Chromosomes DNA and Genes Date Organization of DNA

Chromosomes, DNA, and Genes Date _______

Organization of DNA • Includes… – DNA – Genes – Chromosomes • What are each of the above? What do they do?

DNA • Made up of nucleotides • Recipe for making proteins – Proteins are determined by the order of nitrogenous bases – Proteins are made up of amino acids…amino acids are coded for by sets of 3 DNA base pairs

Genes • Specific location on a chromosome • Segment of DNA that codes for a particular protein • Proteins determine an organism’s characteristics • Each chromosome contains hundreds to thousands of genes

Chromosomes • Contained within the nucleus of a cell • One long thread of DNA that is tightly coiled • DNA Chromosome Wrapping

Organization of DNA

DNA is the Code of Life • Every organism uses the exact same building blocks! • DNA contains the code for every protein an organism needs… • And every cell in an organism’s body contains a complete set of chromosomes

Trivia! • Do all organisms have the same amount of chromosomes? • What eukaryotic organisms do you think have more chromosomes? – Humans: 46 chromosomes (23 pairs) – Dogs: 78 chromosomes (39 pairs) – Potatoes: 48 chromosomes (24 pairs)

“Most Chromosomes” award goes to… • Adder’s tongue fern at 1200 or 1260 chromosomes! (600 or 630 pairs)

And the least… • Jack jumper ant, ant with only 2 chromosomes! (1 pair)

Chromosomes…the Details • In eukaryotic cells… – Sex chromosomes determine the sex of the organism—male or female. • There is only a SINGLE PAIR of sex chromosomes – Autosomal chromosomes, or autosomes, are all other chromosomes not involved in sex determination

Where do chromosomes come from? • All cells EXCEPT sex cells contain one pair of EVERY chromosome – Each pair = 2 chromosomes with genes for the same types of proteins – One chromosome of each pair comes from mom, one from dad • This is how you inherit traits from your parents!

• Genes…not the kind you wear! Every chromosome has hundreds to thousands of genes • Unique characteristics are the result of different proteins • There are many unique proteins that an organism has to make to live and survive – Closely related organisms may have genes that code for the same or similar proteins – Organisms that are not closely related share fewer genes than organisms more closely related

Question for you: • Approximately how many genes do humans have? – 20, 000

Focus Questions 1. DNA is a recipe for _______. 2. What is a gene? 3. How many genes does a chromosome hold? 4. Where are chromosomes stored in the cell? 5. How many chromosomes do humans have? 6. What organism has the most chromosomes? 7. What organism has the least chromosomes? 8. How many sex chromosomes do humans have? 9. How many genes do humans have? 10. What are the sex chromosomes for males? Females?