One common example of an extra-chromosome disorder is Down syndrome ( Figure 1.1). Children with Down syndrome are mentally disabled and also have physical deformities. Down syndrome occurs when a baby receives an extra chromosome 21 from one of his or her parents. Usually, a child will receive one chromosome 21 from the mother and one chromosome 21 from the father. In an individual with Down syndrome, however, there are three Chromosomes of a person with Down Syndrome. Notice the extra chromosome 21. copies of chromosome 21 ( Figure 1.2). Therefore, Down syndrome is also known as Trisomy 21. These people have 47 total chromosomes. Another example of a chromosomal disorder is Klinefelter syndrome, in which a male inherits an extra X chromosome. These individuals have an XXY genotype. They have underdeveloped sex organs and elongated limbs. They also have difficulty learning new things.
Some children are born with genetic defects that are not carried by a single gene. Instead, an error in a larger part of the chromosome or even in an entire chromosome causes the disorder. Usually the error happens when the egg or sperm is forming. Having extra chromosomes or damaged chromosomes can cause disorders.
Chromosomal disorders also occur when part of a chromosome becomes damaged. For example, if a tiny portion of chromosome 5 is missing, the individual will have cri du chat (cats cry) syndrome. These individuals have misshapen facial features, and the infants cry resembles a cats cry.
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chromosomal mutations usually happen when the organism is forming.
a. true --> b. false
down syndrome people have 47 chromosomes.
--> a. true b. false
down syndromw is also known as
--> a) trisomy 2 b) trisomy 20 c) trisomy 21 d) trisomy 22
what is the genotype of males with klinefelter syndrome?
a) yyy b) xyy --> c) xxy d) xxx
cri du chat individuals have an extra part of chromosome
a) 1. --> b) 5. c) 15. d) 25.
a normal genotype can be described as 46, xx (or 46, xy). turner syndrome can be described as 45, x. what would this refer to?
a) one less autosome --> b) one less sex chromsome c) one more sex chromosome d) only 1 chromosome
what are the sex chromosomes in a female with klinefelter syndrome?
a) xxx b) xxy c) xyy --> d) females do not get klinefelter syndrome, so the sex chromosomes are xx.
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