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Chromosomes and Cell Reproduction

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2 Chromosomes and Cell Reproduction
Chap. 6 Section 1

3 Chromosomes – Formation of new Cells by Cell Division
Cell division occurs in humans & other organisms at different times in their lives The type of cell division differs depending on the organism & why the cell is dividing Reproduction, growth, development, repair, or asexual reproduction, or formation of gametes

4 Gametes – an organism’s reproductive cells- such as sperm or ovum (egg) cells
All information stored in DNA must be present in each resulting cells DNA is first copied – then distributed Each cell ends up with a complete set (copy) of DNA

5 Prokaryotic Cell Reproduction
Prokaryote’s single DNA molecule is circular & is attached to the inner cell membrane Binary fission – a form of asexual reproduction that produces identical offspring Occurs in 2 stages – 1st,DNA is copied 2nd, cell divides

6 Binary fission animation

7 Bacterial Growth

8 Eukaryotic Cell Reproduction
Information encoded in DNA organized into units called genes Gene- a segment of DNA that codes for a protein or RNA molecule Genes play an important role in determining how a person’s body develops & functions

9 Chromosomes – the DNA & the proteins associated with DNA- are copied and become visible
Chromatids – the exact copies of DNA that make up each chromosome Centromere – point of attachment of the chromatids Chromatids become separated during cell division, new cell will have same genetic information as original cell

10 How Chromosome Number and Structure Affect Development
Somatic cell – any cell other than sperm or egg cell Humans normally has two copies of 23 different chromosomes which differ in size, shape, and set of genes Each chromosome contains thousands of genes which determines how you develop & function

11 Sets of Chromosomes Homologous chromosomes-chromosomes that are similar in size, shape, and genetic content 23 – from each parent Diploid- containing two sets of chromosomes, such as somatic cells Haploid- contains one set of chromosomes, such as gametes

12 The symbol n is used to represent one set of chromosomes
Zygote- is a fertilized egg cell, the first cell of a new individual Each organism has a characteristic number of chromosomes P. 121 Table 1 see chart

13 Sex Chromosomes Autosomes-chromosomes that are not directly involved in determining the sex (gender) of an individual in humans 22 pairs Sex chromosomes –contain genes that will determine the sex of the individual Often referred to as “X” and “Y” chromosomes

14 In humans, a female is XX; while a male is XY
The structure & number of sex chromosomes vary in different organisms Some insects there is no Y chromosome- the female is XX, but the male is XO (O indicates the absence of a chromosome) In birds, moths, & butterflies, the male has two X, while female has only one

15 Change in Chromosome Number
The presence of all 46 chromosomes is essential for normal development & function Trisomy- humans with more than two copies of a chromosome, will not develop properly Karyotype-a photo of the chromosomes in a dividing cell that shows the chromosomes arranged by size

16 Make a Karotype

17 Trisomy 21(an extra 21 chromosome), also Down syndrome all have similar characteristics
Mothers younger than 30,1 in 1500 births Mothers 37 & older, 1 in 290 births Mothers over 45, as high as 1 in 45 births As a female ages, her eggs can accumulate an increasing amount of damage

18 Disjunction-when sperm and egg cells form, each chromosome & its homologue separate
Nondisjunction- chromosomes fail to separate-one new gamete ends up with both chromosomes & the other gamete none Trisomy occurs when the gamete with both chromosomes fuses with a normal gamete

19 Prenatal Testing Amniocentesis Choriconic villi

20 Change in Chromosome Structure
Mutations- change in an organism’s chromosome structure Deletion- a piece of a chromosome breaks off completely- can be fatal Duplication-a chromosome fragment attaches to its homologous chromosome, which will now carry two copies of certain set of genes

21 Inversion – the chromosome piece reattaches to the original chromosome but in reverse orientation
Translocation-a piece reattaches to a nonhomologous chromosome

22 Homework Do section 1 key terms (definitions) 13 words
Section 1 review p. 124 Questions 1-5 write the question

23 The Cell Cycle section 2

24 Cell Cycle

25 The Life of a Eukaryotic Cell
The Cell Cycle is a repeating sequence of cellular growth and division during the life of an organism Cell usually spends 90% of its time in the first 3 phase of the cycle, which are called interphase Last 2 phases of cell cycle will only occur if the cell is about to divide

26 First growth (G1) phase-cell grows rapidly- carries out routine functions- some cells stay in this phase Synthesis (S) phase- Cell’s DNA is copied-two chromatids attached at the centromere Second growth (G2) phase- preparations are made for the nucleus to divide – microtubules are rearranged in preparation for mitosis- repair of DNA mistakes

27 Cell Cycle Animation

28 Mitosis- process during cell division in which the nucleus of a cell is divided into two nuclei-same number & kinds of chromosomes as original cell Cytokinesis- the process during cell division in which the cytoplasm divides Cell cycle may be summarized as follows: G1 - S – G2 - M - C

29 Cell cycle virtual lab

30 Control of the Cell Cycle
Cells have a set of “red light-green light” switches that are regulated by feedback information from the cell Cell cycle is controlled by many proteins Cell growth (G1) checkpoint- makes the decision of whether the cell will divide

31 During S phase, DNA is copied, if conditions not favorable, cells can typically stop the cell cycle
DNA synthesis (G2) checkpoint - DNA repair enzymes check DNA replication – if okay, mitosis occurs Mitosis checkpoint – triggers the exit of mitosis – also signals the beginning of the G1 phase

32 When Control is Lost: Cancer
Genes contain information necessary to make proteins Proteins control cell growth & development Cancer- uncontrolled growth of cells – a disorder of cell division Mutations over producing growth-promoting molecules or inactivating the control proteins that act to slow or stop cell cycle

33 Cancer Map

34 Cancer Biology

35 Homework Section 2 review 1-4 page 127 Section 2 Key terms page125
Chapter review page 134 2, 7-8,12,14,17

36 Mitosis & Cytokinesis section 3
Cells receiving the signal to divide continue past the G2 phase – enter the last 2 phases of the cell cycle-mitosis & cytokinesis During mitosis, chromatids are physically moved to opposite sides of the dividing cell with the help of spindles

37 Forming the Spindle Spindle-cell structure made of both centrioles & microtubule fibers that move chromosomes during cell division Centrosome – organelle that organizes the assembly of the spindle Centrioles & spindle fibers of hollow tubes of protein –microtubules Spindle fiber-individual; centrioles- 9 triplets arranged in a circle Plants don’t have centrioles

38 Separation of Chromatids by Attaching Spindle Fibers
Microtubules attach to the centromeres & poles, the two chromatids can be separated Once separated, the chromatids move along paths described by microtubules When chromatids are separated, they are called chromosomes

39 Mitosis & Cytokinesis Divided into 4 phases:
Step 1 Prophase – chromosomes coil up & become visible; nuclear envelope dissolves & a spindle fiber forms Step 2 Metaphase – chromosomes move to the center of the cell & line up along the equator; spindle fibers link the chromatids of each chromosome to opposite poles

40 Step 3 Anaphase – chromatids divide (now called chromosomes) move toward opposite poles as spindle fibers shorten Step 4 Telophase – nuclear envelope forms around the chromosomes at each pole; chromosomes begin to uncoil & spindle dissovles & disappear – Mitosis complete

41 Cytokinesis The cytoplasm divides in half, cell membrane grows to enclose each cell, forming two separate cells Two genetically cells where there was one Cells lacking cell walls, the cell is pinched in half by protein threads

42 Cells with cell wall - vesicles formed by Golgi apparatus fuse at midline to form cell plate
Cell wall forms on either side of cell plate Offspring cells – about equal size; identical copy of the original chromosomes; & receives about ½ of original cytoplasm & organelles






48 Homework Write question Section 3 Review page 132 1-4
Chapter review page 134 1,3-6,9,10,11 STP 1-3 Bonus Page 129 Calculating the number of cells resulting from Mitosis show work

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