動(dòng)物遺傳學(xué)遺傳信息的改變-展示頁(yè)
2025-05-08 04:54本頁(yè)面
【正文】 ifetime of use. The elastin protein is made only during embryo development and childhood, when blood vessels are formed. Because they lack the elastin protein, people with Williams Syndrome have disorders of the circulatory system, also known as vascular disorders. Cri du chat is a rare syndrome (1 in 50,000 live births) caused by a deletion on the short arm of chromosome 5. The name of this syndrome is French for cry of the cat, referring to the distinctive cry of children with this disorder. The cry is caused by abnormal larynx development, which bees normal within a few weeks of birth. Infants with cri du chat have low birth weight and may have respiratory problems. Some people with this disorder have a shortened lifespan, but most have a normal life does the abnormal chromosome 5 e from? In 80 percent of the cases, the chromosome carrying the deletion es from the father39。 染色體畸變 一、 缺失 缺失（ deletion）：是指一個(gè)正常染色體某區(qū)段的丟失，位于該區(qū)段的基因也隨之丟失。 第一節(jié) 染色體畸變 第二節(jié) 基因突變 第三節(jié) 突變的抑制與 DNA的修復(fù) 第四節(jié) 重組與轉(zhuǎn)座 染色體畸變 (chromosomal aberration): 是指在自然突變或人工誘變的條件下，由于染色體數(shù)目或結(jié)構(gòu)的改變，從而改變了基因的數(shù)目、位置和順序，導(dǎo)致個(gè)體性狀發(fā)生改變。染色體結(jié)構(gòu)和數(shù)目的改變稱(chēng)為染色體畸變 (chromosomal aberration)。第四章 遺傳信息的改變 變異是生物界存在的一種普遍現(xiàn)象，變異可以使生物具有多樣性，使生物通過(guò)自然選擇產(chǎn)生進(jìn)化，影響生物的性狀。 遺傳信息的改變可以發(fā)生在染色體上，也可以發(fā)生在 DNA分子水平上。 DNA分子結(jié)構(gòu)發(fā)生的化學(xué)變化稱(chēng)為基因突變（ gene mutation）。主要包括染色體數(shù)目改變和染色體結(jié)構(gòu)改變兩類(lèi)，其中染色體結(jié)構(gòu)改變包括缺失（ deletion）、重復(fù) (duplication)、倒位 (inversion)和易位 (translocation) 4種類(lèi)型。 1 缺失的種類(lèi) 2 缺失的產(chǎn)生 ⑴ 染色體損傷和非重建性愈合 ⑵ 不等交換 斷裂 融合 橋 （ breakagefusionbridge,BFB） ⑵不等交換 a ⑷ 轉(zhuǎn)座 ⑶ 染色體紐結(jié)、斷裂和非重建性愈合 3 缺失的細(xì)胞學(xué)特征 玉米缺失雜合體粗線(xiàn)期缺失環(huán) 果蠅唾腺染色體的缺失圈 3 缺失的遺傳與表型效應(yīng) ① 致死或出現(xiàn)異常 ② 假顯性或擬顯性 假顯性或擬顯性（ psedo dominant）：是指顯性基因的缺失使其同源染色體上的隱性非致死基因的效應(yīng)得以顯現(xiàn)的遺傳現(xiàn)象。s sperm. Cri du chat syndrome 重復(fù) (duplication)：是指一個(gè)正常染色體增加了與本身相同的一段。 倒位（ inversion）：是指一個(gè)染色體上某區(qū)段的正常排列順序發(fā)生了 180度的顛倒。 ② 改變基因的連鎖群，影響重組頻率。 ④ 新物種的形成。 四、易位 reciprocal translocation Robertsonian translocation simple translocation 1 易位的分類(lèi) 2 易位的產(chǎn)生 ① 斷裂非重建性愈合 ② 轉(zhuǎn)座 Robertsonian translocation reciprocal translocation 3 易位雜合體的聯(lián)會(huì)和分離 ⑷ 基因重排導(dǎo)致癌基因的活化，產(chǎn)生腫瘤 ⑵ 假連鎖現(xiàn)象 ⑶ 位置效應(yīng) ⑴ 改變正常的連鎖群 ⑸ 降低繁殖機(jī)能和生產(chǎn)性能 4 易位的遺傳與表型效應(yīng) Philadelphia Chromosome This person has 46 chromosomes with a translocation of material between chromosome 9 and chromosome 22 (monly known as the Philadelphia chromosome). Detailed studies of the Philadelphia chromosome show that most of chromosome 22 has been translocated onto the long arm of chromosome 9. In addition, the small distal portion of the short arm of chromosome 9 is translocated to chromosome 22. This translocation, which is found only in tumor cells, indicates that a patient has chronic myelogenous leukemia (CML). In CML, the cells that produce blood cells for the body (the hematopoietic cells) grow uncontrollably
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