Genetics (BIOL 3000) lectures 13 & 14
Genetics (BIOL 3000) lectures 13 & 14 BIOL3000
Popular in Genetics
Popular in Department
This 11 page Class Notes was uploaded by Kennedy Finister on Friday February 19, 2016. The Class Notes belongs to BIOL3000 at Auburn University taught by Rita Graze in Fall 2015. Since its upload, it has received 47 views.
Reviews for Genetics (BIOL 3000) lectures 13 & 14
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 02/19/16
Genetics Lectures 13 &14 February 15, 2017 LECTURE 13 Topics: 1. Visualizing chromosomes 2. Chromosome characteristics 3. Revisiting genes, loci, & gene maps KARYOGRAMS • Cells are prepared for chromosome visualization & arranged largest to smallest, then sex chromosomes • DNA dyes stain the chromosomes that are actively dividing in metaphase • To make karyograms you stop division & match chromosome with the same banding pattern & image. Do it according to size then sex chromosomes (x/y) o Works like Photoshop • Just an image arranged artificially KARYOTYPES • Complete set of chromosomes possessed by an organism, can be determined with the karyogram • Information of the individual that are determined from the karyogram • Chromosomal abnormalities are determined here by comparing karyogram & looking at deviation • Example: karyotype is 46, XY CHROMOSOME CHARACTERISTICS 1. Size 2. Banding pattern à produced from the stain 3. Centromere position BANDING PATTERNS • Don’t just exist the way they are shown naturally. They are made to visualize chromosome morphology differences & reflect the way DNA is wound up and organized • “land marks” on a chromosome Genetics Lectures 13 &14 February 15, 2017 • distinct for every chromosome & made from karyogram • main number is the band & the decimals are the subbands IDEOGRAMS • a schematic depiction of the characteristics: size, centromere position & banding patters • helps understand physical location relative to “land marks” CHROMOSOME SIZE • determined by DNA amount • unit à base pairs o MBà million base pairs • Not 100% relation between base pairs & gene count (very broad) CENTROMERE LOCATION NOT SHOWN: Telocentric (doesn’t exist in humans) à centromere at the end CYTOGENETIC LOCATION Genetics Lectures 13 &14 February 15, 2017 • Use to talk about where genes are located • Examples: o CFTR (mutation for cystic fibrosis) o Located at 7q31.2 § 7 à chromosome number § q à long arm § 3 à region number § 1 à band number § .2 à sub-‐band number § o ABO Blood Groups Locus § 9q34 o Red Green Color Blindness locus § Xq28 o SRY (male determining gene) § Yp11.3 • Used in medical genetics SUMMARY 1. Cytogenetics is the study of chromosomes & their role in heredity 2. Chromosome structure can be visualized & diagrammed in different ways Genetics Lectures 13 &14 February 15, 2017 3. Standard methods of staining chromosomes have provided landmarks that are used to identify gene location 4. Locations are given as chromosome#___arm (p/q)___ region___ band.sub-‐band 5. Chromosomal landmarks & gene locations are mapped to provide info on physical location o a gene in the chromosomal location Genetics Lectures 13 &14 February 15, 2017 LECTURE 14 TOPICS 1. Chromosome abnormalities 2. Euploidy 3. Types of polyploidy (anything not diploid) a. Autopolypoloidy b. Allopolyploidy CHROMOSOMAL ABNORMALITIES • TWO MAJOR TYPES 1. Changes in the number of chromosomes a. Euploidy i. Different multiples of entire sets of chromosomes ii. Can be atypical or typical iii. Human cells typically have 2 sets – diploid b. Aneuploidy i. An abnormal number of chromosomes usually gain or loss of a (single) chromosomes within the set 2. Changes in chromosome structure a. Example: i. Deletions (remove), inversions (add), & translocations (move location) MONOPLOID & HAPLOID NUMBERS • Haploid number (N): o Number of chromosomes in a gamete o ½ the total number § humans 23 • Monoploid o Number of chromosome in a unique set o Number in one set § Humans 23 • For diploids This is the same but it can be different for species are normally polypoid • This includes normal (example à 2N for humans) & abnormal (example à 3N for humans) Genetics Lectures 13 &14 February 15, 2017 EUPLOIDY # in set Total # Total sets Monoploidy 23 23 One Diploidy 23 46 Two POLYPLOIDY # in set Total # Total sets Triploidy 23 39 3 Tetraploidy 23 92 4 Hexaploidy 23 138 6 EUPLOIDY & MONOPLOID NUMBER Monoploid # X= N= Diploidy 2X X= 23 N=23 N=X POLYPLOIDY Tetraploidy 4x X=23 N=23 N=2x Hexaploidy 6x X=23 N=69 N=3x Haploid number (N)= ½ number, ½ the total When we generate gametes we’re ½ the number of chromosomes & if we have more than 2 sets, in tetraploid state for example, we will have 2 sets of “DNA” in each gamete instead of one NORMAL CHANGES IN PLOIDY • Certain cells are polyploidy within normally diploid organisms • Endopolyploidy o Polyploidy cells (typically very specialized cells) within a diploid body & the number of chromosome sets are increased above normal state of 2x o Example: vertebrate liver cells • 4x, 8x, 16x (normal for them) o example: gerris water strider • 1024x to 2048x in larva salivary glands • 2N = 22 chromosomes • endopolyploidy = 40,000 chromosomes Genetics Lectures 13 &14 February 15, 2017 POLYPLOID CELLS • endomitosis o go around cell cycle, go thru mitosis but skip cytokinesis, so it doesn’t produce 2 daughter cells , but nucleus divides, ending with a single multinucleate cell. Instead of 1 nucleus with diploid number youre going to have 2 nuclei & a tetraploid cell • endocycling o go thru cell cycle, hit s-‐phase, skipping mitosis. Doubling chromosomes each round. o (multiple replications with no nuclear division) • Polytene chromosomes o Happens when you go thru s-‐phase repeated with no division o Theyre big stacks of chromosomes § Instead of 2 chromatids you have 4+, all making up a single packaged entity (chromosome) with one centromere o • Multinucleate o Happens when you go thru mitosis but skip cytokinesis o Many nuclei in one cell o Example: Megakaryotypes (bone marrow stem cells) • Produce platelets which aid in blood clotting Genetics Lectures 13 &14 February 15, 2017 • End with 64x cells § LONG STORY SHORT: These are normal cases where polyploidy is okay, in fact it is required to have typical function of that cell ABNORMAL EUPLOIDY • The addition or deletion of entire sets of chromosomes o X, 3x, 4x, etc • Cant finish development & live birth cannot occur in humans • Causes 1. Fertilization errors à polyspermy (rare) 2 sperm penetrate one egg resulting in 3 sets of data (triploid) Genetics Lectures 13 &14 February 15, 2017 (1 from mom 2 from dad) 2. Unreduced gametes à more common chromosomes didn’t separate into 2 daughter cells & they stay in one cell. Instead of haploid we have diploid being fertilized unreduced in polyploidy à gives you higher numbers 3. Hybridization two species with two different ploidy levels producing a hybrid zygote POLYPLOID ORGANISMS Genetics Lectures 13 &14 February 15, 2017 Type is determined by how the species arose. What error or hybridization occurred to create new species • Autopolyploidy o Primarily unreduced gametes o Duplication of same genome & one ancestor § Only one species contributing to make new species o Example: lilies • Allopolyploidy o Duplicate the genetic content because you united 2 ancestral species genomes increasing genetic content & ploidy level o Hybridization of 2 species o More than one ancestor o Example: grey tree frog AUTOPOLYPLOIDY, HOW? VIA MITOSIS nondisjunction: failure of sister chromatids (or homologus chromosomes) to separate in mitosis or meisosis no division AUTOPOLYPLOIDY, HOW? VIA MEIOSIS Genetics Lectures 13 &14 February 15, 2017 nondisjunction of ALL chromosomes in meiosis I COMMERCIAL CROPS Autopolyploid examples Ploidy Chromosome # Potatoes 4n 48 Banana 3n 33 Allopolyploid Examples ploidy Chromosome # Cotton 4n 52 Strawberries 8n 56 SUMMARY • A karyotype can be described as euploid (some number of full sets) or aneuploidy lubrications in individual chromosome numbers • Polyploidy can be normal in some species or cell types & can also result from mistakes in cell division producing atypical ploidy levels • Polyoloid species are either autopolyploid or allopolyploid. The difference between the 2 classifications is based on whether ploidy changes due to unreduced gametes alone or involved hybridization between species