Genetics: Mendelian Inheritance, Chromosomal Abnormalities, and Human Trait

Inheritance

the study of Heredity, It is the process by which genetic Information is passed From parents to their offspring

Gregor Mendel

pioneered the Field of genetics. Czech monk, studied physics, botany, math, published results in 1865 from experiments using 30,000 garden pea plants

Self-Fertilization

mating of egg and pollen from the same plant

Hybridizations

mating of egg and pollen from different true-breeding plants with different traits creates hybrids

True Breeding

parents and offspring always show the same traits (AA, aa)

Hybrids

offspring that have different traits

Traits

physical variation or inherited characteristic

Characteristic

is a feature of an organism that can be observed or measured

Dominant Alleles

only needs one allele to show trait (S)

Recessive Alleles

need two alleles to show trait (ss)

Genotype

organism's genetic makeup (CSS, Ss, ss)

Phenotype

list of observable traits (smooth, wrinkled)

Homozygous

when both chromosomes have the same allele at the locus (AA)

Heterozygous

when each chromosome carries different alleles at the locus (Aa)

Albinism

defective enzyme for melanin production; normal pigmentation is (AA, Aa)

Sickle-cell Anemia

defective hemoglobin inside red blood cells; normal is (AA, Aa)

Huntington's Disease

defective protein kills brain cells leading to loss of motor control; symptoms appear at age 30-50

Marfan Syndrome

defective Fibrillin-I connective tissue protein; symptoms include tall stature, long limbs, and curved spine

Monohybrid Cross

when fertilization occurs between two true-breeding parents that differ in only one characteristic

Dihybrid Cross

when fertilization occurs between two true-breeding parents that express different traits for two characteristics

Incomplete Dominance

heterozygote is a blend of the two homozygous phenotypes (e.g., RR=Red, WW=White, RW=Pink)

Codominance

both alleles are completely expressed in the heterozygote (e.g., AB Blood type)

X-linked Traits

coded for genes carried on the X chromosome; males show recessive traits more often

X-linked Pedigrees

family tree diagram used to trace the inheritance of traits or genetic disorders carried on the X chromosome

Hemophilia

lack of blood clotting factors needed to stop bleeding; found in European Royal Families

Sex determination

Decided on the sex chromosome 23rd; XX = Female, XY = Male.

X-linked genes

Genes that are only carried on the X chromosome.

Law of Dominance

In a heterozygote, one trait will conceal the presence of another trait.

Law of Segregation

Paired genes separate equally into gametes, giving offspring an equal chance of inheriting alleles.

Law of Independent Assortment

Genes do not influence each other regarding the sorting of alleles into gametes.

Polygenic Inheritance

More than one gene controls a trait, such as height, eye color, skin color, and fur color.

Epistasis

One gene inhibits the expression of another gene.

Karyotype

An individual's set of stained chromosomes from mitosis.

Nondisjunction

Failure of sister chromatids to separate properly during meiosis, causing aneuploidy.

Aneuploid

An individual with a non-standard number of chromosomes for their species.

Euploid

An individual with the standard number of chromosomes for its species.

Monosomy

Loss of one chromosome.

Trisomy

Gain of one chromosome.

Barr body

The condensed inactive form of one of the two X chromosomes in female mammals.

Down Syndrome

Caused by Trisomy 21, leading to developmental delays and various physical traits.

Turner Syndrome

Monosomy X, leading to infertility and underdeveloped secondary sex characteristics.

Trisomy X

Condition where a female has three X chromosomes instead of two.

Klinefelter Syndrome

XXY Trisomy in males, leading to infertility and physical traits such as taller stature.

Jacobs Syndrome

XYY Trisomy in males, characterized by high testosterone levels and potential learning disabilities.

Cri-du-chat Syndrome

Deletion of most of the short arm of chromosome 5, leading to intellectual disability and a cat-like cry.

Chromosome Inversion

A chromosome segment detaches, rotates, then reinserts, potentially disrupting gene expression.

Translocation

A chromosome segment detaches and reattaches to a different, non-homologous chromosome.