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I’ve been writing up my talks and am surprised how long it has taken me to get through the first part of chromosomes. I promise to move on to some more interesting things – or at least change topics – soon. For now, I thought I’d address some common questions:

• what is a chromosome vs. a sister chromatid?
• what n value do you use? (especially during meiosis)

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We can mix up our strings of DNA (chromosomes) in a few ways. This week, we’ll talk about translocations.

We’ve talked about the correct number of chromosomes in a karyotype and banding. To refresh, humans have 46 chromosomes or 23 pairs of chromosomes in our regular (somatic cells). Eggs have 23 chromosomes and sperm have 23 so when they pair up, we get the full chromosome complement.

A chromosome translocation is when a piece of a chromosome is found on a different chromosomes (e.g. a piece of chromosome 7 is found on the tip of chromosome 11).  You may have heard it described in fancier terms = abnormality due to rearrangement of pieces between nonhomologous chromosomes. Nonhomologous just means different chromosomes. We’ll go through the basic concepts – it’s easier than you think!

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Our DNA is pretty cool. We get half our DNA from our mom and half from our dad and we function best when we have two copies of each chromosome. Having too much or too little of each section of DNA can lead to disease.

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Humans have 23 pairs of chromosomes and having too much or too little chromosomes or sections of chromosome can lead to disease. As mentioned in the introduction to karyotypes, size is one way to distinguish chromosomes but chromosome bands also help label the chromosomes.

One pet peeve is the way that non-experts say the location within a chromosome but you’ll be an expert by the end of this piece.

(c) Hybrid Medical Animation

We will start talking about human genetics at the point of chromosomes.We need to know the basics of chromosome organization and identification to understand the mechanisms and tests for common chromosome disorders.