Biological Anthropology On Cells, DNA, and Proteins

Cell Theory A set of explanatory principles used to understand cells Cells are the smallest unit of life Consist of smaller (non-alive) parts: organelles

A Cell

Two Types of Cells Somatic cells The vast majority of cells in our bodies Reproduce through mitosis Sex Cells (gametes) Only found in ovaries and testes Reproduce through meiosis

Two Types of Cell Division Mitosis Occurs in somatic cells Produces 2 daughter cells Genetically identical diploid Meiosis Occurs in sex cells (gametes) Produces 4 daughter cells Genetically unique haploid

Mitosis Asexual reproduction Occurs in somatic cells Produces 2 genetically identical diploid daughter cells

Meiosis Occurs in sex cells (gametes) Produces 4 daughter cells Genetically unique haploid

Crossing-Over # of fingers cerumen ABO group 6 5 6 5 wet dry dry wet A

Cell Division Mitosis Meiosis

Karyotype Species-specific set of chromosomes Differs from species to species in terms of The number of chromosomes The sequences of genes contained in the chromosomes

Human karyotype 46 chromosomes Arranged in 23 pairs 1 set from each parent

Human karyotype Autosomes Are homologous Pairs 1-22 same length same sequence of genes (may be different alleles)

Human karyotype Sex chromosomes X & Y XX – homologous Pair 23 X & Y X longer than Y XX – homologous XY – partially homologous

So what’s in a chromosome?

Let’s take a look!

A chromosome contains genes

and genes contain… Deoxyribonucleic Acid Present in all living organisms Amount varies from organism to organism Species can read each others’ DNA

DNA Sugar-phosphate backbone” Bases are “rungs” adenine = thymine cytosine = guanine

the total DNA/genes of a species Genome the total DNA/genes of a species Homo sapiens app. 3,000,000,000 DNA bases 35,000 – 40,000 genes Honeybee – 300,000,000 DNA bases Fruit fly – 13,600 genes Bacteria – a few hundred to a few thousand genes

DNA Replication Produces two identical strands from one original strand Each side of the original is a template for making a new copy of its complement

The Three Problems How is the variation present within a species at any time affected by the environment? Darwin How is variation passed on from one generation to the next? Mendel Where does variation come from? Watson & Crick

But what are genes used for?

Protein Synthesis A two stage process Our players: Transcription Translation Our players: Messenger RNA (mRNA) – the locks Transfer RNA (tRNA) – the keys Ribosome (“locksmith) Amino Acids

Protein Synthesis 1: Transcription messenger RNA (mRNA) copy of gene is made mRNA copy leaves nucleus and goes to cytoplasm

Protein Synthesis 2: Translation mRNA copy is “read” by ribosomes Ribosomes match tRNA to codons on mRNA

Proteins: the End Result One gene codes for one protein Differences between individuals due (in part) to differences in their proteins

Protein Synthesis, once again… A two stage process 1) transcription 2) translation The process whereby the DNA message is converted into a protein product

for more information… DNA replication Web sites Key words DNA replication Protein synthesis DNA translation Transcription http://www.dnalc.org/resources/ http://www.johnkyrk.com/