topic 3 Flashcards
(39 cards)
advantages of asexual reproduction
rapid reproductive cycle - can produce lots of offspring quickly and colonise a new area quickly.
no need to find a mate- only one parent- can produce whenever conditions are favourable
disadvantages of asexual reproduction
no variation- If the conditions change the whole population will be affected
advantages of sexual reproduction
variation- if the conditions change it is more likely that some will survive
disadvantages fo sexual reproduction
need a mate- means they can produce fewer offspring, a problem for isolated individuals
what is the genome
all the DNA of an organism
found on 46 molecules of dna
each molecule is inside a chromosome
what is a gene
a section of a DNA molecule that codes for a specific protein
what is the meiosis process
the cell is diploid
the chromosome replicate and pairs stay attached forming 23 pairs
pairs separate into 2 cells
the cells divide again to make 4 cells
what are the products of meiosis
4 daughter cells
haploid
genetically different
what are the DNA bases
4 bases
A,T,C,G
A pairs with T and C pairs with G- complementary base pars
what is the structure of a nucleotide
each base is attached to a deoxyribose sugar and a phosphate
what is the structure of DNA
a molecule of DNA contains 2 strands coiled to form a double helix
the 2 strands are joined by bases and hydrogen bonds
what is the DNA code
everyone has a slight difference in genes caused by a different order of bases- this means DNA can be matched to specific people
what are hydrogen bonds
parts of bases are slightly charged, a slightly positive one attracts and slightly negative one.
this forms a weak force of attraction- a hydrogen bond
C and G form 3 bonds
A and T form 2 bonds
how does the order of bases affect the protein
the order of bases controls the order of amino acids.
each amino acid is coded for by a base triplet
the amino acid chains fold up to make a protein depending on the order of bases- this means each protein has a specific shape and so each protein has a specific function. this is why enzymes have a active site with a specific shape
how to extract DNA
dissolve salt in water and add washing up liquid- the washing up liquid breaks down the cell surface membranes around the nucleus and the salt makes the DNA more likely to clump
mash fruit, and then add to the solution and stir
put solution in a water bath for 15 min
filter the solution]add protease neixyme
tilt tube and pour ice cold ethanol down the side
a white precipitate should form
process of transcription
RNA polymerase attaches the DNA in-front of gene in a non coding region and separates the strands
it moves along the template strand adding complementary RNA nucleotides
U replaces T
the nucleotides link to form a strand of mRNA
process of translation
mRNA travels out of the nucleus through the nuclear pores and attached to a ribosome in the cytoplasm
a ribosome moves along the mRNA strand 3 bases at a time.
each 3 bases is a codon
at each mRNA codon a molecule of tRNA with complementary bases line up.
each tRNA molecules has an amino acid attached
as the ribosome moves along it joins up the amino acids forming a polypeptide chain
mutations in coding dna
if a mutation happens in a gene it produces an allele
the allele may code for a different sequence of amino acids which may change the shape of the protein and so its activity
this could end up changing the phenotype of an organism
mutations in non coding dna
before transcription RNA polymerase has to bind to a region of non coding DNA in front of a gene. if a mutation happens in this region it could affect the ability of the RNA polymerase to bind
how well it bind will affect how much mRNA is transcribed and therefore the amount of protein produced. depending on how much protein is produced it could affect the phenotype
laws of inheritance
each gamete receives only one factor for a characteristic
the version of a factor that a gamete receives is random
some versions of a factor are more powerful than others
what difficulties did Mendel have
people couldn’t see how factors could explain the many variation in characteristics or how it fitted with the theory of evolution
when chromosomes were discovered his work was understood
how do alleles affect characteristics
you have 2 copies of every gene
each copy may have a different allele
the different combination of alleles in each person gives us different characteristics as different genes control different characteristics
what is a chromosome
a structure found In the nucleus
each contains long molecule of DNA
what is homozygous
when both the alleles for an organism are the same
