University:
Missouri State University
Course:
BIO 235 | Genetics
Academic year:

2021
Views:

369

Pages:

80
Author:

sapela015a

DNA Chromosomes & Replication RNA & Protein Synthesis Mutations Karyotype Gregor Mendel Probability Beyond Dominant Hippocrates: Pangenesis Particles (pangenes) from each part of the body moved to the egg and sperm Changes in organisms over their lifetime would be passed on to offspring Aristotle: Rejected Hippocrates What was inherited was the potential to produce body featuresnot particles of the actual feature *How about weightlifting? 19th century biologists offered “blending” hypothesis Hereditary materials contributed by mother and father mix to form offspring and cannot be unmixed Blending of blue and yellow paint Make green Gregor Mendel Genes & Dominance Genetics = the scientific study of heredity Rural upbringing Austrian Monk; teacher of science & math DUTIES 1822 in the Czech Republic; Died in 1884 OCCUPATION BORN Gregor Mendel- The father of genetics In charge of the monastery garden; experimented with PEA plants Mendel observed seven traits that were easily recognized and only occured in one of two forms: Mendel knew an important fact of his pea plants: The flowers have both male & female reproductive parts. POLLINATION SELF Pollination Pea plants contain both male & female parts True Breeding: Natural process for pea plants CROSS Pollination Fertilization of a plants egg by the pollen of another plant Had to prevent self pollination! Remove immature stamens before they produce pollen! Filial- “Son” Did the recessive alleles disappear, or were they still present? Mendel’s Results and Conclusions: 1. Biological characteristics are determined by genes. (Genes are passed from parents to their offspring.) Mendel’s Results and Conclusions: 2. Some forms (alleles) of a gene may be dominant and others may be recessive. Mendel’s Results and Conclusions: 3. In most sexually reproducing organisms, each adult has two copies of each gene—one from each parent. These genes are segregated/separated from each other when gametes are formed. (Law of Segregation) Homologous chromosomes separate from each other during Anaphase I of Meiosis Mendel’s Results and Conclusions: 4. The alleles for different genes usually segregate independently of one another. (Law of Independent Assortment) Genes & Dominance 1. Gene- a section of DNA that controls a specific trait 2. Allele – alternative form of a GENE 3. Trait—a characteristic of a species determined by specific genes 4. Dominant gene—the presence of this type of gene will mask/hide the other gene 5. Recessive gene—this gene is hidden by the other gene unless there are two copies of the recessive form. 6. Hybrid– offspring of crosses between parents with different traits 7. Homozygous – Both pairs of genes for a specific trait are the same 8. Heterozygous – Both pairs of genes are different Genes & Dominance 9. Genotype – the genetic makeup of an organism (ie. AA, Aa, aa) 10. Phenotype – the physical appearance of an organism (ie. Hair color, eye color, etc.) If you know the genotypes of the parents, you can predict the probability of the offspring receiving those traits There is a big difference between probability and what actually happens (think of a coin toss). We can use Punnett squares to show the probable outcomes. Punnett Squares!!! = tool used to determine the probability of offspring of a cross between two parents Monohybrid Crosses A cross between individuals that involves ONE pair of contrasting traits Probability The likely hood that a particular event will occur Probability predicts the average outcome of large numbers. Past outcomes do not affect future outcomes Punnett Squares Can be used to predict & compare the genetic variations that will result from a cross = recessive (lower case) MonoHybrid Cross = DOMINANT (capital letter) Punnett Squares Can be used to predict & compare the genetic variations that will result from a cross = DOMINANT HOMOzygous = organisms letter) that have (capital 2 IDENTICAL alleles for the same trait = recessive HETEROzygous = organisms (lower case) that have 2 DIFFERENT alleles for the same trait To determine the GENOTYPE of an organism expressing the dominant phenotype. Testcross= a mating between an individual with an unknown genotype and an individual that is HOMOZYGOUS RECESSIVE. – Look at offspring to determine parent genotype Example: Labrador Retriever B- black fur b= chocolate brown fur Black lab X chocolate lab B___ X bb Used to determine the genotype Mating between unknown genotype and homozygous recessive In humans, long eyelashes (E) is dominant short eyelashes (e). A man with long eyelashes marries a woman with short eyelashes and they have three children, two of whom have long eyelashes and one of whom has short eyelashes. Draw the Punnett squares that illustrates this marriage. What is the man’s genotype? What are the genotypes of the children? Independent Assortment Dihybrid Cross Two-Factor Cross Do the genes that determine round/wrinkled have anything to do with seed color? Remember!!! The alleles for different genes usually segregate independently of one another. (Law of Independent Assortment) RRYY -> RY, RY, RY,RY rryy -> ry, ry, ry, ry Patterns of Inheritance Some alleles are neither dominant nor recessive, & many traits are controlled by multiple alleles or multiple genes Incomplete Dominance Codominance Multiple Alleles Polygenic Traits Incomplete Dominance One allele is not completely dominant over another “Blending” - the heterozygous phenotype is somewhere in between the two homozygous phenotypes Codominance Both alleles are fully and separately expressed Both colors appear in phenotype – spotting, striping, etc. Multiple Alleles More than 2 possible alleles (options)exist for a given trait ONLY receive 2 alleles Multiple Alleles: Blood Type Multiple Alleles and Codominance: Blood Type Blood Groups: 3 Alleles = A (IA), B (IB), O (I) The four blood types are Type A, Type B, Type AB, Type O A and B are NOT dominant to each other, They are Codominant A and B are always dominant to O AO= A blood type BO= B blood type Cross a woman Heterozygous for A-blood and a man with AB-blood Parent Genotype: Genotypes: Phenotypes: Polygenic Traits Traits controlled by 2 or more genes The greater the number of dominant alleles, the darker the color Only The X Chromosome carries genes. So, if a gene is on the X chromosome, a female would have to have TWO of those genes and the male would only have ONE. Male with Disorder Female with disorder Female carrier A genetic disorder that is found on the X chromosome Females can be carriers and not have the disorder Would need both copies of the gene to have disorder Males express all sex linked genes because they only have one X chromosome If the X chromosome has it, they have it Males cannot be carriers Examples: Hemophilia and colorblindness A woman is heterozygous for normal vision She marries a man who is colorblind What is the predicted colorblindness outcome for their children? N= Normal vision n= Colorblind Parent Genotype: Genotype: Phenoype: Pedigree- A chart which shows the relationships within a family Phenotypes are used to infer genotypes Pedigrees  Studying humans:  It genetic disorders in is unethical to use humans as test subjects (plus it would take too long to get the results), so one of the best ways to study human patterns of inheritance is to use a PEDIGREE Definition A chart which shows the relationship within a family Pedigree Basics = normal male = normal female = affected male = affected female = carrier female = marriage line = children Pedigrees can be used to predict if a trait is dominant, recessive, or sex-linked Dominant At least one parent must show the trait if it is dominant Recessive Recessive disorder can be passed from any combination of parents, as long as the dominant parent is heterozygous. X-linked Females can be carriers More males may be affected Sex Linked Pedigree A.Single Gene B.Multifactorial C.Chromosomal D.X-Linked Genetic Traits and Disorders Genes that control human traits can be altered (mutated) and then be inherited by offspring Images from: http://www.aldanaanatomy.com/category/skin/page/2/, http://www.eyesurgeonspc.com/lasik-rock-island/cataract_surgery_rock_island/cataract-surgery-rock-island.html, http://en.wikipedia.org/wiki/Polydactyly Mutation Definition= a change in DNA sequence that affects genetic info KEY = The result of some mutations are genetic disorders. Image from: http://alsn.mda.org/news/c9orf72-mutation-most-common-cause-als-ftd-als-ftd How are disorders passed or inherited? Four main ways: Single gene Multifactorial Chromosomal abnormality X-linked a. Single Gene Disorders The problem trait is controlled by a single gene and can be passed in a dominant/recessive manner. DD = Dd = dd = b. Multifactorial Disorders Environmental factors can also affect the severity/onset of these disorders Difficult to study and treat! impairments in social interaction & communication; restricted interests and repetitive behavior ~the roof of the mouth (palate) has an opening (cleft) that may go through to the nasal cavity C. Chromosomal Abnormality In these disorders entire chromosomes or large segments of chromosomes are missing, duplicated, or otherwise altered. Image from: http://ghr.nlm.nih.gov/handbook/illustrations/chromosomaldeletion Ways chromosomal abnormality can occur: Nondisjunction •Failure of a chromosome to separate from its homologue during meiosis •One gamete receives an extra copy of a chromosome and the other gamete lacks the chromosome entirely Ie. GCCATA → GCATA Ie. GCCATA → GCCATCA Ie. GCCATA → CCCATA Ie. GCCATA → GCCGCCATA Majority with KS live as men Many don’t feel comfortable with masculinity and may choose to live as women May have gender reassignment surgery High pitched cry – sounds like a cat Microcephaly (small head) wide spaced eyes extra skin creases in the inner edge of the eye Poor weight gain Developmental delay Behavioral problems 3. X-Linked Traits More common in males → Females need 2 copies of the defective gene Disorders in which the mutation or errors are in genes found on the X chromosome. Examples are… 1. Hemophilia 2. Muscular Dystrophy 3. Colorblindness •Bleeding disorder •Blood fails to clot properly

Genetics Study Guide

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