Chapter 14: Mendel and the Gene Idea Flashcards
Mendel
discovered the basic principles of inheritance by breeding pea plants and cross-pollinating them
True Breeding
plants or animals that produce the same variety when self-pollinating
Hybridization
mating 2 contrasting, true-breeding varieties; combining genes from 2 breeding groups
Alleles
alternate versions of a gene Example: pea color: -purple -white
Law of segregation
2 alleles for a heritable character separate during gamete formation (during meiosis one) and end up in different gametes (meiosis 2)
Homozygote/Homozygous
2 of the same alleles, either both dom or both recessive
Heterozygote/Heterozygous
2 different alleles, dom and recessive
Phenotype
the way a gene presents physically
Genotype
genetic make-up
Monohybrid
heterozygous for one character (flower color, seed smoothness)
Dihybrid
the offspring of 2 true-breeding parents, with 2 different characters
Law of independent Assortment
each pair of alleles segregate independently of any other pair of alleles during gamete formation
Complete dominance
when phenotypes of the heterozygote and the dominant homozygote are identical
Pleiotropy
genes have multiple phenotypic effects, show themselves physically multiple ways (responsible for multiple symptoms of hereditary diseases like Cystic Fibrosis and Sickle Cell Disease)
Epistasis
one gene affects the phenotype of another due to the interaction of their gene products
Polygenic inheritance
multiple genes that affect a single trait (like height or skin color)
Pedigree
family tree that describes the interrelationship of parents and children across generations
Multifactorial inheritance
traits that depend on multiple genes combined with environmental influences
Carrier
heterozygous individuals who carry the recessive gene but are phenotypically normal
Consanguineous matings
between close relatives (like in-breeding); increases the chance that both parents carry the same rare allele
What are the limitations to Mendell’s experiments?
Mendel only experimented on the characters of only 2 distinct alternative forms. He only experimented with true-breeding plants, on only 1 character. Chose only characteristics in 2 alternate forms, and only chose objects that were true-breeding. Meaning they were homozygous plants. He didn’t experiment, initially, with heterozygous plants until F1.
Describe the four models of heredity proposed by Mendell
Hypothesis of 3:1 model in F2 offspring. Mendel observed this 3:1 ratio of inheritance.
- Alternate versions of genes account for variations in characters
- gene for color exists in 2 versions (purple, white) aka Alleles, reside at specific locus on gene - Each character: 2 alleles from each parent
- If 2 alleles differ, then the dominant allele denotes appearance, and the other (recessive) has no effect
- law of segregation- 2 alleles for a heritable character separate during gamete formation (during meiosis one) and end up in different gametes (meiosis 2)
What three situations deviate from simple mendellian patterns of inheritance
When alleles are not completely dominant or completely recessive
When a gene has more than 2 alleles
When a gene produces multiple phenotypes
Give example of multifactorial disorders
Heart disease, cancer, alcoholism. These are disorders that are somewhat genetic but also influenced by the environment. Eating a diet heavy in sugar and fat leads to an increased risk of CAD, increasing your risk of heart attack and stroke. Sugar feeds cancer. Alcoholism destroys your liver.
How is polygenic inheritance different from pleiotropy?
Polygenic inheritance: multiple genes independently affect a single trait. There are many genes that go into eyecolor, skin color, height. These genes are inherited independently but work together to produce one trait.
Pleiotropy: genes have multiple phenotypic effects. In cases of hereditary diseases, like cystic fibrosis or sickle cell disease, there are multiple symptoms that can be observed because of the single CF or SC trait