Analysis of Human Chromosomes 1. Karyotype preparation and analysis Cells (from blood‚ amniotic fluid‚ etc) are grown in vitro (in a cell culture dish) to increase their number Cell division is then arrested in metaphase with colchicine (prevents mitotic spindle from forming) Cells are centrifuged and lysed to release chromosomes Chromosomes are stained‚ photographed‚ and grouped by size and banding patterns This is a photograph of the 46 human chromosomes in a somatic cell‚ arrested in metaphase
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Independent assortment: During gamete formation‚ the segregation of any pair of hereditary determinants is independent of the segregation of other pairs Random sampling error N+N sperm N egg 3n endosperm Degrees of freedom Tetrad (bivalent) Mitosis produces daughter cells that are genetically identical Meiosis produces daughter cells that are not genetically identical The daughter cells contain only one homologous chromosome from each pair The daughter cells contain many different combinations
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diploid complement of chromosomes‚ the gametes‚ which fuse to form this zygote must contain half the number of chromosomes. This reduction of chromosome number occurs in two distinct sequential phases of meiosis‚ termed meiosis I and meiosis II. Both divisional sequences have sub-stages such as‚ prophase (I‚ II)‚ prometaphase (I‚ II)‚ metaphase (I‚ II)‚ anaphase (I‚ II)‚ and telophase (I‚ II) that is continued by cytokinesis (I‚ II)‚ which is not part of meiosis. The cell undergoes different changes
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any living cell of an organism‚ meiosis occurs only in special cells. In animals‚ meiosis is restricted to cells that form gametes (eggs and sperm). Each species has a characteristic number of chromosomes per somatic cell. Fruit flies have 8; normal humans have 46. They exist as homologous pairs (partners) that are similar in size and shape and carry the same kinds of genes. Thus humans have 23 homologous pairs. The full complement of 46 chromosomes is referred to as the diploid number (referring
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Science 9-Biology Observing Cell Division Lab Purpose: To use the microscope to observe and sketch plant cells and animal cells in various stages of the cell cycle. Equipment and Materials: Compound Microscope Laptops Prepared Slide of Onion (Allium) Root Tips Prepared Slide of Whitefish Mitosis BC Science 9 Text pg. 162-163 Part 1-Plant Cells Procedure: 1. Take a prepared slide of an onion tip root and observe it under low power
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Write your name here Surname Other names Edexcel International GCSE Centre Number Candidate Number Biology Unit: 4BI0 Science (Double Award) 4SC0 Paper: 1B Monday 9 January 2012 – Morning Time: 2 hours You must have: Ruler Calculator Paper Reference 4BI0/1B 4SC0/1B Total Marks Instructions Use black ink or ball-point pen. Fill in the boxes at the top of this page with your name‚ centre number and candidate number. Answer all questions. Answer the questions in the spaces provided
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Chromosome 13 Chromosomes are organized structures of DNA and protein found in a cell. There are normally 46 chromosomes in a human cell- 23 pairs. You should get 23 from your mother’s egg & another 23 from your father’s sperm. Sometimes these chromosomes can encounter a problem. The two main problems being deletion of a chromosome or an extra chromosome. Chromosome 13 is a chromosome that everyone has a pair of. It normally takes up about 3.5-4% of the total DNA in cells. There are
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Chapter 10 – Production of Gametes Gonads: Are the primary sex organs Secondary sex organs: Everything else‚ e.g. Seminal Vesicles Males Spermatozoa (sperm): Male gametes Scrotum: Single pouch of skin‚ divided into two sacs internally Lobules: Compartments filled with fine tubes called seminiferous tubules Seminiferous tubules: Fine tubes lined with cells that produce the male gametes. They eventually join together to form a short straight tubule. Interstitial cells: Between the seminiferous
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Sex Chromosomes Introduction Few people every wonder or care about their gender and why they are male or female.. Sex-determination system is a complex but fascinating progress‚ especially within reptiles‚ birds and insects. All living organisms begin with one eukaryotic cell; inside the nucleus of each cell contain thread-like structures called chromosomes. Chromosomes are once theorized to be derived from autosomes (chromosomes that are not sex chromosomes) and have changed into specific
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1. 2. 3. All of Allison’s eggs will carry the X chromosome and 50% of Allison’s egg cells will carry the recessive allele (hexa). 4.a. There is a 25% chance that Allison and Tim will have a baby boy who is heterozygous for Tay-Sachs. b. No‚ the baby boy will not have Tay-Sachs he will be a carrier for the disease. The boy would only have the disease if he was homozygous recessive. | X | Y | X | XX | XY | X | XX | XY | 1:2 1:2 | T | t | T | TT | Tt | t | Tt | tt
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