1. Cell Reproduction

2. Cell Reproduction – Chromosomes 4.3
Each type of organism has a specific chromosome number.
Fly 8 Corn: 20 Dog: 78 Human: 46

3. Chromatin in Interphase
During interphase the chromosomes are not visible.
The DNA appears as a mass in the nucleus; the mass is called ___________.
chromatin

4. Chromosome in M-Phase
As the M phase begins the DNA coils up to form _______________.
When the chromosome first become visible, each chromosome consists of two identical ____________ joined by a ______________.
chromosomes
chromatids
centromere

5. One half of a duplicated chromosome is a chromatid.
centromere
One half of a duplicated chromosome is a chromatid.
Sister chromatids are held together at the centromere.
Sister chromatids

6. Now go to your Biology handout pages 120 -124 to complete the next set of questions:

7. Body Cells
Every cell in the human body other than sperm and egg cells are called __________ cells.
Each somatic cell contains 46 chromosomes or two sets of ______.
The 23 different chromosomes differ in size, shape and __________________.
A complete set of chromosomes is essential to survival.
somatic 23
Set of genes

8. Chromosomes
Each of the 23 pairs of chromosomes consists of two ______________ chromosomes (AKA homologues).
Each homologue in a pair comes from one of the two ___________. Therefore, the 46 chromosomes in somatic cells are actually 2 sets of 23 chromosomes, one set from the ____________ and one set from the _____________.
homologous
parents
mother
father

9. Chromosomes
When a cell contains two sets of chromosomes it is said to be _________.
Diploidy is represented as _______.
In humans, the diploid number is _______.
diploid 2n 46

10. Sex Cells
The sex cells, also called ___________, have only 1 set of chromosomes.
Gametes are ___________.
Haploid is represented by ________.
In humans, the haploid number is _____.
gametes
haploid n 23

11. Sex Cells
Why does it make sense that gametes have the haploid number of chromosomes?
sperm (23 chromosomes/1 set) + egg (23 chromosomes/1 set) = human zygote (46 total chromosomes)
***The human zygote is diploid

12. Chromosomes
Of the 23 pairs of human chromosomes, 22 are ______________.
Autosomes are not directly
involved in determining the
______ of an organism.
autosomes
sex
1 through 22 = autosomes

13. Determining Gender
There is 1 pair of chromosomes that will determine the sex of the organism called _____ chromosomes.
In humans and many other organisms, these two chromosomes are referred to as _____ and _____ chromosomes.
sex X Y

14. Determining Gender
The genes that cause a fertilized egg to develop into a male are located on the _____ chromosome.
An organism with a _____ chromosome is male, and without a _____ chromosome the organism is ___________. Y Y Y
female
male

15. Determining Gender
In humans, a male’s sex chromosomes are written as ______ and a female’s sex chromosomes are written as ______.
The sex (gender) of a human child is determined by the _________ parent.
Why?
Females have only XX to donate, but males may donate the X or Y; so males determine whether a male or female is produced. XY XX
male