This document discusses human chromosomes and karyotypes. It begins by explaining that each species has a specific number of chromosomes, and that humans do not have the greatest number. It then provides details on human chromosomes, including that humans have 46 total chromosomes composed of 23 pairs, with 22 pairs being autosomes and 1 pair being sex chromosomes that determine gender as either XX or XY. The document explains how to read a karyotype, including identifying the numbered chromosome pairs and whether it represents a male or female. It concludes with assigning a karyotype lab for students to complete.

1. Think. Pair. Share:
• Do humans have the greatest number of
chromosomes per cell because we are “the
most intelligent animals on Earth?”
– Why or why not? Write your ideas down in your
notebook
– Share with a partner
– Discuss as a class

2. Human Heredity
Chapter 8
Miss Pollack

3. Chromosome Numbers
• Each species has a set number of
chromosomes in each cell

4. Insects
Ant
# of
chromosomes:
2
Plant
Adder’s fern
# of
chromosomes:
1262
Mammals
Dog
# of
chromosomes:
78
Humans
Mr.
Manuppelli
# of
chromosomes:
46
Organisms & Their Chromosomes

5. Be aware that
• So no… we don’t have the greatest amount of
chromosomes and the number of chromosomes
does not relate to intelligence
• Some species of organisms have the same
number of chromosomes: (48)
– Potatoes
– Plums
– Orangutan
– Gorilla
• FOR THE MOST PART each species has a
different number

6. Humans & Chromosomes
• Total of 46 individual chromosomes
– kid gets an equal amount of chromosomes from
mom & dad
• 23 from mom’s egg = 1 set = haploid (1n)
• 23 from dad’s sperm = 1 set = haploid (1n)

7. Mom
23
Individual
chromosomes
Dad
23
Individual
chromosomes
Child
46
total
chromosomes
(2n = diploid)

8. • Chromosomes come in pairs (2)
• If we know we have 46 individual
chromosomes… how many pairs do we have?
– 46 ÷ 2 = 23 pairs
• Humans have 23 pairs of chromosomes
46
individual 23 pairs

9. What is a karyotype?

10. • Photograph shows the complete set of
chromosomes for an organism
• Photograph organizes chromosomes by pairs
– Pairs are matched together as homologous
chromosomes
– You can look at a karyotype and identify:
1. Species
2. Sex
Karyotype

11. 23

12. • Sex chromosomes
– Carries genetic information: male or female
• Autosomes
– Carries genetic information: what the species
will look like
– Information for everything else the cell requires
to live
2 Types of Chromosomes

13. • 2 chromosomes (1 pair) are called sex
chromosomes
– Always the last pair, #23, in the photograph
• They determine your sex
– Female
– Male
• If you are a female you get XX (large in size)
• If you are a male you get XY (X is large but Y is
only ½ the size)
Sex Chromosomes

14. the last pair
#23
23

15. • Other 44 chromosomes (22 pairs) are called
autosomes
– Perfectly matched up
– The first 22 pairs in the photograph
• They tell us what the species will look like, and all
other information required for the cell to live
• Get 1 copy from mom, 1 copy from dad to get a
pair
– 2 copies of each autosome are called homologous
chromosomes; same size, shape and genes
Autosomes

16. the first 22 pairs
# 1 -22

17. Human Karyotyping
• How do you write what you see in a
karyotype of a healthy, normal male
or female? “#, sex chromosomes”
Male = 46, XY
Female = 46, XX

18. • Chromosomes are in ordered pairs
numbered 1-23
– Pairs 1 through 22 are the autosomes
– The last pair, the 23rd pair, are the sex chromosomes
(XX or XY)
• Pairs are matched up as close as possible, based
on their “bands” or “stripes” which are genes
– These are the HOMOLOGOUS chromosomes
How to read a Karyotype

21. • Egg carry 23 chromosomes
– 1 is an X sex chromosome
• Sperm carry 23 chromosomes
– 50:50 chance that the sex chromosome is
X or Y
Who determines the sex of the child?
Sex Determination
Males, fathers

22. KARYOTYPE LAB
• Pass out the packets.
• Go over instructions together.
• PART C in class today
– Materials on front table

23. Homework
• Section 1 review:
– Questions 1-8
– Complete sentences for all except:
• 1 and 5