(02) Cytogenetics Flashcards
What is more dense - DNA during metaphase or interphase?
- DNA during metaphase
What is the process of capturing dividing cells at metaphase to examine chromosomal characteristics called?
- karyotyping
(Karyotyping)
What does G banding detect? What is used? What did this allow?
What does R banding detect?
What does C Banding Detect? What is used?
- High A and T – trypsin + Giemsa Stain – allowed for differentiation using banding (in addition to size and shape)
- Reversed Patterns (reversed G bands)
- identifies heterochromatin (repetitive DNA such as centromeres - so mostly the centromere just stains darks) – BaOH and Giesma
- Somatic cells in diploid organisms have ___ copies of each autosomal chromosome. One from the ___ and one from the ____.
What is the diloid number? What is it?
How much variety in total chromosome number across species? Genes? DNA?
- 2, father, mother
- 2N – the total chromosomes in a somatic cell
- a lot (dogs have 78, cats have 38) – very similar (~20,000) – very different (1.1 - 3 billion bp (haploid))
(Chromosome Nomenclature)
- Chromosomes have a ___ and a ____ arm. Where they join is called the _____. The two pairs of identical chromosomes (left and right side of X) are called _____.
Name from left to right
- short (p), long (q) – centromere – sister chromatids
- metacentric, submetacentric, acrocentric, telocentric
How many sex chromosomes does each individual have?
- in mammals?
- in birds?
- Reptiles?
- 2 sex chromosomes
- XX females and XY males
- ZZ males and ZW females
- a bunch of different stuff (temperature dependent sex differentiation sometimes - temp of an egg)
(Fluroescence in situ Hybridization)
What is it?
How is it done?
What combines with DNA easier - large or small fragments?
How far has this advanced (in humans)?
- A technique that allows you to take a known piece of DNA, tag it with a fluorescent probe, and hybridize to a chromosome to see where it goes
- DNA (of chromosome) is denatured (heat or acid) – then a apply a small piece of DNA that you have designed with a fluorescent tag on it - then it will hybridize and you can follow it
- small (don’t have as much steric hindrance)
- Now possible to color entire chromosomes one color (to pair them or see if they recombine) - called Multi-color fish?
What can cytogenetic abnormalities that affect the integrity of a chromosome be referred to as?
What are the two types of chromosomal abnormalities?
What does each type include?
- structural aberrations
- Balanced and unbalanced (transolcations)
- balanced - no net gains or loss of DNA (as in peri- or paracentric inversions and reciprocal translocations)
- unbalanced - duplication, deletions, and non-reciprocal translocations
What can cryogenetics be used for in a clinical setting?
Investigation of infertility/reproductive disorders and evaluation of tumors
- If a chromosome change causes a problem it is either the result of something that occurred during ______, or the problem is that it causes problems with _____.
In meiosis starts out with a ____ cell, produces ______ by way of ___ divisions
What separates in first division? second?
- meiosis, meiosis
- diploid, haploid gametes, two
- homologous chromosomes - sister chromatids
(Abnormal Chromosome Number)
What is Aneuploidy? What is it most commonly seen in? What causes it? What is the percentage of this occuring?
- What have monosomy and trisomy of autosomes been observed in (what animals)?
What is down syndrome in humans?
- karyotypes with more or fewer than the normal euploidy state – most commonly seen with sex chromosomes (or small autosomes) – non-disjuction during meiosis – 5% of all meioses have a disjunction (these are usually destroyed)
- cattle and horses
- trisomy of Hsa21
(Inter-species crosses)
- Female Horse + Male Donkey =
- do the parents have the same number of chromosomes?
- does mitosis occur normally?
- Does the mule have an even number of homologous pairs? Why or why not?
What is the result?
- infertile mule
- no (horses 64 and donkeys 62)
- yes
- no - has 63 chromosomes (cause his parents had different numbers)
- meiosis is disrupted and viable eggs and sperm are not formed
(Nondisjuction of Sex Chromosomes)
- If you have a non-disjuction in the first division what do you end up with? In the second?
- What is XO called? symptoms?
- XXX?
- XXY?
- Which animal does this occur in?
- (XY) XXY, (XY) XXY, (O) XO, (O) XO – (XX) XXX, (O) XO, (Y) XY, (Y) XY (normal)
- Turner’s syndrome - normal appearing but sterile
- often fertile - Kleinfelter’s syndrome (predominantly male, sterile)
- alpaca (XXX) - infertile
What is the deal on reciprocal translocation?
Result in individual?
Gametes?
- portion of one chromosome gets stuck onto another
- often normal phenotype (still has balanced chromosomal material)
- Unbalanced gametes form during meiosis
What occurs in a Roberstian Translocation?
Can it have an effect on fertility?
- 2 acrocentrics form a metacentric and one centromere fragment (for example) – have one less chromosome but still have balanced amount of DNA
- yes
(Meiosis)
What is a ribbon-like protein structure that forms between homologous chromosomes during prophase 1 of meiosis?
What does this structure help do?
- synaptonemal complex
- mediate chromosome pairing (synapsis) and recombination (crossing over) (maybe)
_:_ centric fusion in cattle
what happens?
- do you go through normal disjuction (balanced gamete)?
Will chromosomal rearrangement always affect fertility?
- 1:29
- one 1 and one 29 pair up
- no
- not always, depends on how organism deals with it
(Inversion)
- What one is on top? on bottom?
example?
How are these a problem? What does this result in?
- paracentric inversion (does not involve centromere)
- pericentric inversion (involves centromere)
- tobiano coat color
- during meosis need to get homologous genes paired up correctly - so one of these has to loop a bunch for this to work
- One chromosome with deletions and one with duplications
- Chromosome problems are problematic if they ______ or if they ______.
- change amount of DNA, interrupt meiosis
Is it possible to get XX male or XY female?
How?
- yes
- SRY (sex determining region on Y) makes someone male - if this gets sent to X during recombination fuck up can result in that
What is the small region of X and Y that are homologous? where? Significance?
How does this cause XX male?
- pseduo-autosomal region (PAR) – one on short and one on long arm – behaves as though autosomal - recombination occurs here (has to meisos to occur)
- SRY is close to PAR - if there is a mess up the SRY can get sent to X
How are mosaics and chimeras similar? different?
Examples of this?
Is tortoiseshell coat color an example of this? what is it?
- Both have more than one genetically distinct population of cells
- mosaics - arise from one zygote
- chimeras - arise from more than one zygote
- intersex chicken (female on side, male on other)
- not really - different inactivation of X - one that codes for orange - one for black or whatever
What is freemartinism in cattle?
How does this occur?
What does this result in ?
- if you have twin cattle - one male and female - the female will be sterile
- exchange of hormones and hemotopoetic cells
- masculization of tubular female reproductive tract, lack of female gonad development, ovatestes
