Lecture 10 (pt. 2) Mendel and the Gene idea

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Flashcards on Lecture 10 (pt. 2) Mendel and the Gene idea , created by Sydney Franko on 11/04/2016.
Sydney Franko
Flashcards by Sydney Franko, updated more than 1 year ago
Sydney Franko
Created by Sydney Franko almost 8 years ago
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Gregor Mendel (1840s) – Austrian monk – Background as a farmer – Statistician (strong background in mathematics) - counted the different types of offspring – Worked with pea plants Pisum sativum – He was a plant breeder and a mathematician
Pea Plants are great genetic model organism – Inexpensive – Short lifetime – Many observable traits – Lots of progeny – Self-fertilizing – Can be cross-fertilized – Pea plant offspring can be used to describe the heredity patterns of traits (how information is passed from parent to offspring)
Genes – Units of information about specific traits, passed from parent to offspring – Each gene has a specific location (locus) on a chromosome.
Locus The specific location or position of a gene, DNA sequence, on a chromosome
Chromosome – DNA and its associated proteins - involved in the hereditary information of cells
Alleles – Different molecular forms of the same gene – Example: The gene for eye color has 2 alleles. The allele can either contain the gene for blue eye color or the gene for brown eye color.
Diploid - (2n) = pairs of genes on pairs of homologous chromosomes (the chromosomes of the same chromosome type - have the same size and shape) -A cell containing two complete sets of chromosomes, one from each parent.
Haploid – (n) = has half the number of chromosomes (gametes)
True-Breeding Lineage – When offspring of genetic crosses (breeding) that inherit two identical alleles for the same exact trait. All offspring will have the same trait as their parents. – Example: All offspring of a true breeding purple flowered pea plant will have purple flowers.
True breeding Also called a purebred, is an organism that always passes down certain phenotypic traits to its offspring.
Hybrid offspring – When offspring of a genetic cross inherit a pair of non-identical alleles for a trait – Example: Two purple flowered plants produce a white flowering offspring – Aa, aA
Homozygous dominant –Both alleles for the same trait are dominant -AA
Homozygous recessive – Both alleles for the same trait are recessive -Aa
Genotype –The particular genes an organism carries. Show you the pattern of alleles AA (purple flower) Aa (purple flower) aa (white flower)
Phenotype An individual’s observable physical traits (purple flower, white flower)
Homozygous -When both alleles of the pair for a certain trait are identical. -2 of the same alleles
Heterozygous – When the two alleles of a pair for a certain trait are different
Terms used for tracking the inheritance of traits through generations of offspring -P= Parental generation - F1= First generation of offspring (first filial) -F2= Second generation of offspring (second filial)
Monohybrid –Only one trait is followed through a series of genetic crosses.
Dihybrid -Two traits are followed through a series of genetic crosses
Mendel's theories -Theory of segregation -Theory of independent assortment
Theory of segregation During meiosis, the two genes of each pair segregates from each other and end up in different gametes. (alleles separate into different gametes) • Monohybrid cross • Gene segregation
Theory of independent assortment By the end of meiosis, the genes on pairs of homologous chromosomes have sorted independently (into gametes). Deals with different traits
Probability The likelihood that a particular event will happen (flipping a coin)
Probability and Punnett squares –A possibility of outcomes and crosses –Test crosses
–What are five factors that can influence patterns of heredity? -Incomplete Dominance -Codominance -Multiple Alleles -Continuous Variations -Environmental influences
Incomplete Dominance -An individual displays a trait that is intermediate between the 2 parents (snapdragons). -If you have one allele of each you’re going to have a blend of dominant and recessive. (EX. 1 recessive White and 1 dominant red blended heterozygous pink)
Codominance -Two alleles are expressed at the same time (roan coat). -Heterozygous dominant is going to have both alleles showing both colors (ex. Red D and white R the flower will have some of each).
Multiple Alleles -Genes that have traits with more than 2 alleles-blood type has 3 alleles (A,B,O) that determine blood type. -More than just A and a. -When there is a third option of an allele for one genotype. More than one gene interacting to form a trait.
Continuous Variation -Traits for which you see a variety of phenotypes on a continuum from one extreme to another (height, weight). -Many genes and 1 trait.
Environmental Influences -An individual’s phenotype often depends on conditions in the environment. -Example: Many animals such as the arctic fox develop white fur during the cold winter and dark fur in the summer.
How blood types are inherited and expressed: –Type A (AA) –Type AB (AB) –Type B (B i) (BB) –Type O (I I )
Pleiotropy Effects on two or more traits Ex. Sickle cell anemia
Epistasis  -Interactions among products of two or more gene pairs  -Two alleles of one gene may mask the expression of another gene’s alleles- so some expected phenotypes may not appear.
Hair color in mammals -Variation in melanin products (Ee, EE, ee) ››allele “E” allows full deposition of melanin -Albinism (total absence of melanin product)
Comb shape in poultry -Interaction between two gene pairs produces a phenotype that neither pair can produce alone
Hair color in Labrador Retrievers (epistasis) -Black (Dominant pigment, dominant 2nd pair)  -Yellow (recessive pigment and dominant or recessive 2nd pair)  -Brown (dominant pigment and recessive for 2nd pair)
Continuous variation -Eye color -Different amounts of melanin -Different enzymes affect the production
Continuous variation (normal distribution) -Height -The greater number of genes and the environmental factors, the more continuous will be the expected distribution of the trait.
-Examples of environmental effects on phenotypes – Himalayan rabbit – Siamese cat – Heat-sensitive version of enzyme needed for melanin production  Warm= white fur  Cold= dark fur
Hydrangea -Plants that have the same alleles and have flowers colors raging from pink to blue depending on the acidity of the soil.
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