Fraccaro M, Laudani U, Marchi A, Tiepolo L
Chromosoma. 1976 Mar 31;55(1):27-36. doi: 10.1007/BF00288324.
Anopheles atroparvus has two pairs of autosomes similar in length and morphology and two sex chromosomes with equal, heterochromatic, late replicating long arms with homologous C-, G-, and Q-bands. The short arm of the Y is shorter than that of the X and both are euchromatic. The mean number of chiasmata per cell in the male is 3.2. During mitosis there is a high grade of somatic pairing but X and Y, which form a heteropycnotic mass in the interphase nucleus, have a differential behaviour. The chronology of DNA replication was studied in spermatogonia and brain cells by autoradiography. It is hypothesized that the present sex chromosomes of A. atroparvus evolved by accumulation of sex determining factors and gene deterioration resulting in heterochromatinization of the long arms, followed by structural rearrangements.--The homology of the two sex chromosomes requires limited dosage compensation which is achieved either as in Drosophila by modifier genes or by accumulation on the short arm of the X, only of female determining factors which do not require dosage compensation.
阿氏按蚊有两对长度和形态相似的常染色体以及两条性染色体，其性染色体长臂等长、异染色质化、复制延迟，具有同源的C带、G带和Q带。Y染色体的短臂比X染色体的短臂短，且两者均为常染色质。雄性细胞中每个细胞的交叉平均数为3.2。在有丝分裂期间，体细胞配对程度较高，但X和Y染色体在间期核中形成异固缩团块，表现出不同的行为。通过放射自显影术研究了精原细胞和脑细胞中DNA复制的时间顺序。据推测，阿氏按蚊目前的性染色体是通过性决定因子的积累和基因退化而进化的，导致长臂异染色质化，随后发生结构重排。两条性染色体的同源性需要有限的剂量补偿，这可以通过修饰基因（如在果蝇中）或仅通过在X染色体短臂上积累不需要剂量补偿的雌性决定因子来实现。
