I understand mostly about how traits are passed through parents to children, but how does the exact mutation for sickle cell get passed down onto a child? I’m so confused.
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It does get passed from parent to child. The sickle cell variant of one specific gene causes sickle cell anemia. Only if a person has the sickle cell variant from each parent will that person suffer from sickle cell anemia (really bad news). If a person has one sickle cell variant gene and one non-sickle cell variant, that person is immune to malaria (fantastic news, if that person lives in a place where malaria).
Sickle cell is a genetic trait like any other – it gets passed down the same exact way that a gene for blond hair gets passed down, or a gene for colorblindness, or any number of other traits that we have.
Different versions of a gene are called “alleles,” so for example there are alleles that code for brown eyes, and alleles that code for blue eyes. Sickle cell is one allele of a gene that makes hemoglobin, which in an important protein in our blood – it mutated randomly thousands upon thousands of years ago, and then was copied and passed on just like any other trait. All of us have some mutations in us, some are mostly harmless, some quite harmful. And sickle cell is what’s called a “recessive” allele – if someone receives a “healthy” allele from one parent and a sickle-cell version from the other (a hybrid trait), they’ll have very few problems; because the healthy version can still do its work, it covers up the bad trait for the most part.
The fun part, though, is that people with that sickle cell gene are actually much more resistant to malaria, and even if they get it, they’ll usually have a much more minor case. Which is theorized to be why the disease has stuck around, especially in parts of Africa, the Mediterranean, the Middle East, etc. where malaria has been a big problem. For people in those areas, having the hybrid trait is the best of both worlds – few worries from sickle-cell, and few issues from malaria.
Sickle trait is a mutation in the beta chain of hemoglobin, the protein that moves oxygen in your blood cells. Every protein is coded for by a sequence of DNA, which is transcribed to RNA then translated to a protein. Each person has two copies of every gene (thousands of genes) and puts one copy or the other of each gene into an egg cell or sperm cell. When an egg is fertilized by a sperm, the offspring have two copies of every gene. One they got from mom and one from dad. It’s a back up system so that if you have a mutation, the other copy of the gene probably works, so at least one copy gives you the proteins you need.
In some regions having a copy of the mutated sickle gene from one parent and a normal gene from the other parent let’s you have good resistance to malaria, but fairly normal blood. Half the proteins that the normal gene makes is normal, but the other half is mutated. So people with one of each are at an advantage. But if a child inherits a mutated copy from mom and a mutated copy from dad, the only hemoglobin proteins they make don’t fold up correctly and stick together, making the blood cells stretch out and look like sickles. These don’t get oxygen to all of the body and clog up blood vessels, so it’s a pretty harmful disease.
It’s genetic. That’s how *all* traits are passed from parent to child, so if you don’t know that, you don’t know how traits are passed from parent to child. That’s ok though.
We inherit our genes from our parents. Each parent provides us with half of our genetic material. Half from the sperm, and half from the egg. When the sperm fertilizes the egg, these genes mix and create a new genome that is uniquely yours, but made up of genes from your mom and dad.
If both parents either have sickle cell or have 1 copy of the gene with the mutation (it takes 2 copies to have the disease) any child can wind up as a carrier (has 1 gene with the mutation) or have the disease itself (got 2 copies of the gene with the mutation).
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