1. Heredity

2. Heredity: the passing of genetic traits from parent to offspring
Characteristics:
Hair Color
Earlobes
Fingers
Traits:
Type of hair color- brown, blonde, red
Attached/unattached
Longer index or ring finger
A feature that has different forms in a population
Different forms of a characteristic governed by genes

3. How traits are passed on….
Traits are determined by genes. Genes are the instruction manuals for our body. They provide directions for building all the proteins that make our bodies function.
DNA is found within a gene. Genes are carried in chromosomes.

4. How traits are passed on…
Chromosomes are found in the nuclei of our cells.
Everybody has 46 chromosomes (23 pairs)

5. How traits are passed on…
When a zygote (baby) is formed, it too has 46 chromosomes. It receives a copy of one of each of Mom’s chromosomes and a copy of each of Dad’s chromosomes for a total of 23 pairs of chromosomes.
Not all living things have 23 pairs of chromosomes.
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6. Genes are made up of two parts…
These parts are called alleles. An allele is one of the alternative forms of a gene that governs a characteristic.
Alleles are represented by letters
Capital letters represent dominant traits
Lower case letter represent recessive traits
A = dominant
a = recessive

7. Traits are either dominant or recessive…
Dominant trait- the trait that always appears when a dominant allele is present in gene
The trait observed in F1 when parents that have different traits are bred
Recessive trait- the trait that does not appear unless there are 2 recessive alleles present in gene
The trait that reappears in the F2 after disappearing in the F1 when parents with different traits are bred
Ex) Brown hair is dominant over blonde hair, so if one brown allele is passed on from the parent the offspring will have brown hair
Ex) In order for someone to have blonde hair both parents must have passed on a recessive gene, resulting in 2 recessive alleles

8. Traits and Inheritance
Phenotype: An organism’s appearance
Detectable physical characteristics
What an organism looks like
Genotype: The entire genetic makeup of an organism
the combination of genes for one or more specific traits
Homozygous- 2 of the same type of allele (2 dominant or 2 recessive)
Heterozygous- 2 different alleles, one dominant and one recessive (purebred)
Ex. Yellow or green seed color
Ex. For a recessive trait to show up the offspring must receive 2 recessive alleles, making it homozygous

9. Punnett Squares
Used to organize all the possible combinations of offspring from particular parents

10. Gregor Mendel Born 1822 in Heinzendorf, Austria
Worked in Monastery garden
Patterns of inheritance not always clear, sometimes a trait appeared in one generation (parents) and not in the next generation (F1, offspring), but then it reappears again in the generation after that (F2).
Began investigating with pea plants
Grow quickly
self-pollination create true-breed
parts of a flower
cross-pollination

11. Mendel studied one characteristic at a time…
Characteristics
Mendel's Experiments with peas

12. Genetic Instructions
Mendel realized that each parent must have 2 “sets of instructions” for each trait
When parents reproduced they each gave their offspring one set of each of their instructions (the child will then end up with 2 “sets of instructions” for each trait
Mendel published his work in 1865 and not until 30 years later was his work rediscovered and understood
A Gene is one set of instructions for an inherited trait
An Allele is one of the alternative forms of a gene that governs a trait (ex. If earlobes are attached or unattached)

13. Punnett Squares
Used to organize all the possible combinations of offspring from particular parents
Cross of homozygous purple flower and homozygous white flower
P = Purple (dominant) , p = white (recessive)
Parent 1
Parent 2
Phenotype
Purple
white
Genotype PP pp
P P Pp
F1 Generation:
Genotype: Pp
Phenotype:
Purple p

14. Mendel’s 2nd Experiment
Like Mendel’s 2nd experiment, we will self pollinate the F1 generation
Parent 1
Parent 2
Genotype Pp
Phenotype
Purple
purple
F2 Generation:
Genotype:
1PP, 2Pp, 1pp
Phenotype:
3purple, 1white
Genotype Ratio:
1:2:1
Phenotype Ratio (dominant:recessive):
3:1
P p PP Pp pp P p

15. t t T t Tt Tt
2 Tt : 2 tt or 1:1 tt tt
2 Tt : 2 tt or 1:1

16. Incomplete dominance