Molecular Genetics

(1)

Molecular Genetics

(2)

• Molecular biology is the branch of biology that study gene structure and function at the molecular level.

• The Molecular biology is the field overlaps with other

areas, particularly genetics and biochemistry.

(3)

Hist ory

‘‘DNA is the genetic material’’

 T.H. Morgan (1908)

 genes are on chromosomes

 Frederick Griffith (1928)

 a transforming factor can change phenotype

 Avery, McCarty & MacLeod (1944)

 transforming factor is DNA

 Hershey & Chase (1952)

 confirmation that DNA is genetic material

 Watson & Crick (1953)

 determined double helix structure of DNA

 Meselson & Stahl (1958)

 semi-conservative replication

(4)

• Eukaryotic cells are found in animals, plants, fungi and protists cell;

• Cell with a nucleus, where the genetic material is surrounded by a membrane;

• Eukaryotic genome is more complex than that of prokaryotes and distributed among multiple

chromosomes;

• Eukaryotic DNA is complexed with proteins called histones;

• Numerous membrane-bound organelles;

• Cell division by mitosis.

• Eukaryotes are generally more advanced than

prokaryotes

(5)

protein RNA

DNA

transcription translation

Flow of genetic information in a cell.

(6)

Mutations are changes in the genetic material of a cell



Large scale mutations: chromosomal; always cause disorders or death



nondisjunction, translocation, inversions, duplications, large deletions



Point mutations: alter 1 base pair of a gene

1.

Base-pair substitutions – replace 1 with another Missense: different amino acid

Nonsense: stop codon, not amino acid

2.

Frameshift – mRNA read incorrectly; nonfunctional proteins

Caused by insertions or deletions

(7)

The Genome



Totality of genetic information of an organism.



Encoded in the DNA.

(8)

Species and Number of Chromosomes

Species Number of

chromosomes

Human 46

Mouse 40

Rat 42

Fruit flies 8

Bacteria 1

(9)

Human Genome

Human Genome; Arranged on multiple chromosomes;

twenty three pairs of chromosomes;



Twenty two pairs (autosomes).



One pair (sex chromosome) (xx) (female) or (xy) (male).

Humans have 23 pairs of chromosome in every cell (except mature red blood cells..); Gametes or sex cells (sperm and eggs) have half the normal

complement of chromosomes.

(10)

General Structure of Nucleic Acid

DNA and RNA are long chain polymers of small chemical compound called

nucleotides.

(11)

Nucleotides

Nucleotides; ring shaped structures composed of:

 Nitrogenous base; these bases are classified based on their chemical structures into two groups:

Purine: double ringed structure (Adenine and Guanine).

Pyrimidine: single ring structures (cytosine and thymine).

 ^Sugar

 Phosphate group

(12)

Nucleotides



DNA: Four different types of nucleotides differ in nitrogenous base:



A is for adenine;



G is for guanine;



C is for cytosine and



T is for thymine.

 RNA: thymine base replaced by uracil base.

(13)

Nucleotides

(14)

The DNA

 Deoxyribonucleic Acid (DNA) is the genetic material of all cellular

organisms and most viruses.

 DNA; the gigantic molecule which is used to encode genetic information for all life on Earth.

 DNA responsible for preserving,

copying and transmitting information

within cells and from generation to

generation.

(15)

Molecular Cloning or Recombinant DNA Technology:

To clone means to make identical copies. DNA cloning

involves separating a specific gene or DNA segment from a larger chromosome, attaching it to a small carrier DNA. The resultant hybrid DNA is called recombinant DNA, which is transferred to a proper host (bacteria, virus or yeast) and replicated to make multiple copy of the selected gene.

When cloned under an appropriate expression vector, a gene can be expressed (transcribed and translated), at desired level to produce recombinant proteins.

This technology has made it possible to isolate, clone and

produce DNA for all the genes in appropriate quantity so that

they can be sequenced and characterized. Similarly, some of

the genes which are expressed at very low level, can be cloned

and desired amount of recombinant proteins can be produced.

(16)

Proteins made in animals

Use recombinant DNA technology to express a human protein in the mammary glands of a cow, sheep, goat, (rabbits and hamsters used in early experiments) then patients drink the milk from these transgenic animals.

Molecular Genetics

Molecular Genetics

• Molecular biology is the branch of biology that study gene structure and function at the molecular level.

• The Molecular biology is the field overlaps with other

areas, particularly genetics and biochemistry.

Hist ory

‘‘DNA is the genetic material’’

• Eukaryotic cells are found in animals, plants, fungi and protists cell;

• Cell with a nucleus, where the genetic material is surrounded by a membrane;

• Eukaryotic genome is more complex than that of prokaryotes and distributed among multiple

chromosomes;

• Eukaryotic DNA is complexed with proteins called histones;

• Numerous membrane-bound organelles;

• Cell division by mitosis.

• Eukaryotes are generally more advanced than

prokaryotes

protein RNA

DNA

transcription translation

Flow of genetic information in a cell.

Mutations are changes in the genetic material of a cell

Large scale mutations: chromosomal; always cause disorders or death

nondisjunction, translocation, inversions, duplications, large deletions

Point mutations: alter 1 base pair of a gene

Base-pair substitutions – replace 1 with another Missense: different amino acid

Nonsense: stop codon, not amino acid

Frameshift – mRNA read incorrectly; nonfunctional proteins

Caused by insertions or deletions

The Genome

Totality of genetic information of an organism.

Encoded in the DNA.

Species and Number of Chromosomes

Species Number of

chromosomes

Human 46

Mouse 40

Rat 42

Fruit flies 8

Bacteria 1

Human Genome

Human Genome; Arranged on multiple chromosomes;

twenty three pairs of chromosomes;

Twenty two pairs (autosomes).

One pair (sex chromosome) (xx) (female) or (xy) (male).

Humans have 23 pairs of chromosome in every cell (except mature red blood cells..); Gametes or sex cells (sperm and eggs) have half the normal

complement of chromosomes.

General Structure of Nucleic Acid

DNA and RNA are long chain polymers of small chemical compound called

nucleotides.

Nucleotides

Nucleotides; ring shaped structures composed of:

 Nitrogenous base; these bases are classified based on their chemical structures into two groups:

Purine: double ringed structure (Adenine and Guanine).

Pyrimidine: single ring structures (cytosine and thymine).

 Sugar

 Phosphate group

Nucleotides

DNA: Four different types of nucleotides differ in nitrogenous base:

A is for adenine;

G is for guanine;

C is for cytosine and

T is for thymine.

 RNA: thymine base replaced by uracil base.

Nucleotides

The DNA

 Deoxyribonucleic Acid (DNA) is the genetic material of all cellular

organisms and most viruses.

 DNA; the gigantic molecule which is used to encode genetic information for all life on Earth.

 DNA responsible for preserving,

copying and transmitting information

within cells and from generation to

generation.

Molecular Cloning or Recombinant DNA Technology:

To clone means to make identical copies. DNA cloning

involves separating a specific gene or DNA segment from a larger chromosome, attaching it to a small carrier DNA. The resultant hybrid DNA is called recombinant DNA, which is transferred to a proper host (bacteria, virus or yeast) and replicated to make multiple copy of the selected gene.

When cloned under an appropriate expression vector, a gene can be expressed (transcribed and translated), at desired level to produce recombinant proteins.

This technology has made it possible to isolate, clone and

produce DNA for all the genes in appropriate quantity so that

they can be sequenced and characterized. Similarly, some of

the genes which are expressed at very low level, can be cloned

 ^Sugar