Chapter Nine

Key Terms:
Character- a heritable feature that varies among individuals.
Trait- Each variatn for a character
Self-Fertilize- sperm- carrying pollen grains released from the stamens land on the egg containing carpel of the same flower.
Cross fertilization-fertilizaition of one plant by pollen from a different plant.
true-breeding- varieties for which self fertilizaiton produced offspring all identical to the parent.
hybrids- usually come from cross-fertilization.
alleles- alternative versions of a gene.
homozygous- an organism that has two identical alleles for a gene.
heterozygous- an organism that has two different alleles for a gene.
Law of segregation- When sperma nd egg unite at fertilizaiton, each conributes an allele restoring the paired condition in the offspring.

Reading Journal:
1) why did Mendel use pea? Short life span, bisexual, many traits known and cross- and self-pollinating.
2) how did Mendel work on peas? he controled other characters but make one variable, by cross-pollination, then record the data.
3) why did Mendel record so many data? for the sake of geting accurate datas

Five Facts:
1) Mendel used the scientific approach to identify two laws of inheritance.
2)The laws of probability govern Mendelian inheritance.
3)Inheritance patterns are often more complex than predicted by simple Mendelian genetics.
4)Many human traits follow Mendelian patterns of inheritance.
5)Inheritance is pretty random but follow laws.

In the 1860s, Gregor Mendel formulated a theory of inheritance based on experiments with garden peas, introduced that parents pass on to their offspring discrete genes that retain their identity through generations. In a diploid organism, the two allels of a gene separates during gamete formation. Each sperm or egg carries only one allele of each pair with a ratio of F2 3:1. In heterozgotes, the two alleles are different , and the dominant allel phenotypic effect of the recessive allele. Homozygotes have identical alleles of a given gene and are true-breeding. Each pair of alleles segregates into gametes independently of the pair of allels for any other gene. in a cross between dihybrids, the offspring have four phenotypes in a 9:3:3:1 ratio.
The expresion of a genotype can be affected by environmental influences. The phenotypic range of a particular genotype is called its norm of reaction. Polygenic characters that are also influenced by the environment are called multifactorial character.

Here is an example of genetics. Taco tongue, or tongue rolling, is a recessive gene that can be carried on from parent to child.












Video Link Mendel:
http://www.youtube.com/watch?v=EvR_Sdm1orU