Mendelian Transmission of Alleles Flashcards
if we know the genotypes of two parents we can…
predict the genotype of their offspring
a cross btw 2 homozygotes always gives…
a heterozygote
a cross between diploids where all 4 alleles in the parents are different…
4 possible combinations all with equal frequencies
a cross of 2 heterozygoes Aa x Aa genotypes
genotype AA 1/4
Aa 1/2
aa 1/4
ratio is 1:2:1
a cross of 2 heterozygotes Aa x Aa phenotypes
AA + Aa 3/4
aa 1/4
ratio is 3:1
mendelian ratio
a cross btw 2 heterozygoes yields ratios
genotypic: 1:2:1
phenotypic: 3:1
mendel worked with ___ which are normally ____
peas, self-fertilizing
how to cross peas
cut open flower before sex parts are mature
transfer pollen from one flower to another
put pollen on the pistil (gateway to female gamete)
pollen is the ___ gamete
male
mendel’s question
what happens when you cross two distinct true-breeding strains?
mendel first…
crossed pairs of strains with distinct alternative traits
purple x white flowers
first thing mendel noticed
in every cross, one was dominant
mendel secondly…
allowed hybrids to self-fertilize
mendel noticed secondly…
offspring of 2nd generation showed both traits again
ratio of 3:1 dominant:recssive
particulate inheritance
information is copied and passed on in some physical form
diploidy
individuals have 2 copies of the info for each trait
one from each parent
dominance/recessivity
some copies only produce their effect when the other copy is absent
random segregation
2 copies for each trait are passed on independently and randomly
mendel’s 1st law
segregation
alleles of genes are copied and passed on independently through haploid and diploid phases
phenotypic ratio of 3:1 results from…
cross of 2 heterozygotes if there is dominance
phenotypic ratio of 1:1 results from…
cross of a heterozygote with a recessive homozygote
phenotypic ratio of 2:1 results from…
crossed heterozygotes if a dominant allele is recessive lethal
in offspring with a 3:1 phenotypic ratio….
2/3 of the dominant types are carriers (heterozygotes)
genotypic ratio of 1:2:1 at conception…
result from a cross of 2 heterozygotes
achondroplastic dwarfism
cross heterozygotes Dd x Dd
genotypic ratio at conception 1:2:1
phenotypic ratio at birth 2:1 (DD babies die)
dd gives normal height
mexican hairless dogs
all are heterozygotes
cross Hh x Hh
genotypic ratio at conception 1:2:1
phenotypic ratio at birth 2:1 (HH babies die)
hh gives dog with hair
