1. Chapter 9- Patterns of Inheritance
Hybrids
Incomplete dominance
Linked genes
Monoecious
Monohybrid cross
P generation
Pedigree
Phenotype
Pleiotropy
Polygenic inheritance
Principle of independent assortment
Principle of segregation
Punnett square
Recessive allele
Recombination frequency
Rule of addition
Rule of multiplication
Self-fertilize
Sex chromosomes
Sex-linked genes
Testcross
Ultrasound imaging
ABO blood groups
Alleles
Amniocentesis
Carrier
Chorionic villus sampling
Chromosome theory of inheritance
Codominance
Cross
Cross-fertilization
Cystic fibrosis
Dihybrid cross
Dominant allele
F1 generation
F2 generation
Genetics
Genotype
Hemophilia
Hermaphroditic
Heterozygous
Homozygous

2. Genetics
Study of heredity

3. Gregor Mendel Monk, father of modern genetics, 1860’s
Discovered genetic principles by meticulous breeding of pea plants
Used peas because they were readily available, easy to grow, had many distinguishable traits, could control mating

4. Pea Traits

5. Genetic Cross Vocabulary
Self-fertilize- sperm from pollen fertilizes egg containing carpel
Cross-fertilization- fertilizing one plant from pollen of another plant
Offspring produced are hybrids
P generation (parent)
F1 generation – offspring of P
F2 generation- offspring of F1, can be self- or cross- fertilized

6. Genetic Cross Vocabulary con’t
Monohybrid cross- parents differ in only one trait
Alleles- alternate forms of a gene A (dominant) or a (recessive)
Homozygous- alleles for a trait are identical, AA
Heterozygous- alleles are different, Aa
Phenotype- organism’s physical trait expressed
Ex: purple flower
Genotype- genetic make up of trait
Ex: PP

7. Alleles for a gene are at the same locus (point) on homologous chromosomes

10. Mendel’s hypotheses:
There are alternative forms of genes (units that determine traits)
For each characteristic- an organism has a gene from each parent, they can be the same allele or different
Sperm and egg each have 1 allele for a trait
Idea of dominant and recessive alleles

11. Mendel’s Principle of Segregation
Pairs of genes segregate (separate) during gamete formation (what is that process called?)
gametes fusing during fertilization regain pairs of genes

12. Mendel’s Principle of Independent Assortment
Each pair of alleles segregates independently during gamete formation

14. Dihybrid cross- cross between parents that differ in 2 traits

15. Mendel’s principles reflect probability

16. How can we determine an unknown genotype?
Testcross- mating between an unknown individual and a homozygous recessive individual
Rule of multiplication- probability that a compound event is the product of the separate probabilities of the independent events
Ex: b from mom (1/2), b from dad (1/2)
baby being bb ½ x ½ = ¼
Rule of addition- probability that an event can occur in 2 or more alternative ways is the sum of the separate probabilities of different ways
Ex: in Punnet square Bb = ¼ the other Bb is ¼
probability of being Bb is ¼ + ¼ = 2/4 = ½

17. What about humans? To find human inheritance information:
Collect as much family data as possible
Construct pedigree chart
At first heterozygotes are not known, must determine phenotypes of offspring then could lead to information on carriers (heterozygotes)

18. Chart Key

19. Pedigree Chart
Can you figure out carriers and genotypes from this pedigree?

21. Many genetic disorders are a result of a single gene
Most are recessive
family may not know of defect until offspring with two recessive alleles is born
Ex: CF cystic fibrosis
Dominant traits are not always prevalent just because they are dominant, usually due to lethality of disorder (death before reproduction)
Ex: polydactyly, achondroplasia

22. How can we detect genetic disorders?
Fetal testing
Amniocentesis- cells from amnionic fluid is tested
CVS- chorionic villi sampling- fetal tissue from placenta is tested

23. Ultrasound/sonogram- uses sound waves to product picture of fetus

24. Genetic screening Most test DNA but some test enzymes
Most tell risk of disorders that depend on multiple genes
Types of testing
Carrier- determine if you are a carrier of a harmful allele
Diagnostic- confirm or rule out disorder
Prenatal- checks for disorders in fetuses
Newborn- catches inherited disorders quickly so medical attention can be given, “heel prick”
Predictive- test at any time to determine risk for developing disorder
Ex: BRAC1 and 2- linked to breast cancer, Huntington’s disease

25. Variations of Mendel’s Principles
Genotype/phenotype relationship is not always straightforward
Incomplete dominance
produces intermediate phenotypes
Ex: hypercholesterolemia
HH= normal, Hh=slightly affected, hh=has disease severely

26. Codominance when both alleles are expressed in the phenotype
Ex: ABO bloodgroups
Some genes have more than 2 alleles, each individual can only have 2
A, B, AB or O bloodgroups –AB is codominant

27. Pleiotrophy impact of single gene on more than one characteristic
Ex: sickle-cell disease – abnormal hemoglobin molecules are produced

28. Polygenic inheritance
affect of 2 or more genes on a single phenotype trait
Ex: human skin color, height

29. Other genes are on sex chromosomes
Sex chromosomes- determine sex in species
Humans- X and Y are sex chromosomes
Each have 44 autosomes (22pairs) and 1 pair of sex chromosomes XX-female or XY- male
Males determine sex of offspring because they can pass X or Y, females only pass X
SRY gene on Y chromosome triggers testes development, without it, ovaries are developed
Fruit flies- # of X’s determine male or female, however presence of Y is essential for sperm production

30. Sex chromosomes con’t X-O system- grasshoppers, crickets, roaches
Female- XX male- XO (O=absence of chromosome)
Z-W system- fish, butterflies, birds
Males-ZZ females-ZW, eggs determine sex
Determination by chromosome #- ants and bees
Females- diploid- develop from fertilized eggs
Males- haploid- develop from unfertilized eggs

32. Some can produce both sperm and eggs
Monoecious- plants that produce sperm and eggs
ex: corn
Hermaphroditic- animals that produce sperm and eggs
ex: earthworms

33. Sex- linked genes Genes located on sex chromosomes
Not related to sex determination
Mostly found on X
In humans X-linked recessive traits mostly affect males
Females are carriers and pass to sons, sons have no other X to dominate over the recessive allele
Ex: colorblindness, hemophilia

35. Chromosome behavior accounts for Mendel’s principles:
Chromosomal Theory of Inheritance
Genes are located on chromosomes, the behavior of chromosomes (segregation and independent assortment- Mendel’s ideas) during meiosis and fertilization accounts for the inheritance patterns

36. Linked Genes Don’t follow Mendel’s rules
If genes are located close together they tend to be inheritted together

37. Linked Genes con’t
Data from crossing over can lead to mapping genes, farther apart they are greater chance of crossing over in between the genes
Crossing over accounts for new gene combinations
Morgan worked with fruit flies to develop:
Recombination frequency- % of recombinants in offspring

39. Gene Map