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Lecture 4

BIOL 3P51 Lecture Notes - Lecture 4: Somatic Cell, Gamete, Webbed Neck
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21 Pages
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Fall 2018

Department
Biological Sciences
Course Code
BIOL 3P51
Professor
Amanda Lepp
Lecture
4

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BIOL 3P51 Lecture 4 15/10/2018
Chapter 9: Ploidy
Variation in # of Chromosomes
o Euploids
Contain ONLY complete sets of chromosomes
Usually diploid (2n)
Can also be monoploid (1 set) or polyploid (3 or more complete sets)
Can have polyploid at a cell level -> will cause disease.
Changes in the entire set of the chromosomes
Complete sets
1 complete set, 2 complete sets duplicated.
o Aneuploids
Chromosome number is not an exact multiple of haploid number (n)
E.g. Monosomic (2n -1) or trisomic (2n +1)
o Changes with in the 23 chromosomes ( lost 1)
o Humans are only aneuploids
Can’t handle polyploidy
The larger the chromosome that is duplicated (i.e. 1 vs 10) the more lethal
o Plants are polyploidy
Not just diploid
# of genomes
o Monoploid 1N
o Diploid 2N
o Triploid 3N
o Tetraploid 4N
o Pentaploid 5N
o Hexaploid 6N
o And so on……
o Difference between “haploid” and “monoploid”:
They are the same number, but haploid is the number of chromosomes in a
gamete -> ½ of the total chromosome number goes in each. A monoploid is the
complete set, how many different chromosomes are present in the organism’s
genome.
o Haploid refers to the number of genomes (and chromosomes) in a gamete. Monoploid is
a cell or individual with one complete genome as the genetic complement.
X vs N
o In most precise terms:
Haploid number = N = is the number of chromosomes in a gamete
i.e. half of 46, so 23
Monoploid number = X = is the number of chromosomes in a genome
# of unique chromosomes in a genome
Humans -> 23 -> the value is the same as haploid because it is diploid
Chromosome number = total number of chromosomes in a somatic cell
Ploidy number = number of chromosome sets
BIOL 3P51 Lecture 4 15/10/2018
SO… This table is incorrect
o Monoploid 1N
o Diploid 2N
o Triploid 3N
o Tetraploid 4N
o Pentaploid 5N
o Hexaploid 6N
o And so on……
Corrected: Numbers of Chromosomes
o Monoploid 1X and 1N
o Diploid 2X and 2N -> synonymous
o Triploid 3X -> no haploid number because they cannot divide equally
o Tetraploid 4X and 2N
o Pentaploid 5X -> no haploid number because they cannot divide equally
o Hexaploid 6X and 2N
o And so on……
o
BIOL 3P51 Lecture 4 15/10/2018
The common potato is a tetraploid, carrying 4 sets of chromosomes. Each vegetal (somatic) cell has a
complement of 48 chromosomes
1) What is the ploidy # -> 4
2) What is the chromosomes # -> 48
3) What is the haploid # -> 24
4) What is the monoploid # -> 12 (48/4=12)
Monoploid= total number of chromosomes divided by the ploidy number
Q1: if the haploid chromosome # of a plant is 16, how many chromosomes would a tetraploid have?
a) 16
b) 32
c) 24
d) 64
Monoploid number is 8
Hexaploid has 66 chromosomes
Ploid -> 6
N=33
X=11 -> 66/6
Monoploidy
o 1 of each unique chromosomes
o One genome
o Occurrence?
o Male wasps, ants are monoploid (some species)
Females reproduce sexually and are diploid and the males are produced from an
unfertilized egg (parthenogenesis)
o -> N’s are wrong in the diagram

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Description
BIOL 3P51 Lecture 4 15/10/2018 Chapter 9: Ploidy Variation in # of Chromosomes o Euploids Contain ONLY complete sets of chromosomes Usually diploid (2n) Can also be monoploid (1 set) or polyploid (3 or more complete sets) Can have polyploid at a cell level -> will cause disease. Changes in the entire set of the chromosomes Complete sets 1 complete set, 2 complete sets duplicated. o Aneuploids Chromosome number is not an exact multiple of haploid number (n) E.g. Monosomic (2n -1) or trisomic (2n +1) o Changes with in the 23 chromosomes ( lost 1) o Humans are only aneuploids Cant handle polyploidy The larger the chromosome that is duplicated (i.e. 1 vs 10) the more lethal o Plants are polyploidy Not just diploid # of genomes o Monoploid 1N o Diploid 2N o Triploid 3N o Tetraploid 4N o Pentaploid 5N o Hexaploid 6N o And so on o Difference between haploid and monoploid: They are the same number, but haploid is the number of chromosomes in a gamete -> of the total chromosome number goes in each. A monoploid is the complete set, how many different chromosomes are present in the organisms genome. o Haploid refers to the number of genomes (and chromosomes) in a gamete. Monoploid is a cell or individual with one complete genome as the genetic complement. X vs N o In most precise terms: Haploid number = N = is the number of chromosomes in a gamete i.e. half of 46, so 23 Monoploid number = X = is the number of chromosomes in a genome # of unique chromosomes in a genome Humans -> 23 -> the value is the same as haploid because it is diploid Chromosome number = total number of chromosomes in a somatic cell Ploidy number = number of chromosome sets BIOL 3P51 Lecture 4 15/10/2018 SO This table is incorrect o Monoploid 1N o Diploid 2N o Triploid 3N o Tetraploid 4N o Pentaploid 5N o Hexaploid 6N o And so on Corrected: Numbers of Chromosomes o Monoploid 1X and 1N o Diploid 2X and 2N -> synonymous o Triploid 3X -> no haploid number because they cannot divide equally o Tetraploid 4X and 2N o Pentaploid 5X -> no haploid number because they cannot divide equally o Hexaploid 6X and 2N o And so on o BIOL 3P51 Lecture 4 15/10/2018 The common potato is a tetraploid, carrying 4 sets of chromosomes. Each vegetal (somatic) cell has a complement of 48 chromosomes 1) What is the ploidy # -> 4 2) What is the chromosomes # -> 48 3) What is the haploid # -> 24 4) What is the monoploid # -> 12 (48/4=12) Monoploid= total number of chromosomes divided by the ploidy number Q1: if the haploid chromosome # of a plant is 16, how many chromosomes would a tetraploid have? a) 16 b) 32 c) 24 d) 64 Monoploid number is 8 Hexaploid has 66 chromosomes Ploid -> 6 N=33 X=11 -> 66/6 Monoploidy o 1 of each unique chromosomes o One genome o Occurrence? o Male wasps, ants are monoploid (some species) Females reproduce sexually and are diploid and the males are produced from an unfertilized egg (parthenogenesis) o -> Ns are wrong in the diagram BIOL 3P51 Lecture 4 15/10/2018 o Take the gametes from a diploid plant (pollen grains already through meiosis)and plate them on special media that will induce mitotic growth. Turn into embryoids then treated with plant hormone to induce the growth of shoots/roots and will have a monoploid plant that is sterile What is the benefit? Only have 1 copy of each chromosome so you can bring out any recessive traits you want usually only recessive alleles are resistant to herbicides o Have the herbicide to kill everything but tomatoes o If any of the cells are able to gain resistance, they will grow into embryoids Treat with plant hormone to growth up as a resistant plant Colchicine Induces the cells to double their chromosome number, messes up meiosis Can have a normal diploid plant that still has the mutation and is homozygous for it
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