Why does Cytosine not pair with thymine?

In order to make H bond with the both we require a hydrogen attached to an electronegative atom as well as an electronegative atom both in a particular configuration. These conditions are met by thymine and not cytosine.

Why can’t adenine pair up with Cytosine?

They both have to -OH/-NH groups which can form hydrogen bridges. When one pairs Adenine with Cytosine, the various groups are in each others way. For them to bond with each other would be chemically unfavorable.

Why does Cytosine make pair with guanine and not with thymine?

Cytosine make pair with guanine and not with adenine because hydrogen bond forming functional groups are not complementary between C and A.

Does guanine bind with cytosine?

Guanine is one of the building blocks of DNA. It’s the G in the A, C, G, or T. Guanine in the double helix pairs with cytosine, so you will see CG pairs; one on one strand and one on the other.

What would happen if adenine paired with guanine and cytosine paired with thymine?

How would the shape of a DNA molecule change if adenine paired with guanine and cytosine paired with thymine? The DNA molecule would have irregular widths along its length.

Why does a cytosine not match with thymine?

A cytosine cannot match with thymine because the shape of cytosine will only match with the shape of a guanine. To look at it in another way: Thymine(uracil in RNA) and cytosine are pyrimidines. Pyrimidines are single-ringed organic base that will only attach to purines, or adenine and guanine by hydrogen bond.

Why can’t purine and cytosin be combined?

1- Bonds b/w adenine and thymine create the similar shape as done by guanine and cytosin to accommodate the diameter of 2nm. 2- Purine can’t combine with Purine (as they r doubled ring structure) , diameter of 2 nm can’t accommodate two purines together.

Can cytosine and adenine bond with each other?

Adenine and Thymine also have a favorable configuration for their bonds. They both have to -OH/-NH groups which can form hydrogen bridges. When one pairs Adenine with Cytosine, the various groups are in each others way. For them to bond with each other would be chemically unfavorable.

Is thymine a purine or pyrimidine?

Thymine(uracil in RNA) and cytosine are pyrimidines. Pyrimidines are single-ringed organic base that will only attach to purines, or adenine and guanine by hydrogen bond. Because cytosine and thymine are both pyrimidines, it cannot form a hydrogen bond with each other.