Genetics populations evolution and ecosystems
Genotype
genetic constitution make up of an organism
determines the limits within which characteristicsmay vary
Phenotype
appearancecharacteristicdue tointeractionsbetweengenotype environmen
Gene
a lengthof DNAthatcodes for the sequence ofaminoacids of a polypeptide
Allele
one of the different formsof a gene
Locus
position of a gene on a DNA molecule
Homologouschromosomes
chromoses occur in pairs in diploidorganisms calledhomologouschromosome
onechromose from each parent
2 loci each carry one allele of a gene
Homozygous
allele on each of thechromosomes is the same
Heterozygous
Salles on each of the twochromosomes is different
Dominant allele
alwaysexpressed in phenotype
Recessive allele
onlyexpressed in phenotype when homozygous12alles present
codominance
both alleles are expressedin phenotype
sex linked gene
gene located on one sex chromosome X or Y
1
, Monohybridinheritance themono
hybrid
inheritance of characteristicscontrolled byageing
Meengdgninevestigated
theanoffispbridnsghowingfrideh
punnettsquares usedto predict the characteristic in
e g if the dominant P allele produces purple
flowers and the recessive p allele produces
white flowers we can see that breeding two
heterozygous individuals will produce offspringwith
a 3 1 ratio of purple flowers to white flowers
statistical errors mean that ratio is not exactly 3 1
only one of each pairof alleles can be present
in a single gamete
Gamete
Dihybrid inheritance
looks at how 2charactersdetermined by two different genes located on
different chromosomes are inherited
need to write the the 2
2 alleles for different different traits in
every possible comabinrggtmionetrhe.gg ohdappear in the gamete
Egthiewiosdiibite heterozygotes
RIP gametes RBRb RB rb
phenotypes of offspring is in
the 9 3 3 1 ratio
if ratio is not a 3 3 1 then either
parents are not heterozygous or
alleles may be linked
codominance
neither of the alleles are recessive
influences phenotypic ratio of monohybrid and dihybrid crosses
Multiple alleles
a gene may have more than 2
alleles
human ABO blood groups
is an example of codominance
IA leads toproduction of
antigen A
1B leads to productionof
antigenB
is 10leads to productionof
neither antigen A or B
IA and 1B are dominant
10is recesstoboth laand113
I
Genotype
genetic constitution make up of an organism
determines the limits within which characteristicsmay vary
Phenotype
appearancecharacteristicdue tointeractionsbetweengenotype environmen
Gene
a lengthof DNAthatcodes for the sequence ofaminoacids of a polypeptide
Allele
one of the different formsof a gene
Locus
position of a gene on a DNA molecule
Homologouschromosomes
chromoses occur in pairs in diploidorganisms calledhomologouschromosome
onechromose from each parent
2 loci each carry one allele of a gene
Homozygous
allele on each of thechromosomes is the same
Heterozygous
Salles on each of the twochromosomes is different
Dominant allele
alwaysexpressed in phenotype
Recessive allele
onlyexpressed in phenotype when homozygous12alles present
codominance
both alleles are expressedin phenotype
sex linked gene
gene located on one sex chromosome X or Y
1
, Monohybridinheritance themono
hybrid
inheritance of characteristicscontrolled byageing
Meengdgninevestigated
theanoffispbridnsghowingfrideh
punnettsquares usedto predict the characteristic in
e g if the dominant P allele produces purple
flowers and the recessive p allele produces
white flowers we can see that breeding two
heterozygous individuals will produce offspringwith
a 3 1 ratio of purple flowers to white flowers
statistical errors mean that ratio is not exactly 3 1
only one of each pairof alleles can be present
in a single gamete
Gamete
Dihybrid inheritance
looks at how 2charactersdetermined by two different genes located on
different chromosomes are inherited
need to write the the 2
2 alleles for different different traits in
every possible comabinrggtmionetrhe.gg ohdappear in the gamete
Egthiewiosdiibite heterozygotes
RIP gametes RBRb RB rb
phenotypes of offspring is in
the 9 3 3 1 ratio
if ratio is not a 3 3 1 then either
parents are not heterozygous or
alleles may be linked
codominance
neither of the alleles are recessive
influences phenotypic ratio of monohybrid and dihybrid crosses
Multiple alleles
a gene may have more than 2
alleles
human ABO blood groups
is an example of codominance
IA leads toproduction of
antigen A
1B leads to productionof
antigenB
is 10leads to productionof
neither antigen A or B
IA and 1B are dominant
10is recesstoboth laand113
I
