Genetics: Chromosomes, Alleles, Genes, Mutations Genetics (the study of inheritance): The scientific discipline involved with studying how genes/traits are passed from parent to offspring.

Genes and Alleles Gene: a heritable factor that controls a specific characteristic Located in specific places on chromosomes Humans have roughly 20,000-25,000 genes. Alleles: alternative forms of gene Example: Gene: eye color Alleles: blue vs. brown

Chromosomes Prokaryotes: ‘Naked DNA’ Eukaryotic Chromosomes: Made of DNA and proteins Two Types: Autosomes (non sex chromosomes) Sex Chromosomes Two parts Sister Chromatids Centromere Homologous Chromosomes: chromosomes that have the same genes as each other, arranged in the same sequence, but not necessarily the same alleles (forms) of those genes

Chromosome & Gene Numbers of Different Organisms

Karyotyping A karyotype is a display (micrograph) of the number and type of chromosomes a nucleus contains. Cells are examined in metaphase of mitosis. The stained chromosomes are arranged according to size, structure, centromere position, and banding pattern.

Human Karyotype (Male or Female?)

How are Karyotypes Useful? One of the main reasons for karyotyping is to find out whether a fetus has Down Syndrome or other chromosomal abnormalities. Karyotyping can be done by extracting and examining fetal cells (amniocentesis) or through chorionic villus sampling (examining cells from the placenta).

What are ‘genes’? (Click Here for a Helpful Animation) Genes are segments of DNA molecules (specific sequences of A, T, G & C) that code or carry the instructions for making a protein. Humans have approximately 20,000 different genes across 46 chromosomes.

Chromosome 21

Sample Gene Sequence

Transcription & translation Protein synthesis

Protein Synthesis Protein synthesis is the process by which DNA in the nucleus of a cell directs the production of protein(s). Proteins determine virtually everything about you. Proteins are polymers (polypeptides) made up of long chains of amino acids (monomers). They have very complex 3 dimensional shapes. The specific shape of a protein will determine its function in the body. Proteins can be structural (make up muscle), function as enzymes, participate in the immune system, etc.). The production or lack of production of a particular protein can have dramatic effects on the body

There are 2 major stages to protein synthesis The classic view of the Central Dogma of biology states that the basic mechanism of reading and expressing genes is from DNA to RNA to Protein. This chain of events occurs in all living things—from bacteria to humans. DNA CODES FOR RNA, WHICH GUIDES THE SYNTHESIS OF PROTEINS

A Summary of RNA Types we’ll be working with FUNCTION mRNA Messenger RNA is a complimentary copy of a DNA gene and is enough genetic information to code for a single polypeptide. tRNA Transfer RNA will transfer 1 of 20 amino acids to the ribosome for polypeptide formation. rRNA Ribosomes are composed of ribosomal RNA and protein.

A Brief Overview of protein synthesis

The Genetic Code is Written in Triplets (Codons) When a triplet is found in an mRNA molecule, it is called a codon or codon triplet. Each code corresponds to 1 of 20 amino acids.

*PRACTICE TRANSCRIBING AND TRANSLATING A GENE* Helpful Animations Protein Synthesis Step-by-Step Animation Transcription and Translation (Stolaf) Transcription Detail and Translation Detail (UofNeb) Transcription and Translation (McGraw Hill) mRNA Splicing (McGraw Hill) Crash Course Biology (Transcription & Translation) http://www.bioplek.org/ *PRACTICE TRANSCRIBING AND TRANSLATING A GENE*

The one gene--one polypeptide hypothesis Scientists used to believe that one gene coded for only one protein (polypeptide). This, however, isn’t entirely accurate. Why? mRNA transcribed from one gene may be spliced in different ways to form different proteins. RNA molecules produced from one gene may themselves be functional.

Eukaryotic Gene Regulation (Transcription Factors) Eukaryotic cells MUST control what genes are expressed at different times in the organism’s lifetime.

Mutations Mutations are heritable changes in the sequence of bases in a gene. Changes in the sequence of bases can cause changes to the amino acid sequence, altering the structure and function of the protein to be made.

DNA Mutations (Explore Further) Point Mutations: Caused by base pair substitutions The replacement of one nucleotide and its partner with another pair May cause a change to the protein being made (missense/nonsense mutation) or not (silent mutation). Missense  amino acid change Nonsense early stop codon Frameshift Mutations: Caused by inserting or deleting a nucleotide pair Changes the amino acid sequence from the point of the mutation to the end of the polypeptide chain. A shift in the DNA changes how the codons are read and potentially a big change to the protein being made. Causes of DNA mutations include random cell errors and chemical, radiation and/or UV exposure. Mutations are heritable if the mutation is carried in the gametes (sex cells – sperm or egg) Link: TYPES OF DNA MUTATIONS

DNA MUTATIONS

Chromosomal Mutations (Explore Further) Deletion Removes a chromosomal segment Duplication Repeats a segment Inversion Reverses a segment within a chromosome Translocation Moves a segment from one chromosome to another nonhomologous one Alteration of Chromosome number Nondisjunction (we will discuss this more during Meiosis)

Sickle-Cell Anemia (Symptoms can be relatively mild to severe) Signs & Symptoms: Anemia Shortness of breath, dizziness, headaches, coldness in hands/feet, pale skin, jaundice. Pain Throughout the Body Blocked Blood Flow Infections Pulmonary Hypertension Stroke Multiple Organ Failure *Sickle-Cell Disease Offers Protection Against Another Disease Called Malaria*

SICKLE-CELL ANEMIA Hemoglobin, found in RBC’s, carries oxygen throughout the bloodstream. All cells require oxygen for cellular resp. Sickle-Cell Anemia results from a single point mutation that alters the shape of the hemoglobin molecule, resulting in sickle-shaped red blood cells.

The Most Unusual Mutations Sickle Cell Anemia The Most Unusual Mutations ADDITIONAL VIDEOS

Detecting Fetal Abnormalities Amniocentesis Chorionic Villus Sampling

The Human Genome Project Genome: the whole of the genetic information of an organism The Human Genome Project Completed in 2003 The mapping of human chromosomes/genes.

The Human Genome Project