chromosome number and karyotype
TRANSCRIPT
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
• 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
• 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
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