You are a Tatooine scientist studying inheritance patterns in banthas. Some of y
ID: 216051 • Letter: Y
Question
You are a Tatooine scientist studying inheritance patterns in banthas. Some of your banthas have aggressive dispositions while some are docile. You determine that the gene for attitude is encoded by a single locus.
You cross true-breeding docile male banthas by true-breeding aggressive female banthas and notice that all of the off-spring (male or female) are aggressive.
a. What are the possible modes of inheritance of angry dispositions in your banthas? (there may be more than 1 possibility
Autosomal dominant
Autosomal recessive
Sex-linked dominant
Sex-linked recessive
b. For each of the inheritance patterns you selected in (a.), cross an F1 generation aggressive, female banth with an F1 generation aggressive, male bantha. What will be the phenotypic AND genotypic ratios of the resulting offspring?
Use (a) to refer to the allele conferring dominant attitude phenotype, and a to refer to the allele conferring recessive attitude phenotype.
Assume aggressiveness is not a sex-linked trait. You notice that oftentimes the aggressive bantha have long tails while the docile banthas have short tails. You determine that the short-tailed phenotype is dominant while the long-tailed phenotype is recessive.
You want to determine if tail length and attitude are linked. You cross a true-breeding, aggressive, long-tailed male banth with a true-breeding, docile, short-tailed female bantha to get an F1 progeny. You then cross your F1 generation animals and look at the results in the F2 generation.
c. What are the genotypes of the parental generation?
Use T to refer to the allele conferring dominant tail length phenotype and t to refer the allele conferring recessive tail length phenotype.
d. What is(are) the genotype(s) of the F1 generation animals?
e. What is(are) the phenotype(s) of the F1 generation animals?
f. What ratio of phenotypes do you expect to see in F2 generation if the traits are not linked?
g. What ratios of genotypes do you expect to see in the F2 generation if the traits are not linked?
h. The F2 generation yields the following results:
Aggressive, short-tailed (93); Aggressive, long-tailed (30); Docile, short-tailed (30)
Explain these results in genetics terms.
i. Based on the results observed in (h), are tail length and attitude linked traits? Explain your answer.
Explanation / Answer
Answer:
a). It is autosomal recessive trait as only one type of phenotype produced in F1.
b).
Aggressive = (a) ; Docile = a
Docile -aa x Aggressive- (a)(a)---------Parents
a (a) ----------------------Gametes
(a)a -----aggressive)---------------F1
(a)a x (a)a --------------------------F1 x F1
(a)
a
(a)
(a)(a)--aggressive
(a)a-aggressive
a
(a)a---aggressive
aa-docile
Phenotypic ratio= Aggressive : docile = 3 : 1
Genotypic ratio = (a)(a) : (a)a : aa = 1 : 2 : 1
c, d & e).
Aggressive, long-tailed- (a) t / (a) t x docile, short-tailed—a T / aT -----P1
(a) t / a T (aggressive, short-tailed) -----------F1
f).
(a) t / a T x (a) t / a T ----F1 x F1
(a) T
(a) t
a T
a t
(a) T
(a)T / (a) T –Aggressive, short-tailed
(a)T/(a)t ---Aggressive, short-tailed
(a) T / a T ---Aggressive, short-tailed
(a) T / a t---Aggressive, short-tailed
(a) t
(a) t / (a) T ---Aggressive, short-tailed
(a) t / (a)t ------Aggressive, long-tailed
(a) t / a T---Aggressive, short-tailed
(a) t / a t ------Aggressive, long-tailed
a T
a T / (a) T ---Aggressive, short-tailed
a T / (a)t ---Aggressive, short-tailed
a T / a T ---docile, short-tailed
a T / a t ---docile, short-tailed
a t
a t / (a) T ---Aggressive, short-tailed
a t / (a)t ------Aggressive, long-tailed
a t / a T ---docile, short-tailed
a t / a t ---docile, long-tailed
Aggressive, short-tailed = 9
Aggressive, long-tailed = 3
Docile, short-tailed = 3
Docile, long-tailed = 1
g).
(a)(a) TT = 1
(a)(a)Tt = 2
(a)aTT= 2
(a)aTt = 4
(a)(a)tt=1
(a)a tt = 2
aaTT = 1
aaTt=2
aa tt = 1
(a)
a
(a)
(a)(a)--aggressive
(a)a-aggressive
a
(a)a---aggressive
aa-docile
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