Trihybrid Maps

BIO 239: Genetics Laboratory: Week 4: Wednesday, September 17th: Trihybrid Fly Test Cross & Gene Maps; Week 6: Monday, September 29th: Forked Diagrams; Probability; Trihybrid Maps

_______ indicates the location of a gene on a chromosome

gene mapping

_______ is the cause of which genes that are close together are inherited together

linkage

true or false: genes that are far apart are more likely to separate via crossing over

true

early linkage analysis used a _______ of 1: Rf = 1 map unit (centiMorgan, cM)

recombination frequency (Rf)

the formula for Rf is 

(recombinants/total)100

Sturtevant explained gene mapping with a _______ trihybrid test cross

heterozygote

F₂ phenotypes that dont return a 1:1:1:1/1:1:1:1:1:1:1:1 ration indicate _______

linkage

this test cross reveals gene order, estimates distacne between genes, and finds double cross-overs (DCOs)

3 point test cross

with 3 genes, a test produces _______ possible phenotypes, which is _______

8, 2³

mendelian ratios suggest independent assortment. if the ratios are skewed, it means that _______ occurred

linkage

_______ are the parental types; they’re identical to the parents, are reciprocals of one another, and are most frequently if genes are linked

non-recombinants (NRC)

_______ occur in two types from regioun 1 (between genes 1-2) and two from region 2 (between gene 2-3)

single crossovers (SCO)

_______ reflects crossing over in both regions, are least frequent, and used to identify the middle gene by comparing them with the NRC

double crossovers (DCO) 

the _______ is the allele that changes compared to the NRC and DCO

middle gene

_______ is when one crossover reduces the likelihood of another crossover

interference (I)

if interference is 0, that means _______

no interference occured, and genes are independently assorted

if interference is 1, that means _______

interference occured, and no cross overs occurred

the formula for interference is _______

1- COC

the _______ is how much interference occurred based o the number of DCos observed compared to how many were estimated

coefficient of coincidence

the formula for coefficient of coincidence (COC) is _______

observed DCO/expected DCO

true or false: Haldane assumed cross-over regions will always be predicted, and that they’re the same for each generation

false. Haldane assumed cross-over regions will always be random, and that they’re never the same for each generation

the formula for calculating the distance between outer genes (1-3) is

(SCO1 + SCO2 + DCO(2))/total length of the gene

_______ is when some recombinants occur while favoring “parental” types (NRCs)

partial linkage

a _______ shows loci of genes based on novel phenotypes, whereas a _______ shows genes as a segment of nucleotides on a single strand of DNA

recombination map, physical map

an _______ is a drawing of a chromosome, whereas a _______ is Giesma-stained bands of chomosomes, which are simialr between homologs

ideogram, karyotype

the _______ is the gene locaiton on a chromosome

locus/loci

the centromere has _______, where kinetochores form

satellite DNA

_______ is the p-arm’s telomore, where as _______ is the q-arm’s telomere

p-ter, q-ter

loci are number from _______ (small numbers) to _______ (bign numbers) in either direction

centromere, telomeres

the adjusted distance adds the total DCOs twice, which is calculated by

(SCO1 + SCO1 + SCO2 +SCO2 + (2(DCO1 + DCO2))/total)100 or (gene 1-2 sum or % + gene 2 and 3 sum or %/total)100

true or false: greater number of ecombinants mean the gene pair is farthest apart from one another

true

_______ are alleles that have opposite genes (AbC vs aBc)

reciprocals

true or false: SCO in region 1 results in recombinants with 1 new allele and 2 originals

false. SCO in region 1 results in recombinants with 2 new alleles and 1 original

true or false: SCO in region 2 results in recombinants with 2 new alleles and 1 original

false. SCO in region 2 results in recombinants with 1 new allele and 2 originals