UNIT 3 GENETICS - Weebly · 2018-09-05 · UNIT 3 GENETICS LESSON #33: Meiosis and Genetic...

7
UNIT 3 GENETICS LESSON #33: Meiosis and Genetic Variation People copy every possible detail to try to impersonate Elvis. Do they come close to being like the King? Objective: Discuss how independent assortment and crossing over during meiosis results in genetic diversity.

Transcript of UNIT 3 GENETICS - Weebly · 2018-09-05 · UNIT 3 GENETICS LESSON #33: Meiosis and Genetic...

Page 1: UNIT 3 GENETICS - Weebly · 2018-09-05 · UNIT 3 GENETICS LESSON #33: Meiosis and Genetic Variation People copy every possible detail to try to impersonate Elvis. Do they come close

UNIT 3 GENETICS

LESSON #33: Meiosis and Genetic Variation

People copy every possible detail to try to impersonate Elvis.Do they come close to being like the King?

Objective: Discuss how independent assortment and crossing over during meiosis results in genetic

diversity.

Page 2: UNIT 3 GENETICS - Weebly · 2018-09-05 · UNIT 3 GENETICS LESSON #33: Meiosis and Genetic Variation People copy every possible detail to try to impersonate Elvis. Do they come close

Main Idea #1Sexual reproduction creates unique gene combinations.

Human cells have how many pairs of chromosomes?

Genetic variation within sexual reproduction results largely from: the independent assortment of chromosomes during meiosis and the mixing of alleles as gametes that join during fertilization.

23

Sexual reproduction produces offspring through the combination of ….?

Gametes

Gametes with 223 or about 8 million different combinations can be produced through the process of meiosis.

If sperm cells and eggs were combined at random, the total number of possible combinations is the product of 223 x 223 or more than 7 trillion.

Page 3: UNIT 3 GENETICS - Weebly · 2018-09-05 · UNIT 3 GENETICS LESSON #33: Meiosis and Genetic Variation People copy every possible detail to try to impersonate Elvis. Do they come close

Main Idea #1

Fruit fly gametes each have four chromosomes, representing 24 or 16, possible chromosome combinations. How many chromosome combinations could result from fertilization between a fruit fly egg and a sperm cell?

Sexual reproduction creates unique combinations of genes. The offspring of sexual reproduction is a mixture of both parents’ traits.

Each egg and sperm has 16 possible chromosome combinations, so the total number of possible combinations would be 16 x 16 = 256.

Page 4: UNIT 3 GENETICS - Weebly · 2018-09-05 · UNIT 3 GENETICS LESSON #33: Meiosis and Genetic Variation People copy every possible detail to try to impersonate Elvis. Do they come close
Page 5: UNIT 3 GENETICS - Weebly · 2018-09-05 · UNIT 3 GENETICS LESSON #33: Meiosis and Genetic Variation People copy every possible detail to try to impersonate Elvis. Do they come close

Main Idea #2Crossing over during meiosis increases genetic diversity.

Crossing over: the exchange of chromosome segments between homologous chromosomes during prophase I of meiosis.

Two homologous chromosomes pair up with each other during prophase 1 in meiosis.

In this position, some chromatids are very close to each other and segments cross.

Some of these segments break off and reattach to the other homologous chromosome

Crossing over results in new combinations of genes, and thus is also called recombination.

Page 6: UNIT 3 GENETICS - Weebly · 2018-09-05 · UNIT 3 GENETICS LESSON #33: Meiosis and Genetic Variation People copy every possible detail to try to impersonate Elvis. Do they come close

According to Mendel’s research, genes located on separate chromosomes assort independently. This independence is caused by the random assortment of chromosomes during meiosis.

What happens when two genes are both on the same chromosome? Will they display independent assortment as well? Or will they travel together as a unit?

It depends.

Page 7: UNIT 3 GENETICS - Weebly · 2018-09-05 · UNIT 3 GENETICS LESSON #33: Meiosis and Genetic Variation People copy every possible detail to try to impersonate Elvis. Do they come close

Genetic Linkage: genes located close together which tend to be inherited together.