Animal cell- where is the DNA?

You have about 1014 cells in your body

Cellular membrane, fosfotriglycerides

DNA-molecule divides -replication

RNA synthesised from DNA- transcription

Protein synthesised from RNA-translation

DNA- DeoxyRibonucleic AcidRNA- RiboNucleic Acid

Nucleic acids- consists of nucleotides

• DNA – polymer containing our genes

• Double stranded

• RNA- smaller polymer formed using DNA as template

• Single stranded• Used for protein-

synthesis

Phosphate

Ribose

Nitrogen base

Ribose is a monosaccharide with 5 carbon atoms (pentose)

In RNA

In DNA

OHOCH2

OH OH

OH

OHOCH2

OH

OH

Ribos

Deoxyribos

Nitrogen bases

NH2

N

N N

N

H

N

N N

NH

O

HNH2

NH2

H

H

N

ON

NH

O

O

N

H

NH

O

O

N

H3C

NH2

N

N N

N

H

N

N N

NH

O

HNH2

NH2

H

N

ON

Adenin Guanin Cytosin

Uracil

Tymin

Adenin Guanin Cytosin

In RNA

In DNA

PyrimidinesPurines

Nucleotides- a condensation of ribose, nitrogen base and phosphate (phosphoric acid)

Nucleotides polymerise (a polycondensation) to form DNA

The two strands run in opposite directions

Hydrogen bonds keep the two different DNA-strands together in the

double helix

T-A

C-G

Adenine and Thymine can form two H-bonds

Cytosine and Guanine can form three H-bonds

DNA replicationAt cell divisionThe double helix is unwinding to two single strandsFree–floating nucleotides join the strands- If A on the strand then T nucleotide. At the other strand at same place- T and then A nucleotide.Enzymes, polymerases, bind the free-floating nucleotides and condense them to a complementary DNA polymer.Two identical DNA molecules are formed.

DNA transcription and translation- protein synthesis

Transcription: DNA RNA• Takes place in the nucleus of the cell• Like replication, but only one of the DNA

strands will be copied to form RNA and only a part of the strand = the gene for a specific protein.

Three different kinds of RNA

• mRNA: messenger; brings the genetic information of the protein primary structure

• tRNA: transfer; transfers the amino acids to the protein

• rRNA: ribosome, rRNA+protein makes up ribosomes; the place in the cell were the proteins are buildt

Translation RNA ProteinA 3-nucleotide sequence, a triplet or a codon codes for a specific amino acid. There is also a starting codon and stop codon

The sequence of triplets on the mRNA will give the sequence of amino acids in the polypeptide

The mRNA is brought out from the nucleus to the cytoplasm

Translation, cont.• The mRNA is sent to a ribosome. A tRNA-

amino acid with an anticodon that fits the first triplet on mRNA join the ribosome, then a second tRNA-amino acid that fits the second triplet. The two amino acids condensates to form a dipeptide. Then the third tRNA comes etc.

hyperphysics.phy-astr.gsu.edu/.../ribosome.html

DNA polymeras

DNA profiling

• DNA is extracted from cellular material; e.g. blood, semen, hair, saliva

• Sample degraded by restriction enzymes

• DNA fragments separated by gel electrophoresis- patterns are compared

Sections of non-coding DNA — DNA that does not code for a protein-short tandem repeats (STR’s)-made up of repeats of short base sequences, such as CATG in the sequence CATGCATGCATG.

Parentage

Exercize