Skip to main content
UploadLanguage (EN)Support
BusinessMobileSocial MediaMarketingTechnologyArt & PhotosCareerDesignEducationPresentations & Public SpeakingGovernment & NonprofitHealthcareInternetLawLeadership & ManagementAutomotiveEngineeringSoftwareRecruiting & HRRetailSalesServicesScienceSmall Business & EntrepreneurshipFoodEnvironmentEconomy & FinanceData & AnalyticsInvestor RelationsSportsSpiritualNews & PoliticsTravelSelf ImprovementReal EstateEntertainment & HumorHealth & MedicineDevices & HardwareLifestyle
I Wonder Why Science, profile picture
Uploaded byI Wonder Why Science
2,793 views

Intro to Genetics

This document discusses basic concepts of genetics and inheritance, including: - Germ cells undergo meiosis to form gametes like eggs and sperm, which are haploid. - Gregor Mendel conducted experiments on pea plants in the 1800s and discovered dominant and recessive traits are inherited based on predictable ratios. - Traits are determined by alleles, or variations of genes. Dominant alleles are expressed over recessive alleles in heterozygotes based on genotypes. - Meiosis and fertilization allow for genetic variation through independent assortment and recombination of parental chromosomes.

Education◦
Introduction to Genetics How Traits are Passed from Parents to Offspring Life Science What is Inheritance?
In your lab notebook, please answer as best you can: 1. What are germ cells? • Cells which divide by meiosis to become gametes (eggs or sperm). 1. How is metaphase I of meiosis different than metaphase in mitosis? • Homologous pairs line up in the middle and divided into the new cells. 1. A small segment of DNA that codes for a specific protein which determines a certain trait in an organism is called a… • Gene 1. What is the ploidy of a germ cell after it divides by meiosis? • Haploid (or n) 1. When homologous pairs line up during Metaphase 1 of meiosis, they often swap sections of DNA. This process increases genetic variation in the resulting gametes and is called… • Crossing over Week 10 Review Quiz Bonus: How are the daughter cells of mitosis different than those formed by meiosis? Mitosis ends with two, identical, diploid daughter cells while meiosis yields four, unique, haploid daughter cells.
 Life begins when two gametes (sperm + egg) join  A complete set of chromosomes results (23 + 23)  The zygote starts as a single cell, but soon begins to divide (via mitosis = identical cells)  Genes are "turned" on and off, causing cells to differentiate (change to have different forms/jobs) Fertilization: new life is formed
Differentiation  Genes signal different cells to create proteins that give them unique shapes & functions  These cells grow & divide to make tissues that form the organs of the developing baby
 The chromosomes from your mom and dad have given your cells instructions to make YOU!  Each characteristic you inherited from your parents is called a trait (eye color, earlobe shape, height, personality traits, etc.)  For each trait, you have a pair of alleles (one from your mother and one from your father) Heredity & Inherited Traits
Alleles: variations of a gene Gene Alleles Eye Color Blue, brown, green, hazel Pea height Tall, short Pea color Yellow, green Flower position Axial, terminal
1822-1884 Gregor Mendel  An Austrian scientist-turned-monk noticed patterns in the monastery's garden  Studied the inherited traits of pea plants and found predictable, numerical ratios in the offspring  Observed some traits were dominant over others (i.e. yellow peas overpowered or occurred more often than green pea seeds)
Mendel's Experiments  He wondered if traits seen in different generations of pea plants were • determined by environmental factors (soil composition, temperature, sunlight) OR • "handed down" by parents (chromosomes weren't even discovered yet, so he had no idea how)  In his highly controlled experiments, he tested the hypothesis that each trait was determined by a set (not one, but TWO) inherited factors from each parent  Do you see the Scientific Method at work here?
Dominant and Recessive Traits
 Observed phenotype, the outward expression of the genes  the F1 generation are tall, showing that trait is dominant  The dwarf plant has the recessive trait (it is overpowered by the tall allele) Mendel’s Crosses
Genotypes: Genes and Alleles  The genetic make- up of an organism is its genotype  Every organism is diploid (has 2 copies of each chromosome)  Each trait is designated by a different letter  DOMINANT ALLELES ARE CAPITAL LETTERS  Recessive alleles are lowercase letters
Genotype Genotype Phenotype Homozygous dominant TT Dominant Homozygous recessive tt Recessive Heterozygous Tt Dominant  Homozygous means the two alleles are the same  Heterozygous means the two alleles are different Genotype determines Phenotype
Punnet Square: Monohybrid Cross  Used to predict the outcome of a genetic cross
The Law of Segregation  Diploid chromosomes of parents undergo meiosis  Alleles separate as they become haploid egg or sperm  They are combined again during fertilization to produce a diploid offspring
Independent Assortment & Segregation
Which traits are dominant?
 Heterozygotes express an intermediate phenotype  Instead of overpowering one another, both traits are partially expressed  Flower color traits separate again during meiosis and can be seen in the F2 generation Incomplete Dominance
Co-Dominance  The inheritance of ABO blood groups demonstrates co-dominant inheritance  Two alleles are dominant (Type A and Type B)  Both phenotypes are expressed in the heterozygote (Type AB)
Polygenic Traits  The control of a trait by more than one gene • Skin color is controlled by at least 6 alleles or genes  Each gene product is additive to others  The hallmark of a polygenic trait is • A bell curve distribution • A continuous distribution
The Human Genome Project  In the 1950's, scientists were first able to view a set of human chromosomes  In 2003, scientists finished mapping the human genome  Now every gene of each human chromosome is know by location and trait
Human Karyotype: 23 homologous pairs
X + X = GIRLX + Y = BOY  The X and Y chromosomes determines gender Sex Chromosomes  The mother always donates an X chromosome. Why?  The father gives either an X (female) or a Y (male).