MOLECULAR BIOLOGY AND GENETICS

BY: SREELAKSHMI (MSIWM012)

Molecular biology is the study of the chemical and physical structure of biological macromolecules. Genetics is a branch of science dealing with the study of heredity and variation.

 Molecular Biology is an overlapping with other areas of biology and chemistry. It is the understanding of the interactions between DNA, RNA and protein. It is basically of two steps: transcription and translation. It is called Central Dogma. Synthesis of RNA from DNA is called transcription and synthesis of Protein and DNA translation.

TRANSCRIPTION

  • Transcription involves synthesis of new strand of nucleic acid complementary to a DNA template strand.
  • To transcribe a gene, RNA polymerase proceeds through a series of well-defined steps which are grouped into three phases- initiation, elongation and termination.
  • The bacterial core RNA polymerase can initiate transcription at any point on a DNA molecule.
  • RNA polymerase can initiate a new RNA chain on a DNA template and therefore do not require a primer.
  • The elongating polymerase is a processive machine that synthesize and proofreads RNA.
  • Ribonucleotides enters the active site and the added to are growing RNA chain.
  • Termination of transcription is activated by the presence of terminator sequence which results in the elongating polymerase to dissociate from the DNA and release the RNA chain.

TRANSCRIPTION

In eukaryotes, they have three different polymerases and several initiation factors.

TRANSLATION

Translation converts the genetic information present within the mRNA to a linear sequence of amino acids in proteins

The decoding of mRNAs into the language of proteins is composed of four components which are Trna,aminoacyl tRNA synthetasesand also ribosome.mRNa template provides the information that must be interpreted.Aminoacyl Trna synthetase couple amino acids to specific tRNAs that recognize the appropriate codon. The protein coding region of each mRNA have contiguous and non-overlapping string of codon called an open reading frame. Translation starts at 5’end and ends at 3’end.it starts with start codon and ends with a stop codon.AUG is usually a start codon, whereas UAG,UGA,UAA are stop codon.

GENETICS

Genetics is the study of hereditary and variation. The term was first introduced by W Bateson.

Gregor Mendel is known as the Father of Genetics.

Mendel was the first one who told that there are some factors which give you a particular phenotype (eye color, hair texture).The pioneering study on generics was by Mendel on pea plants. He looked at how the size, height, colur.He selected only pure breeds. From result of this experiment he came up with the hypothesis:

  • LAW OF SEGREGATION:

It is studied with the help of monohybrid cross. It states that the alleles of a given locus segregate into separate gametes. It is also called as law of purity.

MONOHYBRID CROSS

  • LAW OF INDEPENDENT ASSORTMENT:

It can be explained with the help of dihydrid cross. Mendel considered seed form and cotyledon color for the cross. This law states that the factors or alleles of each character assort or segregate independent of the factors of other character at the time of gamete formation and get randomly rearranged in the offspring.

DIHYBRID CROSS

POST MENDELIAN

Basics of genetics was given by Mendel, later studies provided information on various genetic interactions which also led to the studies on various genetic disorders.

COMPLEMENTARY GENES

If two genes present on different loci produce the same effect when present alone but interact to form a new trait when present together .They are called complimentary genes.

SUPPLEMENTARY GENES

They are pair of non-allelic genes one of which produces its effect independently in the dominant state.

LINKAGE

It is an exception of principle of independent assortment.

CHROMOSOME THEORY OF LINKAGE

It was given by Morgan and Castle. It states that

  • The genes which show linkage are situated in the same chromosome and remain bounded by chromosomes by material.So,they cannot be separated during the processes
  • The degree or strengthen of linkage depends upon the distance between the linked genes on the chromosomes, closely located genes show strong linkage.
  • Genes lie in linear order in the chromosome.

CROSSING OVER

It is one of the two exceptions of Mendel’s law of independent assortment. It produces new combinations or recombination of genes by interchanging of corresponding segments between non sisters chromatids of homologous chromosomes at prophase 1 of meiosis the non-sister chromatids in which exchange of segments has occurred are called cross overs.

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