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Lecture 4

BIOL 3P51 Lecture Notes - Lecture 4: Somatic Cell, Gamete, Webbed NeckPremium

21 pages101 viewsFall 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
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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
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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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