Unit A – Biological Diversity How do species have genetic variation?

Outcomes investigate the movement of characteristics from parents to offspring, and identify examples of characteristics in offspring that are: the same as the characteristics of both parents the same as the characteristics of one parent intermediate between parent characteristics different from both parents distinguish those characteristics that are heritable from those that are not heritable, and identify characteristics for which heredity and environment may both play a role identify examples of dominant and recessive characteristics describe, in general terms, the relationship of chromosomes, genes and DNA; and interpret their role as repositories of genetic information  distinguish between cell division that leads to identical daughter cells, as in binary fission and mitosis, and cell division that leads to formation of sex cells, as in meiosis

DNA- Transmitter of Genetic Code What is DNA? Also known as Deoxyribonucleic Acid The genetic material found in the nucleus of cells. It is the inherited material responsible for variation. Every single cell has DNA in its nucleus A nucleus is the “brain-center” of the cell and the DNA helps to make the cell.

DNA and the Genetic Code James Watson and Francis Crick were the first to discover the shape of DNA DNA looks similar to a twisted ladder- the sides of the ladder are the same in all DNA molecules, but the rungs are what makes the variation. Each rung is made up of a pair of chemicals called guanine, cytosine, thymine, adenine. A always bonds with T G always bonds with C

The Genetic Code The arrangement of the four pairs can be read by cells and is called the genetic code. All organisms have DNA from the same “instructions”

Edible DNA Ms. Deanne will demonstrate Materials: Licorice, Toothpicks, Coloured Marshmallows

Chromosomes Cells need lots of DNA to code for all the characteristics of an organism If the DNA from a human cell was stretched out, it would be about 2m long! More than 1 000 000 times the length of the cell! DNA is packaged into smaller groupings called chromosomes. Each cell has 2 sets of chromosomes, for humans we receive 23 from our mom and 23 from our dad

Chromosomes Each organism has a different amount of chromosomes in a complete set Humans complete set is 46 chromosomes Dogs a complete set is 78 Most chromosomes are organized into pairs and therefore a dog would have 39 pairs of chromosomes If a cat has 39 chromosomes in a complete set, how many pairs of chromosomes would it have?

Genes A gene is a single uninterrupted segment of DNA, which contains the coded instructions for the organisms Researchers found out by studying fruit flies that: Genes are located in the chromosomes Each chromosome has numerous genes on it Genes come in pairs like chromosomes Both genes in a pair carry DNA instructions for the same thing ex. Leg length Specific characteristic genes occupy matching locations on the two chromosomes DNA code may not be exactly the same in both locations.

Genes Because the same gene on 2 pairs of chromosomes can have different DNA and can give different results (blue eyes or brown eyes) the different possible forms are called alleles.

To Do Allele Draw this picture in your notes.

Cell Division

Review from last class What is a chromosome? What is a gene? What is an allele?

Cell Division and Asexual Reproduction When a single-celled organism, as well as most cells in our body divide, the cells contents are divided equally into 2 separate cells What does this mean about the DNA? Because both cells need the correct amount of DNA the original cell doubles its DNA before splitting so that each cell will receive the proper amount This process is called mitosis

Mitosis

Cell Division and Sexual Reproduction If a male gamete and a female gamete both had regular amounts of DNA, then when they combined there would be twice as much as was needed. To solve this problem gamete cells undergo a process called meiosis. Meiosis is a type of cell division where each cell ends up with only half the DNA of a normal cell so when they combine the zygote has a complete set of DNA Meiosis involves two cell divisions, not just one.

Meiosis

Drawing Mitosis and Meiosis Use figure 3.11 on page 47 to draw and label the steps of mitosis and meiosis. This will be done in your notes. You also need to include in your own words what mitosis and meiosis is. Do not quickly do this. Spend time on it making it detailed.

Patterns of Inheritance Long before research scientists discovered chromosomes and genes, plant and animal breeders were conducting experiments in controlled breeding. Phenotypes are characteristics physically seen Genotypes are traits that are found in genetics

Purebred Purebred is an animal or plant who ancestors have all had the same form of trait. Also known as homozygous Example: Cats whose ancestors have only produced white offspring for several generations. If we were to look at the alleles they would be the same. AA or aa

Hybrid An organism produced by crossing two individuals purebred for different forms of a trait. Also know n as heterozygous Example: Breeding a purebred black cat with a purebred white cat. If we were to look at the alleles they would be different Aa

Dominant Trait The outward form observed when two opposite-acting alleles are inherited Example: Long leg length in fruit flies; an offspring with one short leg allele and one long leg allele will grow long legs because it is the dominant allele. Example: Black coat colour in cats. If you bred a white purebred with a black pure bred they will always have a black coat. Would these kittens be considered purebred or a hybrid?

Recall that offspring of sexual reproduction inherit genes from both parents. Both genes in a pair carry DNA instructions for the same thing: coat colour. However the specific DNA instructions carried by the alleles may not be identical (black or white)

Recessive Trait The outward form observed only when two same-acting, non-dominant alleles are inherited. Example: Short leg length in fruit flies. An offspring with two short leg alleles will grow short legs. There short-leg allele has no influence if the dominant long leg allele is present

Incomplete Dominance Sometimes an allele is not completely dominant or recessive and can show as a blend of traits. Example: A purebred red snapdragon breeds with a purebred white snapdragon and their offspring will be pink Neither allele is truly dominant or recessive so both are somewhat expressed.

Offspring Unlike Either Parent Sometimes offspring do not look like either parent or like a mixture of the two Example: A black hair brown eyed father and a brown hair brown eyed mother having a baby with red hair and blue eyes This can occur because inheritance might not be just as simple as dominant or recessive traits. There may be many gene locations and several possible alleles involved in certain characteristics. This is why it is possible to have one brown eye and one blue eye

Punnett Square Example Mendel’s Peas Scientist who researched traits with pea plants. Recorded observations in plants This picture looked at plant height

Punnett Square Examples

Punnett Square Examples

Think about it! Does Environment have to do anything with phenotypes and genotypes

Environmental Factors The action of genes is greatly influenced by the environment in which an offspring develops. Example: FASD. If a mother drinks alcohol while pregnant it can interfere with the normal development, even though the DNA is still normal. Example: Many mothers in the 1950’s took the drug thalidomide to help with morning sickness. One of it many effects on the fetus was the abnormal development of limbs. Many babies were born without their limbs. However when they had children as adults their children were born normal. Therefore the DNA was normal.