1. Lecture #22 Honors Biology Ms. Day
Haploid vs Diploid
Lecture #22
Honors Biology
Ms. Day

2. REVIEW: Draw and Label the Pieces of a Duplicated Chromosome
chromatid
Sister chromatids
kinetochore
Spindle fibers
centromere
Gene band
(Duplicated) chromosome

3. Think: “t” for TWO chromatids
and
“d” for DUPLICATED

4. Different Types of Cells
There are 2 types of cells in an organism
Somatic cells: all body cells
2. Gametes: reproductive cells (sperm and egg)

5. Different cell types  different cell divisions
Eukaryotic cell division consists of
Mitosis = division of the nucleus
Called karyokinesis
Cytokinesis = division of cytoplasm
Occurs in somatic cells
In meiosis
Gamete cells are produced after chromosome number is cut in ½

6. Chromosome Number Gametes (sperm/egg) have 1 copy of each chromosome
called haploid (1n)
Somatic (body) have 2 copies of each chromosomes
called diploid (2n)

7. Haploid vs. Diploid
Haploid= when a cell has 1 copy of each chromosome.
Expressed as n = 23
Diploid= when a cell has 2 copy of each chromosome. (a.k.a TOTAL # of C’s in organisms)
Expressed as 2n = 46 n
Haploid sperm cell
Haploid egg cell n
Fertilization 2n
Diploid Zygote cell

8. Pairs of Chromosomes
Chromosomes have a “twin” (matching pair)
Ex: Human somatic cells have 23 PAIRS of chromosomes (total 46 C’s)
All pairs of chromosomes differ in size, shapes, and set of genes.
Homologous Chromosomes = chromosomes that are similar in shape, size, and genes.

9. Homologous Chromosomes
SIMILAR:
1. Size
2. Shape
3. Genes they carry
DIFFERENT
specific gene information (order of ATCG’s) B b

10. ZYGOTE = 1st diploid body cell of organism
Set of Chromosomes
Each chromosome set contain 2 “homologues” or “twins”
Each homologue is also called an autosome
A chromosome that does NOT determine gender
Each homologue in a pair comes from each parent!
Also have a “sex chromosome” pair
Chromosomes that DO determine gender
fertilization
ZYGOTE = 1st diploid body cell of organism

11. Sex cell has MANY chromosomes including 1 sex chromosome
Sex chromosomes vs. Sex cell (sperm/egg)…are NOT the same!!!
X or Y= sex chromosome
Sex cell has MANY chromosomes including 1 sex chromosome

12. Practice #1…How many chromosomes are present in…?
Organism Clue
Body Cell #
Sex cell #
Diploid # (2n)
Haploid # (1n)
a leaf cell of corn has 20 chromosomes
an egg cell of a gorilla has 24 chromosomes
a human liver cell has 46 chromosomes
a gamete of a housefly has 6 chromosomes 20 10 20 10 48 24 48 24 46 23 46 23 6 12 12 6

13. Practice #2…How many chromosomes are present in…?
What is the DIPLOID (2n) number of this organism?
Hint: Count ALL the chromosomes!!
2n = 8
X X
X X
X X XX
nucleus
What is the HAPLOID (1n) number of this organism?
n = 4

14. Practice #3…How many chromosomes are present in…?
What is the DIPLOID (2n) number of this organism?
2n = 12
X X
X X
X X
X X XX
X X
nucleus
What is the HAPLOID (1n) number of this organism?
1n = 6

15. Chromosomes Determine Your Gender
Humans have 23 pairs of chromosomes
22 pairs are autosomes (chromosomes that are NOT involved in making gender)
Also called homologous chromosome pairs
1 pair are sex chromosomes (NOT HOMOLOGOUS; different genes)
The sex chromosomes are “X” and “Y”
“XX” is a girl
“XY” is a boy X
Egg cells ALWAYS have “X” chromosome Y X Y

16. an ordered, visual representation of ALL chromosomes in a human cell
A karyotype
an ordered, visual representation of ALL chromosomes in a human cell
Arranged according to homologous pairs
5 µm
Pair of homologous
chromosomes
Centromere
Sister
chromatids

17. Chromosomes are photographed during METPHASE
(middle of mitosis)

18. Karyotypes (pictures of chromosomes)
Used to study chromosomes & look for LARGE mutations (ex: chromosomal translocations, deletions, extra chromosomes)
To make a karyotype
1. scientists take a picture of a cell’s chromosomes during metaphase and STAIN the chromosomes
2. Cut out the chromsomes and arranged them according to size and gene band pattern
3. They # the chromosome pairs
**Use #1 through 23
4. #23 = ALWAYS sex
chromosome pair
(not homologous…
NOT similar in genes it holds)

19. a REAL view…wow!!!