4.In humans,the allele for a widow's peak (W) is dominant and the allele for a straight hairline (w) is recessive.This trait shows complete dominance.Which of the following represents the possible phenotypes in the offspring of two parents,both with

4.In humans,the allele for a widow's peak (W) is dominant and the allele for a straight hairline (w) is recessive.This trait shows complete dominance.Which of the following represents the possible phenotypes in the offspring of two parents,both with
4.In humans,the allele for a widow's peak (W) is dominant and the allele for a straight hairline (w) is recessive.This trait shows complete dominance.Which of the following represents the possible phenotypes in the offspring of two parents,both with a straight hairline?
A All offspring will have a widow's peak.
B Each offspring will show both phenotypes.
C Most of the offspring will have a straight hairline,but it is possible for an offspring to have a widow's peak.
D All offspring will have a straight hairline.
5.Testosterone is responsible for the development of the male reproductive system,and it is produced by the testes.The development of the testes depends on the presence of a Y chromosome.What might occur if the Y chromosome is present,but the testes are unable to produce testosterone?
A normal female development
B The testes would be present,but further male development would be arrested.
C normal male development
D The testes and ovaries would be present.
6.An infant born with the genotype XYY will __________.
A.be phenotypically male,often tall,and usually of normal intelligence
B.be phenotypically female and fertile
C.be phenotypically male,short,and mildly retarded
D.show partial male and partial female development

4.In humans,the allele for a widow's peak (W) is dominant and the allele for a straight hairline (w) is recessive.This trait shows complete dominance.Which of the following represents the possible phenotypes in the offspring of two parents,both with
4 D 父母均呈现出由隐性基因w控制的隐性性状straight hairline
父母基因型均为ww 他们的后代只能是为ww,表现隐性性状straight hairline
5 B
正常情况下,男,女的性器官睾丸和卵巢都会产生D,只是含量不同.但题目中提到the Y chromosome is present,那么就只能是男性个体[性染色体组 成为XY 或是XYY]
6 A http://baike.baidu.com/view/839712.htm 不过这个应该在英文原文应该能找到,你应该只写出了题目的部分内容吧.……基础知识生物高一下 遗传进化有学,结合上下文情境……

6.A 解析：基因型为XYY的新生婴儿，长大之后表现型为男性，一般较高，且通常情况下具有正常的智力。

4.D
5.C
6.D