topic 3 - genetics Flashcards
advantages of asexual reproduction
produces lots of offspring very quickly so it can colonise a new area quickly
only one parent needed so no need to wait for a mate, can reproduce when conditions r favourable e.g. lots of food
disadvantages of asexual reproduction
no genetic variation between offspring: if conditions of environment change, whole population may be affected
advantages of sexual reproduction
creates genetic variation within population - more likely at least some individuals will survive if environment changes
this can lead to natural selection and evolution as species become better adapted to new environment
disadvantages of sexual reproduction
takes more time and energy than asexual reproduction so organisms produce fewer offspring spring
two parents needed - problem if individuals are isolated
what are dna strands
polymers made up of lots of nucleotides
what do nucleotides consist of
one sugar molecule, one phosphate molecule and one base.
sugar and phosphate molecules in the nucleotide form a backbone to the DNA strands. they alternate
how are complementary base pairs joined together
by weak hydrogen bonds
DNA extraction practical
mash strawberries into a solution of detergent and salt
mix
detergent breaks down cell
membranes to release DNA
salt will make DNA stick together
filter mixture to get insoluble bits out
add ice cold ethanol as DNA is not soluble in cold ethanol and will come out the solution
DNA will appear as stringy white precipitate.
how do amino acids chains give proteins different shapes
they fold up
how do genes code for a particular protein
uses a different sequence of bases
explain transcription
DNA in nucleus can’t move out because it’s too big
so to get the DNA to the ribosome in the cytoplasm:
-mRNA nucleotides join together which is a template of the original DNA
-enzyme called RNA polymerase binds to non-coding DNA in front a gene
-two DNA strands unzip and RNA polymerase moves along one of the strands of DNA
-it uses the coding DNA in the gene as a template to make mRNA
-base pairing between DNA and RNA ensures mRNA is complementary to the gene
-mRNA molecule moves out of nucleus and joins with a ribosome
explain translation
amino acids brought to ribosome by tRNA
order of amino acids matches order of base triplets (codons) in mRNA
anticodon in tRNA is complementary to codon for amino acid
anticodon and codon pairing makes sure amino acid are brought to ribosome in correct order
animal acid joined together by ribosome which makes a polypeptide protein
what’s a mutation
a rare random change to an organism’s DNA base sequence
how does mutation affect RNA polymerase
if a mutation happens at the region of non-coding DNA in front of a gene, it can affect the ability of RNA polymerase being able to bind to it.
this will affect how much mRNA is being transcribed and therefore how much protein is produced.
therefore, phenotype may be affected depending on the function of the protein
what are alleles
different versions of the same gene
