Molecular Genetics Overview

Study Notes

Histones

H1, H2A, H2B, H3, and H4 are all involved in the packaging of DNA into nucleosomes.

Griffith's Experiment

Heat-killed virulent S-cells transformed the living non-virulent R-cells into virulent S-cells, killing the mice they were injected into.
This experiment demonstrated that genetic material can be transferred between bacteria.

Nucleic Acids

Adenine and Guanine are double-ringed purines.
Cytosine, Thymine, and Uracil are single-ringed pyrimidines.

Chargaff's Rule

The number of purines is always equal to the number of pyrimidines in a DNA molecule.
This is because adenine pairs with thymine (A-T), and guanine pairs with cytosine (G-C).

Meselson and Stahl Experiment

Meselson and Stahl used the heavy isotope nitrogen-15 (15^{15}15N) during DNA replication to demonstrate that DNA replication is semiconservative.
This means that each new DNA molecule consists of one original strand and one newly synthesized strand.

DNA Replication

DNA polymerase is the enzyme responsible for synthesizing new DNA strands.
Single-stranded binding proteins (SSBPs) prevent the separated strands of DNA from recoiling during replication.

Transcription

mRNA is a copy of a gene sequence from DNA.
tRNA is a small RNA molecule that carries amino acids to the ribosomes.
The genetic code is degenerate, meaning that multiple codons can code for the same amino acid.
The wobble hypothesis explains how some tRNA molecules can recognize multiple codons.

Translation

The sigma factor helps RNA polymerase bind to the promoter region of a gene.
The sigma factor is released during elongation of the polypeptide chain and is reused.
Peptidyl transferase is the enzyme responsible for forming peptide bonds between amino acids during translation.

RNA Splicing

Exon segments are separated by non-coding introns.
RNA ligase joins the exons back together after splicing.

Lac Operon

The lac operon is a group of genes that are involved in the metabolism of lactose in bacteria.
Lactose acts as an inducer of the lac operon, meaning it causes the operon to be turned on.
The repressor protein binds to the operator gene, blocking transcription of the lac operon in the absence of lactose.

DNA Structure

Each nucleotide consists of a phosphate group, a sugar (deoxyribose), and a nitrogenous base.
Phosphate groups link nucleotides together to form DNA strands.

Description

This quiz covers essential concepts in molecular genetics, including the role of histones, Griffith's experiment on transformation, the composition of nucleic acids, and Chargaff's rule. Additionally, it touches on Meselson and Stahl's groundbreaking experiment that revealed the semiconservative nature of DNA replication.