Honors Biology - Unit 11: Genetics (Patterns of Inheritance)

Students should be able to do: 1. Solve genetics problems using simple probability (Punnett Squares) to predict outcomes (phenotypes and genotypes) of various crosses for all patterns of inheritance. 2. Interpret a pedigree showing inheritance of traits and disease. 3. Interpret a karyotype. 4. Describe the Mendelian Laws of Segregation, Independent Assortment and Dominance. 5. Describe and/or predict observed Patterns of Inheritance : Dominant and Recessive (Monohybrid and Dihybrid) , Incomplete Dominance, Codominance, Multiple Alleles, Polygenic , Sex-Determination, Sex-linked, Sex Influenced.

allele

the various forms of a trait (alternate form of a gene)

gene

a segment of DNA that contains coding for a polypeptide or protein; a unit of hereditary information

codominance

an inheritance relationship in which both alleles are present in the offspring (Ex: Black and white chickens breed to have a white chicken with black speckles)

sex-influenced trait

a trait which is influenced by the presence of male or female sex hormones. Expressed in only one sex, and located on autosomes (Ex: Balding is dominant in males but recessive in females)

homozygous / pure

a gene pair in which two alleles code for the same trait (Ex: BB or bb)

P generation

the “parent generation”

F1 generation

the first filial generation. The offspring of the P generation

F2 generation

the second filial generation. The offspring of the F1 generation

Punnett Square

a model used to establish the probabilities of the results of a genetic cross between two parents

recessive

the allele that is masked by the presence of another allele for the same characteristic. The allele is not expressed unless both alleles are _________ (Ex: bb)

sex chromosome

chromosomes which determine the sex

sex-linked

traits which are controlled by genes on the X or Y chromosome. Most X-linked traits are recessive and Y-linked traits are passed from father to son

heterozygous / hybrid

when the alleles are different (Ex: Bb)

Gregor Mendel

The “Father of Genetics.” An Austrian monk who studied the inheritance of traits in pea plants and created the laws of inheritance between 1856 to 1863. His work would not be recognized until the 1900’s

dominant

the allele that masks the presence of another allele for the same characteristic

phenotype

the physical appearance of the individual

genotype

the genetic makeup of the individual which can be represented by two letters

incomplete dominance

when dominant and recessive alleles are blended together (Ex: Pink snapdragon flowers from red and white parents)

test cross

crossing the tested organism with the recessive phenotype. If a homozygous recessive phenotype is among the offspring, the parent must be heterozygous

karyotype

a picture of an individual’s chromosomes. 23 pairs, 46 in total

agglutination

the clumping of blood cells due to matching antigens and antibodies, creating a jelly-like texture (Ex: A antigens will clump when exposed to A antibodies)

antigens

a protein or carbohydrate that acts as a signal and enables the body to recognize foreign substances. Found on the surface of red blood cells

antibodies

proteins which help destroy substance, such as pathogens, that enter the body and can cause diseases

universal donor

O-

universal recipient

AB+

multiple alleles

when there are more than just two possible alleles for a particular trait (Ex: Blood types; A, B, and O)

parent cross

the first set of parents in a genetic cross who are crossed to produce offspring; the P generation

pedigree

constructed to show the pattern of inheritance of a characteristic within a family across multiple generations. Males are squares, females are circles, shaded shapes mean the person expresses the trait, unshaded shapes mean the person does not express the trait, and half-shaded shapes mean the person is a carrier

polygenic

traits which are influenced by multiple genes, but NOT alleles (Ex: height, eye color, hair color, and skin color)

syndrome

a group of symptoms which consistently occur together, or a condition characterized by a set of associated symptoms

amniocentesis

a sampling in which a small amount of amniotic fluid is extracted from the amnion (sac surrounding fetus), which is where fetal cells and proteins can be analyzed and be prepared as a karyotype

Sickle Cell Anemia

an autosomal recessive trait in which there are abnormal hemoglobin molecules and sickle-shaped red blood cells, causing impaired blood circulation and organ damage

Duchenne Muscular Dystrophy

a recessive X-linked trait in which muscle fibers degenerate, causing a wasting away of muscles and shortened life expectancy

Huntingtons’ Disease

an autosomal dominant disease in which an inhibitor is produced, blocking brain cell metabolism and gradual deterioration of brain tissue at middle age; shortened life expectancy

Cystic Fibrosis

an autosomal recessive trait where a failure of chloride ion transport mechanism occurs, leading to mucus clogs in the lungs, liver, and pancreas; victims typically don’t survive to adulthood

Hemophilia

an X-linked recessive trait where there is a defective form of blood-clotting factors, leading to blood-clotting to fail

albinism

a genetic condition that results in reduced or absent melanin production, leading to lighter skin, hair, and eyes

color blindness

a recessive X-linked disorder in which a person cannot distinguish between colors

PKU / phenylketonuria

a genetic disorder in which the body cannot metabolize the amino acid phenylalanine, causing an accumulation of phenylalanine and severe brain damage

epigenetics

the study of how your behaviors and environment can cause changes that affect the way your genes work

epigenome

chemical compounds and proteins that can attach to DNA and direct such actions as turning genes on or off, controlling the production of proteins in particular cells