Exploring Gregor Mendel's Genetics Discoveries

1. Biology Genetics Unit

2. Gregor Mendel • Considered the father of modern genetics • He was an Austrian monk in the mid 1800’s • He did many experiments with pea plants

3. Mendel Continued • He discovered the basics for genetics as we know it today • In the following slides, we will cover his major discoveries

4. Dominant Traits • In a pair of traits, this one always has an effect • These traits get represented with a capital letter (B)

5. Recessive Traits • A trait that is only seen when two copies of the gene are present • Recessive traits are represented with a lowercase letter: b

6. Alleles • Different forms of the same trait or gene • Examples would be blue and brown eyes, or hitchhikers and straight thumbs

7. Homozygous • A term describing an organism that has two of the same genes • This could be two dominant traits (BB) or two recessive traits (bb)

8. Heterozygous • A term describing organisms that have two different genes for a trait. • This means they have one dominant and one recessive trait (Bb)

9. Genotype • The genes that an organism has for a trait. • For example, attached earlobes are a recessive trait, so a person with them must have two copies of that trait. • Therefore, their genotype is “ee.”

10. Phenotype • This is the actual, physical trait that a person has. • For example, if a person has the genes “Ee” for earlobe shape, their phenotype will be the dominant trait, which is free earlobes.

11. Incomplete Dominance • Sometimes, one trait does not dominate the other, and both the dominant and recessive traits are seen.

12. Codominance • With some traits, there can be more than one dominant allele. • A good example is blood type. Type O is recessive, but types A and B are both dominant.

13. Punnett Squares • Punnett Squares are charts that are made in order to predict the results of two organisms reproducing. • Usually only one or two traits are analyzed at a time.

14. Single Trait Punnett Square • The Problem: Brown eyes are dominant and blue eyes are recessive. Cross a heterozygous woman with a homozygous recessive male. • Step 1 – define letters to represent the traits B – brown b – blue Step 2 – write down Mom and Dad’s genotypes Mom Dad Bb bb

15. Single Trait Punnett Square • Now make the chart and put Mom and Dad’s genes on the chart.

16. Single Trait Punnett Square • Now, bring the genes across and down to determine the genes the possible offspring will have.

17. Two Trait Punnett Square • In this problem we will look at two traits at the same time. • Problem – make a Punnett Square using the following combinations of genes. Mom Dad AaBb AABb

18. Two Trait Punnett Square • Now, find the combinations of genes Mom and Dad can pass on. Mom - AaBb Dad - AABb AB AB Ab Ab aB AB ab Ab

19. Two Trait Punnett Squares • Now, take those traits and put them on a chart.

20. Two Trait Punnett Squares • Finally, fill in the boxes.

21. Sex-Linked Punnett Squares • These are traits that are only found on the “X” chromosome. • Females have “XX” and males have “XY” • The X chromosome is very large and the Y is very small. Because of this, there is not enough room on the Y for all of the genes on the X.

22. Sex-Linked Punnett Squares • The Problem – Color blindness is a sex-linked recessive trait. Normal vision is dominant. Cross a heterozygous woman with a man who has normal vision. • Step 1 – assign letters to the trait B – normal b – color blind

23. Sex-Linked Punnett Squares • Step 2 – add genes to Mom and Dad’s X chromosomes Mom Dad XBXb XBY

24. Sex-Linked Punnett Squares • Now, add Mom and Dad’s genes to the chart.

25. Sex-Linked Punnett Squares • Finally, fill in the squares on the chart.

26. Pedigree Charts • Pedigrees show the occurrence of specific genetic traits in a family. • Each generation is designated by a Roman numeral • Females are circles and males are squares • When possible, the oldest person in a generation goes on the left. As you go to the right, the people should get younger.

27. Pedigree Charts • In the chart below, the man and woman are connected by a horizontal line. This means they are married.

28. Pedigree Charts • The vertical line dropping from the marriage line indicates children being born.

29. Pedigree Charts • Marriages in generation II are shown below. A first marriage is always shown to the left, the second to the right.

30. Pedigree Charts • Children are then added and generation III is formed. Note how twins are shown.

31. Pedigree Charts • People with the recessive trait are shaded and a key is added to explain the traits.

32. Pedigree Charts • Finally, genotypes are added to the chart.

33. Genetic Mutations • Sometimes errors in mitosis or meiosis cause genetic abnormalities.

34. Non-Disjunction • Daughter cells are made with the wrong number of chromosomes. • Chromosomes don’t separate properly in mitosis or meiosis. • Meiosis daughter cells don’t function and mitosis daughter cells may lead to cancer.

35. Non-Disjunction

36. Duplication • A chromosome ends up with an extra copy of a gene. • Several types of replication errors can cause this.

37. Translocation • Rearrangement of parts of non-homologous chromosomes. • Depending on the cells affected, it can cause cancer or infertility.

38. Deletion • Part of a chromosome is lost during replication. • Can cause diseases, male infertility and death.

39. Frameshift Error A mutation made by inserting or deleting nucleotides from a DNA strand, not in multiples of 3. Results in the wrong amino acids being made in a protein. There are two types, deletions (deleting nucleotides) and insertions (inserting them).

40. Frameshift Errors

41. Inversion • A segment of a chromosome is reversed end to end. • There are no known affects, but it is suspected that they may cause a risk for infertility or miscarriage.