“The human Y chromosome is only present in males and thus genes and linked traits are inherited from male to male but are those always expressed? Let’s find out.”
Do you know?
- The Y chromosome is the only human chromosome that doesn’t have identical pair. The y chromosome is only present in males.
- The total length of the Y chromosome is 59 million base pairs. And approx. 150 to 200 known genes.
- The major genes or portion of the Y chromosome are associated with infertility.
- The Y chromosome evolved before the autosomes 3,00,000 years ago.
To know more you can read our previous article: Explaining the Y chromosome.
The human Y chromosome is a smaller chromosome and contains only a few genes. It follows unidirectional Y- y-linked inheritance in which traits are inherited between only the male individuals of the family.
Among the two broad human chromosomes, viz autosomes and sex chromosomes, the Y-chromosome belongs to sex chromosomes. Another human sex chromosome is X. males have one X and a Y chromosome while females have two XX chromosomes.
Notedly, the X chromosome is bigger in size in comparison with the Y and thus contains more genes. Studies depict that a Y chromosome has a predominant role in male sex development and discrimination hence, crucial for maleness.
Some people often said that the more the Y genes the more maleness they produce. But scientifically that’s not true. The number of genes on any Y chromosome are same and remains the same, rather, the expression of genes has a strong effect on maleness.
However, it’s noteworthy that if any major genes are absent or not present, it causes serious associated problems. But in ideal conditions, all the genes are there on the Y chromosome. The expression is important not the number.
So you may wonder what is Y-linked genes and expression. Are Y-linked genes always expressed? Let’s findout. To clarify the topic more comprehensively, I will explain several terminologies first and then get back to the topic.
What does Y linked mean?
Y-linked means that the traits, genotypes or genes are associated or linked with the Y chromosome. For example the Y chromosome. It transmits along with the Y chromosome to the next generation. And only show phenotypes when the Y chromosome is present.
Here are examples of some Y-linked traits.
Examples of Y-linked traits:
Examples of Y-linked traits are Y-linked infertility, azoospermia, oligospermia, Webbed toes, Hypertrichosis etc.
It’s noteworthy to understand that Y-linked inheritance can’t be classified into dominant or recessive. The reason is its presence as a single entity. The Y-chromosome is present only in male individuals.
So any gene, disease mutations, alterations, traits or CNV present on the Y chromosome is directly inherited in the male individual of progeny. However, it can’t be present in females. Meaning, if a father has some Y-linked abnormal trait, his daughter has nothing to do with it.
When genes or traits are inherited, located on the Y chromosome, are inherited from male-to-male individuals of the family, such traits or genes are known as Y-linked.
Take a look at the pedigree here.
No known inherited disorder or condition is still known in which the Y-linked inherited is involved. Any abnormality in the Y chromosome majorly causes infertility and is not inherited (because the infertile person can’t produce a baby).
In support of the present question, it is also crucial to understand what type of genes are located on the Y-chromosome. Keep in note that the Y chromosome is so tiny and contains only around a few hundred genes. Here is the list of 10 important genes on the Y chromosome.
|Gene||Cytological location||Full name||Function||Associated disease (if any)|
|SRY||Yp11.2||Sex-determining region of the Y||Male sex development and sed determination||Infertility|
|ZFY||Yp11.2||Zink finger protein Y-linked||Transcriptional factor|
|AZFa||Yq11.21||Azoospermic factor-a||Potential role in spermatogenic development||Spermatogenic failure and infertility|
|AZFb||Yq11||Azoospermic factor-b||Spermatogenesis||Spermatogenic failure and infertility|
|AZFc||Yq11||Azoospermic factor-c||Spermatogenesis||Spermatogenic failure and infertility|
|DAZ family||Yq11.22||Deleted in Azoospermia||spermatogenesis||infertility|
|CDY family||Yq||Chromodomain protein Y linked||Gene repressor|
|PRY||Yq11.22||Putative tyrosine phosphatase protein-related Y||Produce a protein that expresses in testis||Testicular developmental problems|
|SHOX||Yq11.3||Short stature homeobox-containing||Short stature|
Now coming to our main question are Y-linked traits always expressed?
The broad answer is “Yes.”
As we aforementioned, the Y chromosome is inherited from male to male and thus traits, genes and genotypes are also transferred. In addition, as there is no other identical chromosome like the X or other autosomes, the genes and traits present on Y chromosomes are always expressed.
However, the only condition is that it is only expressed in male individuals. So we can say that the Y-linked traits are always expressed in male individuals of the family.
the Y chromosome is mysterious, literature suggests that it’s dying and losing sequence. While some literature suggests that it originated from the X chromosome or autosome. But the point is, the Y chromosome is so important for mankind.
Genes located on this are directly involved in male sex differentiation, sex determination, gonadal development, testicular development and development of other male sexual phenotypes. I hope you like this article. Please share it and bookmark our blog.