Genetic info Flashcards
Gene
a section of DNA that contains a
code for making a polypeptide
and functional RNA
locus
the location of a particular gene on a chromosome
allele
a different version of the same gene
chromosome
threadlike structure
composed of tightly coiled DNA
wrapped around histones (if it
is a eukaryotic cell)
homologous chromosome
a pair of chromosomes that have the same genes
therefore, they are the same size
eukaryotic DNA
DNA is stored as chromosomes inside the nucleus
linear chromosomes
DNA is tightly coiled and wrapped around proteins called histones
prokaryotic DNA
DNA molecules are shorter and circular
DNA is not wound around histones. Instead, it supercoils to fit in the cell
codon
3 bases on mRNA that code for an amino acid
start codon
3 bases at the start of an mRNA sequence which help to initiate
translation
stop codon
3 bases at the end of every gene that do not code for an amino acid
this causes ribosomes to detach
and therefore stops translation
genetic code
an amino acid is coded for by 3 DNA bases which are described
as the “triplet code”
what is meant by the genetic code is degenerate
each amino acid is coded for by
more than one triplet of bases
what is the advantage of the genetic code being degenerate
if a substitution mutation occurs, the new triplet of bases may still code for the same amino acid
therefore the mutation will have
no impact on the final protein
produced
what is the advantage of the genetic code being universal
genetic engineering is possible a human gene can be inserted into another organism
e.g human gene for insulin
inserted into bacteria to make
insulin
what is the advantage of the genetic code being non-overlapping
if a point mutation occurs, it will only affect one codon and therefore one amino acid
triplet code
an amino acid is coded for by 3
bases
mutation
a change in the DNA
can be a gene or chromosome
mutation
what is meant by the genetic code is universal
the same triplet of bases codes
for the same amino acid in all
organisms
what is meant by the genetic code is non-overlapping
each base in a gene is only part of one triplet of bases that
codes for one amino acid therefore each codon is read as a discrete unit
introns
non-coding sequence of DNA
exons
sequence of DNA that code for amino acids
what is splicing
post transcription modification
removing introns
genome
the complete set of genes in a cell
proteome
The full range of proteins that a
cell is able to produce
anticodon
3 bases on the tRNA which are
complementary to the codon on
mRNA.
mRNA structure
single-stranded
made up of codons
a copy of one gene
tRNA structure
single-stranded, folded to create a cloverleaf shape
held in place by hydrogen bonds
has an anticodon and amino
acid binding site
mRNA function
a copy of a gene from DNA
created in the nucleus, and it then leaves the nucleus
to carry the copy of the genetic
code of one gene to a ribosome
in the cytoplasm
tRNA function
a specific amino attaches at the binding site
transfers this amino acid to the ribosome to create the polypeptide chain
transcription
the first stage in protein synthesis
one gene in DNA is copied into mRNA
occurs in the nucleus
translation
the second stage in protein synthesis
the polypeptide chain is created using both the mRNA
base sequence and the tRNA occurs on ribosomes in the cytoplasm
which enzymes are involved in transcription
DNA helicase
RNA polymerase
DNA helicase
catalyses the breaking of hydrogen bonds between the two strands of DNA
RNA polymerase
joins adjacent RNA nucleotides together
forming a phosphodiester bond
pre-mRNA
mRNA in eukaryotes that still contain the introns
How is pre-mRNA modified
the introns are removed by a protein called a spliceosome
this leaves just the exons
what is ATP used for in translation
forming the peptide bond between amino acids
Compare the DNA in the mitochondria/ chloroplast to prokaryotic DNA
the DNA is similar to prokaryotic DNA, in that it is:
short
circular
not histone bound
How does transcription differ between prokaryotes and eukaryotes
Transcription in prokaryotic
organisms results in mRNA
that requires no modification
because prokaryotic DNA does
not contain any introns
eukaryotic transcription results
in pre-mRNA that needs introns
removed
What is the role of ribosomes in translation
it holds two tRNA molecules
to enable peptide bonds to form
between the amino acids
What is the role of tRNA in translation
it carries a specific amino acid anticodons align opposite
complementary codons on the
mRNA
