AP Biology - Topics 6.1 & 6.2

Transformation

a change in genotype and phenotype due to assimilation of foreign DNA

bacteriophages

viruses that infect bacteria. Bacteriophages consist only of proteins and DNA.

DNA is the genetic material

polymer of nucleotides, DNA composition varies from one species to the next, A and T bases are equal and the number of G and C bases are equal

nucleotides

a nitrogenous base, a sugar, and a phosphate group

Purine

A/G, 2 organic rings, 2X the size, 2 hydrogen bonds

Pyrimidine

C/T, single ring, X size, 3 hydrogen bonds

Why do purine and pyrimidines bases always pair together?

because of the number of hydrogen bonds they are able to form

Semiconservative model

the two strands of the parental molecule separate, and each functions as a template for synthesis of a new, complementary strand

origins of replication

The site where replication occurs where the two DNA strands are separated, opening up a replication "bubble".

DNA polymerase

Enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule

RNA Primase

enzyme that creates an RNA primer for initiation of DNA replication.

replication fork

a Y-shaped region where new DNA strands are elongating that is located at the end of the replication bubble.

Single-strand binding proteins

bind to and stabilize single-stranded DNA

Helicases

enzymes that untwist the double helix at the replication forks.

Topoisomerase

Enzyme that functions in DNA replication, helping to relieve strain in the double helix ahead of the replication fork.

leading strand

The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction.

lagging strand

The strand in replication that is copied 3' to 5' as Okazaki fragments and then joined up.

Other functions of DNA polymerases

proof reading by replacing any incorrect nucleotides

Okazaki fragments

Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.

mismatch repair

repair enzymes correct errors in base pairing

nucleotide excision repair

a nuclease cuts out and replaces damaged stretches of DNA

Telomeres

Repeated DNA sequences at the ends of eukaryotic chromosomes.

bacterial chromosome

circular and single thread of DNA that contains the cell's genetic information

eukaryotic chromosome

linear, large amount of protein

chromatin

a complex of DNA and protein, is found in the nucleus of eukaryotic cells

euchromatin

Loosely packed chromatin

heterochromatin

densely pack chromatin

What is a gene?

region of DNA that can be expressed to produce a final functional product, either a polypeptide or an RNA molecule