Building Blocks Of Life 2

Question 0

What is DNA helicase?

Answer 0

It unwinds DNA strands at 100 np per min to create a replication fork.

Question 1

What type of replication is DNA replication and what exp confirmed this?

Answer 1

It is semi conservative replication whereby each strand acts as a template. This was found via the melshon stahl exp whereby bacteria was first grown in n15 media before being transferred to n14. After three rounds DNA contained only n14.

Question 2

Is DNA replication continuous?

Answer 2

No, it is semi discontinuous. The replication fork has an asymmetrical structure and the lagging strand is synthesised semi dis continuously to create Okazaki fragments.

Question 3

How does polymerisation occur on the lagging strand?

Answer 3

In the opposite direction to overall chain growth. this means only 5’-3’ DNA polymerase is needed.

Question 4

How is fidelity of replication increased?

Answer 4

DNA pol has 3’ to 5’ endonuclease activity used to excise incorrectly paired bases. Increase fidelity by 100 fold. Correct nucleotide has higher affinity for DNA pol due to more energetically favourable bp.

Question 5

How are primers added to the lagging strand?

Answer 5

RNA primer is syn by DNA primase. DNA pol then adds the primer to the start of a new Okazaki fragment. DNA pol finishes the DNA fragment. The old RNA primer is erased and replaced by DNA. Nic sealed by DNA ligase.

Question 6

What makes up nucleosomes?

Answer 6

Nucleosomes is made up of 8 histone cores. 146 nucleotide pairs winds around a histone core 1.65 times.

Question 7

What is a histone core?

Answer 7

Made up of two of each of the following histone proteins. H2b h2a h3 h4

Question 8

What does H1 do?

Answer 8

The histone protein H1 links the histones providing structure.

Question 9

What are the stages of mitosis?

Answer 9

Prophase, prometaphase, metaphase, anaphase, telophase.

Question 10

What is prophase?

Answer 10

Prophase is when chromosome condense and become visible. The spindle forms.

Question 11

What is prometaphase?

Answer 11

Nuclear envelope dissolves and chromosomes migrate towards the equatorial planes.

Question 12

What is metaphase?

Answer 12

Chromosomes fully condensed at Equatorial plane.

Question 13

What is anaphase?

Answer 13

Centromere splits and chromatids pulled to two poles.

Question 14

What is telophase?

Answer 14

Chromosomes reach the poles and decondense. Nuclear membrane reforms. Cytoplasm starts to divide.

Question 15

What other DNA do we have?

Answer 15

Mitchondrial DNA is circular and ds and is inherited from the mother. Evolved from symbiosis between anaerobic eukaryotic cells and anaerobic eubacteria.