李华有耳垂，母亲也有耳垂，但李华的两个姐妹无耳垂，请回答下列问题。
（1）耳垂特征在遗传学上称为________。
（2）李华母亲有耳垂，他也有耳垂，这是一种________现象；李华母亲有耳垂，他的两个姐妹无耳垂，这是一种________现象。
（3）李华体细胞的染色体数是46条，那么他母亲通过配子给他______条染色体。
（1）性状
（2）遗传、变异
（3）23
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| Canada is the second largest country is the world. It is over 7,000 kilometres from the __1__ coast to the east. It __2__ six time zones. __3__ it is 9 a. m. in Vancouver on the west coast,it is 1:30 p, m. in St John's on the east coast. English and French __4___ the two main languages in Canada. About 60 percent of __5 _ people speak English, and about 25 percent speak French. More __6_ 70 percent of its population live in cities near the US border (边缘). Ottawa is the capital. Every year millions of tourists go there to __7__ museums and take part in the cultural activities. Toronto is the largest city of the country __8__ about 2. 5 million people. Montreal is __9_ second biggest French-speaking city in the world. The maple leaf (枫叶) is the national symbol of Canada. The Canadian flag has a red maple leaf on a red __10_ white background (背景). | ||||
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