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1．ceugh(v) to expel air and mucus，with force，from the lungs through the mouth 咳嗽 People With colds cough and spread the cold Virus through the air． 得感冒的人咳嗽，把感冒病毒扩散到空气中。2．sneeze(v) to expel air and mucus，With force，from the lungs throughthenose 打喷嚏 If you have a cold，you should cover your nose when you sneeze． 如果你得了感冒，那么你打喷嚏时应捂住鼻子。3．Spit(v) to release saliva with force through the mouth 吐痰 Infectious organisms found in saliva are released when people spit. 人们吐痰的时候唾液中传染疾病的生物就释放出来了。4．Spread(v) to scatter，to release over a large area 扩散，传播 Infections are spread by coughing，Spitting，and sneezing． 传染病通过咳嗽、吐痰和打喷嚏传播。5．crowd(n) a large number of people Or things in a small space (拥挤的)人群 crowded(adj) many people or things pushed together 拥挤的 A crowd Of people transmits many disease-causing organisms． 许多致病的生物体在人群中传播。 An epidemic can start on a crowded bus． 流行病有可能从拥挤的公共汽车上开始传播。 Different pedigrees illustrate different patterns of inheritance. Pedigrees involving genetic diseases are usually studied rather than pedigrees concerned with normal traits because there are more pedigrees of diseases and abnormal conditions. An autosomal gene exhibits the same pattern of transmission whether the trait it determines is normal or abnormal. We will examine pedigree charts of autosomal dominant and autosomal recessive patterns of heredity. Diagram A is an example of a pedigree chert of a family-in which an autosomal dominant trait was transmitted to many of the kindred (members of a family). Certain characteristics of the pattern of transmission lead the geneticist to conclude that the trait isdetermined by an autosomal gene. First, equal numbers of women and men are affected. Second, the affected man in the third generation transmitted