Meiosis & Karyotypes

By Mr. Simonds

EQ: How are traits passed from parents to offspring?

Vocabulary

Meiosis – A type of cell division that produces sex cells with half the normal number of chromosomes.

Meiosis I

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Meiosis II

Gametes – Sex cells (sperm and eggs)

Haploid – The name for a cell that has half of its normal number of chromosomes. Ex. Gametes

Somatic Cells – Every non-sex cell (skin, nerves, muscle, etc)Diploid

Diploid – The name for a cell that has two of every type of chromosome.

Humans have 23 pairs of chromosomes. That makes a total of 46 chromosomes.So our diploid number is 46.

In each of our sex cells we have 23 chromosomes, one of each type.So our haploid number is 23.

Healthy Human Male

If the diploid number of an organism is 10, what is the haploid number?5

If the haploid number of an organism is 15, what is the diploid number?

Homologous Chromosomes – A pair of the same type of chromosomes. You get one from your mom and one from your dad.

Review

How many chromosomes would one of your skin cells have?46

What is the haploid number for humans?23

Review

What are gametes?Sex cells (sperm and eggs)

How many chromosomes do human gametes have?23

If an organisms haploid number is 20 what is its diploid number?40

Karyotyping

By Mr. Simonds

What is a Karyotype

Karyotype - a picture of a person’s chromosomes matched by pairs and arranged in order.

To make a karyotype you need a picture of a persons DNA in chromosome form

Then you match up chromosomes in pairs (23 pairs, including sex chromosomes)

Reasons for Karyotyping

To check for genetic (chromosomal) disorders such as:Down syndromeKlinefelter syndromeTurner syndrome

What are the pairs?

Autosomes – Chromosomes 1-22, they control most of the traits that make you.

What are the pairs? Sex Chromosomes – The 23rd pair of chromosomes

(X & Y), they determine your sex (male or female).

Chromosomes & Gender

A female has two X chromosomes.

A male has one X and one Y chromosome.As long as there is a Y chromosome the

fetus will become a male.

Karyotype of a Healthy Female

Karyotype of a Healthy Male

Down Syndrome – A disorder caused by an extra 21st chromosome. It causes delays in physical and intellectual development

Also called Trisomy 21 Occurs in 1 out of every 800 live births

Down syndrome is not related to race, nationality, religion or socioeconomic status. The most important fact to know about individuals with Down syndrome is that they are more like others than they are different.

What is Down Syndrome?

Down Syndrome

Turner Syndrome

Turner Syndrome – caused by having only one X chromosome. People with Turners become female.

Occurs in 1 in 2000 to 1 in 2500 live births.

Symptoms include short stature and lack of ovarian development. (They are sterile.)

Klinefelter Syndrome

Klinefelter Syndrome – Caused by having two X and one Y chromosome. People with this become male.

Occurs in 1 in 500 to 1 in 1000 live births.

They are often tall and usually do not develop secondary sex characteristics such as facial hair, or underarm and pubic hair.

How do these disorders occur?

Prophase II Metaphase II

Anaphase II

*Note that two of the chromosomes did not separate during anaphase

How do these disorders occur?

Non-disjunction – When chromosomes fail to separate during meiosis. This causes most chromosomal disorders.

Anaphase II

*Note that two of the chromosomes did not separate during anaphase

How non-disjunction occurs.

Telephase Gamete A Gamete B

* Note that Gamete A has one extra chromosome and Gamete B has one less chromosome

Review

Mitosis & Karyotypes (+ a little DNA)

Meiosis

Does the father or the mother cause the sex of the baby?Father

Why?The mother can only donate an X

chromosome

Healthy Human Female

Metaphase

Down Syndrome

Prophase

Chromosomes formed

Nucleus membrane breaking down

Healthy Human Male

Meiosis

What cells undergo Meiosis?Sex Cells

How much DNA or Chromosomes do you have after Meiosis?Half as much

What cells undergo Mitosis?Body cells (Everything except for Sex cells)

Meiosis

What does Haploid mean? Half the number of Chromosomes

An organisms Diploid number is 12. What is its haploid number? 6

You have two of each type of chromosomes. Where do you get them from? One from your mom & one from your dad

Anaphase

Chromosomes separating

What happened?

Metaphase II Anaphase II

Non-Disjunction

Telephase/ Cytokinesis

Which ones pair together?

DNA

What do you make during Transcription?mRNA

What process makes protein from mRNA?Translation