Exam 6 pt. 2

Chargaff's Rule

A=T and G=C

Chargaf's experiment

laid the foundation for determining base pairing in DNA by observing the amount of the four nitrogenous bases found in different samples of DNA. Paper chromatography was used to separate the substances found in DNA and UV spectrophotometry was used to count the amount of each base found in each sample.

Griffin and Avery

experiments were pivotal in identifying DNA as genetic material. he established the concept of a "transforming principle" that could change harmless bacteria into harmful ones. her team built on his work to prove DNA was the hereditary material.

Hershey and Chase

concluded that the genetic material of the bacteriophage was DNA, not protein.used radiolabeled isotopes to confirm DNA as genetic material. They infected bacteria with viruses labeled with radioactive phosphorus (DNA) or sulfur (protein) and observed which component entered the bacteria. Only the DNA-labeled phosphorus entered the bacteria, indicating DNA is the genetic materia

Franklin and Wilkins

Used X ray diffraction to take pictures of DNA structure; discovered two forms of DNA. Determined DNA was a double helix.

Watson and Crick

Figured out structure of DNA was a double helix

Know the components of a nucleotide

sugar, nitrogenous base, phosphate groups

Nucleotide

A building block of DNA, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group.

Structure of DNA molecule

Double stranded helix, 2 strands of nucleotides, phosphate group deoxyribose and A-T, C-G

Know the events of DNA replication

1. Initiation 2. Unwinding 3.primer synthesis 4. Elongation

semi-conservative model

Type of DNA replication in which the replicated double helix consists of one old strand, derived from the old molecule, and one newly made strand.

DNA helicase

Unwinds DNA at replication fork

DNA vs RNA structure

DNA: Double strand RNA: Single strand

RNA contains the sugar …

Ribose

DNA contains the sugar ….

Deoxyribose

Okazaki fragments

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

DNA structure and function

DNA is a double helix consisting of 2 polynucleotides each oriented in opposite directions. Each polynucleotide is made of a covalently bonded 5 carbon sugar-phosphate backbone, with nitrogenous double bases called purine and single bases called pyrimidines. The A and G of the purines on one polynucleotide complement the T and C of the pyrimidine on the other (A-T, G-C) and connect through hydrogen bonds.

RNA structure and function

RNA is single-stranded
- RNA's sugar molecule is ribose rather than deoxyribose, and
- RNA's fourth base is uracil rather than thymine.

Three types of RNA and the function of each

Messenger RNA (mRNA) carries genetic information from DNA to ribosomes for protein synthesis. Transfer RNA (tRNA) acts as a molecular adaptor, delivering amino acids during translation, while ribosomal RNA (rRNA) forms the ribosome's structural and functional core.

How does DNA control cell activity

The nucleotide sequences that make up DNA are a "code" for the cell to make hundreds of different types of proteins

What is the genetic code?

made up of codons, which are three-letter chains of nucleotides

4 codes of DNA

adenine (A), guanine (G), cytosine (C), and thymine (T).

DNA coded 5 to 3?

single strands of DNA and RNA sequences are written in a 5′-to-3′ direction

1 amino acid=

3 nucleotides

What is the genetic code?

collection of codons of mRNA, each of which directs the incorporation of a particular amino acid into a protein during protein synthesis

An amino acid may be coded for by more than one codon true or false

True

Most often one gene codes for one polypeptide EXCEPT

Sometimes one gene, multiple polypeptides, gene codes for RNA.

Transcription takes place in the…

Nucleus

Mutations definition

Changes in DNA, such as "misspellings" in the gene sequence or incorrect amounts of DNA, that can prevent a gene from functioning properly.

source of mutations

errors in replication and transcription, exposure to mutagens

Mutagens

physical and chemical agents that interact with DNA to cause mutations

Frequency of Mutation

Spontaneous mutation rate = 1 in 109 replicated base pairs or 1 in 106 replicated genes Mutagens increase to 10-5 or 10-3 per replicated gene

Gene Control

the use of genes only where they are needed.

Source of new genes

May be harmful but may be neutral or beneficial

HIV immunity

individuals who lack CCR5 co-receptor tend to be immune to HIV

I gene codes for

1 polypeptide

Exons

Coding sequence

Introns

Noncoding sequence

Translation first step

Messenger rna attaches to the small subunit

Methylation of DNA

inactivates genes or altered gene activity (prevents binding of transcription factors and deacetylation of histones)

When DNA is tightly coiled

Gene is off

To turn gene on

DNA is uncoiled gene is being expressed

Methylation

Muffles a gene

RNA interface

Biological process in which an RNA molecule inhibits gene expression

Hormones

Can turn off or turn off gene activity