Biology chapter 9
9.15
Many characters are affected due to the environment.
9.16
Connection
The environmental affects many characteristics
• Many traits are affected, in varying degrees
9.14
A single gene may affect many phenotypic characteristics
• In pleiotropy
– A single gene may affect phenotype in many ways
Variations of Mendel's Law
The relationship of genotype to phenotype is rarely simple
• Mendel’s principles are valid for all genotypes.
– But genotype often does not dictate phenotype in the simple way his laws describe
New technologies can provide insight into ones genetic legacy
new technologies amniocentesis is checks for genetic disorders in fetal cells. A needle is inserted through the mother's abdomen and avoids the baby using ultrasound technology.
chorionic villus sampling a physician extracts a tiny sample of chorionic villus tissue from the placinta. the speed of CVS is an advantage over amniocentesis another advantage. is that CVS can be performed as early as the 8th week of pregancy.
ultra sound imaging uses sound waves to produce a picture of the fetus.
Many inherited disorders in humans are controlled by a single gene
Many inherited disorders in humans are controlled by a single gene
• Some autosomal disorders in humans
Recessive Disorders
• Most human genetic disorders are recessive
Dominant Disorders
• Some human genetic disorders are dominant
Genetic traits in humans can be tracked throught family pedigrees
• The inheritance of many human traits
– Follows Mendel’s laws
• Family pedigrees
– Can be used to determine individual genotypes
Mendel's laws reflect the rules of probability
• The rule of multiplication
– Calculates the probability of two independent events
• The rule of addition
– Calculates the probability of an event that can occur in alternate ways
• Inheritance follows the rules of rules of mulitplication
Geneticists can use the testcross
• The offspring of a testcross, a mating between an individual of unknown genotype and a homozygous recessive individual
– Can reveal the unknown’s genotype
Law of independent assortment.
• By looking at two characteristics at once
– Mendel tried to determine how two characteristics were passed on to offspring
• Mendel’s law of independent assortment
– States that alleles of a pair segregate independently of other allele pairs during assortment
Subtopic
Homologous chromosomes
• Alternative forms of a gene
– Reside at the same locus on homologous chromosomes
Mendel's Law of Segregation
Predicts that each set of alleles will separate as gametes are formed.
Monohybrid crosses occur when the parent plants differ only in one character, such as flower color.
Law of segregation stats that a sperm or eggg carries only one allele for each inheritted character because allele pairs separate from each other during the production of gametes.
Experimental genetics
Breeding parental plants= P GENERATION. The hybrid offspring of the parents are called the F1 GENERATION. When F1 generations self fertilize or fertilize a different plant, their offspring is called the F2 GENERATION.
The offspring of two different varieties are called hybrids, and a genetic cross is referred to cross fertilization.
Cross fertilization is the fertilization of one plant by a different plant.
Some plants are able to self-fertilize by having sex cells that land on the egg containing carpel of the same flower.
The scientist, Gregor Mendel discovered that heredity is the transmission of traits from one generation to the next. A hereditary feature is called a character, and the variant of that feature is a trait.
Science of genetics
• The ABO blood type in humans
– Involves three alleles of a single gene
– And both are expressed in the phenotype
Many genes have more in the population
• In a population
– Multiple alleles often exist for a characteristic
Incomplete dominance results in intermediate phenotypes
• When an offspring’s phenotype is in between the phenotypes of its parents
– It exhibits incomplete dominance
Sex cells are not changed by the state of your body during conception.
