Electron Micrograph of Chromosomes taken from a somatic cell.
In humans, the diploid (2n) number of chromosomes is…46 chromosomes: 23 from dad, 23 from mom.
Karyotype – a picture of all the chromosomes in a cell of an organism
Single-stranded chromosomes… What stage of mitosis was this cell in?Anaphase or telophase
Homologous pairs are arranged by size and banding pattern;Pairs 1 22 are autosomes;
Pair 23 = sex chromosomes (XX = female, XY = male)
Pair #23Only males have a Y chromosomes. Who
determines baby’s gender?Dad does!
(sperm can have X or Y, egg can only have X)
The Making of a Karyotype
We Start Here
Karyotype PracticeLearn Genetics – University of Utah (in class)
The Biology Project Karyotype Activity (homework)Answer on a separate sheet of paper:
Patient karyotypes and diagnoses (Qs #1 & 2);Add brief description of genetic disorder/syndrome
(research) A1, A2B1, B2C1, C2
H
A
P
L
O
I
D
TRIPLOID
N or 1N, 1 of a kind
2N, 2 of a kind, A homologous pair
Egg cell or Sperm Cell
Body Cell
A term used to decribe if the cell is Haploid or if the cell is Diploid
Add the term Homologous / Homologue
462
FemaleMale
MomDad
Autosomes
Autosomes4422
1
Chromosome #1 is the largest and gets smaller as you progress to Chromosome #22………………………………………..
therefore Chromosomes #1 has more DNA and Chromosome #22 has the least amount of DNA
Cell ACell B
Cell BCell A
Somatic Cells have a full set of DNA, 46 chromosomes
2n = 46
Gametes have a ½ set of DNA, only 23 chromosomes because the other half of genetic material comes from the other parent during fertilization
(see meiosis slides)
Meiosis & Sexual Reproduction
In most sexually reproducing species, organisms have two sets of chromosomes (2n, diploid),
one from each parent…
Being diploid is awesome because…
…you get a backup copy
of each gene!!!
Sexual reproduction is awesome because…… it creates genetic diversity in a
population…
… which increases the chances that at least some will survive challenging
environmental conditions.
Meiosis
Keeps the species’ number of chromosomes constant from one generation to the next by creating haploid
gametes↓
Creates genetic diversity in gametes through crossing-over and random assortment of chromosomes
↓Allows for the sexual recombination of genetically
diverse gametes (during fertilization), creates genetically different individuals