Genetic Inheritance and Traits: Understanding DNA and Chromosomes

1. Unit 5: Heredity Review Lessons 1, 3, 4 & 5

2. SC Standards and Objectives • Standard 7.L.4: The student will demonstrate an understanding of how genetic information is transferred from parent to offspring and how environmental factors and the use of technologies influence the transfer of genetic information. • 7.L.4A. Conceptual Understanding: Inheritance is the key process causing similarities between parental organisms and their offspring. Organisms that reproduce sexually transfer genetic information (DNA) to their offspring. This transfer of genetic information through inheritance leads to greater similarity among individuals within a population than between populations. Technology allows humans to influence the transfer of genetic information. Performance Indicators: Students who demonstrate this understanding can: • 7.L.4A.1 Obtain and communicate information about the relationship between genes and chromosomes to construct explanations of their relationship to inherited characteristics. • 7.L.4A.2 Construct explanations for how genetic information is transferred from parent to offspring in organisms that reproduce sexually. • 7.L.4A.3 Develop and use models (Punnett squares) to describe and predict patterns of the inheritance of single genetic traits from parent to offspring (including dominant and recessive traits, incomplete dominance, and codominance). • 7.L.4A.4 Use mathematical and computational thinking to predict the probability of phenotypes and genotypes based on patterns of inheritance. • It is essential that students obtain and communicate information about the relationship between genes and chromosomes to construct explanations of their relationship to inherited characteristics. • It is essential that students construct explanations for how genetic information is transferred from parent to offspring in organisms that reproduce sexually. • It is essential that students develop and use models (Punnett squares) to describe and predict patterns of the inheritance of single genetic traits from parent to offspring (including dominant and recessive traits, incomplete dominance, and co-dominance). • It is essential that students be able to use mathematical and computational thinking to determine a ratio of phenotypes and genotypes based on the results of a Punnett square (monohybrid cross).

3. Bell Work • Where are genes located? Where is DNA located? Where are chromosomes located? • What are the 3 main functions of DNA? • What are the exception for Mendel’s laws? • What is the difference between codominance and incomplete dominance?

4. what is a Gene? • A gene is a section of DNA in a specific region of a specific chromosome. • Genes code for specific proteins to be produced characteristics in living things. • There are dominant and recessive forms of genes. • Each chromosome consists of hundreds of genes determining the many proteins for an individual organism.

5. Karyotype • The picture to the left show all the chromosomes in a human. • It is called a Karyotype. • There are 3 things a Karyotype shows • Sex of the organism • Total Number of chromosomes • Chromosomal Disorders

6. phosphate group nitrogen-containing base deoxyribose (sugar) What is DNA • DNA: Deoxyribonucleic Acid • A long molecule made up of units called nucleotides.

7. DNA Purpose Has to be responsible for three things: • Genes have to carry info from one generation to the next. • Genes have to put that info to work by determining heritable traits. • Genes have to be easily copied during cell replication.

8. Autosomal Chromosomes • The other 22 pairs of non-sex chromosomes are called autosomal or autosomes. • Humans have 46 chromosomes • 23 from the male parent • 23 from the female parent • Each set of chromosomes is homologous • Each of the 23 chromosomes from the male parent will “match” with each of the 23 chromosomes from the female parent.

9. Sex Chromosome and Sex Determination In humans gender is determined by the sex chromosomes. The 23rd pair. 50% of sperm cells carry X, 50% carry Y. 100% of egg cells carry X. XX = female and XY= male. Which parent determines the gender of the baby?

10. Genetics • Heredity deals with genes and genetics. • Genes come in many forms and determine traits. • This explains the diversity of life. • Genetics is the scientific study of heredity. • A geneticist studies genetics. • Traits are distinguishing characteristics that make each organism a little different. • We study heredity through the field of Genetics.

11. What did all this tell Mendel? Mendel drew three conclusions about heredity through his experiments: • Traits are inherited as discrete units. • Organisms inherit two copies of each gene, one from each parent. • Organisms donate only one copy of each gene in their gametes. The two copies separate (segregate) through gamete formation.

12. Principle of Dominance • The Law (Principle) of Dominancestates that some alleles are dominant and others are recessive.

13. Heterozygous vs. Homozygous • Alleles are the letters that represent traits. • Alleles that are the same are homozygous • Alleles that are different are heterozygous.

14. Phenotype vs. Genotype • Genotype: The actual gene (alleles) • Pp • Alleles are the letters that represent genes. • Upper Caseare dominate • Lower Caseare recessive • Phenotype: The physical trait expressed. • purple

15. Vocabulary • Do not forget to define the term. • Do not give me 5 words define them in your own words. • Use your notes not the book or your laptop

16. Review Questions • What is the difference between genotype and phenotype? • What is the difference between heterozygous and homozygous? • What is the Law of Dominance?

17. Unit 5: Heredity Review Lesson 1, 3, 4 & 5

18. Bell Work • What are the 3 Conclusions that Mendel cam up with? • What is a karyotype and what can it tell us? • Why is studying genetics important?

19. Principle of Segregation • The Law (Principle) of Segregation explains how alleles are separated during meiosis.

20. Principle of Independent Assortment • The Law (Principle) of Independent Assortment states that the segregation of alleles of one trait does NOT affect the segregation of the alleles of another trait. • Holds true unless genes are linked.

21. Types of Crosses • Two types of crosses: • monohybrid cross • One type of characteristic is crossed • Example: TT x tt • 4 square Punnett Square • dihybrid cross • Two characteristics are crossed • Example: TTRr x ttRR • 16 square Punnett Square

22. Genes can be either dominant or recessive. They do not mix to form the phenotype. According to Mendel… R = Red r = yellow

23. Since Mendel’s Time… Due to advances in technology since Mendel’s time, inheritance patterns and genetic variations that could not be explained by Mendelian genetics are now understood using new technology • Incomplete Dominance • Gene Linkage • Crossing Over • Codominance • Multiple Alleles • Polygenic Traits • Sex-linked Traits

24. Sex Chromosomes • Sex chromosomes determines an organism’s sex • Genes located on the sex chromosomes are sex linked genes. • Genes on the Y chromosome are responsible for the development of male offspring. • Thex chromosome has much more influence over phenotype.

25. Incomplete Dominance • In incomplete dominance, neither allele is completely dominant nor completely recessive. • Heterozygous phenotype is intermediate between the two homozygous phenotypes • Homozygous parental phenotypes not seen in F1 offspring

26. Codominance • There are 2 different dominant genes. • A heterozygote shows both other possible phenotypes in a pattern. • Genotypes designated as: PP=pink OO=orange PO=pink & orange

27. Multiple Alleles • Unlike those studied by Mendel, some traits are controlled by more than one gene (allele). • These genes may be dominant or recessive, or dominant to different degrees. Ex: ABO Human Blood Groups • Human Blood types may be A, B, AB or O. • Codominant blood types: A and B • Recessive blood type: O • How would a person have blood type AB?

28. Order of dominance: brown > green > blue. Polygenic Traits • Many genes may interact to produce one trait. • Polygenic traits are produced by two or more genes.

29. Linkage • The closer together two genes are, the more likely they will be inherited together. • Cross-over frequencies are related to distances between genes. • Linkage maps show the relative locations of genes.

30. Review Questions • What are the Laws of Independent Assortment and Segregation? • What is the difference between polygenetic traits and multiple alleles? • What are alleles? What do they represent? • What is the difference between phenotype and genotype?