Transcript Lecture 32 POWERPOINT here

Heredity
Chapter 20 part 2
Genetic terms
• Trait - is a feature of an organism, i.e. hair colour
• Locus - a fixed position on a chromosome, such as the position of a gene.
Akin to the physical address of that gene
• Allele - alternative forms of the same gene that exist in the population.
Red flowers vs. white flowers.
• Wild type - is the typical form of an organism, strain, gene, or
characteristic as it occurs in nature. Wild type refers to the most common
phenotype in the natural population.
• Mutant - is an individual, organism, or new genetic character arising or
resulting from an instance of mutation, which is a sudden structural
change within the DNA of a gene or chromosome of an organism resulting
in the creation of a new character or trait not found in the parental type.
• Dominant - refers to the allele that causes a phenotype that is seen in a
heterozygous genotype. Every person has two copies of every gene, one
from mother and one from father. If a genetic trait is dominant, a person
only needs to inherit one copy of the gene for the trait to be expressed.
• Recessive - refers to an allele that causes a phenotype (visible or
detectable characteristic) that is only seen in a homozygous genotype (an
organism that has two copies of the same allele) and never in a
heterozygous genotype. Every person has two copies of every gene on
autosomal chromosomes, one from mother and one from father. If a
genetic trait is recessive, a person needs to inherit two copies of the gene
for the trait to be expressed. Thus, both parents have to be carriers of a
recessive trait in order for a child to express that trait. If both parents are
carriers, there is a 25% chance with each child to show the recessive trait.
• Homozygous - A homozygote's cells are diploid or polyploid and have the
same alleles at a locus (position) on homologous chromosomes. When an
organism is referred to as being homozygous for a specific gene, it means
that it carries two identical copies of that gene for a given trait on the two
corresponding chromosomes (e.g., the genotype is AA or aa). Such a cell
or such an organism is called a homozygote.
• Heterozygous - a gene or trait if it has different alleles at the gene's locus
for each homologous chromosome. Such an organism must be either
diploid, have two homologous chromosomes in each cell, or polyploid,
having more than two homologous chromosomes. In diploid organisms,
the two different alleles were inherited from the organism's two parents.
These different alleles contain different genetic codes. One allele may
override the other, or they may both be expressed in a trait
simultaneously.
• Phenotype - observable characteristics of an organism produced by the
organism's genotype interacting with the environment.
• Genotype - genetic constitution of an organism.
20_04_haploid_diploid.jpg
20_06_homolo_chromo.jpg
20_08_Chiasmata.jpg
20_09_kinetochore_pull.jpg
20_10_Meiosis_mitosis.jpg
20_12_Errors_gametes.jpg
The Master - Mendel
• Gregor Mendel (July 22, 1822 - January 6, 1884) Born in Heizendorf,
Austria, was an Augustinian abbot who is often called the "father of
modern genetics" for his study of the inheritance of traits in pea plants.
Mendel showed that the inheritance of traits follows particular laws, which
were later named after him.
• Visit these links to learn more if you like;
– http://en.wikipedia.org/wiki/Gregor_Mendel
– http://www.accessexcellence.org/RC/AB/BC/Gregor_Mendel.html
• Learn about his actual experiments here;
– http://anthro.palomar.edu/mendel/mendel_1.htm
20_15_seven_traits.jpg
20_16_exp_heredity.jpg
20_17_combinat_alleles.jpg
20_20_dihybrid_cross_part1.jpg
20_20_dihybrid_cross_part2.jpg
20_18_law_segregation.jpg
20_19_pedigrees.jpg
20_21_meiosis_Mendel.jpg
20_26_Gene_mutations.jpg
20_32_traits_environmen.jpg
LEARN ABOUT THE
EXPERIMENTS ON AN
INTERACTIVE WEBSITE HERE...
• Highly recommended that you try this yourself
• http://sonic.net/~nbs/projects/anthro201/exper/