Please enable JavaScript.
Coggle requires JavaScript to display documents.
Thwin_Grace_Block5_MM9_PatternsOfInheritance (Mendelian laws (Punnett…
Thwin_Grace_Block5_MM9_PatternsOfInheritance
Mendelian laws
The law of segregation
alleles for the same gene will separate into different gametes
The law of independent assortment
alleles for different genes will separate without being affect by the placement of an allele of a different gene
may be broken when genes are linked
linked genes means they are on the same chromosome
parental classes are offspring with phenotypes whose linked genes did not cross over
recombinant classes are offspring with phenotypes whose linked genes did crossover, making them the most frequent class
double crossover classes are offspring with phenotypes whose genes crossed over twice, making them the least frequent class
the closer the genes are to each other, the more probability they will break the law by sorting dependently
Punnett squares
allow you to find the possible genotypes of the offspring and the ratio of their occurrence
uses genotype son parents for monohybrid crosses
uses genotypes of parents' gametes for dihybrid crosses
probability rules
multiply if you are looking to satisfy the word "and"
add if you are looking to satisfy the word "or"
frequency is always written in decimals, never in percentage
Monohybrid crosses
a cross in which you only look at one gene from two parents
there is a dominant allele (A) and a recessive allele (a)
the allele with a + (a+) is wild, and the allele without it (a) is mutant
the problem should tell you which allele is dominant in this case
phenotype is the physical trait that results from the genotype
if both dominant and recessive alleles occur together, the dominant phenotype will show
if both alleles are dominant, the dominant genotype will show
if both alleles are recessive, the recessive allele will show
there are common ratios of offspring genotypes that result from certain crosses
P cross: cross between two true breeding parents
one parent is homozygous dominant and one is homozygous recessive
true breeding individuals have homozygous genotypes
100% of the offspring will result in heterozygous genotypes (1:0)
100% of the offspring will show the dominant phenotype(1:0)
F1 cross: cross between two heterozygous parents
cross between offspring of P generation
both parents have heterozygous genotypes
75% of the offspring will show the dominant phenotype
25% of the offspring will have a homozygous dominant genotype (AA)
50% of the offspring will have a heterozygous genotype (Aa)
25% of the offspring will have a homozygous recessive genotype (aa)
heterozygous x recessive cross (Aa x aa)
50% of the offspring will have heterozygous genotypes (dominant phenotype)
50% of the offspring will have recessive genotypes (recessive phenotype)
genotypes with the same allele twice are called homozygous for that gene
genotypes with different alleles are called heterozygous for that gene
Dihybrid crosses
when using a punnett square for this, be sure to use the genotypes of the parents' gametes in place of what the parents genotypes would be in a monohybrid cross
some common crosses and their offspring frequencies include
Ab/Ab x Ab/Ab
the ratio of phenotypes for the offspring is 9:3:3:1 (D/D:D/r:r/D:r/r)
Ab/Ab x ab/ab
the phenotype ratio of offspring is 1:1:1:1 (D/D:D/r:r/D:r/r)
Ab/Ab x Ab/ab
the phenotype ratio of offspring is 3:3:1:1 (D/D:D/r:r/D:r/r)
this type of cross looks at two genes from the crossing of two individuals
it is disadvantageous to use a punnett square for a cross like this because there are so many combinations of alleles that you can easily make a mistake
Trihybrid crosses
this type of cross looks at three genes from the crossing of two individuals
you can check to see if genes are linked by calculating the frequency of certain genotypic offspring and checking if the observed offspring match the expected
you may have to calculate the middle gene when all the genes are linked in order to find the map distance
map distance is just the percent of recombinant offspring out of the total number of offspring
map distance (measured in map units) is the distance from which the genes are from each other on the same chromosome
count the number of recombinant between each pairs of genes
this will give you map distance between pairs of genes, which you can piece together to draw a chromosome model with the relative location of each gene
the highest