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Transcript
Breeding Corn BELL RINGER If a green pea pod plant is crossed with a yellow pea pod plant, what will the offspring look like? X ALL the offspring will be green! Is it possible for a man & woman (each with dark hair) to have a child with blond hair? Introduction Read the Introduction…Pg. 282 What is SELECTIVE BREEDING? the process by which organisms with desirable traits are mated with the goal of producing even more desirable offspring. What is SEXUAL REPRODUCTION? reproduction in which two parents contribute genetic material to the offspring. Activity 4: Breeding Corn Corn Reproductive Structures Activity 4: Breeding Corn How do traits get passed from parent to offspring? Through GAMETES: sex cells Male gamete is the SPERM Female gamete is the EGG FERTILIZATION: union of egg & sperm ZYGOTE: fertilized egg Activity 4: Breeding Corn Challenge How can information about the genetic makeup of plants help farmers breed plants for desirable traits? Activity 4: Breeding Corn Get Started Answer the 3 questions on the “Traits & Heredity” sheet under “I think…” Activity 4: Breeding Corn Breeding Corn: First Generation Activity 4: Breeding Corn Procedure Read “Basic Genetics” on p. 286 What are alleles? A form of a gene…An organism has two copies of the gene for each of its traits. Distinguish between dominant and recessive traits. Dominant traits will mask another version of a trait; only one dominant allele needed to be expressed… A recessive trait will be hidden by a dominant trait. Activity 4: Breeding Corn GENES VS. ALLELES Segment of DNA that codes for one protein/trait Most traits are determined by TWO genes. Remember chromosomes have a homologous match…two chromosomes with similar genetic information EXAMPLE: hair color eye color height in pea plants Activity 4: Breeding Corn Each form of a gene is called an ALLELE EXAMPLE: brown or blond blue, hazel, brown tall, short RECESSIVE (allele) DOMINANT (allele) Always expressed if present Only need ONE dominant allele to be expressed EXAMPLES: dark hair, brown eyes, tall peas Activity 4: Breeding Corn May be present but will not be expressed if paired w/ dominant allele Requires TWO recessive alleles for recessive trait to be expressed EXAMPLES: light hair, blue eyes, short peas Procedure As a group… Use the “P” allele cards to demonstrate what happened to make all corn kernel babies purple Discuss the 3 questions as a group and fill in under “My group thinks…” Activity 4: Breeding Corn Procedure Creating a Punnett Square Activity 4: Breeding Corn Key Vocabulary Genotype vs. Phenotype All possible combinations using P, p: PP, pp, Pp, pP GENOTYPE: actual genes in the pair; can’t see…they’re on chromosomes…but they determine the individual’s traits Activity 4: Breeding Corn PHENOTYPE: the trait that is expressed; the ‘physical’ appearance Key Vocabulary Describing GENOTYPE… Use terms: homozygous: both genes the same (PP, pp) *follow with ‘dominant’ or ‘recessive’ to distinguish upper case or lower case heterozygous: genes different; 1 dominant, 1 recessive (Pp, pP) Activity 4: Breeding Corn Procedure Read the scenario (step 8 on p.286) Count the number of purple kernels and the number of yellow kernels on corn ear A Record your data Count the number of purple kernels and the number of yellow kernels on corn ear B Record your data Activity 4: Breeding Corn Which describes the cross that produced ear A? Ear B? Punnett Square X Activity 4: Breeding Corn Punnett Square Y Punnett Square Z Procedure Breeding Corn: Second Generation Activity 4: Breeding Corn Revisit the Challenge Complete the “now we know” column of the “traits & Heredity” page Answer the ANALYSIS questions p.289 Activity 4: Breeding Corn Follow Up Analysis 1 How does a Punnett square show the possible results of a cross between two individuals? Activity 4: Breeding Corn Follow Up Analysis 2 Describe how your observations of offspring (corn kernels) allowed you to determine the genetic makeup of the two parents. Discuss how you used ratios in this process Activity 4: Breeding Corn Follow Up Analysis 3 What do you predict will happen if a purple corn plant with the genes Pp is bred with a corn plant with purple kernels and the genes PP? Explain your answer, and include a matching Punnett Square. Activity 4: Breeding Corn Follow Up Analysis 4 How could scientists use selective breeding to help solve a sustainability challenge such as breeding a crop that can survive drought? Activity 4: Breeding Corn Revisit the Challenge How can information about the genetic makeup of plants help farmers breed plants for desirable traits? Activity 4: Breeding Corn Key Vocabulary allele dominant Punnett square recessive selective breeding sexual reproduction trait Activity 4: Breeding Corn