GENETICS Please Help! The answers have been provided under the questions but I r

Question

GENETICS Please Help! The answers have been provided under the questions but I really need to see the work/explanation for each as I do not understand. Thank you very much!!

110. Which classes are the PDs, NPDs and Ts?   
PD – I and IV; NPD – VI, VII; T - II, III and V.

111. Which class(es) are second division segregations?   
For A – III, IV, V and VI; for B – II, IV, V, and VI.

112. What is the map of these genes and any linked centromere(s)?   
A-cent-B; A-cent = 22; cent-B = 14; A-B = 32.

In Neurospora the cross AB x ab was made and 100 asci were scored: A B A, B AB AB AB Ab Ab A, B AB AB AB B A b Ab A B A b a B ab a b a B A b A B A b a B ab a b a B A b a b a B Ab AB Ab A b a B a b A b A B A b A b a B a b a b a b a b a B a B a B a b a b a b a b a B a B a B 39 16 32 1

Explanation / Answer

110. Answer:
Parental ditype (PD)
A tetrad containing 4 haploid cells of the parental class.
So I and IV will be PDs 4 ABs and 4 ab s in both columns.

Nonparental ditype (NPD)
A tetrad containing 4 recombinant haploid cells
All 4 types of recombinant cells (2Ab, 2aB,)are present in VI NAd VII

Tetratype (T)
A tetrad containing four kinds of haploid cells, two different parental class spores
and two different recombinant class spores.
II, II and V contains 4 types af haploid cells (AB, Ab, aB,ab).

111. Answer:
If recombination occurs between gene and the centromere, then a second division segregation
(both types of spores are found on either side of the imaginary line) pattern is observed
For A III, IV, V and VI
III and V - All four types IV- 2ABs and 2abs
VI - 4 Abs, 4aBs all are recombinant
Similary for B -II, IV, V, and VI. - In second division segregation, half of the
chromatids are recombinant and the other half have not participated in crossovers.

112. Answer:
A and B are linked , because PD>NPDs The gene map would be A-Centromere-B

Centromere A=22
Centromere B=14
A-B= 2 *PDS =2*16=32

Related Questions

Navigate

• Browse (All)
• Browse G
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.