule called RNA

What is the role of mRNA

Transcribes DNA and can leave the nucleus

What does the m in mRNA stand for

Messenger

What is a codon

Sequence of three adjacent nucleotides in mRNA that codes for an amino acid

Structure of mRNA

Long strand, linear and single helix

Structure of tRNA

Small, clover shaped, amino acid binding site and the other end binds with anticodon

What happens in transcription

Pre mRNA is made which is the copy of the DNA strand

What is splicing

Process of pre mRNA becoming mRNA

What is translation

mRNA is used as a template, tRNA molecules attach and the amino acids they carry are linked to form a polypeptide 

What des RNA polymerase do during transcription 

Acts on a specific region of DNA causing the two strands to separate and one of them acts as a template strand

What happens to the template strand

Free DNA nucleotide bases pair up due to the complimentary base pairing rule 

How does RNA polymerase join the nucleotides to form pre MRNA

Moves along the strand

What happens when RNA polymerase reaches a stop codon 

It detaches itself 

What happens during splicing 

Introns are removed from the pre mRNA and the exons are joined together 

How does the mRNA leave

Through the nuclear pores

What is an anticodon

A triplet on a molecule of tRNA that is complimentary to particular codons on the mRNA molecule 

Where does the ribosome attach itself to when synthesising a polypeptide 

A start codon at one end of the mRNA molecule 

What helps tRNA to bind to the codon on the ribosome 

Its complimentary anticodon

What does the tRNA carry a specific thing of 

Amino Acid 

What happens when another tRNA molecule with a complimentary anticodon moves to the ribosome

It pairs with the codon and it carries another specific amino acid

What does the ribsosome do after being moved to by 2 tRNA molecules

It moves along the mRNA

How many tRNA molecules can bind to a ribosome at once

2

How are the two amino acids joined together

Using an enzyme and ATP which forms a peptide bond between them

When the ribosome reaches the third codon what happens to the first tRNA 

It is released and able to go collect a new amino acid and the process continues along the whole mRNA strand until the stop codon is reached 

What is the primary structure of a protein 

Sequence of amino acids 

What is a secondary structure of a protein

The polypeptide is either coiled to form an alpha helix or folded to create beta pleated sheets 

What is the tertiary structure of a protein

Determines the 3D structure or the shape of the molecule

What is the quaternary structure of a protein

Multiple polypeptide chains are joined together

What bonds hold together the primary structure of a protein 

Covalent peptide bonds due to a condensation reaction 

What bonds hold together the secondary structure of a protein 

Hydrogen bonds

What bonds hold together the tertiary structure of a protein 

Hydrogen bonds, ionic bonds and disulphide bridges

What bonds hold together the quaternary structure of a protein 

Hydrogen bonds, ionic bonds and disulphide bridges