chapter 6 Flashcards
Centromere
a region of a chromosome to which microtubule fibers attach during cell division
sex chromosomes
X and Y chromosomes are involved in sex determination
Autosomes
Chromosomes other than the sex chromosome (chromosomes 1-22)
Karyotype
a complete set of chromosomes from a cell photographed during cell division and arranged in a standard sequence
Polyploidy
The chromosomal number is a multiple (3n or 4n) of the normal haploid chromosomal number.
Aneuploidy
Chromosomal number that is not an exact multiple of the haploid numbers
Triploidy
Chromosomal number that is three times the haploid number, three copies of autosomes, and three sex chromosomes
Monosomy
One member of a chromosomal pair is missing; one less than the diploid more than the diploid number (2n-1)
Trisomy
One chromosome is present in three copies, and all others are diploid; one more than the diploid number (2n+1)
Nondisjunction
The failure of homologous chromosomes to separate properly during meiosis
Down Syndrome
Trisomy 21: only autosomal trisomy that allows survival into adulthood
Klinefelter Syndrome
(47, XXY); Males have some fertility problems but few additional symptoms
Turner syndrome
(45, X); Monosomy of the X chromosome that results in female sterility
Information that can be obtained from a karyotype
1.) Number of chromosomes
2.) Sex chromosome content
3.) Presence or absence of individual chromosomes
4.) Nature and extent of large structural abnormalities
Interpret a karyotype
A complete set of chromosomes from a cell photographed during cell division and arranged in a standard sequence
The six most common aneuploidies in humans
1.) Trisomy 13 :(Patau Syndrome)
2.) Trisomy 18: (Edwards syndrome)
3.) Trisomy 21: (Down Syndrome)
4.) Turner Syndrome
5.) Chromosome XY
6.) XYY Syndrome
Risk factors for aneuploidy in humans
1.) reproductive failure
2.) cancers
3.) Miscarriages and birth defects
Mechanism that causes aneuploidy in humans
errors in chromosome segregation
four structural changes in chromosomes
1.) Deletion: loss of chromosome material
2.) Duplication: Double of chromosomes
3.) Translocation: exchange of chromosome pairs
4.) Inversion: breaks off and attaches itself to within the same chromosomes but in reverse orientation
