Chromosomal Abnormalities Flashcards by Emily Cottenden

where are gene-poor vs gene-rich genes located on the chromosome

Gene poor- nuclear periphery
gene rich- nuclear interior

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what are chromatin? how does it make up the nucleosome core particle

they are chromosomes complexed into nucleoprotein structures in eukaryotes.

chromatin bound in nucleosomes with 2 molecules each histone make nucleosome core particles

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least to most condensed chromosome state

LEAST: nucleosome
solenoid
chromatin fiber
MOST: metaphase chromasom

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T/F chromosome number directly correlates to genome size and number of genes

FALSE

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T/F in mammals the number of chromosomes is proportional to size/amount of DNA

FALSE

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non mammalian species maximum and minimum number of chromosomes recorded

Max: fern(ophioglossum reticulum)-631 pairs

Min: nematode-1 chromosme
jack jumper ant-1(male)/2(worker) chromosomes

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C-banding chromosome staining

only centromeres are stained

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G-banding chromosome staining

due to differential staining along the length of each chromosome

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ZOO-Fish chromosome staining

cross-species chromosome painting(show where genes from one chromosome different chromosomes from other species)

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what is nondisjunction? how does it affect ploidy

it is the failure of chromosomes and sister chromatids to properly separate during cell division, it can lead to abnormalities in chromosome number

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aneuploidy vs euploidy

aneuploidy: abnormal amount of chromosomes in 1 or more parts of a set of chromosomes

euploidy: chromosome number of an individual is the number of complete sets

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how do disjunction errors in meiosis I vs meiosis II effect gametes?

nondisjunction in meiosis I: all gametes have abnormal number of proteins(2 have +1, 2 have -1)

nondisjunction during meiosis II: half the gametes have abnormal chromosome numbers, half are normal

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is it better to have a disjunction error in meiosis I or meiosis II

meiosis II

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T/F trisomy for many different chromosomes is routinely observed in spontaneous abortions

TRUE

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3 human chromosomes that can be trisomic in newborns

13, 18, 21

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why is autosomal trisomy more tolerable in smaller chromosomes

small chromosomes hold less DNA

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main categories of structural aberrations that can occur in mammalian chromosomes

chromosome breaks
terminal deletion
acentric

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does odd or even ploidy decrease fertility leading to seedless varieties

odd

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acentric definition. how does it occur after chromosome break and terminal deletion

chromosome lacks a centromere. it is a fragment of a broken/deleted chromosome. it can get lost during division

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what is inversion? what are its consequences?

rearrangement in chromosomes, mostly normal unless genes are disrupted

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2 types of inversion and their products

parAcentric: centromere is outside of inverted region
PerIcentric: centromere is within inverted region

what inversion leads to tobiano coat color in horses

paracentric

what is a deletion, and what are its phenotypic consequences

loss of a part of one chromosome arm
-small deletions often have no phenotypic effect
-large deletions can be lethal

syndrome used as example for deletion? where was the deletion

Cri-du-chat syndrome
segmental deletion of chromosome 5p

3 main types of translocation

-nonreciprocal translocation -reciprocal balanced translocation -Robertsonian translocation/chromosome fusion

what type of translocation has developed the Philadelphia chromosome

reciprocal balanced translocation

possible consequences for translocation of gametes

change to the phenotype EX. familial down syndrome caused by Robertsonian translocation

definition of duplications? how can they effect the genome

production of extra gene copies. part of genetic material is larger, widespread segmental duplications can lead to large-scale rearrangements

what gene is involved in Charcot-Marie-tooth syndrome

chromosome 17 on peripheral myelin protein PMP22 gene

what is a fragile site? can they become common?

heritable loci on chromosomes that are visible as gabs/breaks due to cell exposure to DNA replication inhibitors. can be common or rare

are fragile sites associated with diseases all the time

only rare fragile sites are associated with diesease

example of a human disease with fragile sites, what is its mechanism

Fragile X syndrome caused by repeats in FMR1 gene

Klinefelter syndrome -genotype -phenotype

-more than 1 X chromosome(XXY, XXXY, XXXXY) -phenotypically male, tall, long-limbed, underdeveloped sex characteristics, infertile

turner syndrome -genotype -phenotype

-absence of a second X chromosome(XO) -phenotypically female, webbed neck, heart and kidney defects, infertile

XXX/XXY condition

XXX-female, mostly normal, taller, infertile XXY-male, physically normal, over 6ft tall

nucleosome structure

histone H2A and H2B make 1 dimer and H3 and H4 form another. 2 H3-H4, and 2 H2A-H2B dimers pair to form the octamer which is then wrapped with DNA

what does "beads on a string" refer to

chromatin in least condensed state. "beads" are nucleosomes "string" is linker DNA

what histone acts as linker DNA

what gives chromosomes their shape

chromosome scaffold

euchromatin vs heterochromatin

Euchromatin: uncoiled and active DNA(white bands) heterochromatin: condensed and inactive DNA(gray/black bands)

fluorescent in situ hybridization(FISH)

use of gene-specific molecular probes to detect a target sequence

mammalian species with most and least chromosomes

MOST: red vizcacha rat-2n=102 LEAST: Indian muntjac deer-2n=6/7

monosomy in humans

embryos are aborted or are non-viable if born

what is an inversion loop? what does it result in?

it is an alignment of a normal chromosome with its inverted homolog. it results it 2 viable gametes, and 2 nonviable/deleted gametes

genetic consequences of deletions

-loss of chromosome segments -loss of gene(s) and gen products -problems in meiotic pairing -possible changes in phenotype

what is translocation

movement of chromosomal segment to a new location in the genome

nonreciprocal translocation

one chromosome translocates but the other doesn't

reciprocal balanced translocations

two pieces of nonhomologs switch places

Robertsonian translocation

fusion of 2 nonhomologous chromosomes(decreasing the chromosome count by 1)

T/F disorders of sex development are caused by non-disjunction

FALSE. they are caused by mutations in sex-determining genes

XX male DSD what causes it? phenotypic changes

-SRY robertsonian translocation to X OR -mutation in SOX9 gene disorders of sexual development and reproduction

XY female(swyer syndrome) how is it caused phenotypic changes

-deletion or mutation in SRY gene OR mutation in X-linked or autosomal genes mostly normal, tall, sterile