Have you even wondered why only men have hairy ears or certain forms of color blindness? In this lesson you will learn about holandric genes on the Y chromosome and how they are passed from one generation to the next.
Genes: How Traits Are Inherited
If you look at a picture of yourself compared to pictures of your mom or dad at your age, do you look similar? What, biologically, makes you male or female? Let’s investigate.
Traits are passed from parents to offspring on genes that are a part of their DNA. DNA, or deoxyribonucleic acid, is a molecule that carries all the codes for an organism’s characteristics. DNA is like a huge library, except all the books are about you.A gene is a part of the DNA that tells your body to make a particular protein.
Proteins are the key here; they are what control our traits. Think of the genes each as a different book in the library about you. Each book is about a different trait. The first book might cover height, and the next book might be about eye color.Every human being has sex cells in their bodies (egg or sperm, depending on if they are male or female). Each of the sex cells have half of a person’s DNA, or half of their library.
During sexual reproduction, the two sex cells come together and a new set of DNA is created – a new library with a combination of the books from both parents.
Role of Chromosomes
In order to package the DNA in each of the sex cells, the information must be condensed. Think about needing to move the information from every single book in your library. It would be great if you could scan the information in the books and put it on flash drives. That would make the information easier to transport. That is what the body does with the DNA, except it doesn’t use flash drives, it uses chromosomes.Chromosomes are the condensed form of DNA produced during DNA duplication.
Every human has 23 pairs of chromosomes. Each set has different genes, or books from the library. The 23rd set are the sex chromosomes, the chromosomes that determine whether the human is a male or a female. Females have chromosomes that are represented as ”XX” and males have ”XY” as their 23rd set. Females can only pass on the ”X” chromosome to their offspring and males can pass on the ”X” or the ”Y” chromosome.
Now that we’ve explained about genes and chromosomes, it’s time to talk about holandric genes. These are the genes that are carried on the Y chromosome.
They mainly code for testes, which secrete testosterone and are responsible for making an organism male. There are only a handful of genes on the Y chromosome; holandric traits can only be passed from father to son, and holandric diseases are rare.For example, a father may carry the gene for hairy ears, called hypertrichosis pinnae, on his Y chromosome; his daughter will not inherit this gene, but his son would. Some examples of traits caused by holandric genes are:
- Hypertrichosis pinnae – causes excessive hair in the ear
- Male infertility – males can’t produce offspring
- Retinitous pigmentosa – causes gradual decline in vision
- Color blindness – inability to see some color or color differences
- Traits are passed from parents to offspring on genes that are a part of their DNA.
- DNA is a chain of phosphorus and lipids that gives an organism its characteristics.
- A gene is a part of the DNA that tells your body to make a particular protein.
- Chromosomes are the condensed form of DNA produced during DNA duplication.
- Females have chromosomes that are represented as ”XX” and males have ”XY” as their 23rd set.
- The genes that are carried on the Y chromosome are called holandric genes.
- Holandric genes can only be passed by males onto their sons; they code for ‘maleness’ but sometimes cause rare conditions like hypertrichosis pinnae and color blindness.