Genetic information, variation and relationships between organisms Flashcards
explain DNA in prokaryotes
DNA molecules are short, circular and not associated with proteins.
explain DNA is eukaryotes
In the nucleus of eukaryotic cells, DNA molecules are very long, linear and associated with proteins, called histones.
explain DNA is mitochondria and chloroplasts
mitochondria and chloroplasts of eukaryotic cells also contain DNA which, like the DNA of prokaryotes, is short, circular and not associated with protein.
what does DNA code for
the amino acid sequence of a polypeptide and a functional RNA
where on a DNA molecule is a gene
a fixed position called the locus
what is a triplet
sequence of three DNA bases
what does a triplet code for
for a specific amino acid
what are the main features of triplet code
The genetic code is universal, non-overlapping and degenerate.
explain triplet code being degenerate
different codons to code for the same amino acid
explain triplet code being universal
the same codon will code for the same amino acid in every organism
explain triplet code being non overlapping
each codon is read separately to the next
what is an exon
an amino acid coding codon
what are introns
non amino acid coding sequence
what is transcription
the production of mRNA from DNA
explain the process of transcription
in the nucleus part of a dna molecule unwinds catalysed by helicase, This exposes the gene to be transcribed, A complementary copy of the code from the gene is made by mRNA, free RNA nucleotides pair up with hydrogen bonds, the deoxyribose phosphate backbone is bonded together by RNA polymerase, once the gene is transcribes the strand is spliced and the mRNA leaves via nuclear pores
what is the difference in transcription in eukaryotes and prokaryotes
In prokaryotes, transcription results directly in the production of mRNA from DNA.
In eukaryotes, transcription results in the production of pre-mRNA; this is then spliced to form mRNA.
what is translation
the production of polypeptides from the sequence of codons carried by mRNA.
explain the process of translation
occurs in the cytoplasm, After leaving the nucleus, the mRNA molecule attaches to a ribosome, tRNA molecule in the cytoplasm bond an amino acid on one end and has a specific anticodon on the other which binds the the complementary mRNA codon on the ribosome, two tRNA molecules attach to the ribosome at the same time and the two amino acids they carry form a peptide bond, energy in the form of ATP from mitochondria is required for this bond, this continues until a ‘stop’ codon is reached in an mRNA molecule. Finally a polypeptide chain is formed
What is a mutation
A change in the arrangement of bases in an individual gene or in the structure of the chromosome, which,can cause a change to the function of the protein
What is a point mutation
Changes in an individual gene due to miscopying one or more nucleotides
Explain deletion insertion and substitution
Removing, gaining or substituting a nucleotide
Explain the difference between missense, nonsense and silent point mutations
Missense-change in amino acid
Nonsense- codon changes to stop codon
Silent- doesn’t change amino acid (due to code being degenerate)
Explain a frameshift mutation
Deletion or insertion of nucleotides results in a frameshift (unless 3 nucleotides are deleted or inserted)
How can mutations effect enzymes
The primary structure (amino acid sequence) is changed which can change the rest of the protein structure, so eventually the active site of the enzyme
