Molecular Genetics!

3 Nucleotide Components

1. 5-carbon sugar - DNA - Deoxyribose sugar or RNA - Ribose Sugar
2. Phosphate Group
3. Nitrogen Base

Nitrogen Bases

Encodes the genetic information.

Purines

Double ring

Complementary Base Pairing

Adenine (A) and Guanine (G)
Cytosine (C) and Thymine (T)

Pyrimidines

Single ring

Double Helix

Consists of two strands connected in a helical fashion (think spiral staircase).

Semi-conservative Replication

Base pairing allows each strand to serve as a template for a new strand.

DNA Helicase

Unzips the double helix by breaking the hydrogen bonds between the nitrogen bases that connect the two strands together.

DNA Polymerase

Reads the template strand and adds nucleotides to form the complementary DNA strand.

Genome

Consists of all of the genetic material of an organism.

Gene

A short segment of DNA found on a chromosome that contains the instructions for building a protein.

Allele

Variation of a gene.

Locus

Location of a gene on a chromosome.

Genotype

Genetic makeup, seq. of DNA.

Phenotype

The organism’s physical traits.

Gene Expression

Refers to the production of the protein the gene codes for.

RNA (Ribonucleic Acid)

A polymer of a nucleic acid that is found in all living cells and plays a role in protein synthesis.

Messenger RNA (mRNA)

Produced from a DNA template, and carries the information for protein production to the ribosome (where proteins are made).

Transfer RNA (tRNA)

Functions as a translator between nucleic acid and protein languages by carrying specific amino acids to the ribosome, where they recognize the appropriate codons in the mRNA.

Ribosomal RNA (rRNA)

Molecules together with proteins makeup ribosomes.

Transcription

Makes a mRNA copy of the DNA gene.

Introns

Noncoding regions (do not code for the polypeptide).

Exons

Code for the polypeptide.

Alternative Splicing

Genes can code for multiple proteins depending how the mRNA is spliced.

Translation

The synthesis of a protein using the genetic information encoded in an mRNA molecule.

Codon

Three consecutive nucleotides on mRNA that code for a specific amino acid.

Genetic Code

The set of codons and the amino acids they code for.

Anticodon

Sequence on the tRNA that is complementary to the codon.

Mutation

A permanent change in the DNA sequence of a gene.

Point Mutations

Affects one nucleotide.

Chromosomal Mutations

Affects many nucleotides.

Substitution

Change a nucleotide

Insertion

Add a nucleotide

Deletion

Remove a nucleotide

Frameshift Mutation

Mutation that shifts the “reading” frame of the genetic message by inserting or deleting a nucleotide caused by insertion or deletion point mutations.

Chromosomal Mutations

Involves many nucleotides; ex. deletion, duplication, inversion, translocation.

Methyl groups

Tighten chromatin, DNA is not accessible for transcription. Genes are “off” (no gene expression).

Acetyl groups

Loosen chromatin, DNA is accessible for transcription. Genes are “on” (genes are expressed).

Differentiation

The process in which cells become specialized in structure and function.