Asexual Vs Sexual Reproduction
A. Types of Asexual
1. Mitosis: when a plant grows or when your body makes new blood, skin,
or hair cells
2. Fission: cells without a nucleus (bacteria) make 2 identical copies
3. Regeneration: part of an organism breaks off and it grows back
(starfish)
For asexual, if a parent cell has 21 chromosomes, all offspring cells will have
21
What are the advantages of asexual reproduction?
1. No mate is needed, so more offspring produced
2. Faster
3. Less chance for mutations (genetic mistakes)
Disadvantage?
Since offspring is identical to parent, there are no variations, they can’t adapt
B. Sexual Reproduction-requires 2 parents
Female sex cell=egg
male=sperm
Sperm fertilizes the egg
Meiosis: sexual reproduction where (for humans):
1. The egg and sperm’s 23 chromosomes combine to make a zygote, which
has 46
2. This gives offspring traits from each parent
**What is the advantage of sexual reproduction?
Genes from 2 parents make adaptation easier
Disadvantages?
1. A mate is needed
2. Males can’t reproduce
3. Mutations are possible
Genetics and Variation
C. Vocabulary
 Heredity-passing of traits from parents to offspring
 Genetics-the study of how traits are passed
 Gene-basic unit of inheritance, passed from parents to offspring,
determines traits
 Trait-characteristic or feature of an organism (eye color)
 DNA-chemical in nucleus that contains the code that tells an
organism how to grow and function (looks like a twisted ladder,
contains proteins)
 Alleles-different forms of traits that make up a gene pair;
represented by upper and lower case letters
Gregor Mendel’s Pea Plant Experiment (1800’s)
 Dominant: form of a trait that shows and prevents the Recessive
form from being seen
 For pea plantsTall is dominant and short is recessive
 T=Tall t=short (these are the alleles for height)
 Homozygous (Purebred)=TT or tt
 Heterozygous (Hybrid)=Tt
 Genotypes are the letters (TT, Tt, tt)
 Phenotypes are the traits (Tall, short)
Pedigree Chart- diagram that shows the phenotypes of a gene and its
ancestors from one generation to the next (filled in means they have the
trait)
4. This example is for Right-handedness (dominant) and Left-handedness
(rec.)