8 DNA genes and protein synthesis Flashcards
what is a gene?
a section of DNA that codes for amino acid sequences
the genetic code is:
- non overlapping
- degenerate
- universal
what does degenerate mean?
more than one codon codes for an amino acid
what does non-overlapping mean?
each base belongs to only one codon or triplet
wha does universal mean?
the same 3 bases code for the same amino acid in all organisms
what are the non coding sequences called in DNA?
introns
what are the coding sequences called in DNA?
exons
state 3 differences between prokaryotic and eukaryotic DNA
prokaryotic:
- not associated with histones
- circular
- shorter
eukaryotic:
- associated with histones
- linear
- longer
describe mitochondrial and chloroplast DNA
- circular
- short
- not associated with histones
when are chromosomes visible?
when a cell is dividing (start of cell division)
what are the 2 threads of chromosomes called?
chromatids
what is the difference between an allele and a gene?
genes are particular characteristics that can exist in 2 or more different forms called alleles
what are 3 bases called in DNA?
triplet
what are 3 bases called in mRNA?
codon
what are 3 bases called in tRNA?
anti-codon
define genome
the complete set of genes in a cell including those from the mitochondria or chloroplast
define proteome
the complete set of proteins produced by the genome
what does RNA stand for?
ribonucleic acid
what is the structure of RNA?
- pentose ribose sugar
- phosphate group
- adenine, uracil, thymine or guanine
what are the two types of RNA important in protein synthesis?
tRNA and mRNA
describe the structure of a tRNa molecule
- amino acid binding site
- cloverleaf shape
what are 4 differences between mRNA and tRNA?
tRNA
- amino acid binding site
- anti-codon
- cloverleaf shape
- smaller molecule
mRNA
- no amino acid binding site
- codon
- linear
- larger molecule
what are the 2 stages of protein synthesis called?
transcription and translation
explain transcription
- DNA helicase unwinds DNA by breaking H bonds
- one strand of DNA acts as a template strand
- free RNA nucleotides join on the template strand by RNA polymerase (adenine to uracil and cytosine to guanine) and stops once it reaches the ‘stop triplet code’
- pre-MRNA spliced to remove introns
- mRNA leaves nucleus via nuclear pores
