micro 10.2 pt 2

DNA backbone

Alternating deoxyribose sugars and phosphate groups connected by phosphodiester bonds.

Location of nitrogenous bases in DNA double helix

On the inside of the double helix, where they pair with complementary bases.

Location of sugar-phosphate backbone in DNA double helix

On the outside of the double helix.

Type of bond holding complementary DNA bases together

Hydrogen bonds.

Type of bond holding nucleotides together within a DNA strand

Phosphodiester bonds.

Stronger bond: hydrogen bonds or phosphodiester bonds

Phosphodiester bonds.

Importance of hydrogen bonds in DNA

They hold the two DNA strands together while allowing them to separate during replication and transcription.

DNA sequence

The order of nucleotides (A, T, C, and G) along a DNA strand.

Importance of DNA base sequence

It stores the genetic information that determines the traits and functions of an organism.

Determination of genetic information in DNA

The sequence of nitrogenous bases.

Genome

The complete set of DNA in an organism.

Location of DNA in eukaryotic cells

Primarily in the nucleus, with additional DNA in mitochondria and chloroplasts (in plants and algae).

Location of DNA in prokaryotic cells

In the nucleoid region of the cytoplasm.

Chromosome

A DNA molecule containing genetic information packaged with proteins.

Proteins packaging eukaryotic DNA

Histone proteins.

Chromatin

DNA wrapped around histone proteins.

Nucleosome

A segment of DNA wrapped around a core of histone proteins.

Reason for DNA wrapping around histones

To compact DNA so it fits inside the nucleus and to help regulate gene expression.

Organisms using histones to package DNA

Eukaryotes and many archaea.

Do bacteria use histones to package DNA?

No. Most bacteria use nucleoid-associated proteins instead of histones.

DNA supercoiling

The twisting of DNA into a more compact structure.

Importance of supercoiling

It helps compact DNA and allows it to fit inside the cell.

Enzyme introducing or removing DNA supercoils

Topoisomerase.

Consequence of too tightly wound DNA during replication

Topoisomerase relieves the twisting stress by cutting and rejoining DNA.

Function of topoisomerase

To prevent DNA from becoming overly twisted or tangled.

Stability of DNA as a molecule

Its double-stranded structure and sugar-phosphate backbone protect the genetic information.

Reason for DNA separation into two strands

So it can be replicated and transcribed.

Complementary base pair containing three hydrogen bonds

Cytosine and guanine (C-G).

Complementary base pair containing two hydrogen bonds

Adenine and thymine (A-T).

Why GC-rich regions of DNA require more energy to separate

Because G-C base pairs have three hydrogen bonds, while A-T base pairs have only two.