Introduction to Genetics – Part 1

Slide 1

Introduction to Genetics Part 1Genetics Study of heredity is often divided into four major subdisciplines:1. Transmission genetics, deals with the transmission of genes from generation to generation 2. Molecular genetics deals with the structure and function of genes at the molecular level 3. Population genetics, which deals with heredity in groups of individuals for traits determined by one or only a few genes 4. Quantitative genetics, deals with the heredity of traits in groups of individuals where the traits are determined by many genes simultaneouslyMeiosisCell division in diploid cells that results in haploid cells; reduction divisionHomologous chromosomes a pair of chromosomes having the same size and shape and carrying information (alleles) for the same traits (Fig. 11-14)

Diploid vs HaploidDiploid having two sets of chromosomes, or all the homologous chromosomes that are characteristic of the species (2n)Haploid having only one chromosome from each pair of homologous chromosomes (n)

How does a cell go from diploid to haploid?

Phases of MeiosisDuring meiosis the chromosomes replicate once, but the cell divides twice Fig. 11-15

Meiosis results in two haploid daughter cells with half the number of chromosomes as the original cell

Phases of MeiosisProphase I Homologous chromosomes pair (synapsis) to form a tetrad

Phases of MeiosisProphase I Crossing over exchange of segments between nonsister chromatids; **increases genetic variation**

Phases of MeiosisMetaphase ITetrads line up on equatorial plane

Phases of MeiosisAnaphase IDisjunction occurs - homologous chromosomes from each tetrad separate Cytokinesis begins during late anaphase/early telophase

Phases of MeiosisTelophase IEnd of first meiotic divisionhttp://www.phschool.com/science/biology_place/biocoach/meiosis/mei1ani.html

Phases of MeiosisProphase II

Phases of MeiosisMetaphase II

Phases of MeiosisAnaphase II

Phases of MeiosisTelophase II

http://www.phschool.com/science/biology_place/biocoach/meiosis/mei2ani.html

Phases of MeiosisOverview

http://www.johnkyrk.com/meiosis.html

Meiosis vs Mitosis

Meiosis Quizzes

http://biology.about.com/library/weekly/blmeios2a.htm

http://www.phschool.com/science/biology_place/biocoach/meiosis/quiz.html

http://www.cst.cmich.edu/users/benja1dw/bio101/tools/quiz/mitosis.htm

THIS SLIDE ENDS PART ONEIntroduction to Genetics Part 2

Gregor Mendel father of modern geneticsGregor Mendels Peas

Introduction to Genetics Part 2

Fertilization the union of a female and male gamete (specialized sex cell formed during meiosis)Introduction to Genetics Part 2

Pea plants are: - easy to grow - matured quickly - show contrasting traits - control pollination True breeding pure for a particular trait. If plants with yellow seeds were self pollinated for several generations they would always produce plants with yellow seedsGenes and Dominance

Gene a distinct unit of hereditary material found in chromosomes; a sequence of nucleotides in DNAGenes and Dominance

Allele the different forms of the gene for a traitGenes and Dominance

Principle of Dominance states that some alleles are dominant and others are recessive

Homozygous having two identical allelesTT homozygous dominanttt - homozygous recessive

Heterozygous having two different forms of a gene - TtGenes and Dominance

Principle of Dominance states that some alleles are dominant and others are recessive

Genes and Dominance

Principle of Segregation factors that occur in pairs are separated from each other during gamete formation and recombined at fertilization ( Fig. 11-5)

Probability & Punnett Squares

Probability likelihood that a particular event will occur

Principle of Probability if there are several possible event that might happen, and no one of them is more likely to happen than any other, then they will happen in equal numbers over a large number of trials

Example Coin Toss Fig. 11-7

Probability & Punnett Squares

Punnett Square a diagram used to show the results of a cross Fig. 11-7

Phenotype physical trait that appears as a result of genetic makeup

Genotype the genetic makeup of an organism; total set of genesExploring Mendelian Genetics

Principle of Independent Assortment Genes for different traits can segregate independently during the formation of gametes. (Fig. 11-9, 11-10)

http://bcs.whfreeman.com/thelifewire/content/chp10/1002001.html

Exploring Mendelian Genetics

Incomplete Dominance both alleles contribute to the phenotype and neither is dominant over the other Fig. 11-11


Co-Dominance Two dominant alleles are expressed at the same time

Multiple Alleles 3 or more different alleles of a gene; each combination producing a different phenotype


Polygenic Traits traits controlled by two or more genes; genes may or may not be on the same chromosome


Genetics and the Environment environmental factors can influence genetic potential

Linkage and Gene Maps

Genes located on the same chromosome tend to be inherited together in genetic crosses because the chromosome is passed along as a unit. Such genes are said to be linked genes. (Fig. 11-19)


Gene Map an ordered list of the genes along a particular chromosome. The farther apart two genes are , the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency. The distance between genes is expressed in map units and is defined as equivalent to a 1% recombination frequency


Links to Practice Punnett Squares http://biology.clc.uc.edu/courses/bio105/geneprob.htm

http://www.zerobio.com/drag_gr11/blood.htm

http://www.quia.com/quiz/220564.html?AP_rand=1287615174

Introduction to Genetics – Part 1

Documents

Transcript of Introduction to Genetics – Part 1