1. B-4.2 Summarize the relationship among DNA, genes, and chromosomes.
Unit 4: Genetics
B-4.2
Summarize the relationship among DNA, genes, and chromosomes.

2. Key Concepts
Chromosome
DNA
Gene

3. What You Already Know…
In the 7th grade, you summarized how genetic information is passed from parents to offspring using the terms genes, chromosomes, inherited traits, genotype, phenotype, dominant traits, and recessive traits.

4. It is Essential For You to Know…
DNA, genes and chromosomes compose the molecular basis of heredity.

5. OBJECTIVES
Summarize the relationship among DNA, genes, and chromosomes.
Recall the basic structure of chromosomes and genes.
Illustrate or interpret an illustration of the relationship of a chromosome, DNA, and genes using words or diagrams.

6. Zoom in on a Chromosome

7. Packaging DNA Eukaryotic DNA: many levels of packaging:
Fundamental unit is Nucleosome –
DNA wound around proteins called histones.
(CP. 139)
(Hon 151)

8. Nucleosome

9. Nucleosomes Nucleosomes Lowest DNA packaging level
Can be thought of as a length of thread wound around a spool, the thread representing DNA and the spool being histone proteins.

10. The earth is 150 billion meters
DNA - By The Numbers!
Each cell has about 2 meters (6 ft) of DNA.
The average human has trillion cells.
Avg human has enough DNA to go from the Earth to the sun more than 400 times.
DNA has a diameter of only meters (20Ǻ) [1Ǻ =10-10 m]
The earth is 150 billion meters
or 93 million miles from
the sun.
If you unravel all the DNA in the chromosomes of one of your cells, it would stretch out 2 meters. If you did this to the DNA in all your cells, it would stretch from here to sun more than 400 hundred times!

11. Chromosomes DNA is wrapped around histones to create a nucleosome
Nucleosomes are tightly coiled to generate chromosomes
Remember:
The nucleus of a human cell contains approximately
2 meters of DNA!
3.2 billion nucleotides (also called base pairs)
104,380,000,000 possible combinations

12. Genes
Genes are located on chromosomes in the cell’s nucleus. Chromosomes are long threads of DNA tightly coiled.
Each organism must inherit a single copy of every gene from both its parents.
When an organism produces its own gametes those 2 sets of genes must be separated from each other so that each gamete contains just one set of genes.

13. What Exactly is a Gene?
A gene is a section of DNA in a specific region of a specific chromosome.
Genes code for specific proteins to be produced, which cause specific characteristics in living things.
There are dominant and recessive forms of genes.
Each chromosome consists of hundreds of genes determining the many proteins for an individual organism.