1. CH 10 Mendel and Meiosis

2. What is Heredity? Heredity Genes
The passing on of characteristics from parents to offspring through genes
Genes
A section on DNA that carries the information on what type of protein to make; they influence the types of traits an organism inherits

3. What is Heredity? Traits Characteristics that are inherited Genetics
The branch of biology that studies heredity

4. History of Genetics
Gregor Mendel: an Austrian monk that first studied genetics
Experimented with pea plants to discover the general laws of genetics

5. History of Genetics
A pea plant has gametes and both male and female reproductive organs
Gametes: male and female sex cells

6. History of Genetics
Pollination: transfer of pollen (male gametes) from a male reproductive organ to a female reproductive organ in a plant
Mendel allowed pollination to occur within the same flower or between different flowers for his experiments
Pollen
grains
Transfer pollen
Female
part
Male
parts
Cross-pollination

7. History of Genetics
Fertilization: the male gamete unites with the female gamete to form a zygote (a fertilized cell)
In the case of pea plants, the zygote becomes a seed

8. Pea Plant Traits Tested By Mendel
Recessive
trait
Dominant
Seed
shape
color
Flower
position
Pod
Plant
height
round
yellow
purple
axial
(side)
green
inflated
tall
wrinkled
white
terminal
(tips)
constricted
short

9. History of Genetics
Conducted crosses between pea plants to compare traits
Monohybrid cross: when only one trait is compared at a time (like eye color)
Dihybrid cross: when two traits are compared at a time (like eye & hair color)
P1 = Parental generation (parents)
F1 = 1st filial generation (children)
F2 = 2nd filial generation (grandchildren)
Filial means “family”

10. Punnett Squares Used to compare traits
Shorthand way of determining the probability of having a certain type of offspring if you know the parents’ genotypes

11. Section 10.1 Summary – pages 253-262
Punnett Square-Monohybrid cross
Dad
A Punnett square for this cross is two boxes tall and two boxes wide because each parent has two kinds of gametes for this trait, but will only pass one along to each offspring T t T TT Tt t Tt tt
Mom
Possible offspring
Section 10.1 Summary – pages

12. Mendel’s Conclusion 1. The rule of unit factors
Each organism has two factors, or genes, that control each trait
One gene comes from mom, one gene comes from dad
A single gene can exist in different forms called alleles
Example: Blue, brown, and green are alleles for the eye color gene

13. FYI: Alleles Chromosomes = location of genes
Gene = section of DNA on the chromosome that determines the type of protein (Ex. for color) produced
Allele = different forms of a single gene (protein for a purple flower or a protein for a white flower)

14. Mendel’s Conclusion 2. The rule of dominance
Offspring inherit an allele from each parent, but only one trait is observed
Dominant trait: “stronger” trait that shows up when the dominant allele is present
Represented by a capital letter; T is for tallness
Recessive trait: “weaker” trait that shows up only when the dominant allele is not present
Represented by a lowercase letter; t is for shortness

15. The Rule of Dominance T T t Tt Tt Results: All tall plants Tall plant
Short plant t
Tt Tt T T t t T t F1
All tall plants
Results: All tall plants T t

16. Mendel’s Law of Segregation
What is means: Every organism has 2 alleles of each gene
When gametes are made, each gamete receives only one of these alleles
During fertilization, the offspring will receive one allele for each gene from each parent

17. Mendel’s Law of Segregation
Parents: Tt x Tt
Results: 3 tall plants,
1 short plant
T t T t
TT Tt
Tt tt

18. Phenotypes & Genotypes
Phenotype: the physical appearance of an organism
Ex. Blue skin
Genotype: genetic makeup of an organism
Ex. Alleles for skin color are B (=blue) or b (= black)

19. Homozygous vs. Heterozygous
Homozygous: 2 alleles for a trait are the same
BB is homozygous dominant for blue skin
bb is homozygous recessive for black skin
Homozygous offspring are called purebred because their alleles are the same

20. Homozygous vs. Heterozygous
Heterozygous: 2 alleles for a trait are not the same
Bb is heterozygous for blue skin
Heterozygous offspring are called hybrids because their alleles are different
A “zeedonk” is a zebra/donkey hybrid

21. Mendel’s Law of Independent Assortment
Genes for different traits are inherited independently of each other
Example: You have brown hair (Bb) and freckles (Ff)
You can pass on to your children one of the following combinations: B + F, B + f, b + F, b + f

22. Genes, Chromosomes, and Numbers
Diploid cell: has 2 of each kind of chromosome
One came from mom, one came from dad
All body cells, except gametes, are diploid cells
When they divide, this is called mitosis

23. Genes, Chromosomes, and Numbers
Haploid cell: has 1 of each kind of chromosome
Gametes are haploid cells
When they divide, this
is called meiosis

24. Genes, Chromosomes, and Numbers
Each type of organism has a specific number of chromosomes (humans have 46 chromosomes)

25. Genes, Chromosomes, and Numbers
Homologous chromosomes: 2 of the same type of chromosome in a diploid cell
Have genes for the same traits, but might have different alleles for the same gene
Ex: Genes are for eye color, but blue eye color allele is on 1 chromosome and brown eye color allele is on the other chromosome