Topic 1 - Deoxyribonucleic Acid

Biology Topic 1 Flash Cards

What does DNA stand for?

Deoxyribonucleic Acid

What is the purpose of DNA?

Stores the genetic information for the production of protiens

Where is DNA found in Prokaryotes?

The Nucleoid (A Single Circular Chromosome) or Plasmids

Where is DNA found in Eukaryotes?

Nucleus, Chloroplast (Naked) and Mitocondria (Naked)

What protine does DNA in Eukaryotes bind to?

The Histone Protien

What is Naked DNA?

Not bound to any protien

How is DNA stored in Eukaryotes?

As Linear paired chromosomes

What is the structure of DNA?

The two strands are are joined together by pairs of bases to form a double helix

What are the 3 parts of a Nucleotide in order?

Phosphate Group, Deoxyribose (Sugar) and Nitrogenous Base

What are the 4 DNA bases?

Adenine, Thynime, Cytosine and Guanine

What is the base bonding rule?

A:T and C:G

How do bases bond?

Based on their hydrogen bonds A:T has 2 and C:G has 3

What is a the end of DNA that has an unbound Phosphate group refered to as?

5’ or 5 Prime

What is a the end of DNA that has an unbound Hydroxyl group refered to as?

3’ or 3 Prime

Describe the direction and orientation of DNA:

DNA strands runs in opposite directions antiparralel. (Asymmetrical) meaning the 5’ and 3’ ends are on opposite ends.

In what direction is DNA transcribe?

From 3’ to 5’

Define Transcribed:

creating RNA to send protien codes from the DNA to the ribosome inorder to make protiens.

What are the 2 types of Bases?

Purine and Pyrimade

What physical features decide whether a base is a Purine or a Pyrimade?

The amount of nitrogen bases rings in chemical structure, Purine (2) and Pyrimade (1)

Name the Purines:

Adenine and Guanine

Name the Pyrimades:

Thymine, Cytosine and Uracil

List the 4 diffrences between RNA and DNA:

* DNA has dexyribose where as RNA has only ribose
* RNA is single helix where as DNA is a double helix
* In RNA Uracil replaces Thymine
* DNA is longer

Name the 3 types of RNA and include their function:

1. Messenger RNA (mRNA) Template for Translation
2. Ribosomal RNA (rRNA) component of ribosome as catalyst)
3. Transfer RNA (tRNA) delivers Amino acids to ribosome - has 3 bases as an identifer called a condon

How is DNA packed?

It is wrapped around 8 histone protiens in an organised way to form a nucleosome.

Cause of Methylation:

Causes nucleosomes to pack tightly, decreasing expression of the gene.

Cause of Acetylation:

Results in losely packing, increasing gene expression.

Cause of Topoisomerase:

Causes DNA to supercoil

Why is it necessary to pack DNA?

1. In order to fit
2. So it all says organised during cell replication

What is DNA Replication?

The process by which DNA makes a copy of itself.

When does Replication occur?

During Interphase (S-Phase) before mitosis and Meiosis.

In 3-4 steps how is DNA replicated?

1. The DNA unwinds
2. Helicase enzymes break the hydrogen bonds between the 2 strands
3. DNA polymerase adds complemantry bases
4. The DNA rewinds

In what direction does polymerase read DNA? and In turn what direction is the daughter strand created?

The polymerase move from 3’ to 5’

Therefore strands grow from 5’→ 3’

What is it meant by “DNA replication is Semi-Conservative”?

1. One Strand will be the original template
2. The other strand will be the newly synthesized.

Therefore half of the final strand is conserved.

During replication what is and open section of DNA called?

A replication fork which moves in two directions.

Why is DNA replicated at multiple sites?

Speeding up the replication.

Why are there two diffrent types of strands during replication?

As polymerase runs unidirectional it causes a lagging and leading strand.

What is a Leading Strand and from which terminal does it start at?

Assembled continuously, starts replication from the 3’ end.

What is a Lagging Strand and from which terminal does it start at?

Broken up into fragments. Starts replication from the 3’ end.

What are the Lagging strand fragments called and how what enzyme joins them all together?

Okazaki fragments later joined together by the ligase enzymes