Sex Cells and Meiosis

Sex Cells and Meiosis

Sexual Reproduction

• Two cells join= fertilization--->single cell that will develop into new organism

• Each sex cell has half the number of chromosomes found in a body cell

• The process that creates cells with a reduced chromosome count is Meiosis

Multiple Choice

How is the process of meiosis different from mitosis?

• Meiosis creates cells that are genetically identical

• Meiosis creates cells with half of the genetic info

Sex Cells

-Sex cells are also referred to as gametes (GAM-eets)

-Females gametes= egg cells

-Male gametes = sperm cells

-Each sex cell has half the number of chromosomes as the body cells, they are described as HAPLOID

Multiple Choice

What does the term 'haploid gamete' mean?

• A sex cell that has half of the genetic information as the body cell

• A body cell that has the full amount of genetic information as the parent cell

Chromosome Counts

- A single body cell from a particular organism contains a certain number of chromosomes

-Examples?

Human = 46

Dog = 78

Earthworm = 36

-The number of chromosomes in a body cell is called DIPLOID

Multiple Choice

If the body cell of a spider plant is 24, it's diploid number is 24. What is the haploid number of the gametes?

• 48

• 12

Multiple Select

Choose all that apply: How are body cells different from sex cells?

• Body cells contain a diploid number of chromosomes, sex cells are haploid

• Body cells contain the full number of chromosomes while sex cells only have half

• Body cells are found in the body and sex cells are not

Meiosis and Chromosomes

-Meiosis occurs in 2 stages

1. Chromosomes duplicate, cell divides and daughter cells have full chromosome count (like mitosis)

2. Daughter cells divide again, thus reducing the number of chromosomes by half

Multiple Choice

If a body cell contain 46 chromosomes: How many chromosomes will there be after the first meiotic division? How many after the second?

• 46, 23

• 92, 46

• 92, 23

Sperm and Eggs

- After Meiosis, there will be 4 sperm cells created

-After Meiosis, there will be 4 egg cells BUT 3 will not mature. Only 1 egg can be used for reproduction!!

=Ladies!!! Your eggs are limited and precious.

Visualizing Human Chromosomes

A visual called a KARYOTYPE is used to display chromosomes

-Organized by:

Length

Pairs

Genetic bands

Male sex chromosomes: XY

Female sex chromosomes: XX

The Exception to the Rule...

-Sometimes errors occur during meiosis and that can lead to chromosomal disorders like Trisomy 21 (Down's Syndrome)

Multiple Choice

What is the gender of the person who has this karyotype?

• Male

• Female