00:01
A couple is concerned their child will be born with sickle cell anemia.
00:04
The woman doesn't have it, but the woman's mother does.
00:08
Her father was a carrier.
00:10
The man is not a carrier.
00:12
Okay, so sickle cell anemia is recessive.
00:14
So let's have capital a for normal and little a for anemia.
00:19
Okay.
00:21
So the man knows he is not a carrier.
00:23
He knows this is his gene type.
00:25
He doesn't have any copies of the sickle cell gene.
00:28
What's about the woman? well, let's do, let's look at the woman separately.
00:32
So the woman's mother, so we'll have m for her mother, had sickle cell anemia.
00:38
So she had the homozygous recessive.
00:41
The woman's father was a carrier, so he was a heterozygotes.
00:46
What about the woman? well, the trick here is the woman doesn't have sickle cell anemia.
00:53
So we know she has at least one normal copy.
00:57
And she must have got that from her father because her mother doesn't have a normal copy to give...