Biology Questions

DNA is copied during a process called Transcription. It is the first step of gene expression, in which a particular segment of DNA is copied into RNA by the enzyme RNA polymerase.

The number of cell layers and cell types together give rise to 6 different types of epithelial tissue.

1. Simple squamous epithelia

2. Simple cuboidal epithelia

3. Simple columnar epithelia

4. Stratified squamous epithelia

5. Stratified cuboidal epithelia

6. Stratified columnar epithelia

Stratified squamous epithelia is best suited for areas subject to friction.

All living cells arise from pre-existing cells is one component of the cell theory.

The Cell Theory is one of the basic principles of biology.

The Cell Theory states:

1. All living organisms are composed of cells. They may be unicellular or multicellular.

2. The cell is the basic unit of life.

3. Cells arise from pre-existing cells.

Uracil is not found in DNA but found in RNA.

Random mutations are the ultimate source of genetic variation. Mutations are likely to be rare and most mutations are neutral or deleterious, but in some instances, the new alleles can be favored by natural selection. Polyploidy is an example of chromosomal mutation.

Mutations are changes in the DNA. A single mutation can have a large effect.

1) mutation - an alteration in DNA sequence, various types

2) intragenic recombination - results in entirely new associations of genes not present in either parental genome.

Two forms of intragenic recombination:

a) crossing over
b) independent assortment
3) reticulation – acquisition of genetic material from unrelated or relatively unrelated sources (e.g., hybrid species, horizontal gene transfer).