Among 10,000 twin births, there were 4350 male pairs, 4150 female pairs and 1,500 male-female pairs. What are the number of monozygotic and dizygotic twins in this population?
I know that the 1500 male female twins have to be dizygotic. How do I find out about the same sex twins? We're suppose to use probability involving the punnet square to figure it out but I'm not sure how to do it or if there is another method. Thanks.
To determine the number of same-sex twins (monozygotic or dizygotic), we can use the concept of probability and the information provided.
First, let's understand the difference between monozygotic and dizygotic twins:
1. Monozygotic twins (identical twins) occur when a single fertilized egg splits into two embryos shortly after conception. Monozygotic twins share the same genetic information and are always of the same sex.
2. Dizygotic twins (fraternal twins) occur when two separate eggs are fertilized by two different sperm cells. Dizygotic twins can be of the same sex (two males or two females) or different sexes (one male and one female). Dizygotic twins share approximately 50% of their genetic material, just like any siblings.
Given that the 1,500 male-female pairs are dizygotic twins, we can conclude that they account for all the opposite-sex twin pairs in the population.
Now, let's determine the number of same-sex twin pairs (monozygotic or dizygotic). Since we know the total number of twin births is 10,000, we can subtract the number of opposite-sex twins from this total to find the number of same-sex twins:
Number of same-sex twins = Total number of twin births - Number of opposite-sex twins
Number of same-sex twins = 10,000 - 1,500
Number of same-sex twins = 8,500
Now that we have the total number of same-sex twins, we need to determine how many of them are monozygotic and how many are dizygotic.
To do this, you can use the punnet square approach as mentioned. This involves considering the probability of having monozygotic twins compared to dizygotic twins.
In general, monozygotic twins occur spontaneously and are not influenced by genetics. Therefore, the occurrence of monozygotic twins is roughly constant and not dependent on any specific factors.
On the other hand, dizygotic twins are influenced by genetic and environmental factors. The likelihood of having dizygotic twins is higher when there is a family history of dizygotic twins, genetics, or maternal age.
If we assume that the occurrence of monozygotic twins is roughly constant and equal to the occurrence in the general population (around 3-4 per 1,000 births), we can make an estimation.
Let's say the probability of having monozygotic twins is 0.0035 (3.5 in 1,000 births). To determine the number of monozygotic twins, we multiply the total number of same-sex twins (8,500) by this probability:
Number of monozygotic twins = Total number of same-sex twins × Probability of monozygotic twins
Number of monozygotic twins = 8,500 × 0.0035
Number of monozygotic twins ≈ 29.75
Since we can't have fractional values for twins, we can round this to the nearest whole number:
Number of monozygotic twins ≈ 30
To find the number of dizygotic twins, subtract the number of monozygotic twins from the total number of same-sex twins:
Number of dizygotic twins = Total number of same-sex twins - Number of monozygotic twins
Number of dizygotic twins = 8,500 - 30
Number of dizygotic twins = 8,470
Therefore, in this population of 10,000 twin births, it is estimated that there are approximately 30 monozygotic twins and 8,470 dizygotic twins.