Warm UP• Illustrate how the chromosome

number in a sexually reproducing organism with 8 chromosomes remains constant from one generation to the next by drawing a model of meiosis and showing the TOTAL number of chromosomes in each stage, the steps, and the products for male and female.

Warm Up• Deoxyribonucleic acid, the material

that contains the information that determines inherited characteristics

• One of the four possible bases in a string of DNA—it pairs with adenine

• A subunit of DNA that consists of a sugar, a phosphate, and a nitrogenous base

• The complement to guanine

Warm Up

• What letters represent the four bases?• Using X-ray diffraction, what did

Rosalind Franklin show the shape of DNA to be?

• Watson and Crick built a DNA model like a ……

• The sides of the DNA “ladder” are made of…….

• The “rungs” of the DNA ladder are…..

Pick Up Warm Up• On the back of your warm up,

answer the following: • What are the phenotypes based

on the genotypes:Ggbb ____________________ ggBB ____________________ggbb ____________________GgBb ____________________

Warm Up

• A male rabbit with the genotype GGbb is crossed with a female rabbit with the genotype ggBb.

• Determine the phenotypes and proportions in the offspring.

Warm Up

• How many out of 16 have grey fur and black eyes?

• How many out of 16 have grey fur and red eyes?

• How many out of 16 have white fur and black eyes?

• How many out of 16 have white fur and red eyes?

DNA

What is DNA

• Deoxyriboneucleic Acid: a genetic code (like a blueprint) for making new cell parts, new cells, or an entirely new organism.

• DNA wraps around protein cores and forms chromosomes found in the nucleus of eukaryotic cells.

History of DNA

• 1952 – Rosalyn Franklin discovered that DNA is made up of 2 chains of molecules arranged in a spiral form.

History of DNA

Chargaff’s Rule:

-Adenine always equals amount of Thymine.

A = T

-Guanine always equals amount of Cytosine.

G = C

Chargraff’s Rule

History of DNA

• 1953 – James Watson and Francis Crick constructed the first model of DNA and win the Nobel Peace Prize.

DNA Structure

• DNA is often called a “double helix” or “twisted ladder.”

• The sides are made of phosphate and deoxyribose-sugar molecules.

• The middle (rungs) are made of nitrogenous base pairs (adenine/thymine, guanine/cytosine).

Four Nucleotides

• Nucleotide: combination of a phosphate molecule, deoxyribose-sugar molecule & a nitrogenous base.

The Four:AdenineThymineCytosineGuanine

Complementary Bases

Remember Chargaff’s Rule:

The complementary strand/sequence to G-A-T-T-A-C-A would be…

DNA Replication

• Before any cell can make a copy of itself, all the DNA must be copied!

• This is called DNA replication.

DNA Replication

• An enzyme opens the strands of DNA so that they become single stranded.

• Complimentary nucleotides come fill in the missing strand.

• Two DNA strands are formed.

Let’s Model DNA

• Have students stand in two lines that spiral like a DNA molecule. Each line should hold string.

• Students should hold cards labeled A, T, C, or G to represent the nucleotide pairs.

• Have the two lines move away from each other to model how the DNA molecule separates into two strands.

• Have free standing students pair up with matching A, T, C, or G cards to show how the open strands replicate.

• This one example of how models can be similar to yet different from the natural occurrences they represent.

http://www.classzone.com/books/ml_science_share/vis_sim/chm05_pg141_protein/chm05_pg141_protein.html

Making Proteins

• Groups of three nitrogenous bases are a code (codon) for making specific amino acids

• Strings of amino acids form proteins• RNA (riboneucleic acid) makes a

temporary DNA copy

Genes: sections of DNA on chromosomes thatcontrol production of proteins for specific traits such as:hair color, eye color, dimples, freckles….

RNA vs. DNA

Similarities:• Are nucleic acids• Contain nitrogenous

bases• Contain phosphate &

sugar molecules

DNA RNA

Double strand

Single strand

Thymine Uracil

Deoxyribose-sugar

Ribose-sugar

Differences:

Deoxyribose Sugar

Types of RNA

• messengerRNA or mRNA: comes from nucleus w/ genetic information for protein synthesis (mirror image of DNA strand).

• transferRNA or tRNA: carries matching amino acids to ribosomes.

• ribosomalRNA or rRNA: constitutes 50% of a ribosome, decodes mRNA for tRNA to pick-up matching amino acids.