Studied by 26 peopleGregor Mendel
The person who laid the groundwork for genetics
Traits
Distinguishing characteristics that are inherited
Genetics
The study of inheritance patterns & variation
Discrete Units
The name Mendel gave to genes
Pea Plants
The plants Mendel studied
P Generation
The name Mendel gave to the parents
F1
The name Mendel gave to the first generation of offspring
F2
The name Mendel gave to the second generation of offspring
Mendel’s Law of Dominance
States that some traits are recessive, while others are dominant
Law of Segregation
States that organisms inherit two copies of each gene, one from each parent, and donate one copy of each gene in their gametes
Alleles
The different versions of one trait an organisms receives from parents
Homozygous Dominant
Two dominant alleles
Heterozygous
One dominant & one recessive alleles
Homozygous Recessive
Two recessive alleles
Genome
An organism’s genetic material
Genotype
The genetic makeup of a specific set of genes
Phenotype
The physical characteristics of an organism
Monohybrid cross
A Punnet Square involving one trait
Dihybrid Cross
A Punnet Square involving two traits
Law of Independent Assortment
The law that states that allele pairs separate independently of each other during meiosis & genes are inherited separately
Linked Genes
Genes located on the same chromosome that are frequently inherited together
More
Genes that are closer together are _____ likely to be inherited together
Crossing Over
One way genetic variation occurs, during Prophase I genetic information is exchanged between homologous chromosomes
Independent Assortment
One way genetic variation occurs, during metaphase I homologous pairs arrange themselves randomly
Random fertilization
One way genetic variation occurs, male & female gametes that fertilize are selected randomly
Control over breeding
Use of purebred plants
Observation of “either-or” traits
The key decisions Mendel made during his experiment
To map the location of every gene & determine human DNA sequences
The goal of the Human Genome Project
Sex-Linked Gene
A gene found on sex chromosomes, usually X chromosomes
Males
Sex-Linked disorders are most commonly found in ______
X-Chromosome Inactivation
When one of two X-chromosomes are randomly turned off after the organism begins developing
Holandric Genes
Genes found on Y-chromosomes
Cystic Fibrosis
An example of an Autosomal Recessive Disorder
Huntington’s Disease
An example of an Autosomal Dominant Disorder
Color Blindness
An example of a Sex-Linked Chromosome
Hairy Ears
An example of a Holandric Gene
Incomplete Dominance
Traits in which neither allele is completely dominant, so a blending is shown in the phenotype
Codominance
A trait in which both alleles are expressed completely
Multiple Allele Traits
Traits that are determined by multiple different alleles
Polygenic Traits
Traits determined by 2 or more genes
Skin and eye color
Examples of polygenic traits
Epistasis
A trait in which one gene can override the others
Albinism
Example of Epistasis
Methylation
Chemicals that affect the expression of genes that are caused by the environment, often by stress
Pedigree
A chart for tracing genes in families
Karyotype
A picture of all chromosomes in a cell
Identify genetic disorders caused by too many or few chromosomes
What do Karyotypes do?
Down Syndrome
The genetic disorder in which someone has an extra chromosome 21.
Cannot
A child (can/cannot) be born with too few autosomes
Turner’s Syndrome
The genetic disorder in which someone only has one X chromosome
Klinefelter’s Syndrome
The genetic disorder in which someone has and extra X chromosome. (XXY)
Males will mostly be affected, females will mostly be carriers
Using a pedigree, how do you tell it is a sex-linked trait?
Often, traits will skip a generation
Using a pedigree, how do you tell it is an autosomal recessive trait?
Blood type
Example of multiple allele trait
Note
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