Concepts In

Molecular Biology

ByOla Elgaddar

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms

GENE

The fundamental physical and functional unit of heredity, which carries information from one generation to the next; a segment of DNA, composed of a transcribed region and a regulatory sequence that makes transcription possible

CHROMOSOME

In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure

Locus & allele• A locus is the specific location of a gene or DNA sequence on a chromosome.

• A variant of the DNA sequence at a given locus is called an allele. There could be two or more forms, e.g., a gene for eye color could be either brown or blue.

Genetic trait- A physical characteristic brought about by the expression of a gene or many genes. - Examples of traits are height, eye color,...

- Variations in these characteristics are dependent upon the particular alleles an individual has for the genes determining the trait.

(Eye color is the trait; with brown & green alleles)- Alleles are either dominant or recessive

Genotype / phenotypeGenotype: refers to the genetic traits in an organism. It is the genetic load that is copied every time a cell divides, and therefore is inherited down to the next generation.It is something that is not seen (ex. dominant, recessive)

Phenotype: refers to observable, physical characteristics of an organism. phenotype are things that can be seen (ex. colors, growth)

Homologous chromosomes

A pair of chromosomes that are similar in size and shape and also have genes that code for the same traits and characteristics.

One homologous chromosome is inherited from the father, the other from the mother

Homozygous / Heterozygous Cells whose chromosomes have the same allele of a given gene at some locus are called homozygous with respect to that gene, while those that have different alleles of a given gene at a locus, heterozygous with respect to that gene.

PolymorphismWhen alleles are so common that they are found in more than 1% of chromosomes in the general population, the alleles constitute what is known as genetic polymorphism.

Sources include SNPs, sequence repeats, insertions, deletions and recombination

Mutation- Genetic mutations are a kind of genetic polymorphism. - The term "mutation," as opposed to "polymorphism," is generally used to refer to changes in DNA sequence which are not present in most individuals of a species and either have been associated with disease (or risk of disease) or have resulted from damage inflicted by external agents (such as viruses or radiation).

Sequence repeats- A short tandem repeat (STR) in DNA occurs when a pattern of two or more nucleotides are repeated and the repeated sequences are directly adjacent to each other.

- The pattern can range in length from 2 to 50 base pairs (bp) (for example (CATG)n in a genomic region) and is typically in the non-coding intron region.

- A short tandem repeat polymorphism (STRP) occurs when STR loci differ in the number of repeats between individuals.

STR analysis has become the prevalent analysis method for determining genetic profiles in forensic cases. (DNA finger Printing)

SNPs

-A SNP ("snip") is a single base mutation in DNA.

- SNPs are the most simple form and most common source of genetic polymorphism in the human genome (90% of all human DNA polymorphisms).

DETECTION OF

SNPs

1) DNA extraction

2) PCR

3) RFLP

1) DNA Extraction -The release of genomic DNA from white blood cells by cell lysis

-Selective adsorption of genomic DNA to a special spin column.

-Elution of the purified genomic DNA

2) PCR for the specific sequence

Denaturation

Annealing

Extension

3) RFLP

Thank you

OLA