1. Dominance and Punnett Practice
Complete Dominance Gray fur is dominant (G) to orange fur (g). Just like the Punnett squares we have been practicing.

2. Incomplete Dominance
The two alleles “blend” together to create a combination of the traits

3. Co-Dominance
Both alleles are shown in the phenotype. One is NOT dominant over the other.

4. Sex Linked Traits
Because the gene controlling the trait is located on the sex chromosome,
It is linked to the gender of the individual. Usually found on the X chromosome.
The result is that females will have two copies of the sex-linked gene while males
will only have one copy of this gene. If the gene is recessive, then males only need
one recessive gene to have a sex-link trait.
Examples of Sex-linked Traits:
Red-green colorblindness
Male Pattern Baldness
Hemophilia
Duchenne Muscular Dystrophy

5. Dominant vs. Recessive Genotype= the alleles that you have for a trait
Phenotype= the physical expression of those alleles
A person with a dimpled chin can have the genotype DD or Dd
A person with a non-dimpled chin can only have the genotype dd

6. Homozygous= two of same allele (DD or dd)
More Definitions
Homozygous= two of same allele
(DD or dd)
Heterozygous= two different alleles
(Dd- also called hybrid)

7. 46 total chromosomes, 23 pairs
Human Chromosomes
46 total chromosomes, 23 pairs
23rd pair = sex chromosomes (female = XX , male = XY)
The other 22 pairs are called autosomes
ALL egg cells carry a single X; sperm carry either an X or a Y
This means a woman can ONLY give an X chromosome, a man has a 50/50 chance of giving an X or a Y

8. Meiosis Meiosis is the process of making gametes (sperm and eggs)
Gametes have half the number (23) of chromosomes of the original cells (46)
Meiosis turns one 46 chromosome cell into four 23 chromosome cells

9. Meiosis: How it Happens23 46
Chrom 23 46
Chrom 92
Chrom
Interphase
(Double
Chromosomes) 46
Chrom 23
Meiosis I 23
Meiosis II

10. After Meiosis
A sperm cell and egg cell, each with 23 chrom., fertilize to form a zygote. + = The cell of the zygote divides/grows to become an embryo, and eventually a baby! The zygote has 46 chromosomes! 23 23

11. You must half the number of chromosomes to get sperm + egg = 46!
Muy Importante!
Meiosis is necessary because if you merged two cells with 46 chromosomes each to make a baby, you would get a 92 chromosome mutant!
You must half the number of chromosomes to get sperm + egg = 46!

12. Why Meiosis? Evolutionary Advantage
Sexual reproduction increases the genetic variety in a population
Greater variety = stronger population
Sexual reproduction always involves the combining of genes from two different organisms to form a zygote
Plants, animals, fungi, protists…

13. Asexual Reproduction
Asexual reproduction also exists in simple organisms, but makes a clone of the parent
This DOES NOT increase genetic variety
Some organisms do both types of reproduction
Potatoes form sprouts that are clones of themselves.
They can also make seeds/sperm to reproduce with neighboring plants.