storing and using genetic information Flashcards
what is a phenotype?
outward physical manifestation of organism
what is a genotype?
full genetic code of organism (even if not expressed)
entire DNA content
what determines protein function?
protein structure
what are the four different bases in DNA?
A
T
G
C
what sugar is used in DNA monomers?
2-deoxyribose
what is the difference between 2-deoxyribose and ribose sugars?
in ribose sugar there is an OH group on the 2’ carbon as opposed to an H in 2-deoxyribose
what direction do the polynucleotide chains run in in relation to each other?
anti parallel
what bases bind to each other?
A - T (or uracil in RNA)
C-G
where does replication of DNA and the first steps in decoding it for protein production take place?
nucleus
what is the DNA molecule packaged into in the nucleus?
chromosomes
what is a chromosome?
single piece of DNA containing many genes, regulatory elements and other nucleotide sequences
what is DNA wrapped around in order to shorter its length?
histones
what is chromatin?
mixture of DNA, proteins and RNA that package DNA within the nucleus
what are the two forms of chromatin?
heterochromatin (inactive)
euchromatin (active)
why does banding occur in chromosome?
due to different densities of packaged DNA
why does the cell have to copy its DNA completely in order to divide?
so that both daughter cells have a full set of chromosomes
why does the DNA helix have to separate before it can be replicated?
to allow enzymes access to the DNA template
what are the two major mechanisms by which chromatin is made more accessible?
histones can be enzymatically modified
histones can be displaced by chromatin remodeling complexes
what is semi conservative copying?
one half of each new DNA molecule is new and one is old
what is bi-directional replication?
replication in 2 directions
what direction is DNA replicated in?
5’ end to 3’ end
how much of the human genome codes for proteins?
less than 2%
what are introns?
non coding regions
what are exons?
coding regions
what is a codon?
set of 3 bases
what does each codon specify?
a particular amino acid
how many codons are there?
64
how many amino acids are found in proteins?
20
whar is the initiation codon?
methionine
what mutation occurs in sickle cell anaemia?
glutamate is substituted for valine, (GAA or GAG becomes GUA or GUG)
what is the role of RNA?
participate in protein synthesis
what does mRNA carry?
information for protein synthesis
what is alternative splicing?
process by which the exons of RNA produced by transcription of a gene are reconnected in multiple ways - means one gene can code for multiple proteins
what is the purpose of a stop codon?
prevents the wrong protein being synthesised
what is the open reading frame?
set of codons that run continuously and are bounded by a start/initiation codon and a termination codon
what is the role of tRNA?
translate mRNA sequence into amino acid sequence - brings proteins to ribosomes
what does rRNA do?
combines with proteins to form a ribosome
what is a polysome?
several ribosomes translating mRNA at one time.
