Genetics UnitGenetic Materials

• Terms to know:- DNA - genome- RNA - double helix- Chromosome - karyotype- Chromatin- Sister chromatid- Gene- Bases- Nucleotide- Proteins

Watson and Crick- Discovered structure of DNAin 1953- Nobel prize 1962

Watson’s book

Rosalind Franklin (1920 - 1958)

X-ray diffraction patterns of DNA

Her essential work was not recognized by the Nobel Committee in 1962

DNA structure

- DNA is made up of two strands arranged in a double helix structure

- The 2 strands of DNA run anti-parallel to one another

DNA = deoxyribosenucleic acid

DNA structure (cont.)The building block of

DNA is called a nucleotide which is made of 3 parts:

- A phosphate group

- A 5-carbon deoxyribose sugar

- A nitrogen- containing base (A,T,G,and C)

http://www.dnalc.org/resources/3d/

Nitrogen-containing bases of DNA- All organisms have the same 4 bases: Adenine Guanine Thymine Cytosine - A connects with T via 2 hydrogen bonds (A=T)- G connects with C via 3 hydrogen bonds

(G≡C)- Only 4 bases but unlimited ways to code for

proteins (proteins are products of genes)

http://www.dnalc.org/resources/3d/25-basepairing.html

The double helix staircase in Vatican, Italy

Visualizing the double helix structure of DNA

Where is DNA? In the nucleus

Human cell: 23 pairs of chromosomes in every non-sex cell

http://www.dnalc.org/resources/3d/07-how-dna-is-packaged-basic.html

Chromosomes= super-coiled DNA

- Male 46 chromosomes = 23 pairs- Karyotype = a picture of chromosomes arranged in pairs

DNA vs. RNA (ribose nucleic acid)

RNA: single strandedThe nitrogenous bases in DNA are: A, T, C, GThe nitrogenous bases in RNA are: A, U, C, G

Molecular Visualizations of DNA

• http://www.youtube.com/watch?v=-1ZvsYDTxc8&feature=related (Part 1)

• http://www.youtube.com/watch?v=S8DMoDJ8FWA&feature=related (Part 2)

Gene- Genes are small segments on DNA that code for proteins

-Proteins are the products of genes

- A gene can range from 1,000 bases to 1 million bases in humans.

- DNA can have thousands of genes.

- Genes can overlap each other

Examples of Proteins

Proteins Functions

Insulin Enzyme for sugar metabolism

Hemoglobin Oxygen transport in blood

Keratin Forms hair, nails and skin

Actin, myosin Movement

Antibodies Body immune system

Genome = is an organism’s complete set of DNA, including all of its genes

Numbers of Pairs of Chromosomes in Different Species of Plants and Animals

Common name Species Number of chromosome pairs

Mosquito Culex pipiens 3

Housefly Musca domestica 6

Garden onion Allium cepa 8

Rice Oryza sativa 12

Frog Rana pipiens 13

Alligator Alligator mississipiensis 16

Cat Felis domesticus 19

House mouse Mus musculus 20

Human Homo sapiens 23

Potato Solanum tuberosum 24

Donkey Equus asinus 31

Horse Equus caballus 32

Dog Canis familiaris 39

Chicken Gallus domesticus 39

Carp Cyprinus carpio 52

Recall cell cycle and cell division

Mitosis (PMAT)

Before a cell can divide • It must duplicate its chromosome number (i.e. making 2

copies of each)e.g. if the cell has 2 chromosomes, after DNA duplication it

should have 4 chromosomes  Diploid cells: have 2 sets of

chromosomes; often are non-sex or somatic cells; represented as 2n 

e.g. Human skin cells contain 2n=46 chromosomes --> they are diploid cells

Haploid cells: have 1 set of chromosomes; are sperm & egg cells; represented as n 

e.g. Human sperm and egg cells contain n= 23 chromosomes --> they are haploid cells  

2n = 46e.g. Skin, heart cells

n = 23e.g. sperms, eggs