7.5 Flashcards
Define nondisjunction
Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division.
It can lead to an abnormal number of chromosomes in daughter cells.
What is an autosome?
An autosome is any chromosome that is not a sex chromosome.
Humans have 22 pairs of autosomes.
What are sex chromosomes?
Sex chromosomes are the chromosomes that determine the sex of an organism, typically referred to as X and Y.
In humans, females have two X chromosomes, while males have one X and one Y chromosome.
What does SRY stand for?
SRY stands for Sex-determining Region Y.
It is a gene on the Y chromosome that triggers male development.
Why are humans more tolerant to extra sex chromosomes than autosomes?
Humans are more tolerant to extra sex chromosomes because of X chromosome inactivation, which limits the expression of genes on extra X chromosomes.
Autosomes do not have a similar mechanism for dosage compensation.
What happens during X chromosome inactivation?
During X chromosome inactivation, one of the two X chromosomes in female mammals is randomly inactivated, leading to dosage compensation.
This results in the formation of Barr bodies.
Define Barr bodies
Barr bodies are the inactivated X chromosomes in females, which are condensed and not expressed.
Typically, females have one Barr body per cell.
Draw a model of nondisjunction of the Y chromosome in meiosis II.
Nondisjunction of the Y chromosome in meiosis II results in gametes with either two Y chromosomes or none.
This can lead to conditions such as Turner syndrome or Klinefelter syndrome.
Define deletion in genetics
Deletion is the loss of a segment of DNA from a chromosome.
result for gamet missing genes
result for zygote
1 instead of 2
It can result in the loss of one or more genes.
Define duplication in genetics
Duplication is the presence of an extra copy of a segment of DNA on a chromosome.
result of gamete
extra genes
result on zygote
3 instead of 2
This can lead to gene dosage effects.
Define inversion in genetics
Inversion is a chromosomal rearrangement where a segment of DNA is reversed within a chromosome.
result of games
nothing
result for zygote
might have trouble pairing chromosomes for mitosis
It can disrupt gene function if it occurs within a gene.
Define translocation in genetics
Translocation is the movement of a segment of DNA from one chromosome to another.
effect on gametes and zygote
depends on which chromosomes end up in what gametes
This can lead to gene fusion or disruption of gene function.
