DNA & Protein Synthesis

History

• Before the 1940’s scientists didn’t know what material caused inheritance.

• They suspected it was either DNA or proteins.

History

• A series of experiments proved that DNA was the genetic material responsible for inheritance.

DNADNA

OO=P-O O

PhosphatePhosphate GroupGroup

N

Nitrogenous baseNitrogenous base (A, T(A, T,, G, C)G, C)CH2

O

C1C4

C3 C2

5

SugarSugar(deoxyribose)(deoxyribose)

DNA - double helixDNA - double helix

P

P

P

O

O

O

1

23

4

5

5

3

3

5

P

P

PO

O

O

1

2 3

4

5

5

3

5

3

G C

T A

T A

DNA

• The genetic code is a sequence of DNA nucleotides in the nucleus of cells.

DNA• DNA is complementary• Complementary: bases

on one strand match up with the bases on the other strand (A-T and G-C)

• Example: • Strand 1- ATG GGC CTA• Strand 2- TAC CCG GAT

DNA Replication

• Replication– Process by which DNA copies itself– Happens when chromosomes copy

themselves before mitosis and meiosis– Semi-conservative replication: Each new

piece of DNA is made up of 1 old strand and 1 new strand

Original DNA

DNA unzips

Each original strand grows a new strand

DNA never ever leaves the nucleus– DNA is the master copy of the directions a cell needs to live so it

needs to be protected

DNA in the nucleus is

safe

But DNA in the cytoplasm can be destroyed

DNA

• Gene - a segment of DNA that codes for a protein, which in turn codes for a trait (skin tone, eye color, etc.)

• A gene is a stretch of DNA.

RNA is a copy of DNA that goes out into the cytoplasm to tell the cell what to do in order to stay alive

• RNA: ribonucleic acid• You can always make more RNA so it’s ok if

it gets destroyed (You can’t make more DNA!!!)

RNARNA

OO=P-O O

PhosphatePhosphate GroupGroup

N

Nitrogenous baseNitrogenous base (A, (A, UU ,, G, C )G, C )CH2

O

C1C4

C3 C2

5

SugarSugar (ribose)(ribose)

Phos-

phate Group

DeoxyriboseSugar

Nitro-genBase

Phos-

phate Group

Ribose Sugar

Nitro-genBase

T – AG – C

U – AG – C

DNA RNA

How many strands?

2 1

Nucleotide subunit

Deoxyribose sugar Ribose sugar

Bases ______ (T)Adenine (A)Guanine (G)Cytosine (C)

______ (U) Adenine (A)Guanine (G)Cytosine (C)

RNA

• Function: obtain information from DNA & synthesizes proteins

3 differences from DNA

1. Single strand instead of double strand

2. Ribose instead of deoxyribose

3. Uracil instead of thymine

3 types of RNA

1. Messenger RNA (mRNA)- copies information from DNA for protein synthesis

Codon- 3 base pairs thatcode for a single aminoacid.

codon

3 types of RNA

2. Transfer RNA (tRNA)- collects amino acids for protein synthesis

Anticodon-a sequence of 3 bases that are complementary base pairs to a codon in the mRNA

3 types of RNA

3. Ribosomal RNA (rRNA)- combines with proteins to form ribosomes

Amino Acids• Amino acids- the

building blocks of protein

• At least one kind of tRNA is present for each of the 20 amino acids used in protein synthesis.