Make Observations

Standard S7L3 UNDERSTAND THE IMPORTANCE OF AND HOW BIOLOIGICAL TRAITS ARE PASSED ON FROM GENERATION TO GENERATION

I can understand how heredity does not always follow Mendelian rules. Learning Target I can understand how heredity does not always follow Mendelian rules.

Genetics Since Mendel

Gregor Mendel--A Reminder Austrian Monk who is considered the “Father of Genetics.” Mendel’s Rules: Traits are controlled by 2 (or more) alleles. One allele may be dominant. The other may be recessive Alleles separate in gametes during meiosis.

If Gregor Mendel were given a black mouse & a white mouse, What would he have said about the offspring? He would have said that the phenotype of the offspring resembled one of the parents, black or white. If so, how did the mouse get gray fur?

Genetics Today----Not Always Following the Rules

Incomplete Dominance Incomplete dominance is a heterozygous condition in which both alleles are PARTIALLY expressed. The offspring will be a blended form. This will be different than the homozygous forms of either parent.

Incomplete dominance This is a form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other.

Offspring of Incomplete Dominance In incomplete dominance three phenotypes are involved: One for EACH parent and a third SEPARTE phenotype for the offspring. The trait in the offspring is a BLEND (or mixing) of the parental traits.

Broken down, this means …

Incomplete Dominance Neither allele for a trait is dominant. The heterozygous phenotype is intermediate or is between the homozygous parent forms.                                  

For Example Chestnut Horse + Cremello Horse = Palomino Chestnut Horse: Dominant color is chestnut. Cremello Horse: Dominant color is creme/white.                          

                                                                      

Say it Again? A palomino horse will result when a chestnut horse and cremello colored horse are crossed. This is because the heterozygous palomino gets a single allele of a cream colored gene crossed with a red (chestnut) gene.

Incomplete Dominance WW RR RW RR RW WW In Incomplete DOMINANCE, use different letters since neither is stronger WW RR RW RR RW WW

Red (Four O’Clocks) X White Try This: Complete a Punnett square for the following cross. Red (Four O’Clocks) X White

All of the offspring were pink All of the offspring were pink. This is intermediate between red and white.

Answer the Following: In humans hair textured is controlled by incomplete dominance. A curly haired individual and an straight haired individual have all wavy haired children. If two wavy haired people have children, what will the phenotypic ratio be?

CoDominance Codominance –Neither phenotype is dominant. Instead, the individual expresses both phenotypes. Co – both are dominant enough to be expressed!! Dominique Chickens

Co-Dominance “CO” is together. “Cooperate; Co-Captain” As with incomplete dominance, a hybrid offspring will show a THIRD PHENOTYPE. With incomplete dominance, there is a blending. With CO-DOMINANCE, BOTH TRAITS appear TOGETHER in the offspring.

Answer the Following: A cross between a black cat and a tan cat produces a tabby pattern (black and tan fur together). What percent of kittens would have tan fur if a tabby cat is crossed with a black cat?

For Example With incomplete dominance, a red and white flower will produce a pink flower. In CO-DOMINANCE, a red and white flower will produce a red and white flower.

Multiple Alleles Within the population, there may be multiple forms for alleles. Many traits are controlled by more than two alleles. These are said to be controlled by multiple alleles. Two of these alleles are CODOMINANT. Blood type is an example of multiple alleles.

Blood Type/Multiple Alleles The alleles for blood type are A, B, and O. Both A and B are dominant. These are co-dominant. O is recessive. If someone had the A and B alleles, the blood type would be AB. (Both are exhibited/co-dominant.) If someone exhibits blood type A, do both alleles have to be A? For someone to have the blood type O, both parents would have to carry the allele.

Answer the Following: A man with blood type B marries a woman with blood type A. Their first child is blood type O. Predict what other blood types are possible for any children they may have in the future. To answer this, complete a Punnett square.

Or the Y chromosome

Environmental Role The environment plays a role in how some of your genes are expressed. These influences may be internal or external. Example: Some people may be at risk for skin cancer. These people need to limit their exposure to the Sun.

Sex Determination Chromosomes that determine the sex of an organism are XX in females and XY in males. Females produce eggs with an X chromosome only. Males produce sperm with either an X or a Y chromosome. The diagram is of a karyotype. Karyotypes are pictures of homologous chromosomes. (Note the last pair indicates gender.) Homologous chromosomes are identified by size, bands/banding, and centromere placement.

Female Karyotype Male Karyotype

Mutations A mutation may be harmful, beneficial, or have not effect. Mutations occur when a gene is altered or copied incorrectly. Chromosome disorders are caused by more or fewer chromosomes than normal. These can occur because of mistakes made during the process of ______________.

Pedigree A pedigree follows a trait through generations of a family. Circles indicates a female. Square indicates a male. Partial coloring indicates a carrier. (Carrier = has the allele and passes this to offspring.) Completely colored in indicates the trait is present.

Selective Breeding Selecting qualities within individuals of a breed that are desired to be passed on to the next generation.

Selective Breeding Inbreeding - produces individuals with similar characteristics. Hybridization – involves crossing individuals with different traits. (This is done with the hope of producing offspring with the best traits of both organisms.)

What is genetic engineering? Today scientists can use biology or chemistry to change the arrangement of DNA that makes up a gene. This is used today for many reasons. One of those reasons is to produce larger volumes of medicine. Cloning is a type of genetic engineering. In cloning, the genetic information from a single cell of an organism is used to produce another organism with the same genetic information.

What other ways can genes be used? Genes can be changed by scientist to make plants more resistant to disease. Genes from one type of plant may be inserted into another type of plant to help fight crop diseases!