AP BIO V2

A Nucleotide is made of these 3 structures:

Phosphate group, Sugar (deoxyribose), Nitrogenous Base

Adenine and Guanine are:

purines (2 rings)

Cytosine and Thymine (and Uracil) are:

pyrimidines, which have one ring.

Chargaff's rule

A - T (sometimes U)

DNA is antiparallel. What does this mean?

The two strands each run from 3' to 5' and run in opposite directions from one another.

DNA strands are held together by

hydrogen bonds between AT and CG

DNA in prokaryotes

DNA is contained in the cytoplasm and consists of a ring of DNA

DNA in eukaryotes

DNA is stored as rod-shaped chromosomes, in the nucleus

Histones

protein molecules around which DNA is tightly coiled in chromatin

Telomeres

Repeated DNA sequences at the ends of eukaryotic chromosomes, protects genes from degrading during division

DNA is copied in a _____ direction

5' to 3'

DNA replication is semiconservative. What does that mean?

The newly synthesized DNA strands each contain one of the original 'mother' strands

DNA replication occurs during...

S phase of interphase of cell cycle

topoisomerase

A protein that functions in DNA replication, helping to relax the double helix ahead of the replication fork.

Helicase

An enzyme that untwists (unzips) the double helix of DNA at the replication forks.

Single stranded binding proteins

Proteins that act as scaffolding, holding two DNA strands apart during replication

primase

An enzyme that makes the RNA Primers, which join to the DNA and act as a starting point for DNA synthesis.

DNA Polymerase

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

leading strand

the new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5' to 3' direction

lagging strand

The strand that is synthesized in fragments using individual sections called Okazaki fragments

Ligase

An enzyme that connects two fragments of DNA to make a single fragment

Transcription

synthesis of an RNA molecule from a DNA template. Occurs in nucleus of Euk's

Translation

Process by which mRNA is decoded and a protein is produced (Ribosomes, Rough ER in Euk's)

RNA polymerase

Enzyme similar to DNA polymerase that binds to DNA and generates an RNA copy

mRNA is a copy of the _______________ strand

coding

mRNA is a complement of the ___________ strand

non-coding, template

uracil

a nitrogen-containing base found in RNA (but not in DNA). Functions in place of Thymine

Post transcription modification of mRNA =

1. addition of poly-A tail

Bacteria+ Virusus

BOTH RNA +DNA

Introns

A noncoding, intervening sequence within a eukaryotic gene.

Exons

expressed sequence of DNA; codes for a protein

mRNA

messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome

tRNA

transfer RNA; type of RNA that carries amino acids to the ribosome

rRNA

ribosomal RNA; type of RNA that makes up part of the ribosome

Codon

A specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid

Translation starts with initiation. What happens in initiation?

rRNA interacts with mRNA. tRNA starts to bring amino acids to the ribosome

In Translation, initiation is followed by elongation. What happens in elongation?

tRNA brings AA to the ribosome, and using Chargaff's rule, complements the codons on the mRNA. The AA are assembled into a growing polypeptide chain.

What causes termination during translation?

A 'stop' codon, which doesn't code for any tRNA.

Transcription and Translation in Prokaryotes...

occurs simultaneously, both in cytoplasm

Viral reproduction

is 'backwards' (instead of DNA - RNA - AA), goes from RNA to host DNA, then host makes more viral RNA

Promoter

A specific nucleotide sequence in DNA that indicates where to start transcribing RNA.

Operator

Region of DNA that controls RNA polymerase's access to a set of genes with related functions.

Poly-A signal sequence

stretch of DNA that codes for the enzymatic cleavage of the mRNA and the addition of a poly-A tail

Repressor

A protein that binds to an operator and physically blocks RNA polymerase from binding to a promoter site

Inducer

A specific small molecule that inactivates the repressor (stopping transcription and ultimately gene expression)

Operon

A unit of genetic function consisting of coordinately regulated clusters of genes with related functions.

Repressible Operon

transcription is usually on, but can be inhibited (repressed) when a specific small molecule binds allosterically to a regulatory protein (example tryptophan)

Inducible operon

usually off, but can be stimulated (induced) when a specific small molecule interacts with a regulatory protein

lac operon is an example of an

inducible operon

The trp operon is an example of a

repressible operon

Lac operon

gene for lactase production

Repressor

operator always bound to repressor.

Lac Operon

presence of lactose opens operator, causes RNA Polymerase to bind to operator, starts transcription

TRP operon

gene for Tryptophan production, inducer = Tryptophan

Lactose Intolerant

presence of lactose causes inducer to bind to operator, prevents RNA Polymerase to bind to operator, stops transcription

Epigenetics

the study of influences on gene expression that occur without a DNA change

methylation

A chemical modification of DNA that does not affect the nucleotide sequence of a gene but makes that gene less likely to be expressed.

Acetylation

of DNA and histones causes nucleosomes to loosen and spread apart, making transcription easier and therefore increasing expression of the genes