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Diploid to Haploid Donna Huffman Biology Lab Instructor Calhoun Community College.

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Presentation on theme: "Diploid to Haploid Donna Huffman Biology Lab Instructor Calhoun Community College."— Presentation transcript:

1 Diploid to Haploid Donna Huffman Biology Lab Instructor Calhoun Community College

2 Introduction l All living things must reproduce to survive. l All body or somatic cells reproduce by mitosis which is simple cellular reproduction. l All sex cells must reduce their chromosome number as they divide. This reduction division is called meiosis and changes the chromosome number from to l All sex cells must reduce their chromosome number as they divide. This reduction division is called meiosis and changes the chromosome number from Diploid to Haploid. l Each offspring resulting from the combination of haploid sex cells will contain the same chromosome number as their parents.

3 The Big Picture Mitosis Meiosis somatic (body) cells sex cells (sperm or egg) 2N Diploid 2N 1N 2N = Diploid 1N = Haploid

4 Diploid vs. Haploid l = Full complement of chromosomes found in any somatic cell of an organism l Diploid (2N) = Full complement of chromosomes found in any somatic cell of an organism l = Half the number of chromosomes found in a diploid cell. Sex cells have a haploid number of chromosomes. l Haploid (1N) = Half the number of chromosomes found in a diploid cell. Sex cells have a haploid number of chromosomes. Human cheek cells have 46 chromosomes. (Diploid) Human sex cells have 23 chromosomes. (Haploid) For example:

5 Meiosis Fertilization malefemale sex cell production sex cell production spermegg 2N 1N Diploid Haploid Diploid Zygote

6 Somatic Cells Cheek cell nuclei l Each somatic cell nucleus contains the or number of chromosomes. l Each somatic cell nucleus contains the 2N or diploid number of chromosomes. l Each of these human somatic cheek cells contains 46 chromosomes. l Each nucleus has all the information needed for an entire organism. 2N

7 Photomicrograph of Nuclear Chromosomes

8 Meiosis Meiosis in the male and female divides each diploid cell into 4 haploid sex cells. 2N1N

9 At what point in Meiosis does the chromosome number change from Diploid to Haploid? The homologous pair in Prophase I separates in Anaphase I thus changing the number of the chromosomes from Diploid to Haploid. centromere =2N Prophase I 1N Anaphase I 1N Telophase II

10 Female Meiosis: Oogenesis Oogenesis occurs within the ovary as an develops into a containing an Oogenesis occurs within the ovary as an immature follicle develops into a mature follicle containing an egg. immature follicle mature follicle with egg

11 Female: Diploid to Haploid 2N1N Ovary Egg producing Follicle Egg

12 Male Meiosis: Spermatogenesis Spermatogenesis occurs in the testis as cells within the wall of the seminiferous tubule divide from somatic cells into mature sperm. Spermatogenesis occurs in the testis as cells within the wall of the seminiferous tubule divide from diploid somatic cells into mature haploid sperm. 2N 1N seminiferous tubule mature sperm

13 Male: Diploid to Haploid Testis 10X photomicrograph of testis cross section Sperm 2N 1N

14 The haploid sperm nucleus may unite with the haploid egg nucleus resulting in a diploid zygote, and thus the cycle of life begins again. = 2N 1N + 1N Conclusion


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