Question

The size of one copy of the human genome is approximately 3 billion base pairs, and it contains about 25,000 genes organized into 23 chromosomes. a. Human chromosomes vary in size. What would you predict is the size of the average chromosome? b. Assuming that genes are spread evenly among chromosomes, how many genes does an average human chromosome contain? c. About half of the DNA in chromosomes contains genes. How large (in base pairs) is an average human gene?

Answer 1

Answer:

a. Average size of chomosomes = $130.435*10^6$.

b. Average amount of genes per chromosome = 1086,95 genes per chromosome in average.

c. Average length of chromosomes = 1,5 billion base pairs.

Explanation:

a. Assuming the whole human genome is about 3 billion base pairs representing 23 chromosomes (one set), the size of an average chromosome can be estimated as $3*10^9$ base pairs /23, which equals to more  $130,435*10^6$ (more than 130 million base pairs).

This results due to the fact that 23 chromosomes contain $3*10^9$ base pairs (3 billion bp). Then 1 one them (in average) contains  $3*10^9$ base pairs/23. So,

Average size of chomosomes: $3*10^9$ /23=$130.435*10^6$

b. If one assumes that genes are spread evenly among chromosomes, then the total amount of genes would be spread among the 23 chromosomes. Then, if one divides 25000 by 23, we are getting the amount of genes per chromosome.

Average amount of genes per chromosome: 25.000/23=1086,95 genes per chromosome in average.

c. If about half of the DNA in chromosomes contains genes, then half of 3 billion base pairs (representing 23 chromosomes) would be representing genes. Thus:

Average length of chromosomes: 3 billion base pairs / 2= 1,5 billion base pairs=  $1,5*10^9$ base pairs