1. 3.4 Inheritance

2. Understandings
Mendel discovered the principles of inheritance with experiments in which large numbers of pea plants were crossed.
Gametes are haploid so contain 1 allele of each gene.
The 2 alleles of each gene separate into different haploid daughter nuclei during meiosis.
Fusion of gametes results in diploid zygotes with 2 alleles of each gene that may be the same allele or different alleles.
Dominant alleles mask the effects of recessive alleles but co- dominant alleles have joint effects.
Many genetic diseases in humans are due to recessive alleles of autosomal genes.
Some genetic diseases are sex- linked & some are due to dominant or co-dominant alleles.
The pattern of inheritance is different with sex-linked genes due to their location on sex chromosomes.
Many genetic diseases have been identified in humans but most are very rare.
Radiation & mutagenic chemicals increase the mutation rate & can cause genetic disease & cancer.

3. Understanding: Mendel discovered the principles of inheritance with experiments in which large numbers of pea plants were crossed.

6. Mendel’s Raw Data from large sample size

7. Understanding: Gametes are haploid so contain one allele of each gene.

8. Understanding: The 2 alleles of each gene separate into different haploid daughter nuclei during meiosis.

9. Understanding: Fusion of gametes results in diploid zygotes with 2 alleles of each gene that may be the same or different alleles.

12. Understanding: Dominant alleles mask the effects of recessive alleles but co-dominant alleles have joint effects.

13. Codominance vs Incomplete Dominance

14. Understanding: Many genetic diseases in humans are due to recessive alleles of autosomal genes.

16. Autosomes = all chromosomes except the sex chromosomes

17. SEX-LINKED DISORDERS
Understanding: Some genetic diseases are sex-linked & some are due to dominant or co-dominant alleles.
Sex-linked disorders:

18. Some more sex-linked traits:

19. Color-Blind Test

21. Should I stay or should I go?

22. Calico Cats http://www.bio.miami.edu/dana/dox/calico.html

23. Here are some autosomal dominant diseases:

24. Example of a co-dominant autosomal disorder:

26. “Heterozygote Advantage”

28. Understanding: The pattern of inheritance is different with sex-linked genes due to their location on sex-chromosomes.

29. Hemophilia = a sex-linked trait

30. Understanding: Many genetic diseases have been identified in humans but most are very rare.
Genetic Deletion Disorders

31. Extra Genetic Material disorders:

32. Multifactorial Chromosomal Abnormalities:

33. Understanding: Radiation & mutagenic chemicals increase the mutation rate & can cause genetic disease & cancer.

34. Application: Inheritance of ABO blood groups
Human Blood Typing is an examples of:
Multiple alleles – A, B & O
Codominance – A & B are codominant: if both alleles are inherited, you will expressed BOTH phenotypes in the form of blood type AB
See notes on board for more info…

35. Application: Red-green colour-blindness & hemophilia as examples of sex-linked inheritance.
See worksheet for examples

36. Application: Inheritance of cystic fibrosis
Common in Europe (5% of pop carry allele)
Recessive allele of CFTR gene on chromosome 7
Gene codes for poorly functioning Cl ion channel involved in sweat, mucus, digestive juice
Sweat – excess NaCl
Digestive juice & mucus – not enough NaCl, therefore not enough of concentration gradient set up for water to move in by osmosis, resulting in thick dig. Juice and thick mucus
Thick mucus causes build-up in lungs and lung infections
Thick dig juices blocks pancreatic duct leading to small intestine
Chance of one person carrying allele is 1 in 20
Chance of both husband & wife carrying allele is 1/20 x 1/20 = 1/400
Chance of having a child with CF if only one parent is carrier = 0%
Chance of having a child with CF if both parents are carriers = 25%
Eye-opening video of a girl in the UK living with CF:

37. Application: Inheritance of Huntington’s disease
Dominant allele of HTT gene on chromosome 4 (extra long sequence of gene)
Gene codes for protein called huntingtin with a long sticky glutamine tail that clump protein together & cause problems in neurons in brain
Causes degeneration of brain
Symptoms usually begin between ages 30-50
Changes to behavior, thinking, emotions become increasingly severe
Life expectancy is 20 yrs after onset of symptoms, due to heart failure, pneumonia, or other infectious disease
Can have genetic testing if runs in family – though most don’t
Chance of one person having allele = 1 in 10,000
Chance of both husband & wife having allele = 1/10000x1/10000 = 1/100,000,000
Chance of having a child with HD if only one parent has allele = 50%
Chance of having a child with HD if both parents have allele = 75%
Because of late onset, by the time you find out you have HD, you’ve most likely already had kids!
This video explains HD in a nutshell:
This one interview a girl in her 20’s with HD:

38. Application: Consequences of radiation after nuclear bombing of Hiroshima and Nagasaki and the nuclear accidents at Chernobyl.
Radioactive isotopes released into environment in all examples
Atomic bombs over Hiroshima & Nagasaki (1945) killed as many as 250,000 ppl (directly or later on)
100,000 survivors were followed thru 2011: ~17,000 tumors, ~900 from bomb radiation
10,000 fetuses during bombing & 77,000 kids born later: no evidence of mutations caused by radiation
Survivors stigmatized due to predictions of having kids with mutations
Video of Hiroshima bombing:

39. Nuclear accident at Chernobyl, Ukraine (1986)
Nuclear accident at Chernobyl, Ukraine (1986) – explosions & fire in nuclear reactor
Workers got fatal doses of radiation, which also spread over Europe
Widespread results:
4 km2 pine forest turned brown & died
Horses & cattle died of thyroid diseases
Lynx, eagle owl, wild boar, other wildlife increased in Chernobyl
Biomagnification caused high levels of radioactive caesium in fish and lamb
Drinking water & milk contaminated with radioactive iodine
6000+ cases of thyroid cancer due to radioactive iodine
No evidence of increase in solid cancers or leukemia
Three-mile Island in Pennsylvania (1979) had partial meltdown
Led to increase radiation safety at nuclear power plants in US
No evidence of medical effects of workers or anyone nearby

40. Skill: Construction of Punnett grids for predicting outcomes of monohybrid crosses.

41. Skill: Comparison of predicted & actual outcomes of genetic crosses using real data.

42. Skill: Analysis of pedigree charts to deduce the pattern of inheritance of genetic diseases.

43. Autosomal Recessive

44. Autosomal Dominant

45. Sex-linked Recessive

46. Sex-linked Dominant

47. Look for patterns in pedigrees:
If it’s mostly males who are affected with the trait, then the trait is sex-linked.
If it’s about a 50:50 ratio of males & females who have the trait, then the trait is autosomal.
If 2 parents are affected, and they have some kids with the trait and some without, then the parents are heterozygous and the trait is dominant.
If 2 parents are not affected, and they have some kids with the trait and some without, then the parents are heterozygous and the trait is recessive.

49. Pedigrees with Blood Types:

51. Royal Family Pedigree (Hemophilia)

52. How to become your own Grandpa:
It’s possible!

53. Nature of Science: Making quantitative measurements with replicates to ensure reliability: Mendel’s genetic crosses w/pea plants generated numerical data.
Mendel = “Father of Genetics” (along with Thomas Andrew Knight, who discovered that male & female parents contribute equally, inheritance is discrete rather than blending, one trait can show “a stronger tendency” than other)
Mendel = Pioneer of research methods in Bio
“Repeats” are important part of experimental design (large sample size)
Repeats add to reliability of results
Repeats compared to see how close they are
Anomalies can be excluded from analysis
Statistical tests can be performed (such as t-test) to see if difference between treatments is “significant” or not
Repeat whole experiment using different organism or different treatments, to test a hypothesis in different ways