Bio Ch. 10

True Breeding

an organism that always passes down certain phenotypic traits to its offspring of many generations.

Theory of inheritance

genes are the units of heredity and are found in the chromosomes. Involves the reshuffling of the same genes from generation to generation.

Punnett square

Useful tool to do genetic crosses. Looks like a window pane.

P Generation

In Mendel's cross ___ refers to the first set of parents which are used for crossing.

F1 Generation

the first filial generation seeds/plants or animal offspring resulting from a cross-mating of distinctly different parental types

F2 Generation

the result of a cross between two F1 individuals. This generation of plants were of the ration 3:1

Testcross

A cross between a dominant phenotype and recessive phenotype. Determines whether plants are homozygous or heterozygous.

Law of Segregation

Each individual has two factors for each trait.

The factors segregate (separate) during the formation of the gametes.

Each gamete contains only one factor from each pair of factors.

Fertilization gives each new individual two factors for each trait.

Chromosomal theory of inheritance

states that chromosomes are the vehicles of genetic heredity.

Scientist note that parallel behavior of Mendel's particulate factors and chromosomes.

Alleles

Occur on the chromosomes at particular locations. (Gene locus)

Dominant Allele

Masks the expression of the other allele.

Recessive Allele

Only expressed when 2 ___ are present.

Genotype

Refers to the particular genes on individual carries.

Phenotype

Refers to an individual's observable traits.

Homozygous

Having two identical alleles at a locus. AA or aa

Heterozygous

Having two different alleles at a locus. Aa

Law of Independent Assortment

Each pair of factors segregates (assorts) independently of the other pairs.

All possible combination of factors can occur in the gametes.

Autosome

Humans have 22 pairs. Non sex chromosomes.

Sex Linked Chromosome

Determines if male or female. XX or XY

Family Pedigree

A chart of a family's history with regard to a particular trait.

Males are normally represented by a square and females are an oval. If the shape is shaded in, then that person has the trait.

Autosomal Recessive Pedigree

A child can be affected when neither parent is affected.

Parents are called heterozygous carriers.

Will have parents not shaded in on chart.

Heterozygous carrier

you have two different alleles. You inherited a different version from each parent. In a heterozygous genotype, the dominant allele overrules the recessive one. Therefore, the dominant trait will be expressed. The recessive trait won't show, but you're still a carrier.

Autosomal Dominant pedigree

Heterozygous or homozygous dominant parent, then the child is affected.

Complete Dominance

Mendelian norm dominant/recessive. occurs when one allele – or “version” – of a gene completely masks another.

Incomplete Dominance

Blended/intermediate heterozygote. Occurs when the heterozygous is intermediate between the two homozygous.

Codominance

Equal expression in the heterozygote. Non-identical allele specify two phenotype that are both expressed in heterozygotes. Both alleles completely expressed in heterozygous individuals.

Multiple Allele traits

Some factors can have more than two alleles. Each person has only two of these possible three alleles.

Blood type is formed by this...

Polygenic inheritance

More than one pair of alleles determines the phenotype.

Each dominant allele is additive to the overall phenotype.

Human skin color is a polygenic trait.

Multifactorial traits

Polygenes that are all controlled by environmental influences.

There are several examples: skin color, palate and lip disorders, allergies, some cancers.

Pleiotropy

Occurs when one gene has more than one effect.

Often seen in human disease, leading to syndromes or groups of symptoms related to a genetic mutation.

Linkage

Some genes are linked.

Linked genes are inherited together because they cannot segregate during meiosis.

The linked alleles on the same chromosome form a linkage group.

X linked recessive pedigree

Colorblindness: females- mostly carriers; very rare to be colorblind. Males- more common to be color blind

These types of traits will be seen in males but females pass them on to normally males.

X linked dominant pedigree

Rett syndrome- almost always females; very rarely males.

Males pass it onto female offspring.

Science of genetics

Patterns of inheritance

Variations between offspring from one generation to the next.

Gregor Mendel

Father of genetics

In the 1860s developed a theory of inheritance

Discovered the basic principles of heredity by breeding garden peas in carefully planned experiments

Garden peas

Good choice because: easy to cultivate, Short generation time, show obvious difference in traits, self pollination.

Methemoglobinemia

Autosomal Recessive

Harmless, accumulation of methemoglobin, alternate form of hemoglobin in blood (skin appears bluish)

Cystic Fibrosis

Autosomal Recessive

Most common lethal genetic disorder among caucasians in the US. Defect in CI- channel pathways in plasma membranes. Leads to increased accumulation and thickness of mucus.

Osteogenesis Imperfecta

Autosomal Dominant

Results in weakened and brittle bones. Defect in type 1 collagen (provides strength). 1 in 5000 births.

Huntington Disease

Autosomal Dominant

Neurological disorder that leads to progressive degeneration of neurons in the brain. Single mutation in gene