chapter 8 Flashcards
gene
a selection of DNA that contains a code for making of polypeptide and functional RNA
allele
a different form of the same gene
homologous pair of chromosome
pair of chromosome with the same genes but different alleles
locus
location of particular gene on a chromosome
start codon
at the start of every gene there are three bases which help initiate translation
stop codon
causes ribosomes to detach and therefore stop translation
genome
an organisms complete set of DNA in one cell
proteome
the full range of proteins a cell can produce
compare DNA in a eukaryote and a prokaryote
similarities:
- nucleotide structure is identical
- nucleotides joined by a phosphodiester bond
- DNA in mitochondria/ chloroplast have similar structure to DNA
contrast:
- eukaryotic DNA is longer
- eukaryotic DNA contains introns, prokaryotes doesn’t
- eukaryotic DNA is linear, prokaryotic is circular
compare DNA in the nucleus and chloroplast
in chloroplast:
-DNA is shorter
-DNA is circular
-fewer genes
-not associated with proteins
- introns are absent
features of the genetic code
- DEGENERATE:
more than one codon/triplet codes for the same amino acid
-UNIVERSAL:
the same triplet codes for the same amino acids in all organisms
-NON-OVERLAPING:
each base is part of only one triplet
-STOP+START CODONS
-INTRONS+EXONS
what is a codon
a triplet of bases on mRNA that codes for amino acids
difference between exon and introns
exon- coding section of DNA
intron - non-coding section of DNA
mRNA structure
mRNA is a single-stranded molecule
It is made up of a sugar-phosphate backbone and exposed unpaired bases
Uracil bases are present instead of thymine bases (which are found in DNA)
tRNA structure
tRNA is a single-stranded molecule
It has a sugar-phosphate backbone
It has a folded shape
There are hydrogen bonds between some of the complementary bases
Amino acids bind to a specific region of the molecule
The specific anticodon found on the tRNA molecule is complementary to a specific codon on an mRNA molecule
transcription
-The DNA helix unwinds to expose the bases to act as a
template.
-Only one chain of the DNA acts as a template.
-The unwinding is catalyzed by DNA helicase. DNA
helicase breaks the hydrogen bonds between bases.
-Free mRNA nucleotides in the nucleus align opposite
exposed complementary DNA bases.
-The enzyme RNA polymerase bonds together the RNA
nucleotides to create a new RNA polymer chain. One
entire gene is copied.
translation
-mRNA attaches to a ribosome in the cytoplasm. The
ribosome attaches at the start codon.
-The tRNA molecule with the complementary
anticodon to the start codon aligns opposite the
mRNA, which is held in place by the ribosome.
-The ribosome will move along the mRNA molecule to
enable another complementary tRNA to attach to the
next codon on the mRNA.
-The two amino acids that have been delivered by the
tRNA molecule are joined by a peptide bond. This is
catalysed by an enzyme and requires ATP.
- ribosome reaches the stop codon at the end of the mRNA molecule. The stop codon does not code for an amino acid and therefore the ribosome detaches and translation ends.
protein associated with DNA in a chromosome
histone
non-coding base sequence
DNA that does not code for amino acid sequence
positioned between genes
