Chromosomal Abnormalities, Aneuploidy and Non-Disjunction

NOTE! The label for "sister chromatids" at 1:30 should say "homologous chromosomes"! Sadly, Youtube deleted the "annotations" feature that had previously corrected the error. Thanks for the viewers who noticed the problem!

Chromosomal problems can easily occur during reproduction. Continuing our discussion of reproduction, this screencast concerns common chromosomal abnormalities, specifically non-disjunction. During nondisjunction, an incorrect number of chromosomes are allocated into the resulting sex cells.

[ARCHER-chxn]

I learned more things here than the 3 months lecture in school
Thankyou! you saved my semester

[DavidNasr]

This video is absolutely AWESOME! I've been struggling with these as I lack a foundation in Biology for having slacked off in my earlier school years, this helped clear all my uncertainties. Thank you so much!

[Keletsonx]

This is way better than trying to make sense of confusing notes on a textbook thank you 🙏

[sylvialarsson]

Besides the one terminology hiccup at 1:30, which I see you have already made attempts to rectify. This is a wonderful video, clear, concise, and informative. Your students are very lucky!

[tayyabashahid]

This is the best explanation of non disjunction I've had! Thanks a bunch!

[britoronto]

WARNING--incorrect information in this video! At T=2', the chromosomes depicted are NOT sister chromatids, they are homologous chromosomes (ie one you got from mom and one from dad). Sister chromatids result from DNA replication and thus in G2/M phase, each homolog will be made up of two identical sister chromatids that are paired together. Homologous chromosomes however differ from each other, and will contain different versions of each gene (ie alleles).

[laurengao]

I like this lecture a lot! Thanks for making this awesome video. However, I think at 1:43 the chromosomes should not be referred to as sister chromatids as the term chromatids should only be used with replicated chromosomes connected at the centromere.

[smashez]

My partner has pericentric inversion of chromosome 9, p11q13. What does that mean for having children in future? Are we at a higher risks for having children with health problems?!

[cajesnoli]

What cytological abnormalities are expected of aneuploids at mitosis? At meiosis?

[medishine]

Nondisjunction in meiosis I occurs when the tetrads fail to separate during anaphase I. At the end of meiosis I, there will be 2 haploid daughter cells, one with n+1 and the other with n-1. Both of these daughter cells will then go on to divide once more in meiosis II, producing 4 daughter cells, 2 with n+1 and 2 with n-1. -journal

why in this video nondisjunction in meiosis I causes trisomy (2n+1) and monosomy (2n-1)?

[nooonii]

Thank you for this demonstration. I think karyotyping show homologous chromosomes and not sister chromatids?

[milenachaufan]

XY determine the chromosomal sex, not the gender, that’s a social concept. Plus genital sex could be different than chromosomal or different than hormonal sex. We teach this at university of Buenos Aires medicine school and it should be taught in every university

[gregoryhudak]

Insert "homologous chromosomes" @ 1:35 in place of "sister chromatids"
Otherwise well done. Thank you for posting.

[khoa]

1:41 shows wrong information, that two chromatids of the chromosome 5 is homologous chromosomes, not sister chromosome :((

[alighouse]

Came here for clarity on non-disjunction - clear video, well paced with clear info. Thanks!

[anupama]

Your explanation is very very helpful and visuals are very clear and perfect. Thank you so much for this concised video❤️❤️ Love from India 🇮🇳🇮🇳

[skoufoss]

The homologus chromosomes are in synapsis during prophase I. You depict a synapsis among non-homologus.

[ivaniam]

Information is wrong at 2:00. The chromosomes with arrows are homologous chromosomes. Not sister chromatids

[Tnbeazy]

Thank you for this explanation! Very informative. Do you know if one can call the chromatids at the end of meioses (II) chromosomes as well? I think I picked that up somewhere.

[evamandri]

Wow! Is that what happens with high and low mosaic embryos when talking about abnormal MI and MII?