HEREDITY Why do we look like we do?

Learning Targets  Describe how evolution lead to the diversity of species on earth today.  Explain the function of chromosomes, where they are located and what information they carry.  Explain the process of mitosis and why the offspring of sexual reproduction have more diverse characteristics that asexual reproduction.  Understand that genes are passed on independently of each other trait.  Be able to predict the outcome of genetic crosses.  Explain why genetic variation is important to survival of a species.

Read pgs. 110 – 117; Ch.6 Friday 4/23 Vocabulary Definitions of key terms pgs. 110 Questions pg. 115 Read pgs Questions pg. 123 Questions pg. 130 Read pg & Activities Class survey Punnett Squares Corn toss Dragon activity

Opening Tasks 4/5/10 How do the nitrogen bases pair up to code for protein. 4/6/10 What is your definition of genetics? 4/7/10 Which scientist led us to understanding genetics? Where are your genes located? 4/8/10 What are dominant and recessive traits? 4/9/10 What are phenotype and genotypes?

April 6, 2010  ?? of the day  How do the nitrogen bases pair up to code for protein?  Go over DNA/Genes Worksheet  Read Pages  Vocabulary due Thursday, key terms page 110  Pre – activity worksheet  Begin Notes

April 7, 2010  ?? Of the day:  Which scientist led us to understanding genetics?  Where are your genes located?  Go over Video Worksheet  Notes/Review on DNA  Start that genetics!!

DNA Replication  Ensures each daughter cell will have an exact copy of the genetic material it needs to carry out its activities.  Reminder: DNA (and RNA) is made up of nucleic acids – long organic molecules made of – C, O, H, N, and phosphorus  Replication of DNA takes place during Interphase

DNA Replication (cont.)  DNA is made of a sugar molecule called deoxyribose, a phosphate, and nitrogen bases in the shape of a ladder or spiral staircase. –Deoxyribose and phosphate make up the outside supports (or the sides of the ladder) –Nitrogen bases make up the rungs of the ladder The same bases always pair, A-T and C-G and in a specific order determining protein formation. Adenine - Thymine Guanine - Cytosine

The Structure of DNA

DNA Replication Process  Replication begins when the two sides unwind and separate (like unzipping a zipper)  The DNA separate between the paired bases  Nitrogen bases floating in the nucleus pair up with the bases on each half of the DNA molecule to make two new identical strands.

DNA Replication

DNA Replication (in action)

PRINCIPLES OF HEREDITY  Mendel’s research led to our understanding of genetics. The genetic code DNA, determines all our traits inherited from our parents. These traits are passed on by genes which are located on the chromatids in the nucleus.

Mendel’s Experiment  P generation = grandparents  F1 generation are the offspring of the grandparents (your parents)  F2 generation are the offspring of the F1 generation (you)  Trait is a characteristic passed on to the offspring like height.  Traits are controlled by the alleles inherited from the parents  Alleles are different forms of a gene, for example the gene for height has 2 alleles – tall and short.

Inheritance Patterns Continued  Genotypes show the combination of genes that are specific for all traits.  Phenotypes show your physical characteristics like height, eye, hair color & skin color.  Dominant traits are symbolized by capital letters, TT. One letter from each parent.  Recessive traits are symbolized by lower case letters, tt.  In each pair of genes, one comes from the mother and the other comes from the father.

Punnett Squares  These can be used to show the probability of specific traits showing up in the offspring. For Example, sex of the child  X X  X  Y  XX = mother; XY = father genotyoes, now bring the letter over the box into the boxes under it.

Practice  Write mom XX; dad XY  Now draw a square like the last slide and place mom’s traits over the top 2 boxes and dad’s traits next to the boxes on the side.  Start with mom and the first X, bring it down & write it into each box it’s over. Do the same for the second X.  repeat this for dad’s traits bringing each trait across into the boxes it’s next to.  Let’s do some others.

Cell division of the sex cells that form gametes. Parent cell has 23 pairs of chromosomes The chromosomes duplicate in the first stage

Chromosomes duplicate giving 46 pairs Cell divides into 2 cells with half the number of the previous cell. Each has the original number. 23 pairs After the final division 4 gamete cells are formed with ½ the number of chromosomes as the parent. Gametes are the egg cells in females and the sperm cells in males. Fertilization of the egg and sperm form a zygote.

The father determines the sex of the child because he passes on the Y chromosome. Remember mom is XX and dad is XY, therefore Mom can only pass on the X.

These traits can be passed on by mom only. The reason for this is only the X chromosome carries traits. Baldness, colorblindness & hemophilia are examples of these traits.