DNA & Gene Expression

Deoxyribonucleic acid

is composed of building - Block molecules called Nucleotides-

What are the 4 kinds of Nucleotides

Adenine, Thymine, Cytosine and Guanine

what’s the Chargaff’s rule

states that in DNA, the amount of adenine equals thymine and the amount of cytosine equals guanine.

What’s does the DNA must have in Chargaff’s rule

Have a regular structure sine its compositions is always consistent in all living things ( except in viruses)

Where is genetic information held?

In the DNA

Double Helix Model

DNA molecule is composed of two Complementary strands of nucleotides in a spiral (helical) shape

Complementary rule

adenine pairs with thymine(2 hydrogen bonds) and cytosine pairs with guanine( 3 hydrogen Bonds)

DNA replication

How genetic information can be duplicated and transmitted to the next generation of cells

DNA: Deoxyribonucleic acid

Is the genetic material, the substance of genes

What are the 4 nitrogenous bases

adenine, thymine, cytosine, and guanine, a phosphate group (acidic), deoxyribose C5-C(sugar), and nitrogen base

Where are the nitrogen bases found?

Inside of the helix and are H+ bounded

Pyrimidines

T and C single- ring structures

Purines

A and G double-ring structures

The sugar

Phosphate chain occur on the outside of the helix

Anti Parallel

2 strands of double helix run in opposite directions

In RNA what is the sugar called

ribose ( which Uracil occurs instead of Thymine)

DNA Replication

Mother cell duplicates her genetic information in DNA and transmits a copy to each of two daughter cells

Semi conservative replication

DNA molecule and Daughter DNA have a new strand and an original strand of nucleotides

How are enzymes used in DNA Replication?

Used to break the hydrogen bonds in between the complementary strands, allowing other enzymes to go in and “read” the nucleotides and synthesize a new strand of nucleotides

Semi Conservative

Each new double helix consists of an old and one new strand

Protein Synthesis

A two-step process where a gene (DNA) is duplicates into ribonucleic acid(RNA), which in turn is translated into an amino acid

Central Dogma of Biology

“one gene one amino acid” using transcription and then translation

First Step -Transcription ( in the nucleus)

DNA is being duplicates very similarly with DNA replication, only difference is that adenine will be synthesized with Uracil

Messenger RNA (mRNA)

Resulting single-stranded RNA - will be transported into the cytoplasm for the next step

Second Step - Translation

3 specific nucleotides on another RNA molecule- the transfer RNA or tRNA

tRNA in the Cytoplasm

Each one contains its own anticodon and is bound to an amino acid

What is ribosomes in the cytoplasm responsible for?

for attaching the anticodons to the codons properly, resulting in a chain of amino acids held by peptide bonds

Transcription

The transfer of genetic information from DNA into an RNA molecule- it means copying a message into a new medium

DNA - - - > RNA

Translation

the transfer of the information in RNA into a protein, rewording a message into a new language, the new language is the sequence of amino acids in polypeptide chains ( occurs in cytoplasm

RNA - - - > Protein

mRNA

RNA that encodes an amino acid sequence. (messenger) conveys genetic information from nucleus to cytoplasm

tRNA

translates the encoded message of mRNA into the amino acid language of protein

rRNA

coordinates the function of mRNA and tRNA

Gene Expression

The ability of cells to control when particular genes are used to be transcribed into mRNA , or in turn to be translates into proteins or enzymes

A protein called Repressor

used to bind to the regulatory site where transcription begins at a gene, so that transcription is inhibited - how cells “turn off” their genes

To '“turn on” a gene

cells use a signal protein to bind to the repressor, removing its inhibition of transcription

activator protein

to help unwind the complementary strands of DNA during transcription

( particularly eucaryotic cells) use Enhancers

allow signal proteins to bind with the repressor more effectively

Mutation

changes in the nucleotide sequence of DNA molecules

What can cause mutation

accidental errors during DNA replication or protein synthesis, or by factors called “Mutagens”

Point mutation

where only 1 nucleotide is involved

Insertion mutation and Deletion Mutation

long sequence of nucleotides is involved ( rare)

What can mutation cause

can cause sickle cell disease, one amino acid change causes disease

Frameshift Mutations

bases are either deled or added by mistake, causing nonsensical RNA message and nonsensical protein

Genetic Engineering

where gene from one organism are removed and transplanted into the DNA of another organism

Plant Genes

are transplanted into bacterial DNA to produce herbicide-resistance crops

Human Genes

are now inserted into bacterial DNA to produce insulin hormone (to control diabetes), growth hormone, interferons and interleukins

Gene Therapy

will soon be approved to treat many diseases

Where does transcription takes place?

In nucleus

Where does translation take place?

In the cytoplasm