Exam 1 12. In Labrador retriever dogs, coat color is determined by two genes. In
ID: 276277 • Letter: E
Question
Exam 1 12. In Labrador retriever dogs, coat color is determined by two genes. In a dihybrid cross of two black dogs, the offspring produced were: 9/16 black, 3/16 brown, and 4/16 yellow. This is an example of a. codominance d. recessive epistasis C. incomplete dominance b. dominant epistasis e. variable expressivity 13. Interpret the pedigree to the right. This pedigree indicates that the trait is most likely: TT9 a. autosomal dominant c. X-linked dominant e. Y-linked b. autosomal recessive d. X-linked recessive 14. In a study of twins, it was found that monozygotic twins had a 62% concordance in their adult height, while dizygotic twins had a 35% concordance in their adult height, what can you conclude from this evidence? a. there is a genetic component to height c. a and b only b. environment influences height d. nothing, I need more information genes are linked to each other on a chromosome? 15. Which type of genetic cross is the best one to use to determine if c. a self-cross a. a testcross d. a dihybrid cross b. a monohybrid cross e. a reciprocal cross 16. If you identify 15 recombinant progeny in a total population of 60 offspring, what is the recombination frequency? b. 25% ?. 400% d. 20% e. 8096 a. 12.5% 17. The organization of two linked genes on a chromosome, where the wild-type (+) and mutant () alleles of two different genes are found on the same chromosome (shown in the figure to the right) is: b ?. A a. coupling b. repulsion c.parallel d. perpendicular 18. Eukaryotic organisms have histone proteins, but bacterial organisms do not. a. this statement is true b. this statement is false 19. The enzyme responsible for inducing supercoiling in DNA is: b. DNA ligase a. separase c. topoisomerase d. shugoshinase e. supercoilaseExplanation / Answer
Answer-12: Correct answer is Option-d.
Explaination- Ratio obtained in recessive epistatis is always 9:3:4
Answer-13: Correct answer is Option-e.
Explaination- It cannot be autosomal because there are no affected females but only affected male. If it was an autosomal dominant, then it would affect both the sexes in every generation. If it was an autosomal recessive, then it would affect both the sexes but after skipping one generation. It is not X-linked dominant because no affected females are present and neither it is X-linked recessive because it generally show criss-cross pattern of inheritance and affects males after skipping of generation. Therefore, it is Y-linked disorder which is happening in mutation in Y chromosome and there is only one Y chromosome in males and no such alternative to this chromosome is found as in case of females (XX) and moreover, it affects males in every generation.
Answer-14: Correct answer is Option-a.
Explaination- According to the question, no such statement is given which describes about the environmental factors playing its role is deciding the height. So, high percentage concordance among monozygotic twins explains about the contribution of genetic components in regulating the heights because the monozygotic twins have quite similar genetic make up unlike dizygotic twins who are phenotypically and genotypically very different.
Answer-15: Correct answer is Option-a.
Explaination- Test cross involves crossing a dominant (heterzygous) trait with the rcessive trait. So, mor the no. of progenies showing higher percentage of parental character will confirm that the genes are linked. Monohybrid and dihybrid crosses does not define whether the genes are linked or not. Reciprocal cross or back cross is used to determine the genotype of a dominant phenotype. Self cross is also referred to as selfing which involves mating etween two genetically similar organisms.
Answer-16: Correct answer is Option- b.
Explaination- Recombination frequency = No. of recombinants / Total no. offsprings
= 15 / 60
= 1 / 4 = 0.25 or 25%
Answer-17: Correct answer is Option-b.
Explaination- In repulsion, each homologous chromosome would have one dominant and one recessive gene. Whereas, in coupling, one hmologous chromosome will have dominant genes and other one would have recessive genes.
Answer-18: Correct answer is Option-a
Explaination- Eukaryotes have linear DNA which requires histones proteins for their compact packing inside the nucleus. Whereas, bacterial genome are circular in nature and quite shorter in length than the eukaryotic genome. They do not require histone proteins for their compact packing and moreover, prokaryotes lack nucleus.
Answer-19: Correct answer is Option-c.
Explaination- Topoisomerases introduces supercoils in DNA by winding and unwinding of DNA at various sites.
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