3.A Mendelian Genetics

1. 3.A Mendelian Genetics Recommended Reading: Chapter 12 of OpenStax

2. Mendel’s Process

3. Mendel’s Laws • Law of segregation – • Law of independent assortment – • Law of dominance –

4. Mendel’s Laws • Law of segregation - states that allele pairs separate or segregate during gamete formation, and randomly unite at fertilization. • Law of independent assortment - when two or more characteristics are inherited, individual hereditary factors assort independently during gamete production, giving different traits an equal opportunity of occurring together. • Law of dominance - one of the factors for a pair of inherited traits will be dominant and the other recessive, unless both factors are recessive.

5. Probability and Statistical Analysis • Is the fundamental ideas behind this. Possibility and chance abound and account for genetic diversity. • Analyzing the statistics leads to an overlap of math and science! Use math and likelihood of events to occur to make inferences about organisms! • However, why might this not always be accurate?Genetics isn’t just “one gene codes for one trait”, multiple genes can code for one trait.

6. Vocabulary • Heterozygous = • Homozygous = • Allele = A = a = Gene loci = • Genotype = • Phenotype =

7. Vocabulary • Heterozygous = has a genotype composed of two different alleles. • Homozygous = has a genotype composed of two of the same allele. • Allele = a copy of coding for a particular trait or gene loci (one letter). A = capital letter means dominant. a = lower case letter means recessive. Gene loci = location of coding for an organism’s genetics (DNA), typically for a specific characteristic – however, some phenotypes are coded by multiple loci. • Genotype = combination of alleles an individual possesses. • Phenotype = the visible expression of the genotype (the code means we see ________).

8. Vocabulary • Monohybrid Crosses (A monohybrid cross is a mating between two individuals with different alleles at one genetic locus of interest.) • Dihybrid Crosses (A dihybrid cross is a mating between two individuals with different alleles at two genetic loci of interest.) • Codominance – • Sex-linked – • Autosomes –

9. Vocabulary • Monohybrid Crosses (A monohybrid cross is a mating between two individuals with different alleles at one genetic locus of interest.) • Dihybrid Crosses (A dihybrid cross is a mating between two individuals with different alleles at two genetic loci of interest.) • Codominance – when two alleles are both represented in a phenotype. • Sex-linked – chromosomes/genes that are located on X or Y chromosome. • Autosomes – non-sex-linked chromosomes.

10. Vocabulary • Incomplete dominance – • Multiple alleles – • Polygenic inheritance -

11. Vocabulary • Incomplete dominance – one trait isn’t completely dominant over the other so you get a mixed phenotype. • Multiple alleles - we end up with two alleles for every trait in our phenotype • Polygenic inheritance - occurs when one characteristic is controlled by two or more genes.

12. Importance • Why is it important to know about inheritance? • Why might knowing about dominant and recessive genes be important when considering offspring? • Performing a test cross and looking at offspring can help us determine genotypes, how?

13. Importance • Why is it important to know about inheritance? • To get an understanding of potential health problems you have to deal with (some conditions are inherited) • Why might knowing about dominant and recessive genes be important when considering offspring? • Knowing about your partner’s genetic make-up could help you avoid the occurrence of genetic conditions that may be recessive. • Performing a test cross and looking at offspring can help us determine genotypes, how?If you don’t know an organism’s genotype, but breed it with a completely recessive organism – their offspring should tell you what they have.

14. Monohybrid/Dihybrid Crosses - Punnett’s Squares • Include potential combinations of parental genotypes to determine probability of offspring.P = F1 = F2 =

15. Monohybrid/Dihybrid Crosses - Punnett’s Squares • Include potential combinations of parental genotypes to determine probability of offspring.P = parental generationF1 = first generation of offspringF2 = second generation of offspring (using offspring from F1)

16. Sample Diybrid • White hair colour in horses is recessive (w), and brown hair is dominant (W). Long mane length is a dominant trait (M), and short mane length is a recessive trait (m). If a heterozygous male (for both traits), mates with a heterozygous brown-haired, homozygous long maned female, what is the phenotypic and genotypic ratios of offspring? What is the percent chance for the different phenotypes of offspring?

17. Sample Diybrid • White hair colour in horses is recessive (w), and brown hair is dominant (W). Long mane length is a dominant trait (M), and short mane length is a recessive trait (m). If a heterozygous male (for both traits), mates with a heterozygous brown-haired, homozygous long maned female, what is the phenotypic and genotypic ratios of offspring? What is the percent chance for the different phenotypes of offspring? • 25% white, long 75% brown, long

18. Sex-linked traits • Sex-linked traits are found on ___ Chromosomes in Humans. • ___ Chromosome determines “maleness” – it’s small! • So if something was X-linked and recessive, would it be expressed in males? • Some traits are also ___________. Some sex-specific genes only activate in the presence of other sex-specific genes (baldness, milk production).

19. Sex-linked traits • Sex-linked traits are found on X Chromosomes in Humans. • Y Chromosome determines “maleness” – it’s small! • So if something was X-linked and recessive, would it be expressed in males? • Some traits are also sex-limited. Some sex-specific genes only activate in the presence of other sex-specific genes.

20. Nonnuclear inheritance • All of this inheritance is based on mitosis and meiosis of DNA in the nucleus of eukaryotic cells. Mitochondria and chloroplast aren’t in the nucleus. They have their own DNA. They replicate in their own ways. • All of us animals have our mother’s DNA. The egg actually maintains a mitochondria, the sperm does not! • Mitochondria is a big part of our cellular function, what disorders are mitochondrially-based? Diabetes, cancer, Alzheimer’s, many diseases are linked to a disorder of the mitochondria • It’s important to note that much of the genetics we have discussed is dealing with nucleic DNA, but other components of our cells have their own DNA that can mutate/be corrupted.

21. Application of these Crosses • When chromosomes separate, these traits that make up our phenotypes can be found close to other traits on chromosomes and they tend to cross over or transfer together. • But many traits found on a particular chromosome are more likely to transfer together. • And many traits aren’t just coded by one gene. So… Mendelian Genetics is flawed-ish. What is predicted, commonly isn’t what we see. • What are three things we are pretty sure chromosome 1 codes for? • What are three disorders normally attributed to chromosome 1?Are these things related?

22. Application of these Crosses • What are three things we are pretty sure chromosome 1 codes for? • Height, brain size, connective tissue, nerve growth • What are three disorders normally attributed to chromosome 1?Prostate cancer, glaucoma, breast cancer, Alzheimer’s diseaseAre these things related?Mistakes in some of these genes correlate to many disorders that we are familiar with. Ex. Mutation in connective tissue gene could contribute to Alzheimer’s

23. Genetic Disorders • What are some genetic disorders (some of you wrote about schizophrenia, autism, etc.)? • What causes Down Syndrome?An additional chromosome or trisomy at Chromosome 21 – caused by a “nondisjunction” event in meiosis. • Why would this be problematic? You would have extra genes coding for more than you “need” for typical function of human cells. • How does this connect to the idea of the complexity of biological processes?Slight disruptions or changes to a certain specific process can have significant effects on the development and function of the organism

24. Sociocultural Issues with Genetics • Designer Babies – what were some considerations or issues? • Genetic screening – genetic testing to determine disorders/genetic conditions • Potential complications when adjusting offspring genes. • Aesthetic design of children to look a certain way. • Wealth gap – rich afford better babies  better jobs  better babies

25. Sociocultural Issues with Genetics • Designer Babies – what were some considerations or issues? • Genetic ownership • Wealth Gap • Elite division of society • “Natural” process of human life

26. Gene Expression Recommended Reading: Chapter 16 - OpenStax

27. What is gene expression? • Process of turning on a gene to produce RNA. • This can happen in the presence of certain molecules – unwrapping DNA from histones – promoter transcription, translation, lots of things! Why is this a thing? Why wouldn’t they just be left on all the time?

28. What are activators, inducers, and Repressors? • Repressors – • Activators – • Inducers – • Operon – • Tryptophan -

29. What are activators, inducers, and Repressors? • Repressors – proteins that suppress transcription of a gene in response to an external stimulus. • Activators – proteins that increases transcription of a gene in response to an external stimulus. • Inducers – activate or repress transcription depending on needs of cell and availability of the substrate. • Operon - In genetics, an operon is a functioning unit of DNA containing a cluster of genes under the control of a single promoter. • Tryptophan – a protein-receptor-activator. When tryptophan is present, it activates the gene.

30. Figure 16.3 What is a promoter?What is happening here? • The five genes that are needed to synthesize tryptophan in E. coli are located next to each other in the trp operon. When tryptophan is plentiful, two tryptophan molecules bind the repressor protein at the operator sequence. This physically blocks the RNA polymerase from transcribing the tryptophan genes. When tryptophan is absent, the repressor protein does not bind to the operator and the genes are transcribed.https://www.youtube.com/embed/8aAYtMa3GFU

31. How does the repressor work?(think of concentration of solutions) • Water balloon analogy (the wall of the water balloon is the DNA for transcription). More tryptophan in the environment forces the repressors to the wall, blocking them from producing more!

32. Figure 16.4 • When glucose levels fall, E. coli may use other sugars for fuel but must transcribe new genes to do so. As glucose supplies become limited, cAMP levels increase. This cAMP binds to the CAP protein, a positive regulator that binds to an operator region upstream of the genes required to use other sugar sources.https://www.youtube.com/embed/iPQZXMKZEfw

33. Transcription of the lac operon is carefully regulated so that its expression only occurs when glucose is limited and lactose is present to serve as an alternative fuel source. Figure 16.5

34. Gene Expression as a Bio Process This connects to feedback mechanisms (loops) from environmental science 20.How? Positive feedback in organisms? Presence or activation leads to more. What are things in our body that upon use or production will need moreApples! When one apple becomes ripe (or riper), it releases a chemical that causes others to also ripen, which releases more of these chemicals! • Laclabourripe

35. These mechanisms are therefore important because… • Some things need to be stopped. Some things need to keep going! • If not… Dehydration (due to decreased ADH), hyperthyroidism, blood clotting

36. Figure 16.6 • DNA is folded around histone proteins to create (a) nucleosome complexes. These nucleosomes control the access of proteins to the underlying DNA. When viewed through an electron microscope (b), the nucleosomes look like beads on a string. (credit “micrograph”: modification of work by Chris Woodcock)

37. Figure 16.7 • Nucleosomes can slide along DNA. When nucleosomes are spaced closely together (top), transcription factors cannot bind and gene expression is turned off. When the nucleosomes are spaced far apart (bottom), the DNA is exposed. Transcription factors can bind, allowing gene expression to occur. Modifications to the histones and DNA affect nucleosome spacing.

38. Figure 16.8 • Histone proteins and DNA nucleotides can be modified chemically. Modifications affect nucleosome spacing and gene expression. (credit: modification of work by NIH)

39. An enhancer is a DNA sequence that promotes transcription. Each enhancer is made up of short DNA sequences called distal control elements. Activators bound to the distal control elements interact with mediator proteins and transcription factors. Two different genes may have the same promoter but different distal control elements, enabling differential gene expression. Figure 16.9

40. Figure 16.10 • Pre-mRNA can be alternatively spliced to create different proteins.

41. Figure 16.11 • There are five basic modes of alternative splicing.

42. Figure 16.12 • The protein-coding region of mRNA is flanked by 5' and 3' untranslatedregions (UTRs). The presence of RNA-binding proteins at the 5' or 3' UTR influences the stability of the RNA molecule.

43. What causes/is cancer?