Chapter 8 Mr. Garofalo period 9

Watson and Crick

They DID NOT Discover DNA But They Were The First Scientists To Suspect DNA Was In The Form Of A Helix During The 1950'S

Chargraff rule

His rule stated that there is the same amount of thymine and adenine in DNA , also there is the same number of cytosine and guanine

(A = T and G = C)

How do the base pairs bind?

Base pairs. Attached to each sugar ring is a nucleotide base, one of the four bases Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). ... The hydrogen bonding between complementary bases holds the two strands of DNA together. Hydrogen bonds are not chemical bonds.

What is a chromosome?

threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

What is a karyotype?

1. the number and visual appearance of the chromosomes in the cell nuclei of an organism or species.

2. an image of an individual’s diploid set of chromosomes

How does DNA replicate?

The first step in DNA replication is to ‘unzip’ the double helix structure of the DNA? molecule.

This is carried out by an enzyme? called helicase which breaks the hydrogen bonds? holding the complementary? bases? of DNA together (A with T, C with G).

The separation of the two single strands of DNA creates a ‘Y’ shape called a replication ‘fork’. The two separated strands will act as templates for making the new strands of DNA.

One of the strands is oriented in the 3’ to 5’ direction (towards the replication fork), this is the leading strand?. The other strand is oriented in the 5’ to 3’ direction (away from the replication fork), this is the lagging strand?. As a result of their different orientations, the two strands are replicated differently:

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By. Jose Peña

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