DNA, genes and chromosomes Flashcards
differences between prokaryotic and eukaryotic DNA
eukaryotic
- linear
- associated with histones (makes it compact into chromosomes = chromatin)
prokaryotic
- shorter
- circular
- no proteins
DNA in chloroplasts and mitochondria
prokaryotic like
- circular
- no proteins associated
what is a gene?
sequence of amino acids that code for a particular polypeptide
or functional RNA
(multiple in a chromosome)
position of gene in chromosome called locus
what is a chromosome
long DNA molecule wrapped around histones
- contains multiple genes
sister chromatids - identical, contain same genes
- make up a chromosome
genome and proteome
complete set of genes in a cell
full range of proteins a cell is able to make
what are introns?
non coding sections of DNA
(don’t code for an amino acid)
within genes
removed in splicing
(non-coding multiplier repeats found between genes)
what is an allele?
different versions of the same gene
what is a homologous pair?
chromosomes of the same shape and size that contain the same genes
(could have different alleles, so not genetically identical)
alleles coding for same characteristic found on same locus on each
describe mRNA
single polynucleotide strand
- contains codons (3 bases) complementary to anticodon
made during transcription
carries genetic code from DNA to ribosomes for translation
describe tRNA
single polynucleotide strand, folded into a clover shape
- held by hydrogen bonds between specific bases
contains anticodon (3 bases) complementary to codon on mRNA
used in translation
- carries specific amino acids to ribosome (complementary to binding site)
steps to making a protein
transcription of DNA into pre-mRNA
in nucleus
pre-mRNA spliced to remove introns (only in eukaryotic as prokaryotic have no introns)
= mRNA
mRNA moves to ribosome to be translated
= amino acid chain
features of the genetic code (3)
non-overlapping
- each triplet read sequentially and separate
degenerate
- more than one base triplet can code for the same amino acid
universal
- same base triplets code for the same amino acids in all living organisms
similarities between prokaryotic and eukaryotic DNA
structure of nucleotides
- phosphate, deoxyribose and base
phosphodiester bonds
bases - A,T,C,G
what is a frame shift?
mutation has a knock on effect to bases along the polypeptide
changes how to triplets are read
= change to amino acid sequence
what is a silent mutation?
a mutation that doesn’t affect the sequence of amino acids
due to the degenerate nature
