ntron in the correct stack. Use critical thinking skills Be mechani stic and app

Question

ntron in the correct stack. Use critical thinking skills Be mechani stic and apply the concepts from class. Be careful of assumptions. Make drawings, when helpful. * 18) Which one of the follouving genotypes generates A) Cf/cf B) IA/IB C) IA/i D) HbA/Hbs E) Ach/ach a codominant phenotype? 19) Which of the following is a true statement about polygenic inheritance? A) The three genes involved in the ABO blood types are polygenic. B Recessive genes are retained in a population due to heterozygotes. C) We have many genes in our cells. D) A single trait results from the interactions of several genes E Based on simple dominance, one can always predict the offspring's phenotype. 20) An XYY individual results from a mistake in gamete formation A) due to high doses of radiation. B) due to a problem with copying DNA in S phase. C) due to likely nondisjunctions in meiosis I D) due to likely nondisjunctions in meiosis II. E) either C or D can cause this result. 21) The gene q is recessive and lethal in the homozygous condition, resulting in a miscarriage. The Q gene is norma dominant. If two heterozygotes decide to have children, what proportion of surviving offspring will be heterozy A) 0 B) 2/3 C) D) 1/2 E) An individual has three X chromosomes. Her condition 22) A) is improved due to extra genes from the X chromosome. B) results in delayed menopause. C) is normal due to X-inactivation. D) is lethal due to too many genes from the X chromosome. E) None of the above. 23) The chance of two heterozygotes carrying a gene for an autosomal recessive disease having a son with the A) 1/2 B) 1/6 C) 1/8 D) 1/3 E) 1/4 24) A person with the genotype HbS/HbA for hemoglobin living in a region where malaria is not present A) would not be selected for (their genotype does not give them an advantage or disadvantage relative to B) would have sickle cell anemia. Q would be selected for (their genotype gives them an advantage relative to all other genorypes) D) E) would contract malaria. would be selected against (their genotypes). genotype gives them a disadvantage relative to all other

Explanation / Answer

Ans 18:

(B) IA/IB

IA/IB genotype refers to an individual with both IA & IB alleles who express AB blood Phenotype.

They are co-dominant because when these two dominant alleles are together, both are expressed in the Phenotype.

Ans19:

(D) a single trait results from action of many genes.

Ans 20:

(e) either C or D.

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