Topic 4 - Genetic information, variation and organism relationships Flashcards
what are the similarities between DNA in eukaryotic cells with DNA in prokaryotic cells
- nucleotide structure is identical: deoxyribose attached to phosphate and a base
- adjacent nucleotides joined by phosphodiester bonds, complementary bonds joined by hydrogen bonds
- DNA in mitochondria/chloroplasts have similar structure to DNA in prokaryotes: short, circular, not associated with proteins
what are the differences between DNA in eukarotiyc and prokaryotic cells
- eukaryotic DNA is longer
- eukaroytic DNA is linear, prokaryotic DNA is circular
- eukaroyitc DNA is associated with histone proteins, prokaryotice DNA isn’t
- eukaryotic DNA contain introns, prokaryotic DNA doesn’t
what is a chromosome
long linear DNA and is asssociated with histone proteins found in the nucleus of eukaryotic cells
what is a gene
a sequence of DNA (nucleotide) bases that code for:
- the amino acid sequence of a polypeptide
or
- a functional RNA e.g. ribosomal RNA or tRNA
what is a locus
the fixed position a gene occupies on a particular DNA molecule
describe the nature of the genetic code
triplet code, universal, non-overlapping, degenerate
what does triplet code mean
a sequence of 3 DNA bases, called a triplet, codes for a specific amino acid
what does universal mean
the same base triplets code for the same amino acids in all organisms
what does non-overlapping mean
each base is part of only one triplet so each triplet is read as a discrete unit
what does degenerate mean
an amino acid that can be coded for by more than one base triplet
where are non coding bases sequences found
- btwn genes e.g. non coding multiple repeats
- w/n genes - introns
fact
in eukaryotes, much of the nuclear DNA doesn’t code for polypeptides
what are introns
base sequence of a gene that doesn’t code for amino acids in eukaryotic cells
what are exons
base sequence of a gene coding for amino acid sequences
define genome
the complet set of genes in a cell incl. those in mitochondria and/or chloroplasts
define proteome
the full range of proteins that a cell can produce coded for by the cell’s DNA/genome
what are the two stages of protein synthesis
transcription and translation
describe transcription
production of mRNA from DNA in the nucleus
describe translation
production of polypeptides from the sequence of codons carried by mRNA at ribosomes
what is the similarity btwn tRNA and mRNA
both single polynucleotide strand
what are the differences btwn tRNA and mRNA
- tRNA is folded into a clover leaf shape whereas mRNA is linear/straight
- tRNA has hydrogen bonds btwn paired bases, mRNA doesn’t
- tRNA is a shorter, fixed length whereas mRNA is a longer, variable length (more nucleotides)
- tRNA has an anticodon, mRNA has codons
- tRNA has an amino binding site, mRNA doesn’t
describe how mRNA is formed by transcrription in eukaryotic cells
- hydrogen bonds btwn DNA bases break
- only one DNA strand acts as a template
- free RNA nucleotides align next to their complementary bases on the template strand. in RNA uracil is used instnead of thymine
- RNA polymerase joins adjacent RNA nucleotides
- this forms phosphodiester bonds via condensation reactions
- pre-mRNA is formed and this is spliced to remove introns forming mature mRNA
describe how production of mRNA in eukaryotic cell is different from the production of mRNA in a prokaryotic cell
- pre-mRNA is produced in eukaryotic cells whereas mRNA is produced directly in prokaryotic cells
- genes in prokaryotic cells don’t contain introns so no splicing in prokaryotic cells