Chapter 9 Flashcards
Chromosome Mutation
variation in the number and structure of chromosomes
Metacentric Chromosome
Centromere is in the center f the chromosome, chromosome has arms of equal length
Submetacentric Chromosome
centromere is displaced towards one end, creating a long arm (q) and a short arm (p)
Acrocentric Chromosome
centromere is near one end
Telocentric Chromosome
cntromere is at one end of the chromosome
Chromosome Rearrangement
alter the structure of chromosomes
Chromosome Duplication
a mutation in which part f the chromosome have been doubled
either in tandem (adjacent to the original segment), displaced (not next to the original segment) or reversed (the duplication is inverted)
Chromosome Deletion
the loss of a chromosome segment; in individuals heterozygous for deletions, the normal chromosome must loop during the pairing of homologs in prophase I to allow the homolog regions to align and undergo synapsis
if the deletion includes the centromere, the chromosome ill not be able to separate in mitosis or meiosis and will be lost
Pseudodominance
a result of chromosome deletion; an expression of a normally recessive mutation
Haploinsufficient Gene
a result of chromosome deletion; when a single copy of a gene is insufficient to produce a wild-type phenotype; some genes must be present in 2 copies for normal function
Chromosome Inversion
when a chromosome segment is inverted (turned 180 degrees); the chromosome is broken in 2 places
Pericentric Inversion
inversions that include the centromere
Paracentric Inversion
inversions that do not include the centromere
Position Effect
when the position of genes are altered by an inversion and they are expressed at inappropriate times/in inappropriate tissues
Translocation
the movement of genetic material between nonhomologous chromosomes or within the same chromosome
Nonreciprocal Translocation
genetic material moves from one chromosome to another without any reciprocal change
Reciprocal Translocation
more common, a two-way exchange of segments between 2 nonhomologous chromosomes
Robertsonian Translocation
when the long arms of 2 acrocentric chromosomes become joined to a common centromere through a translocation, generating a metacentric chromosome with2 long arms and another chromosome with 2 short arms
Aneuploidy
a change in the number of individual chromosomes
Polyploidy
a change in the number of chromosome sets
Nullisomy
the loss of both members fa homologous pair of chromosmes; 2n-2
in humans, 2n=46, so nullisomy = 44
Monosomy
the loss of a single chromosome; 2n-1
in humans, 2n=46 so monosomy = 45
Trisomy
the gain of a single chromosome, meaning 3 homologous copies of one chromosome; 2n+1
in humans, 2n=46 so trisomy = 47
Tetrasomy
the gain of 2 homologous chromosomes, meaning 4 homologous copies of one chromosome, 2n+2
in humans, 2n=46, so tetrasomy = 48
Down Syndrome
the most common aneuploidy in humans, 1/700 births are D.S. births, maternal in origin, usually arises in meiosis I, little hereditary tendency
Trisomy 21
a.k.a. down syndrome
Translocation Carrier
people with the translocation gene (usually between chromosomes 14 and 21); these carriers do not have down syndrome, only possess 45 chromosomes but their phenotypes are normal. increased chance of offspring with D.S.
Turner Syndrome
when cells contain an X chromosome and no Y chromosome (XO); people with this condition are female, don’t undergo puberty, broad chest, folds of skin on neck, and are normally sterile and have normal intelligence; 1/3000 births
Klinefelter Syndrome
contain one or more Y chromosome and multiple X chromosomes (XXY, XXXY, etc.), male, small tested, breast enlargement, reduced facial and pubic hair, often tall, sterile, normal intelligence. 1/1000 births
Uniparental Disomy
when both chromosomes are from the same parent; probably originate as a trisomy
Mosaicism
a nondisjunction that leads to regions of tissue with different chromosome constitutions; very common
