Family connections: genes and heredity

1. Family connections: genes and heredity

2. From yesterday: What is evolution?

3. From yesterday: What is evolution?The process of genetic change in populations of organisms over time

4. What is necessary for evolution to occur: Three things: • Organisms multiply in number (“reproduce”) • Children tend to resemble their parents • Not everybody is the same

5. Mechanism by which evolution works: Natural selection

6. Mechanism by which evolution works: Natural selection • Variation between individuals: some are more likely to survive than others. • Some variation is heritable, since children tend to resemble their parents • Next generation resembles those who did best in previous generation • Given time, lots of small changes add up to make large changes

7. What is evolutionary theory good for? Evolution by natural selection also explains why: • Organisms become good at what they do: “adapted” to their environment & lifestyle • In many cases historical contingencies prevent “optimal” adaptation: “bad design” • Organisms have changed over time, as evidenced by fossils

8. Thus, fossils are another piece of evidence for evolution Fossils show transitional forms For any major changes in animal form, we have fossils that show the transitions “Archaeopteryx”

9. What is evolution? Fossils show transitional forms For any major changes in animal form, we have fossils that show the transitions “Tiktaalik”

10. What is evolutionary theory good for? Evolution by natural selection also explains why: • Organisms become good at what they do: “adapted” to their environment & lifestyle • In many cases historical contingencies prevent “optimal” adaptation: “bad design” • Organisms have changed over time, as evidenced by fossils

11. Other evidence for evolution Animal “family trees” • Some classification works better than others • The ones that work all give the same result! • I.e. the number of legs, the type of skeleton, the genetic similarity, all give the same consistent “family tree”

12. Other evidence for evolution Biogeography • Every species of plant or animal originates somewhere. It then may spread, but not if there is an ocean in between! • How organisms have spread at different times agrees with what we know about continental drift. Americas: • Tomato plant • Teosinte/Corn • Potato plant • Turkey • Saguaro (almost all cacti) Eurasia: • Starling • Elephant • Honey bee • Euphorbia plants

13. Summary: what evolution is Variation, Natural selection, and Inheritance leads to change in a population over generations • A logical consequence of what we know about heredity & survival • An explanation for the appearance of design in living things (adaptation) • An explanation for many other observations that would otherwise seem random coincidences • The intellectual framework for all of biology & medicine Joanna Masel: What evolution is and what it isn’t

14. Heredity & genes Evolution requires inheritance of traits. We know today that traits are inherited via genes.What is a gene, and where are the genes in the body?

15. Heredity & genes Animals and plants are built of thousands of cells (~50 trillion in a human) - and each one contains your whole genetic material!

16. Heredity & genes What else is in a cell? • Membrane • Genetic material • Machinery

17. Heredity & genes Important molecules in the cell • Proteins: enzymes (machines), actin filaments (skeleton, transport) • Lipids (build membranes) • DNA (information/blueprint to build proteins)

18. Heredity & genes How DNA works

20. Enzyme copying DNA DNA double helix chromosome

21. Heredity & genes Genes • Each cell contains a complete copy of an organisms genome on a long strand of DNA • A “gene” is a section of DNA that gets translated into a protein • Proteins make up machines, skeleton, and color of cells  and therefore determine form and function

22. Heredity & genes Genes • Humans probably have about 30 000 genes – other animals can have fewer or more • Similarity between parents and offspring – “heritability” – is a result of genes: each child gets a copy of some of the mother’s and some of the father’s genes.

23. Heredity & genes Gregor Mendel • A monk who grew peas • Discovered that inheritance is based on discrete units (which were later called “genes”)

24. Heredity & genes Two genes for every trait • One from mother, one from father • Some are dominant, others recessive RW RW RR WW

25. Heredity & genes Two genes for every trait • One from mother, one from father • Some are dominant, others recessive • In humans, blue eyes are a recessive trait, brown eyes are a dominant trait If my dad has blue eyes, what is my eye color? (What is my brother’s eye color?)

26. Genes and behavior

27. Genes and behavior How do genes influence not only eye color etc. but also behavior?

28. Heredity & behavior Neurons (=nerve cells) • Transmit and process information • Connect to sense organs and muscles • Brain is an aggregation of neurons

29. Heredity & behavior How is the network created? • During development, neurons grow along certain paths • Experience influences the connections neurons make

30. Heredity & behavior Heritability of behavior Behavior can be heritable, • because the formation of the brain and specific circuits, even the potential to learn, all require information before learning: genetic information. • Any variation in that genetic information is heritable.

31. Genes and behavior Very complicated behaviors can be determined by genes (and thus be heritable and evolve) There is plenty of evidence for this, even though we don’t always understand exactly which genes influence which neurons, and in which way.

32. Genes and behavior Exp 1: solitary animals – cannot learn from parents or conspecifics Fiddler crabs: ‘wave’ to attract females, build burrows in mud to hide at high tide

33. Genes and behavior Exp 2: computers – can be hardwired or programmed to do complex things without learning

34. Genes and behavior Exp 3: human infants – can do many things Infants know that two piles of sand poured in a bucket can be made into any number of sand piles, but two dolls in a bucket are still two dolls afterwards

35. Genes and behavior Exp 3: human infants – can do many things Infants know that two piles of sand poured in a bucket can be made into any number of sand piles, but two dolls in a bucket are still two dolls afterwards

36. Genes and behavior Exp 4: breeding studies – if animals can be bred to do something, it must be heritable Swallows were bred to fly south or west; honey bees can be bred to hoard more or less pollen; dogs were bred to retrieve or point

37. Genes and behavior ALL competitors at high-level sheep-herding dog trials are Border Collies – not other breeds of dog

38. Genes and behavior And why not cats??You cannot teach a cat to herd sheep, because it is genetically different from a Border Collie

39. Heredity & behavior

40. Heredity & behavior Evidence that behavior is heritable Many kinds of evidence! • Artificial selection / purebred strains / twin studies • Specific genes identified / heritable malfunction / mutants • Differences between species if raised in lab under same conditions

41. Heritability vs. aquired traits However, many traits are not heritable! Why? Because • Developmental effects • Plasticity • Learning can cause differences between individuals.

42. Heritability vs. aquired traits However, many traits are not heritable! Why? Because • Developmental effects • Plasticity • Learning can cause differences between individuals. NO evolution of these differences!

43. Heredity & genes Genes • Each cell contains a complete copy of an organisms genome on a long strand of DNA • A “gene” is a section of DNA that gets translated into a protein • Proteins make up machines, skeleton, and color of cells  and therefore determine form and function

44. Summary: what evolution is Variation, Natural selection, and Inheritance leads to change in a population over generations • A logical consequence of what we know about heredity & survival • An explanation for the appearance of design in living things (adaptation) • An explanation for many other observations that would otherwise seem random coincidences • The intellectual framework for all of biology & medicine Joanna Masel: What evolution is and what it isn’t