Genetics Chapter 13 Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Outline Genetics--> Definition Structure of DNA DNA Functions Transcription Translation Mutation Cytogenetics Mendelian Genetics Quantitative Traits Linkage Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Genetics can be defined as The biological discipline involving the study of heredity the study of genes. the inheritance of physical traits. the study and inheritance of DNA. the study and inheritance of chromosomes all of the above. Focus on the MOLECULAR-->DNA (deoxyribonucleic acid) Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

5-Carbon Sugar (Deoxyribose) Phosphate Group Structure of DNA DNA molecule organized into chain of nucleotides composed of three parts: Nitrogenous Base 5-Carbon Sugar (Deoxyribose) Phosphate Group Nucleotides bonded to each other forming a helix. Hydrogen bonds hold each base on one side of the helix to another base on the other side. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Three Parts of DNA Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Structure of DNA-->nucleotides Four types of DNA nucleotides: Purines--Adenine (A) and Guanine (G) Pyrimidines--Cytosine (C) and Thymine (T) Nitrogenous Base Part Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Stern - Introductory Plant Biology: 9th Ed Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Two chains binding together using hydrogen bonds Helix structure: Two chains binding together using hydrogen bonds (base pairs) Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Storage of Genetic Information DNA Functions (ACGT) Storage of Genetic Information Gene - Segment of DNA that directs protein synthesis. Protein may act as an enzyme influencing cell activities. Genome - Sum total of DNA in an organism’s chromosomes. Codon - Groups of three nucleotides. (in a row, ex. AAT; AAA; GCT; etc…) Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Replication of Information Occurs during S phase of cell cycle. DNA Functions Replication of Information Occurs during S phase of cell cycle. Strands of double helix unzip allowing DNA polymerase (enzyme) to pair individual nucleotides with the template strands. Semi-Conservative Replication Occurs simultaneously in both directions, and begins at several points simultaneously. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

DNA Replication Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Expression of Information DNA Functions Expression of Information Different subset of the genetic information is read in each cell type. Expression requires two processes. Transcription - Copy of gene message using RNA (intermediate nucleic acid). Translation Messenger RNA (mRNA) translated to produce proteins. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Outline Genetics--> Definition Structure of DNA DNA Functions Transcription Translation Mutation Cytogenetics Mendelian Genetics Quantitative Traits Linkage Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Language metaphor Central Dogma of Molecular Biology Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Three different types of RNA produced: Transcription Three different types of RNA produced: Messenger RNA (mRNA)-->proteins Transfer RNA (tRNA)-->translation Ribosomal RNA (rRNA) RNA Synthesis (ACGU nucleotide parts) Nucleotides added to single stranded DNA molecule by RNA polymerase. Only portions of the genome replicated. Remainder is noncoding DNA (includes directions for expression!). Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Stern - Introductory Plant Biology: 9th Ed Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

mRNA transcripts are decoded into proteins. Translation mRNA transcripts are decoded into proteins. Genetic code based on codons. 64 possible combinations of ACGT/U) (43) Code for 20 amino acids. tRNA acts as a translator. Anticodon binds to mRNA codon. Ribosomal RNA (rRNA) binds to mRNA and facilitates translation Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Genetic Code/ codons encode for 20 amino acids = proteins Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Stern - Introductory Plant Biology: 9th Ed Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Mutations - Changes in DNA sequence. Mutagens - Agents that alter DNA. Ultraviolet light Ionizing radiation (Pasta wheat/Ruby red) Somatic Mutation - Occurs in body cell. Germ-Line Mutation - Occurs in tissues that will produce sex cells. Passed on to future generations. All genetic variability due to mutations. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Changes in Chromosome Structure Cytogenetics Cytogenetics is the study of chromosome behavior and structure, from a genetic point of view. Changes in Chromosome Structure Inversion - Chromosomal piece is broken and reinserted in the opposite orientation. ABCDE ABDCE Translocation - Chromosomal piece breaks off and attaches to another chromosome. Important in speciation (rye) Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Changes in Chromosome Number Cytogenetics Changes in Chromosome Number Mistakes during chromosome pairing and separation can result in gametes carrying extra or missing chromosomes. Aneuploid - Carries, or is missing, an extra chromosome(s). Polyploid - Has at least one complete extra set of chromosomes. Many cultivated plants are polyploid because they are bigger and produce more. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Tetraploid Diploid S. tuberosum Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Genetics from Mendel to Today Gregor Mendel (Austrian Monk) inheritance of traits (1850-1865); rediscovered in 1900s Used peas Watson & Crick model of DNA (1954) Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Crossed a tall plant with a short plant. Parental Generation (P) Mendelian Genetics Mendel crossed self-pollinated pea plants and recorded his observations. Crossed a tall plant with a short plant. Parental Generation (P) All offspring were tall. First Filial Generation (F1) Cross offspring yielded a ratio of three tall individuals to one short individual. Second Filial Generation (F2) Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Stern - Introductory Plant Biology: 9th Ed Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Mendelian Genetics Law of Unit Characters Factors (Alleles), which always occur in pairs, control the inheritance of various characteristics. Genes are always at the same position (locus) on homologous chromosomes. Law of Dominance For any given pair of alleles, one (Dominant) may mask the expression of the other (recessive). Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Phenotype refers to an organism’s physical appearance. Mendelian Genetics Phenotype refers to an organism’s physical appearance. Genotype refers to the genetic information responsible for contributing to the phenotype. Homozygous - Both alleles identical. Heterozygous - Alleles are contrasting. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

start Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Monohybrid Cross (one trait) A cross is made between two true-breeding parents differing for a single trait, producing an F1 generation. RR X rr These plants are intercrossed to produce an F2 generation. R r R R RR Rr Rr Rr R r Rr rr Rr Rr r r Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Mendelian Inheritance Pattern The phenotype of the F1 resembled one parental form. All F1s looked the same. The “hidden” parental form reappeared in the F2 generation. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Stern - Introductory Plant Biology: 9th Ed Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Cross made for parents differing in two traits. Dihybrid Cross Cross made for parents differing in two traits. Mendel’s Law of Independent Assortment Factors (genes) controlling two or more traits segregate independently of each other. Linked genes do not segregate independently. Punnett Square used to determine genotypes of the zygotes. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Dihybrid Cross Parents differing in 2 unlinked genetic traits Green pod, Tall plant (GGTT) X yellow pod, dwarf plant (ggtt) Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

A cross between a hybrid and one of its parents. Mendelian Genetics Backcross A cross between a hybrid and one of its parents. Can be used to test inheritance theory. Incomplete Dominance Some genes exhibit traits in which a heterozygote is intermediate in phenotype to the two homozygotes. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Incomplete Dominance Camellias Snapdragons Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Quantitative Traits Quantitative traits exhibit a range of phenotypes rather than discrete phenotypes studied by Mendel. Molecular geneticists are able to identify chromosomal fragments, quantitative trait loci, associated with quantitative traits. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Inheritance of Corn height (Quantitative) Cross Tall corn (6 m) x short corn (2 m) F2 are not 3:1 tall to short but all heights between 1.5 m and 8 m P1 P2 # of plants Plant height Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Occurs with 2 traits - often located close together on chromosome Linkage Occurs with 2 traits - often located close together on chromosome Often segregate like a single trait No recombination occurs Get a shortage of unique gamete genotypes in F1 generation Get fewer genotypes in F2 generation Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Stern - Introductory Plant Biology: 9th Ed Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Genes that are together on a chromosome are said to be linked. Linkage and Mapping Genes that are together on a chromosome are said to be linked. Each gene has a specific location (locus) on a chromosome. Crossing-over should be more likely between two genes located far apart on a chromosome that between two genes located closer together. Crossing over frequency can be used to construct a genetic map. 1 map unit = 1% crossing over. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Review Structure of DNA DNA Functions Transcription Translation Mutation Cytogenetics Mendelian Genetics Quantitative Traits Linkage Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Entranuclear DNA is found in both mitochondria and chloroplasts. Extranuclear DNA Entranuclear DNA is found in both mitochondria and chloroplasts. Endosymbiont Hypothesis theorized mitochondria and chloroplasts were free-living, and at some point became incorporated into cells of organisms that evolved into plants and established a symbiotic relationship. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Promoter Region signals transcription enzymes to attach to the DNA. Single-stranded RNA transcript produced. Chromosomes contain genes for building tRNA. Each form of tRNA has a specific anticodon loop. Base pairs with codon. Genes for rRNA also transcribed in the nucleus - Used to construct ribosomes. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Hardy-Weinberg Law Hardy-Weinberg states the proportions of dominant alleles to recessive alleles in a normally interbreeding population will remain the same from generation to generation in the absence of external forces. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Central Dogma of Molecular Dogma Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies