chapter 10 Flashcards
What are chromosome numbers?
Different species have different diploid chromosome numbers (e.g., humans have 46, fruit flies have 8)
What are chromosome territories?
Chromosomes are confined to specific regions (territories) in the nucleus during interphase but can move, twist, and turn during transcription and DNA replication.
Chromosomes are categorized based on what?
the position of their centromeres
What is Metacentric?
Centromere in the middle
What is Submetacentric?
Centromere between middle and tip
What is Acrocentric?
Centromere close to one end.
What is Telocentric?
Centromere at the tip.
What are Karyotypes?
Visual displays of chromosomes, useful for identifying abnormalities in chromosome number or structure.
What are banding patterns?
Chromosomes can be identified based on size, shape, and banding patterns using techniques like G-banding.
What is euchromatin?
Less condensed, gene-rich, and actively expressed chromatin
What is heterochromatin?
Tightly condensed, gene-poor, and less expressed chromatin
What is nondisjunction?
Failure of chromosomes to separate properly during meiosis, leading to aneuploidy (abnormal chromosome number)
What is meiotic Nondisjunction?
Can occur in meiosis I (homologs fail to separate) or meiosis II (sister chromatids fail to separate).
What is Aneuploidy? give an example
Leads to monosomy (missing a chromosome) or trisomy (extra chromosome), which alters gene dosage and affects phenotype.
ex: trisomy 21 results in Down syndrome.
What is Polyploidy?
Presence of three or more sets of chromosomes (common in plants).
What is Autopolyploidy?
Chromosome duplication within the same species.
What is Allopolyploidy?
Combining chromosome sets from different species.
What causes polyploidy?
Meiotic and mitotic nondisjunction
What is Meiotic Nondisjunction?
Leads to diploid gametes (e.g., 2n + n = 3n plants)
What is mitotic nondisjunction?
Chromosome number doubles in somatic cell
What are the consequences of Polyploidy?
Increased size of fruits and flowers, decreased fertility (especially in odd-numbered polyploids), and hybrid vigor (more robust growth and disease resistance).
Polyploidy can lead to what?
the formation of new species in a single generation by reproductive isolation.
Centromeres divide chromosomes into what?
chromosome arms of unequal length
what is the short and long chromosome arms?
the short arm is the p arm and the ling arm is the q arm
What is the Fluorescent in situ hybridization (FISH) staining for?
Uses molecular probes to detect a target sequence
What is the standard for human banding?
The G (Giemsa) banding; the patterns are distinct and reproducible
What is hybrid vigor?
more rapid growth, increased fruit and
flower production, and improved resistance to disease that occurs in heterozygous progeny of inbred lines
What is the euploid number of chromosomes?
the number of complete sets (e.g., n, 2n, 3n)
What is mosaicism?
can develop as a result of mitotic nondisjunction early in embryogenesis
look more at gene dosage
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What is uniparental disomy?
when both copies of a homologous
chromosome pair arise from the same parent. A rare abnormality in humans
What is trisomy rescue?
one copy of the trisomy chromosome is
randomly ejected in one of the first
mitotic divisions after fertilization
Chromosome breakage can cause mutations through what?
the loss, gain, or rearrangement of chromosomes, resulting in gene dosage imbalances
The process of chromosome breakage and mutation can lead to what?
partial deletions or duplications, affecting gene function and potentially causing disorders
Chromosome breaks result in what?
partial deletions where fragments can be lost if they lack a centromere.
Terminal deletions occur where?
at the end of the chromosome, while interstitial deletions involve loss within the chromosome.
What is Cri-du-Chat Syndrome?
It is caused by a terminal deletion on chromosome 5, leading to characteristic symptoms like the “cat-cry” sound. it is caused by partial deletion heterozygotes
What is unequal crossover?
Occurs rarely when homologous chromosomes misalign, leading to duplications in one and deletions in another. ex: williams-beuren syndrome (on the PMS gene, chromosome 7)
What are detection methods?
Large deletions or duplications can be detected microscopically via altered chromosome banding patterns, while smaller changes require techniques like FISH (fluorescent in situ hybridization)
What are chromosomal rearrangements?
Inversions and translocations occur when chromosome fragments reattach incorrectly, potentially leading to fertility issues due to abnormal chromosome segregation.
What are the 2 types of inversions?
paracentric (centromere outside inverted region) and pericentric (centromere within the inverted region).
What is reciprocal translocations?
involve switching fragments between nonhomologous chromosomes
What is Robertsonian translocations?
Lead to chromosome fusion and changes in chromosome number.
What is a chromosome break point?
When a chromosome breaks, both DNA
strands are severed at a location
What are interstitial deletion?
Its the loss of an internal portion of
a chromosome, and results from two chromosome breaks
What is an unpaired loop?
A normal genetic material if one chromosome carries a deletion or is duplicated genetic
material if one homolog has a duplication
What is Pseudodominance?
It occurs when a recessive allele is
“unmasked” by a deletion that removes the dominant allele on the homologous chromosome
What is crossover suppression?
Inversion suppresses the production of recombinant chromosomes
About half of the proteins are what?
histone proteins, small basic proteins that tightly bind DNA
Position effect variegation (PEV) in Drosophila illustrates what?
the effect of chromatin compaction on gene expression
What is M A Rs (matrix attachment regions?
Chromatin loops of 20 to 100 k b
are anchored to the chromosome
scaffold by nonhistone proteins at sites
read more about high order chromatin and solenoid structure
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