A Tour of the Chromosomes

Humans, giraffes, chickens, gorillas or watermelons are made of cells

a nucleus

chromosomes

46 chromosomes in all BODY cells
23 chromosomes in all SEX cells
Testes contain sperm cells
(23 chromosomes)
Ovaries contain egg cells
(23 chromosomes)
(23 pairs) (23 single chromosomes)

38 chromosomes in all body cells
...and in the sex cells??????
19 chromosomes in all sex cells

Why would sex cells have half the number of chromosomes as body cells?
This is perfect! I have 19 chromosomes in my egg cells as well. Together we can make a new kitten 1 cell big ....
with 38 chromosomes!!

Summarize What you have learned so far…

• A cat has 38 chromosomes in all body cells but 19 (half the amount) in its sex cells. Sex cells are called sperm cells in males and egg cells in females.
*Some organisms have male and female parts on the same organism
• The number of chromosomes varies depending on the organism
*chromosomes contain tightly wound DNA. When you uncoil it you can see the double helix.

Sex Cells Body Cells

DNA

• is D eoxyribo n ucleic a cid
• In one chromosome there is about 2 meters of
DNA (in a human body there are 3 trillion cells so there is 10-20 billion miles of DNA)
• That’s from here to Pluto 20 times + back 20 times

http://www.youtube.com/watch?v=VegLVn_1oCE&safe=active
• Watson was a _________________. Crick was a __________________. They worked at
Cambridge University in England.
• What did Rosalyn Franklin contribute to the discovery of DNA?
• What is the structure of DNA?

• Describe the structure of DNA.

• Describe the structure of DNA.
• Double helix (twisted ladder)
• Small sections of your DNA are your genes which determine your traits.
• Phosphate and sugar “backbone”
• 4 nitrogen bases
– Adenine (A)
– Thymine (T)
– Cytosine (C)
– Guanine (G)
A & T always pair together
C & G always pair together

• holds the genetic codes that determine your traits (hair color, eye color, height, probability for certain diseases)
• can be mutated
• holds information for directing all cell activities!!

DNA has to be copied to all new cells.
How does this happen?
• DNA (and all other cell parts) are “photocopied by MITOSIS!!!!!!!!!
Watch this mitosis video!
http://www.youtube.com/watch?v=-G-3BDlnK58
Mitosis helps you
*grow new cells
*replace injured/damaged cells

• Reproduce cells
• I nterphase, chromatin, chromosome
• Mitosis
– P rophase, disappear, spindle fibers, double stranded chromosome (called centromere)
– M etaphase, line (middle)
– A naphase, contract, apart , opposite sides
– T elophase, DNA, spindle fibers, nuclear membrane, chromatin
Cytoplasmic Division
-sets of DNA, cell membrane, cell plate
Daughter cells, begins again

• Homework
– Survey at least 20 people for 4 traits. Record results.
– Create a bar graph (see p. 588)
– Answer 3 questions on “Reading Human
Blueprint”
• In-class
– Onion cell mitosis (hand in as you finish)
• Mitosis Project due: Friday Sept 27

9-4 Projects for Friday, Tuesday Oct 1,
Wednesday Oct 3
• Victor-story
• Cyril Garry Alex – ppt
• Kenny Milan Peter-ppt
• Ella, Rachel – animation part 1, news report
• Harleen,Prasansa-music video-
IPAD
SMARTBOARD
PROJECTS FOR TUESDAY, OCT 1
• Falicity, Emily, Josh – candy poster
• Muge, Kirndip, Somin-3D model
• Owen, Vincent, Daniel, Devon
– animation
- song (live)
Shirliz, Bacy, Noelle, Melina – video
CANDY
WEDS
WEDS

• Review “Onion Cell
Mitosis”
• Hand in bar graphs
(with chart) AND 3 questions
ON SEPARATE PAPER!!
• Homologous
Chromosomes
• Homework: Patterns in
Human Traits
• Overdue work
• Tuesday is Lab B (Day 3)
• TEST-Fri Oct 4
-Weds Oct 9

• Hand in bar graphs
(with chart) AND 3 questions
ON SEPARATE PAPER!!
Today
• Homologous Chromosomes
• Homework: Patterns in
Human Traits
• Overdue work
• Quiz Wednesday (day 3,
3 periods)
*Mitosis
(higher level)
*DNA Structure
*Patterns in Human
Traits
• TEST-Mon Oct 7

Project Schedule for Next Week 9-9
• Tuesday Oct 1 • Wednesday Oct 2
(triple)

1. metaphase______
2. prophase________
3. telophase_______
4. interphase______
5. interphase_______
6. interphase_______
7. anaphase________
8. interphase______
9. anaphase______
10. interphase______
11. metaphase_______
12. telophase_______
13. interphase____
14. prophase_____
15. interphase_____
16. interphase______
17. metaphase_____
18. interphase_____
Math Problems
19. What percentage of the cells are in interphase?
8 out of 18
8/18 x 100 = 44%
20. What percentage of the cells are in metaphase?
3 out of 18
3/18 x 100 = 17%
21. A cell spends much more time in interphase than in mitosis.
22. The cell cycle is the continuous cycle of interphase, mitosis and
CYTOPLASMIC DIVISION
23. tissue, stomach lining or muscle, organ, lungs or stomach, organ system, digestive system or nervous system.

• Study of genes
• Genes for a certain trait are found on homologous chromosomes
• (see handout)

Review: Inside every human body cell’s nucleus….there are
46 chromosomes

Think of the 46 chromosomes instead as
23 pairs of homologous chromosomes
For example, chromosomes labelled “1” carry GENES for the same TRAIT

What does it mean to be dominant?
• powerful

• Raise your hand if you have blue eyes
• Keep it raised if you have one brown-eyed parent and one blue-eyed parent
• How was your eye color determined?
• It was determined by the genes found on your homologous chromosomes.
• We call the list of the 2 genes that an organism has for a particular characteristic their GENOTYPE
• Geneticists study genotypes

• 2 letter symbol
• Capital letter for the dominant gene and the same letter in lowercase for the recessive gene
• Examples: BB, Bb, bb
• Example: Genotype for brown eyes BB or Bb
• Example: Genotype for blue eyes bb
• Example Genotype for free earlobes Ff or FF
F dominant f (not dominant) recessive

• When a single characteristic has only 2 traits
(“either-or”) traits, we call the traits opposite traits
• Refer to the chart in your booklet
• A dominant gene is one that functions even when paired with a gene for the opposite trait.
• A recessive gene is one that does not function when paired with a gene for the opposite trait. It can only function (show) when it is paired with another recessive gene like itself.

• A person can be homozygous for brown eyes or heterozygous for brown eyes

• Refer to your chart
• Remember that the dominant gene is written in capital letters
• The recessive gene is written in lowercase letters
• Write the following genotypes: a) heterozygous brown eyes b) homozygous blue eyes

GREGOR MENDEL (1822-1884)- the
“father of genetics”

Mendel’s Observations & Conclusions
Conclusions Observations
• (A) Tall x tall 
• (D) Short x short 
• (C) Tall x short 
• (B) Tall x tall 

Mendel’s Observations & Conclusions
•
•
•
Observations
(A) Tall x tall
• (D) Short x short  offspring short
(C) Tall x short tall
(B) Tall x tall

 offspring tall
 offspring
¾ tall, ¼ short offspring
Conclusions
• All tall pea plants had PURE traits (homozygous tall)
• All short pea plants had
PURE traits (homozygous short)
• Short is recessive and so tall is dominant (short trait
DISAPPEARS)
• 75% dominant tall and 25% short

• Tall x tall
• Short x short
• Tall x short
• Tall x tall

Mendel’s Contributions:
• Alleles- the different forms a gene has for a trait
Examples: If the trait is eye color the alleles are: blue, green, brown

• Variation:
• Dominant:
• Recessive:
• Pure (homozygous)
• heterozygous

• Pure (homozygous):
• Heterozygous:

• Variation:
• Dominant:
• Recessive:
• Pure (homozygous)
• heterozygous

Complete “Writing Genotypes”
Complete Review
• Josh, Emily – if you are sitting together you need to move!!!
• Can a non-tongue roller be HOMOZYGOUS for that trait? (Note: tongue rolling is dominant)