Flashcards For NEET Biology - Molecular Basis of Inheritance

Phosophoester linkage- Phosphate group attached to OH of 5’C of deoxyribose or ribose sugar

Named it ‘Nuclein’

Present in the nucleus and acidic

Backbone- sugar-phosphate

Bases are bonded by hydrogen bonds and projected inside

Adenine bonds to thymine by two hydrogen bonds

Guanine bonds to cytosine by three hydrogen bonds

Pitch- 3.4 nm and 10 bp in each turn

The flow of genetic information from DNA → RNA → Protein

The region where DNA is concentrated within a cell associated with positively charged proteins

Eight molecules of histones associated with DNA to form a nucleosome

200 bp of DNA in each nucleosome

Appear as beads on chromatin threads

Shows active transcription

Inactive for transcription

He concluded that there was some transforming principle in the heat-killed S-strain, which transformed R strain Streptococcus pneumoniae to virulent

They showed that proteases and RNAases did not affect transformation, whereas DNAase inhibit transformation

They worked on bacteriophages

Radioactive ³⁵S labelled- protein capsule

Radioactive ³²P labelled- DNA

E.g. TMV, QB bacteriophage, etc.

ds RNA- reovirus, etc.

Experimentally proved by Matthew Meselson and Franklin Stahl in 1958 using ¹⁵N isotope in the growing medium for E.coli

Taylor and colleagues worked on Vicia faba using radioactive thymidine

Polymerisation in 5’→3’ direction

Template strand- 3’→5’ DNA

Coding strand- 5’→3’ DNA, has the same sequence as newly synthesised RNA strand

Polymerisation in 5’→3’ direction

Promoter- present at 5’ end of a structural gene, RNA polymerase binds here

Terminator- at 3’ end of the coding strand

Monocistronic- eukaryotes

Polycistronic- prokaryotes

mRNA- template for protein synthesis

tRNA- adapter molecule, brings amino acids and reads codon on mRNA

rRNA- structural and catalytic role

RNA polymerase II – hnRNA (mRNA precursor)

RNA polymerase III – tRNA, 5S rRNA, snRNA

Capping – addition of methyl guanosine triphosphate at 5’ end

Tailing – addition of adenylate residues (200-300) at 3’ end

Codes for Methionine

They do not code for any amino acids

Anticodon loop- complementary mRNA codon for specific codon

Acceptor arm- binds to amino acid

DHU loop, TψC loop and variable loop

Function- Adapter molecule, brings amino acid for translation and reads codon

The first step is charging of tRNA, aminoacylation or binding of tRNA to amino acid

Peptide bond formation takes place between the amino acid of growing chain and newly brought amino acid in two sites present in the large subunit of ribosomes

28S rRNA in bacteria

Present on both 5’ and 3’ ends

Required for efficient translation

Contains multiple genes, which are regulated by a promoter and an operator

E.g. lac operon, val operon, his, ara, trp, operon, etc.

Structural genes-

z – beta-galactosidase (β-gal)

y – permease

a – transacetylase

Inducer – lactose or allolactose

3 x 10⁹ base pairs (haploid)

20,000-25,000 genes

Largest gene- Dystrophin gene of the X chromosome (2.4 million bp)

Smallest gene- SRF/TDY gene of the Y chromosome (14 bp)

Single base differences exist at

1.4 million places in the human genome

Involves identifying of repeated DNA sequences

Satellite DNA forms smaller peaks and shows a high degree of polymorphism

Mini-satellite

Number and position differs from person to person

Flanked by restriction sites

Used to detect DNA sample in blood or tissue