Genetics and Heredity

1. Genetics and Heredity Chapter 5

2. Characteristics • Species Characteristics • Traits or features that every member of the species possess • Individual Characteristics • Distinguishing or unique features that a person or organism has that sets them apart from others of their own species • Genes • Are specific segments of DNA that code for the proteins that make us unique • We are not only a combination of both our genes (physical makeup) and our environment but our spiritual nature or soul

3. Mechanism of Heredity • Geneticsor the study of heredity (passing on of traits from parent to offspring) is both the oldest and one of the newest of the biological sciences • Biblical – selective breeding of cattle • Babylonians and Assyrians – breeding and improvement of plants • Greeks – mixing of blood “pure bloods” and “blood relatives” • Gregor Mendel – pairs of “factors” in organisms were divided and passed on to next generation

4. Inheriting Traits • Generally, genes on a chromosome control what traits show up in an organism • Each parent has two genes for a trait. These specific genes are called alleles. • The different forms of a trait that a gene may have are called alleles(uh- LEELZ)

5. Chromosomes • Chromosome • Long strand of DNA that is coiled around protein histones when not being used to make RNA or to move the genetic material during cell division • Made of two identical sister chromatids • Humans have 23 pairs of chromosomes or one set from each parent • These pairs are known as homologous chromosomes • Each homologue(chromosome from one parent) has the same type of genes as the other but different ALLELES

6. Chromosomes continued

7. Chromosomes cont. • When a cell has homologous chromosomes or 2 sets it is said to be diploid or 2n • Humans have a diploid number of 46 (23+23) • 22 autosomal or non-sex chromosomes • 2 sex chromosomes – determine gender and gender characteristics • Watermelons  2n=22 • Dogs  2n = 78 • Jumping ant  2n= 2 • When cells have only one set of chromosomes they are known as haploidor n • When cells have multiple sets of chromosomes (3+) they are known as polyploid • Adder’s tongue fern  2n= 1,260

8. Inheriting Traits • During Meiosis, the alleles for different traits (located on different Chromosomes) are mixed up (crossing over) and separated randomly (gene segregation) to insure that the offspring will be a genetically diverse individual • When a pair of chromosomes separate during Meiosis, alleles for each trait also separate into different, haploid sex cells or gametes • Males- produce sperm (spermatogenesis) • Females- produce eggs (oogenesis) • Genes are passed on once Meiosis has created gametes and those gametes unite through fertilization to form a diploid zygote

9. Gregor Mendel – The Father of Genetics • Gregor Mendel began experimenting with garden peas at his monastery in Austria in 1857 • Mendel made careful use of scientific methods, which resulted in the first recorded study of how traits pass from one generation to the next known as Mendelian Genetics

10. Mendelian Genetics • In the 34 varieties of pea seeds that he planted, Mendel made note of 7 opposingtraits • Height, seed color, seed texture • Mendel was the first to track one trait through several generations • Since the flowers of the pea plants were easily manipulated he was able to cross-pollinate the plants by hand • What was the benefit of cross-pollination?

11. Mendelian Genetics • In his experiments, Mendel used the pollen from purebred tall plants to pollinate by hand the flowers of purebred short plants • The offspring were ALL tall pea plants…

12. Mendelian Genetics • To explain the outcome of this experiment, as well as the similar results he obtained when crossing peas with other sets of opposing characteristics Mendel proposed several concepts – many now have been scientifically validated • Concept of Unit Characteristics • Concept of Dominant and Recessive • Concept of Segregation

13. 1. Concept of Unit Characteristics • This Concept states that an organism’s characteristics or physical traits are controlled by factors or genesthat occur in pairs • Genes (segments of DNA) are found in cells and responsible for inherited features • Genes are located on chromosomes • Most organisms have homologous pairs of chromosomes or one set from each parent

14. 2. Concept of Dominant and Recessive • Mendel called the trait that expressed itself when genes for 2 opposing traits are present the Dominant trait (caused by a dominant gene) • In pea plants this was the allele for Tall height • The trait that was masked or hidden was known as the recessive trait (caused by a recessive gene) • In pea plants this was the allele for short height

15. 3. Concept of Segregation • Mendel reasoned that when a cell forms gametes, the genes separate (segregate) so that there is only ONE gene for each characteristic in each gamete

16. Genetic Terminology • the genotype, or genetic makeup, of an organism. • The actual genes, represented by letters • Example: Tt, TT, tt • The way an organism looksor behaves is a result of its genotype is its phenotype(physical traits) • Example: Tall plant, short plant

17. Genetic Terminology • Purebred-an organism that always produces the same trait, generations after generations; it also has two alleles that are the SAME • Also called homozygous • Ex. bb, TT, • Hybrid-an organism that has two DIFFERENT alleles for a trait • Also called heterozygous • Bb, Tt, Dd

18. Genetic Terminology • Cross– a controlled mating or breeding of two organisms • In genetic problems a cross shows the genotypes of both parents • BB x bb • Monohybrid cross – a cross between individuals that deals only with ONE set of alleles

19. Mutations • A mutagen is anything that can damage or cause changes in DNA. This could happen when your body forms new cells or from environmental agents. • When there is damage/change in an organism’s DNA than a gene will have a mutation. • Many ways to mutate a gene.

20. Mutations cont. • When a mutation happens to cells in your body due to certain exposure it is not passed on to offspring. • If mutations occur in sperm or egg DNA then it is a genetic disease that can be passed on. • Ex. of mutations: diabetes, cancer, heart disease, cystic fibrosis

21. Sex linked traits • If a gene is found only on the X chromosome and not on the Y chromosome, it is said to be a sex linked trait. • Because the gene controlling the trait is located on the sex chromosome, sex linkage is linked to the gender of the individual. • The result is that females will have two copies of the gene while males would only have one.

22. Sex linked traits cont. • If the gene is recessive, then males only need one such recessive gene to have the sex linked trait rather than the normal two recessive genes for non sex linked traits. • This is why males exhibit some traits more frequently than females.

23. Examples of Sex linked traits • Red-green colorblindness • Male Pattern baldness • Hemophilia • Duchenne Muscular Dystrophy

24. Red-green colorblindness genotypes • Normal vision male-XCYo • Colorblind male-XcYo • Normal vision female-XCXC • Normal vision female (carrier)-XCXc • Colorblind female-XcXc

25. Normal Vision father X Colorblind Mother • Dad genotype: • Mom genotype:

26. Normal vision father x normal vision mother (no colorblindness in her family) • Dad genotype: • Mom genotype:

27. Human Genome Project • Completed in 2003, the Human Genome Project (HGP) was a 13-year project coordinated by the U.S. Department of Energy and the National Institutes of Health Some of the project goals were: • identify all the approximately 20,000-25,000 genes in human DNA • determine the sequences of the 3 billion chemical base pairs that make up human DNA • store this information in databases