1. PATTERNS OF INHERITANCE
CAPTER 10

2. Pre-Mendel’s Theories
Blending Hypothesis: when parents with different traits have offspring, they will always show a blending of the traits
Spontaneous generation: Non-living matter giving rise to living matter
Homunculus: The little man inside the sperm

4. Mendel’s experiments with pea plants
Trait: a variation of a particular character
Particulate hypothesis: Parents pass on to their offspring separate and distinct factors (genes) that are responsible for inherited traits
Genetics: the study of heredity

5. Mendel’s experiments started with
True-breeding plants: when self- fertilized, a true-breeding plant produces offspring identical in appearance to itself generation after generation

7. Cross-fertilization, sperm from the pollen of one flower fertilizes the eggs in the flower of a different plant

8. the offspring of two different true-breeding varieties are called hybrids.

9. Monohybrid cross: pairing in which the parent plants differ in only one (mono) character.

11. Mendel’s principle of segregation
There are alternative forms of factors (genes) called alleles.
For each character, an organism has two alleles for the gene controlling that character, one from each parent. Homozygous = same alleles Heterozygous = different alleles

12. Principle of segregation (cont.)
When only one of the two different alleles in an heterozygous individual appears to affect the trait, that allele is called the dominant allele. The allele that does not appear to affect the trait is called the recessive allele
The two alleles for a character segregate (separate) during the formation of gametes (sex cells). Each gamete carries only one allele of each character (Principle of segregation)

13. Phenotype refers to the observable trait (purple flowers)
Genotype refers to the combination of alleles (PP)
Phenotypic ratio: ratio of plants with purple flowers to those with white flowers (3 purple : 1 white)
Genotypic ratio: ratio of possible combinations of alleles (1 PP : 2 Pp : 1 pp)

14. Phenotype refers to the observable trait (purple flowers)
Genotype refers to the combination of alleles (Pp)

15. Phenotypic ratio: ratio of plants with purple flowers to those with white flowers (3 purple : 1 white)
Genotypic ratio: ratio of possible combinations of alleles (1 PP : 2 Pp : 1 pp)

16. Probability and Punnett Squares
Punnett Square: Diagram
used to show the probability
of a genetic cross
Probability: Chance of
Something happening

17. How can you find out the genotype of an individual showing the dominant trait?

18. TESTCROSS
In a testcross, an individual of unknown genotype, but dominant phenotype is crossed with a homozygous recessive individual

20. crossing of organisms differing in two characters
DIHYBRID CROSS
crossing of organisms differing in two characters

23. Principle of Independent Assortment
During gamete formation in an F2 cross, a particular allele for one character can be paired with either allele of another character

24. Intermediate or incomplete inheritance Multiple alleles – codominance
Not all traits are inherited following the patterns found by Mendel in pea plants
Intermediate or incomplete inheritance
Multiple alleles – codominance
Polygenic inheritance
Environment - epigenetics

25. Intermediate or incomplete inheritance
The heterozygotes have a phenotype that is intermediate between the phenotypes of the two homozygotes

26. Multiple alleles - codominance
For many genes several alleles exist in the population.
Multiple alleles control the character of blood type in humans.
There are six possible genotypes.
The alleles IA and IB exhibit codominance, meaning that a heterozygote expresses both traits.

30. Polygenic inheritance
When two or more genes affect a single character
In humans, height and skin color have polygenic inheritance

31. Phenotype depends on environment as well as genes
The environment
Phenotype depends on environment as well as genes
Temperature affects fur color in Siamese cats
In humans
Nutrition affects built
Exposure to sun affects skin tone

32. Chromosome Theory of Inheritance
Genes are located on chromosomes
Behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns – chromosomes undergo segregation and independent assortment during meiosis

34. Gene locus: location at which alleles of a gene reside on homologous chromosomes
Linked genes: genes that are located in the same region of a chromosome
Genetic linkage: tendency for the alleles on one chromosome to be inherited together. The closer two genes are on a chromosome, the greater the genetic linkage

36. Sex-Linked Genes (any gene located on sex chromosomes)

38. Morgan's monohybrid cross for fly eye color produced a 3 : 1 phenotypic ratio of red to white eyes in the F2 generation. However, none of the flies with white eyes were female.