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

Mom or DadDad

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

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

Meiosis Movie Time! 1. Focus on finding differences between meiosis and mitosis –

when you see something different, tell Mrs. Nordstrom “STOP!”

2. Keep your meiosis w.s. on your desk during the movie so you can identify the stages.

3. Complete your meiosis w.s. (due tomorrow, section 8.3 in text)

*Leave ppt*

*During the movie, just refer to the diagrams.*

*Complete the meiosis w.s. by labeling the phases and sorting the stages into the blanks.*

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.