chromosome number and karyotype

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

Human Heredity

Chapter 8Miss Pollack

Chromosome Numbers

• Each species has a set number of chromosomes in each cell

InsectsAnt# of

chromosomes: 2

PlantAdder’s fern

# of chromosomes:

1262

MammalsDog# of

chromosomes: 78

HumansMr.

Manuppelli# of

chromosomes:46

Organisms & Their Chromosomes

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

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)

Mom23

Individual chromosomes

Dad23

Individual chromosomes

Child46

total chromosomes (2n = diploid)

• 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

What is a karyotype?

• 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

23

• 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

• 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

the last pair #23

23

• 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

the first 22 pairs# 1 -22

Human Karyotyping

• How do you write what you see in a karyotype of a healthy, normal male or female? “#, sex chromosomes”

Male = 46, XYFemale = 46, XX

• 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

• 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

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

Homework

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