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Happy Friday! Please do the following: pick up the handouts

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Presentation on theme: "Happy Friday! Please do the following: pick up the handouts"— Presentation transcript:

1 Happy Friday! Please do the following: pick up the handouts
get a chrome-book and get out your Oreo Mitosis lab – you have 15 minutes to submit your video link https://www.youtube.com/watch?v=gwcwSZIfKlM

2 REPRODUCTION All living things can reproduce themselves:
Asexual reproduction Sexual reproduction

3 REPRODUCTION Asexual reproduction occurs when a single organism produces offspring on its own. The prefix a- means without. This produces offspring that are genetically identical to their parents.

4 REPRODUCTION Sexual reproduction begins with the sperm and egg…but where did the sperm and egg come from?

5 Where it all began… Zygote
You started as a cell smaller than a period at the end of a sentence… Zygote

6 How did you get from a single zygote to 100 trillion cells?
And now look at you… How did you get from a single zygote to 100 trillion cells?

7 Answer: Mitosis What is mitosis? Why is cell division important?
amoeba What is mitosis? a parent cell creates two genetically identical daughter cells Why is cell division important? Growth Repair Unicellular organisms Cell division = reproduction Reproduces entire organism& increase population Multicellular organisms Cell division provides for growth & development in a multicellular organism that begins as a fertilized egg Also use cell division to repair & renew cells that die from normal wear & tear or accidents

8 Mitosis Which cells undergo mitosis?
amoeba Which cells undergo mitosis? Somatic cells aka regular body cells Skin cells Fingernail cells Bone cells Somatic cells contain 2 complete sets of chromosomes. That makes somatic cells DIPLOID (2n) Unicellular organisms Cell division = reproduction Reproduces entire organism& increase population Multicellular organisms Cell division provides for growth & development in a multicellular organism that begins as a fertilized egg Also use cell division to repair & renew cells that die from normal wear & tear or accidents

9 You have 2 sets of chromosomes
1 set of chromosomes came from your mother (n) 1 set of chromosomes came from your father (n) Chromosomes are found in homologous pairs (two of each chromosome – 2n) DIPLOID

10 REPRODUCTION Sexual reproduction occurs when two organisms share genetic material to create offspring. This creates offspring that are different from both parents & genetically unique. +

11 Typical Human Family Tree
During sexual reproduction, organisms must share their chromosomes without adding or subtracting from the total number. This means that they must create special haploid cells with only one of each chromosome for sexual reproduction.

12 Creating Haploid Cells
Meiosis Creating Haploid Cells 12 12

13 The zygote is a unique genetic mixture of both parents.
What is Meiosis? Meiosis is: Cell division that halves the # of chromosomes The process that germ cells go through to produce gametes (sperm & egg) Fundamental basis of sexual reproduction Diploid (2n)  Haploid (n) The zygote is a unique genetic mixture of both parents. 13

14 Meiosis Forms Haploid Gametes
Meiosis must reduce the chromosome number by half Fertilization then restores the 2n number from mom from dad child too much! meiosis reduces genetic content The right number!

15 Meiosis – 2 Cell Divisions
15

16 Question: 10 chromosomes (haploid or 1n)
A cell containing 20 chromosomes (diploid) at the beginning of meiosis would, at its completion, produce cells containing how many chromosomes? 10 chromosomes (haploid or 1n) 16

17 Facts About Meiosis daughter cells contain half the number of chromosomes as the parent cell produces gametes (sperm & egg) occurs in the testes in male occurs in the ovaries in females 17

18 Gene Recombination This creates offspring that are similar to
A pair of the same chromosomes, one from mom and one from dad, get blended together to form a single chromosome that is a mixture of both parents DNA. This creates offspring that are similar to both parents, but genetically unique.

19 Increasing the genetic variations in a population is an important role of meiosis. Meiosis does not create new genes; however, it creates new combinations of genes.

20 Homologous chromosomes recombine to create new gene combinations.
Genetic variations are increased even further through the process of crossing over. Homologous chromosomes recombine to create new gene combinations.

21 CROSSING OVER Homologous chromosomes in a tetrad cross over each other
Pieces of chromosomes or genes are exchanged Produces Genetic recombination in the offspring

22 The Significance of Meiosis
Meiosis helps create genetically unique offspring. Meiosis reduces the number of chromosomes to create haploid gamete cells. Meiosis increases genetic variations and creates new combinations of genes.

23 Is there anything that can go wrong during meiosis?
Yes! It is called nondisjunction. Chromosomes don’t separate properly and some gametes end up with too many or not enough chromosomes. Monosomy Trisomy

24 Mutations sperm egg Only mutations that occur in gamete cells are passed on to the organisms offspring. Mutations to gamete cells usually occur during the process of meiosis.

25 Chromosomal mutations are typically the result of mistakes that occur when chromosomes cross-over.

26 Let’s review Mitosis Meiosis makes genetically unique cells
makes genetically identical cells allows asexual reproduction allows sexual reproduction occurs in somatic cells occurs in germ cells new cells have full set of chromosomes (diploid) new cells have half set of chromosomes (haploid) number of divisions – 1 number of divisions – 2 makes 4 daughter cells makes 2 daughter cells 26


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