Module 2 Flashcards
What is chromosomal rearrangement?
A change in the order of base sequences along one or more chromosomes
What two types of large scale events reshape genomes?
) Rearrangements
2) changes in chromosome number
Deletion in DNA sequence
removing of base pair(s)
Duplications in DNA sequence
adding base pairs
inversions in DNA sequence
half-circle, or 180 degree rotation, of a chromosomal region
Reciprocal translocations
two nonhomologous chromosomes exchange parts
Chromosome breakage and subsequent DNA repair can result in which types of chromosomal rearrangements?
All classes of chromosomal rearrangements
What are transposable elements?
DNA sequences that can move from place to place
What is FISH analysis?
Fluorescence in situ hybridization
Deletion; inversion
Crossovers between repeats of the same sequence at two locations on the same chromosome can result in __________ if the repeats are in the same orientation or an _____________ if the repeats are in opposite orientations.
What is spectral karyotyping?
Probes paint each chromosome a different color
What is spectral karyotyping?
robes paint each chromosome a different color
What is multicolor banding?
FISH probes specific for particular regions of chromosomes generate chromosome barcodes
Rearrangement breakpoint
the abnormal juxtapositions of DNA sequences in a chromosome caused by rearrangement; identifies the precise base pairs at which rearranged chromosome segments begin and end
What is haploinsufficiency?
half the normal gene dosage does not produce enough protein for a normal phenotype
Translocation between which chromosomes causes Down Syndrome?
21 and 14
What is a deletion loop?
an unpaired bulge of the normal chromosome that corresponds to the area deleted from the other homolog
Two types of duplications
Tandem and nontandem
What is a tandem duplication?
repeated copies lie adjacent to each other, either in the same order or in reverse order
What is nontandem duplication
AKA dispersed duplication; copies of the region are not adjacent to each other and may lie far apart on the same chromosome or on different chromosomes
What is unequal crossing-over?
recomination resulting from such out-of-register pairing
In Drosophila, tandem duplication of a region of the X chromosome called 16A produces “Bar” mutant phenotype. What do Bar eyes resemble
A kidney bean
What is the difference between pericentric and paracentric inversions?
Pericentric include the centromere; paracentric inversions exclude the centromere
If during anaphase 1, N1 segregates with N2 and T1 segregates with T2, the gametes will be balanced because….?
each gamete will have one copy of each gene
The N1+N2 and T1+T2 pairs are called __________ because of their orientation in the cross shaped diagram.
Alternate pairs
N1 may segregate with T2, and N2 may segregate with T1. These are called ________ because of their orientation in the diagram.
adjacent 1 pairs
N1 may segregate with T1, and N2 may segregate with T2. These are termed ______.
adjacent pairs 2
he adjacent-1 and adjacent-2 combinations produce gametes that are unbalanced because….?
In each combination, some genes are missing and two copies of other genes exist.
When a translocated heterozygote is mated with a normal individual, one can expect that about half of the zygotes will be inviable, a condition called _______.
Semisterility
Leukemic cells have a reciprocal translocation between which two chromosomes?
9 and 22
what are TE’s
Segments of DNA found in all organisms that can most from place to place within a genome
TEs size can range from….?
50 base pairs to 10 kilobases
What are two ways that TE insertion can result in altered phenotype?
- Insertion within a coding region
- Insertion near a gene, thus affecting expression
Retrotransposon synthesizes cDNA by….?
Reverse transcriptase
In retrotransposon, the original copy ______ while the new copy ________.
remains; inserts into another genomic location
Most DNA transposons contain inverted repeats (IRs) of how many base pairs?
10 - 200 bp
Gene encoding transposase recognizes the IRs and ….?
cuts at the border between the IR and genomic DNA
True or False: Barbara McClintock’s primary work on transposable elements was done in Zea mays (corn)
true
True or False: Retrotransposons move via reverse transcription of an RNA intermediate
true
Ture or False: Comparison of the location of DNA transposons in humans shows that some have moved recently
false
True or False: When a DNA transposons moves, a copy always remains in the original location.
false
True or False: Nearly 50% of the human genome is made up of transposable elements.
true
True or False: The ends of retrotransposons are inverted repeats of each other.
false
True or False: DNA transposons require an RNA intermediate to move to a new location.
false
True or False: Transposable elements are only found in Zea mays (corn).
false
True or False: Some TEs have a known function; others are characterized as “selfish” DNA.
true
True or False:
Human LTR retrotransposons are similar in structure to retroviruses.
true
True or False: Transposable elements (TEs) are small segments of DNA that can move from one position to another in a genome.
true
True or False: DNA transposons have inverted repeats at the ends.
true
Some of these have long terminal repeats (LTRs) at both ends, in the same orientation.
retrotransposons
Contains a gene that encodes transposase.
transposons
What is Robertsonian translocation?
A reciprocal translocation occurring near that centromere of two acrocentric chromosomes, producing one large metacentric chromosome and a very small chromosome that may be lost
Which term describes the result of two nonhomologous chromosome exchanging pieces?
Reciprocal translocation
Consider a normal chromosome with the following gene sequence along its length: F G H I J K L.
Which of the following sequences represents an inversion?
F K J I H G L
In meiosis, a chromosome carrying an inversion.
can pair with a normal homologous chromosome; one of the chromosomes forms a loop.
Which mechanism of generating chromosomal rearrangements involves nonhomologous end-joining (NHEJ)?
DNA breakage
Del/Del genotype
> Large multigene deletions are almost always lethal
> Small, single gene deletions are often viable
Deletions in homozygotes
> Del/+ gentoype
> Small, single deletions are usually viable
> May have a mutant phenotype if a mutant allele is uncovered
> A loss-of-function may result in loss of heterozygosity
> Mutant phenotypes may arise due to haploinsufficiency
Deletions in heterozygotes
True or False: If m/Del has a mutant phenotype similar to that of m/m, m may be located within the deleted region.
true
True or False: Deletion mapping can determine the exact boundaries of a deletion
false
If m/Del is wild type, m is located within the deleted region.
false
True or False: Deletion mapping can identify a specific gene that is responsible for a mutant phenotype
true
Few are mobile in humans
> 13% of genome
> contains poly-A
> RNA intermediate
SINEs
Few are mobile in humans
> 20% of genome
> contains poly-A
> RNA intermediat
LINEs
Contains LTRs
> 8% of genome
> RNA intermediate
> None are mobile in humans
HERVs
Has transposase gene
> None are mobile in humans
> 3% of genome
dna transposons
In frame translocations within the open reading frames of two genes may result in a ________.
new protein
rue or False: Some duplication heterozygotes have visible mutant phenotypes because some traits are sensitive to gene dosage.
true
True or False: Unequal crossing over in duplication heterozygotes changes the duplication copy number.
false
True or False: A duplication refers only to segments of DNA that are repeated in tandem.
false
True or False: Two copies of a duplication can be arranged with their base pair sequences in the same order or reverse order.
true
How does a reciprocal translocation result in chronic myelogenous leukemia?
parts of two genes are fused together and a hybrid protein that increases cell division is produced
A gene for antibiotic resistance is flanked on either end by inverted repeats (IRs). Transposase recognizes the IRs and the resistance gene jumps to a new strain of bacteria. This is an example of a….?
composite transposons
When genes are duplicated and then one copy is subsequently altered, groups of similar genes with slightly different function are created. These groups are called….?
gene families
Euploid
Organisms with complete chromosome sets
Aneuploid
Cells are missing one or more chromosomes from a set or have one or more extra chromosomes
What is the difference between monosomic and trisomic?
Monosomic (2n-1) individuals are lacking one chromosome, trisomic (2n+1) individuals have a single additional chromosome
If a human individual was trisomic on chromosome 21 we would expect them to exhibit which syndrome?
Down Syndrome
X-chromosome aneuploidy is usually tolerated in human species because ___________ equalizes the expression of most X-linked genes.
inactivation
XXY males have _______ syndrome and XO females have _______ syndrome.
Klinefelter; Turner
If disjunction occurs during meiosis I causing aneuploidy, what will happen to the zygotes formed?
Two zygotes will be trisomic (2n+1) and two zygotes will be monosomic (2n-1)
