Dihybrid Crosses

genetics

dihybrid cross

applies to 2 traits on different chromosomes, cross 2 double heterozygote

9:3:3:1

what phenotype ratio will the F2 generation of a dihybrid cross have?

product rule

what rule should you use to determine probabilities when using a branch diagram?

white-apricot

light eyed flies

sepia or brown

brown eyed flies

vermillion, cinnibar, scarlet

bright red eyed flies

scarlet-brown

wild type red eyed flies

white-apricot, vermillion, white

which fly eye colors are sex linked?

scarlet-brown

which fly eye colors have 2 genes?

epistasis

name for when the action of one gene is modified by another gene

9:7

What is the phenotype ratio for a dihybrid cross with epistasis?

penetrance

occurs when not all individuals with particular genotype express the expected phenotype or , % of individuals with expected genotype

expressivity

when the mutant phenotype can vary in intensity, Ex. polydactyly in cats!

all or none

penetrance applies to ____ expression

spectrum

expressivity applies to a ____ of a phenotype

number of recombinants, total

to find the recombination frequency, divide the ____ by the ____

lambda

virus used to study gene expression

protein capsule and nucleic acid core

lambda is made up of ___

lytic cycle

life cycle of lambda virus involving attachment, injection, replication, viral DNA expression, packaging, and lysis

lysogenic cycle

alternate route during the lambda life cycle that takes place between the injection and replication phases, virus DNA is inserted into the bacterias cells but does not replicate until the cell experiences stress

plaque

gap in bacteria where virus has destroyed bacteria lawn

phenotypes

the different sizes of plaques represent the virus’ ___

parental

the most common genotype pairs are ____

double recombinants

the least common genotype pairs are the ____

determine gene order

what is the first thing you should do when mapping a 3 factor cross?

not independant

if observed genotype is greater than expected then cross overs are ____

independant

if observed genotype is less than expected than cross over are ____

interference

property that states that a cross over at one locus influences cross-overs at another locus

positive interference (1)

when the cross over at one locus decreases the chances of a cross over at a nearby locus; common in eukaryotes (1)

negative interference (1)

when the cross over at one locus increases the chances of a cross over at a nearby locus; common in prokaryote (1)

coefficient of coincidence

observed frequency of double cross over divided by the expected frequency of double cross over

no interference

if the coef. of coincidence is 1 then ____

positive interference

if the coef. of coincidence is less than 1 then ____

negative interference

if the coef. of coincidence is greater than 1 then ____