1. Heredity and Probability
7th Grade Science

2. Think
What are some traits you have? What are some that you have noticed in your family?

3. Genetics Heredity: Traits being passed down from parent to offspring
Genetics: the study of heredity

4. Asexual Reproduction vs. Sexual Reproduction
Advantages
1 parent
Fast process
Disadvantages
Genetically identical (adaptation unlikely)
Sexual
Advantages
Genetic variation (adaptation)
Disadvantages
2 parents
Slower (gestation periods)
Adaptation: the ability to survive if the environment survives due to behavioral or structural changes

5. What does this have to do with genetics?
You don’t really need to talk about genetics when it comes to asexual reproduction except to say that offspring are genetically identical to parents (like clones). This is true except for in the case of a mutation (a random change in DNA).

6. Asexual reproduction is the main form of reproduction for all unicellular organisms and some multicellular organisms (hydra, some plants, etc.)
Humans only use asexual reproduction for growth and repair.
*You are not bigger cells. You are MORE cells. The zygote divided and divided. The average human is made up of 37.2 trillion cells! Depending on how big you are you may be more or less.
*In humans (and other multicellular organisms) cells differentiate. That means that cells look different depending on what job they do in your body. The original cells that have not differentiated yet are called stem cells. Scientists believe that these cells could hold the key to unlocking cures to some diseases because they can essentially become any cell.

7. Zygote
A zygote is a fertilized egg. This is the product of sexual reproduction.
A zygote would have a full set of genetic information (half from each parent)
Each organism has to get one trait from each parent (carried in the gametes). It is not possible for them to get two traits from one parent.

8. Mitosis vs. Meiosis
The way more cells are made is through cell division. Mitosis and Meiosis are both forms of cell division.
Mitosis is asexual reproduction. It is the division of the material (chromosomes) in the nucleus. The product of this would be considered a diploid cell (a cell that has a complete set of chromosomes).
Meiosis goes with sexual reproduction. It is the formation of sex cells (which have half of the genetic material of the parent cells). Meiosis is very similar to mitosis except for the cell splits twice resulting in half the genetic material

9. Mendel’s peas
Mendel’s experimentation with pea plants is responsible for a lot of what we now know about genetics mainly because it was the starting ground that got scientists thinking about how traits are passed down

11. Genes and chromosomes
Chromosomes contain genes. They are made of DNA that is wound together.
A DNA is a specific segment of DNA that codes for a specific trait.

12. Dominant vs. Recessive
One pattern of inheritance is dominant and recessive
In this case one trait is seen more often than the other because it is dominant.
The recessive trait is shown less often. One parent can be a carrier for recessive traits and not show it.

13. Incomplete dominance
Neither trait is completely dominant so the offspring shows an in between of the two traits

14. Codominance
Both are dominant so offspring that have both alleles show both traits

15. Sex-linked traits
Traits that are carried on the 23rd pair of chromosomes (the set of chromosomes that give you gender.
Sex-linked traits are more common in males due to the small amount of information carried on the Y chromosome

17. Acquired traits Some traits are acquired from your environment
Examples: dyed hair color, scars, ear piercing, tattoos, hair length, tan acquired from sun exposure or UV exposure, conditioned responses (behaviors you learn from your environment)

18. Homozygous Vs. heterozygous
Homozygous – organism has two of the same allele for a trait. They could be homozygous dominant(possessing two dominant alleles) or homozygous recessive (possessing two recessive alleles for a trait); synonyms: purebred
Heterozygous – organism has two different alleles for a trait; synonyms: hybrid, carrier

19. Genotype vs. Phenotype Genotype: the alleles or genes for a trait
Example: Bb, bb, or even BB
Phenotype: the trait that is displayed as a result of the genotype
Example: brown or blue eyes