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February 14, 2011 Honors Biology Block 1 K.J. Gary

February 14, 2011 Honors Biology Block 1 K.J. Gary. Today’s Topics. 1. Chromosomes 2. Karyotyping 3. Cell Cycle. Chromosome. a single piece of tightly coiled DNA Found in the Nucleus (during cell division) in Eukaryotes. Found in the Nucleoid in Prokaryotes Contains Genes

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February 14, 2011 Honors Biology Block 1 K.J. Gary

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  1. February 14, 2011Honors Biology Block 1K.J. Gary Today’s Topics 1. Chromosomes 2. Karyotyping 3. Cell Cycle

  2. Chromosome • a single piece of tightly coiled DNA • Found in the Nucleus (during cell division) in Eukaryotes • Found in the Nucleoid in Prokaryotes • Contains Genes • Humans should have 23 pairs • numbered based upon size and placement of centromere with the largest being 1 and the smallest being 22

  3. Gametes . . . • Male Gamete = the Sperm • single cell containing half of the father’s original genetic composition (DNA) • Female Gamete = the Ovum • Single cell containing • half of the mother’s • genetic composition

  4. Chromosome . . . continued • 23 Pairs. . . • One set of 23 chromosomes is inherited from the biological mother – Ovum (female gamete), The other set is inherited from the biological father - sperm (male gamete) 22 look the same in both males and females- (homologous) Autosomes • The 23rd pair = Sexchromosomes, differ between males and females.

  5. Chromosomes . . . • 23rd Pair . . . Sex Chromosomes differ between males and females. • Females have 2 copies of the X chromosome, males have one X and one Y chromosome. • Human Ovumcan carry only an X chromosome • Sperm may carry either an X or a Y • male sperm determines the sex of a zygote. if the zygote has 2 X chromosomes – female. if it has an X and a Y chromosome – male.

  6. Chromosomes . . . !

  7. Karyotyping – Studying Chromosomes • Chromosomes carry DNA • DNA transcribes Genetic information • (Q & A) What if we could read the information on the • chromosome??

  8. Karyotyping – Studying Chromosomes . . . • Yes We Can… • Karyotyping involves the mapping of chromosomes. • A Map of a all 46 Chromosomes is called a Karyotype • Each Chromosome holds ‘sections’ a.k.a. Alleles • Alleles are specific locations of genetic coding • Ex. Alleles for eye color are found on chromosomes 15 & 19 (homozygous, heterozygous,…)

  9. Karyotyping – Studying Chromosomes • Numerical Abnormalities: • missinga chromosome from a pair (monosomy) • more than 2 chromosomes of a pair (trisomy). Ex. Down Syndrome, also known as Trisomy 21 > 3 of chromosome 21, (rather than two).

  10. Karyotyping – Studying ChromosomesStructural Abnormalities: Structure is altered 1. Deletions: A portion of the chromosome is missing or deleted. 2. Duplications: A portion of the chromosome is duplicated, resulting in extra genetic material. 3. Translocations: A portion of 1 chromosome is transferred to another. 4. Inversions: A portion of the chromosome has broken off, turned upside down and reattached. Genetic material is inverted. 5. Rings: A portion of a chromosome has broken off and formed a circle or ring. This can happen with or without loss of genetic material.

  11. 2 Types of Cells . . . • 1. Germ Cells: a reproductive cell - sperm or ovum • 2. Somatic Cells: ALL other cells in the body. On to Cell Cycle

  12. Cell Cycle • Interphase • Mitosis • Interphase has 3 stages • G1 (Gap 1) [sub phase : Gap- O] • Synthesis (S) • G2 (Gap 2) (Some acknowledgement of a G-0 ‘rest’ phase in cells that divide less frequently or are denied progression on to mitosis)

  13. G1 Phase (. . . follows mitosis) • Growing phase of the cell (ab. 2x in size) (Remember - cell is taking in and releasing molecular products during this time, using active and passive transport.) • Protein synthesis/ enzyme synthesis is occurring • More organelles are being produced

  14. S Phase – DNA Replication • DNA Synthesis commences • Proteins called Histones are produced – condense chromosomes • At start, each chromosome has only 1 DNA molecule • At end each chromosome has 2, genetically identical DNA strands • When the cell divides (in mitosis) Each will have a identical copy.

  15. G2 Phase – Final Prep. • More synthesis of organelles and ribosomes, as well as microtubules • - which will be needed for Mitosis (M)

  16. MITOSIS . . . To come • Cell now DIVIDES – MITOSIS

  17. Review . . . 1. How many Autosomes are there? 2. What is a Karyotype? 3. A Male Zygote would have to have acquired 1___ chromosome and 1 ____ chromosome. 4. What is the 23rd set of chromosomes known as? 5. The female gamete is also known as the ______. 6. The specific site on a chromosome which can indicate genetic expression is called ________. 7. ______ is a genetic disease, and an example of numerical abnormality found at the 21st chromosome.

  18. Review . . . 8. What is the final phase that occurs before Mitosis? 9. ____ and _____ are examples of Germ Cells. 10. _____ refers to a structural abnormality where a portion of a chromosome is missing. 11. The result of the phase is that there are 2 identical strands of DNA.

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