Bio 1201 Chapter 11, 24 Flashcards
Blending concept of inheritance
- Parents of contrasting appearance produce offspring of intermediate appearance
- Over time, variation would decrease as individuals became more alike in their traits.
- blending was a popular concept during Mendel’s time.
who formulated the theory of inheritance?
mendal
Inheritance involves what?
reshuffling of genes from generation to generation
Who is is Greg mendal
An Austrian monk, who at the time of his experiments was a substitute science teacher at a local high school
What was Greg Mendel like?
- had many interests
- had background in mathematics that promotes him to apply statistical methods and laws of probability to his breeding experiments
- was very careful- deliberate, followed the scientific methods very closely and kept detailed, accurate records
- was prepared-carefully and conducted many preliminary studies with various animals and plants.
What did the 2 laws of Mendel describe?
the behavior of these “particular units of heredity” as they are passed from one generation to the next
why did Mendel use gardening peas
Easy to cultivate
Short generation time.
Although peas normally self-pollinate (pollen only goes to the same flower), they could be cross-pollinated by hand by transferring pollen from the anther (male part of a flower) to the stigma (female part of a flower).
Easy to measure:
seed shape, seed color, and flower color.
Law of Segregation
Mendel chose varieties that differed in only one trait (e.g., plant height).
If the blending theory of inheritance were correct, the cross should yield plants with an intermediate appearance of medium height compared to the parents, which were all tall or all short
punnet square
Visually presents Mendelian inheritance
It is a diagram of a breeding cross and displays the possible combinations
what does a punnet square show?
It gives probability for genotype, not phenotype
genotype
It refers to the two alleles an individual has for a specific trait.
phenotype
It refers to the physical appearance of the individual.
alleles
Different versions of a gene
locus
lactation of allele
what represents DNA sequences that code for proteins.
The dominant and recessive alleles
The dominant allele codes for
the protein associated with the normal gene function within the cell.
The recessive allele represents a
“loss of function.”
what happens During meiosis I
the homologous chromosomes separate.
The two alleles separate from each other.
what does the the process of meiosis explain?
The process of meiosis explains Mendel’s law of segregation and why only one allele for each trait is in a gamete
Monohybrid Crossing
Cross of one gene, between individuals who have different alleles
Dihybrid Crossing
Cross of two or more genes
To use punnett square for dihybrid cross, the genes must be independent of each other (independent assortment)
what does a dihybrid cross use?
true-breeding plants differing in two traits.
Mendel tracked each trait through two generations
law of independent assortment.
The pair of factors for one trait segregate independently of the factors for other traits.
All possible combinations of factors can occur in the gametes
Testcrosses
determines the genotype of an individual having the dominant phenotype
Genetic disorders
are medical conditions caused by alleles inherited from parents.
Autosome
is any chromosome other than a sex chromosome (X or Y)
Genetic disorders caused
by genes on autosomes are called autosomal disorders.
Some genetic disorders are autosomal dominant.
Other genetic disorders are autosomal recessive.
Autosomal Recessive Patterns of Inheritance
If both parents carry one copy of a recessive gene they are unaffected but are capable of having a child with two copies of the gene who is affected.
Methemoglobinemia
It is a relatively harmless disorder.
Accumulation of methemoglobin in the blood causes skin to appear bluish-purple.
Cystic Fibrosis
Mucus in bronchial tubes and pancreatic ducts is particularly thick and viscous.
Most common lethal genetic disease affecting Caucasians
Dr. Council’s Dissertation Topic— Why is this build up bad?
Autosomal Dominant Patterns of Inheritance and Disorders
Two parents with a dominantly inherited disorder will be affected by one copy of the gene.
It is possible for them to have unaffected children.
Osteogenesis Imperfecta
Characterized by weakened, brittle bones.
Most cases are caused by mutation in genes
required for the synthesis of type I collagen.
Hereditary Spherocytosis
It is caused by a mutation in the
ankyrin-1 gene.
Red blood cells become spherical,
are fragile, and burst easily
multiple alleles (multiple allelic traits
Some traits are controlled by these-
The gene exists in several allelic forms, but each individual only has two alleles.
example of multiple alleles
The ABO blood type
an example of codominance.
The ABO blood type More than one allele is fully expressed.
Both IA and IB are expressed in the presence of the other.
Incomplete Dominance
Heterozygote has a phenotype intermediate between that of either homozygote.
Homozygous red has red phenotype.
Homozygous white has white phenotype.
Heterozygote has pink (intermediate) phenotype.
what does phenotype reveal
genotype without a testcross.
Familial Hypercholesterolemia (FH)
examples of incomplete dominance:
Homozygotes for the mutant allele develop fatty deposits in the skin and tendons and may have heart attacks during childhood.
Heterozygotes may suffer heart attacks during early adulthood.
Homozygotes for the normal allele do not have the disorder
Incomplete penetrance
The dominant allele may not always lead to the dominant phenotype in a heterozygote.
Many dominant alleles exhibit varying degrees of penetrance.
polydactyly
There are extra digits on hands, feet, or both.
Not all individuals who inherit the dominant polydactyly allele will exhibit the trait.
