chap 10 patterns of inherit fall '08

chap 10 patterns of inherit fall '08 - Today we will Today...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Today we will Today Lecture make up date = dec 6 in lab 9am Final is in this lecture hall Lecture on Lecture – Mendel and the beginning of genetics – How single and multiple traits inherited – How sex determined and what is sex linked – Is Mendel correct in all circumstances – disorders Chapter 10 Chapter Patterns of Inheritance Flo Hyman Marfan syndrome To understand us Sickle cell Hemophilia Turner syndrome But first some terms terms Locus Genes Alleles – Dominant – Recessive Recessive m B m B Homozygous Homozygous Heterozygous = Hybrid Self fertilization True breeding Cross fertilization D d Father of modern genetics Discovered patterns before we knew about DNA, chromosomes, and meiosis Gregor Mendel listen Mendel’s Secrets Mendel’s Right organism Designed experiments correctly Correctly analyzed data Smart & Patient Monk Smart Cross fertilized 1000’s of times P F1 F2 F3 Smart and patient Monk cont. Smart A monohybrid cross Did this 1000s of times for each trait Where did the white flower go??? Why? Here it is. Hidden not destroyed/eliminated Patient Monk Patient F3 generation – Crossed F2 white flowers All >>>> true breeding white All BUT WHY WAS WHITE HIDDEN?? Patient Monk Patient F3 generation – Crossed white flowers Crossed All >>>> true breeding white All – Crossed F2 purple flowers 1/3 >>>> true breeding purple 2/3 >>>> hybrid purple i.e. yielded 3 purple 1 white BUT WHY WAS WHITE HIDDEN?? Patient Monk Patient F generation 3 – Crossed white flowers Crossed All >>>> true breeding white All – Crossed purple flowers 1/3 >>>> true breeding purple 2/3 >>>> hybrid purple i.e.WAS W3 purple IDDEN?? BUT WHY yielded HITE H 1 white Listen please A VERY Smart Monk VERY 6 listen Looks like this Looks Each trait is determined by pairs Each of discrete physical units (genes) of Each gene has 2 forms (alleles) listen Looks like this Looks Each trait is determined by pairs Each of discrete physical units (genes) of Each gene has 2 forms (alleles) There is one allele of the gene There on each homologous chromosome chromosome True breeding white plants have True different alleles than true breeding purple plants breeding listen Looks like this Looks Each trait is determined by pairs Each of discrete physical units (genes) of Each gene has 2 forms (alleles) There is one allele of the gene There on each homologous chromosome chromosome True breeding white plants have True different alleles than true breeding purple plants breeding When 2 different alleles of the When same trait are present, one expresses itself (dominant), and one is masked (recessive) one True breeding organisms have 2 True of the same allele for a given gene gene So, why was the white hidden? Law of Segregation Law Pairs of genes on homologous Pairs chromosomes separate from each other during gamete formation so that each gamete receives only one allele of an organisms pair of genes organisms = Law of segregation tells us how we inherit (pass on) “a” trait from one generation to the next n Pu ne tt u Sq ar e A way to predict the genotypes and phenotypes of offspring of Genotypic ratios Phenotypic ratios Test cross Test Is used to determine Is whether a single trait showing dominance is homo or heterozygous heterozygous Test cross Test Is used to determine Is whether a single trait showing dominance is homo or heterozygous homo Done by crossing the Done dominant with a homozygous recessive (same trait) organism organism Test cross Test Is used to determine whether a Is single trait showing dominance is homo or heterozygous homo Done by crossing the dominant Done with a homozygous recessive (same trait) organism (same If homozygous dominant If then all offspring will express dominant trait express e.g. PP X pp = Pp = all dominant dominant Test cross Test Is used to determine whether a single trait Is showing dominance is homo or heterozygous heterozygous Done by crossing the dominant with a Done homozygous recessive (same trait) organism organism If homozygous dominant then all offspring If will express dominant trait will e.g. PP X pp = Pp = all dominant e.g. If heterozygous, then half will If show dominant trait and half will be recessive will e.g. Pp x pp = ½ Pp & ½ pp e.g. We know that the Law of segregation tells us how we inherit (pass on) “a” trait from one generation to the next But how are multiple traits on different chromosomes inherited?? chromosomes Mendel hypothesized that genes on different chromosomes are inherited independently What led him to think so? listen Mendel hypothesized that genes on different chromosomes are inherited independently What led him to think so? Experiment with seed shape, smooth (S) or wrinkled (s), and seed color, yellow (Y) or green (y). Crossed SSYY X ssyy >>> all smooth & all yellow plants (SsYy) would occur if dependent or independent Self fertilized these (SsYy) plants and got a 9-3-3-1 phenotypic ratio DD Dr rD rr Mendel hypothesized that genes on different chromosomes are inherited independently What led him to think so? Experiment with seed shape, smooth (S) or wrinkled (s), and seed color, yellow (Y) or green (y). Crossed SSYY X ssyy >>> all smooth & all yellow plants (SsYy) would occur if dependent or independent Self fertilized these (SsYy) plants and got a 9-3-3-1 phenotypic ratio and each individual trait showed a 3-1 ratio like unto that for true breed single trait crosses therefore traits acted independently of each other DD Dr rD rr 9 3 3 1 12 4 3-1 Dihybrid cross Genotypic ratio 1-2-2-1-4-1-2-2-1 This info led him to formulate his Law of Independent Assortment Law of Independent Assortment Law The alleles of one gene may be The distributed to gametes independently of the alleles for other genes of Another listen Chromosomes Assorting independently but the alleles on any given chromosome remain “linked” Law of Independent Assortment Law The alleles of one gene may be distributed to gametes The independently of the alleles for other genes independently Applies when the genes are on different pairs of chromosomes different But what if they are on the same chromosome?? How are genes on the same chromosome inherited?? chromosome Answer: They “tend” to be inherited as a Answer: group group The genes are said to be linked The linked But linked genes can be mixed up But Recombination – Crossover – Genetic recombination Sex linked gene inheritance Sex Autosomes Sex chromosomes X Y Although smaller, some part of Y Although chromosome is homologous to X chromosome thus they pair during meiosis meiosis Sex linked gene inheritance Sex Autosomes Sex chromosomes X Y Although smaller, some part of Y chromosome is homologous to X chromosome thus they pair Although during meiosis during Genes that are on one sex Genes chromosome but not on the other are said to be sex linked sex Tidbits re human X & Y chromosomes chromosomes 78 genes on Y (14) – Most deal with male repro 300+ genes on X 300+ – Few deal with female repro – Most have no Y counterpart – Trait examples: color blindness, blood Trait clotting, muscle proteins clotting, Do Mendelian laws apply in all cases??????? Six NOes Six 1. Incomplete dominance Incomplete Red Red pink RR RR white flowers RR’ R’R’ 1. Multiple alleles can govern one trait A, B, O blood alleles 2. Codominance AB blood 4. Polygeneric inheritance polyploid 5. Pleiotropy single gene having multiple effects on phenotypes SRY gene 6. The Environment Himalayan rabbit Skin color Height IQ Human disorders Human Single gene – Recessive – Dominant – Sex Abnormal chromosome # – Sex – Autosomal Autosomal Single Gene Human Disorders Single Recessive allele disorders (rr) – Albinism TRY gene & tyrosinase – Sickle cell anemia Defective hemoglobin produced 8% African-American affected Malaria – Cystic fibrosis CFTR gene Defective chloride pumps Defective Single gene disorders cont. Single Dominant allele disorders (either DD or Dd) Normal Normal Cleft chin Cleft Freckles Diseases Diseases The dominant mutant allele produces a protein that interferes with the normal one with Marfan syndrome Achondroplasia Aa = dwarfism AA = embryonic death Huntington disease Hh = onset @ 40 HH = embryonic death Single gene disorders cont. Single Sex linked disorders Remember most X genes have no counterpart on Y Remember Therefore X based disorders more apt to show in males Recessive sex allele disorders Color blindness Hemophilia Hemophilia Prevents blood clotting Prevents Abnormal sex chromosome # Abnormal Caused by nondisjuction Abnormal autosomal chromosomes chromosomes Produces an organism with 1 or 3 chromosomes Most die as an embryo Trisomy 21 Down syndrome 21 en am ...
View Full Document

Ask a homework question - tutors are online