Term
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Definition
| variations in chromosome number; occurs when an organism gains or loses one or more chromosomes and has other than an exact multiple of the haploid set |
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Term
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Definition
| complete haploid sets of chromosomes are present |
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Term
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Definition
| occurs when more than two sets of chromosomes are present |
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Term
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Definition
| nondisjunction-chromosomes or chromatids fail to disjoin and move to opposite poles during meiosis I or II |
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Term
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Definition
| The loss of one chromosome to produce a 2n – 1 complement |
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Term
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Definition
| (2n + 1 chromosomes) for the sex chromosomes has a less dramatic phenotype than trisomies for autosomes, which are often lethal |
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Term
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Definition
Down syndrome is usually a result of nondisjunction of the maternal chromosome 21 during meiosis.
It shows an increased
incidence with
increasing maternal
age
Genetic counseling is
recommended for women
who become pregnant
late in their reproductive
years. |
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Term
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Definition
| runs in families,these instances involve a translocation of chromosome 21 |
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Term
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Definition
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Term
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Definition
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Term
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Definition
| When a chromosome breaks in one or more places and a portion of it is lost, the missing piece is referred to as a deletion |
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Term
| The deletion can occur... |
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Definition
near one end (terminal deletion)
or from the interior of the chromosome (intercalary deletion) |
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Term
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Definition
| a segmental deletion of a small terminal portion of the short arm of chromosome 5 |
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Term
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Definition
Is a Repeated Segment of the Genetic Material
arise as the result of unequal crossing over during meiosis or through a replication error prior to meiosis |
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Term
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Definition
Rearrange the Linear Gene Sequence
involves a rearrangement of the linear gene sequence rather than the loss of genetic information.
In an inversion, a segment of a chromosome is turned around 180° within a chromosome.
An inversion requires two breaks in the chromosome and subsequent reinsertion of the inverted segment.
-An inversion may arise from chromosomal looping |
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Term
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Definition
| does not change the relative lengths of the two arms of a chromosome. |
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Term
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Definition
| which includes the centromere, does change the relative lengths of the two arms of a chromosome |
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Term
| Synapsis of inverted chromosomes requires |
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Definition
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Term
What happens when crossover occurs
A single crossover within an inversion loop for paracentric inversion heterozygotes |
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Definition
one recombinant chromatid is dicentric (two centromeres)
one is acentric (lacking a centromere)
one NCO with normal sequence
one NCO with inverted sequence |
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Term
What happens when crossover occurs
A single crossover within an inversion loop for pericentric inversion heterozygotes |
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Definition
Two SCO gametes with duplication and deletion
One NCO gamete with a normal sequence
One NCO gamete with an inverted sequence |
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Term
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Definition
| is a movement of a chromosomal segment to a new location in the genome |
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Term
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Definition
| “even swap” between 2 nonhomologous chromosomes (each chromosome loses some of its own genes + gains those from the nonhomologous one). |
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Term
| nonreciprocal translocation |
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Definition
| genes from one chromosome break off and attach to a nonhomologous chromosome (one chromosome loses a section of genes and the other chromosome gains that section of genes). |
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Term
| A reciprocal translocation |
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Definition
| involves the exchange of segments between two nonhomologous chromosomes |
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Term
| A Robertsonian translocation |
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Definition
centric fusion involves breaks at the extreme ends of the short arms of two nonhomologous acrocentric chromosomes
Special type of nonreciprocal translocation |
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