Mendel’s ‘factors’ are now called genes Genotype refers to the specific allelic composition of an individual 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
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Human Biology Stage 2B Revision – Test 1 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.
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* NCERT 1. Reproduction in Organisms INTRODUCTION Biology in essence is the story of life on earth. While individual organisms die without fail‚ species continue to live through millions of years unless threatened by natural or anthropogenic extinction. Reproduction becomes a vital process without which species cannot survive for long. Each individual leaves its progeny by asexual or sexual means. Sexual mode of reproduction enables creation of new variants‚ so that survival advantage is enhanced
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type of nuclear division that occurs to form four genetically different gametes. This produces genetically different offspring which all differ in traits‚ the reason this occurs is because of the way that the chromosomes are handled to make gametes. The general gist of meiosis is that a homologous pair is split twice to make four separate cells that have the haploid number of chromosomes meaning when they fuse with other gametes they form a zygote with the diploid number of chromosomes. There are
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Introduction to sexual reproduction in humans Reproduction is the process by which humans gives rise to new individuals. Sexual reproduction is the process that involves the fusion of two gametes‚ sperm (male gamete) and egg (female gamete). In human these gametes are produced in different sexes‚ the male and female. Reproduction in humans is performed by reproductive systems‚ the male and female reproductive systems. The main organs of male reproductive system are testis and gonads and of female
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to one set (haploid). The cells produced by meiosis are either gametes (the usual case in animals) or otherwise usually spores from which gametes are ultimately produced (the case in land plants). In many organisms‚ including all animals and land plants (but not some other groups such as fungi)‚ gametes are called sperm in males and egg cells or ova in females. Since meiosis has halved the number of sets of chromosomes‚ when two gametes fuse during fertilisation‚ the number of sets of chromosomes in
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A male (♂) organism is the physiological sex which produces sperm. Each spermatozoon can fuse with a larger female gamete‚ or ovum‚ in the process of fertilization. A male cannot reproduce sexually without access to at least one ovum from a female‚ but some organisms can reproduce both sexually and asexually. Most male mammals‚ including male humans‚ have a Y chromosome‚ which codes for the production of larger amounts of testosterone to develop male reproductive organs. Not all species share a
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asexual? Why? Sexual reproduction is a better mode of reproduction. It allows the formation of new variants by the combination of the DNA from two different individuals‚ typically one of each sex. It involves the fusion of the male and the female gamete to produce variants‚ which are not identical to their parents and to themselves. This variation allows the individual to adapt to constantly changing and challenging environments. Also‚ it leads to the evolution of better suited organisms which ensures
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(p. 172) 9.1 Discovery of Meiosis (p. 172; Figs. 9.1‚ 9.2) A. In 1882‚ Belgian cytologist Pierre-Joseph van Beneden discovered that the gametes of the roundworm Ascaris contained two chromosomes while somatic cells contained four. B. Fertilization 1. van Beneden proposed in 1887 that an egg and sperm could fuse to form a zygote. 2. The fusion of gametes is called fertilization or syngamy. C. Meiosis 1. A reduction division is required to reduce the number of chromosomes to half so sexual
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Male: Sperm Female: Ovum (egg) What happens to Gametes at Fertilisation? Fertilisation is the process where sperm (from the male) and the ovum (from the female) fuse together to form the zygote. Each gamete contains 23 chromosomes which combine together‚ in the zygote‚ to combine to a full set of 46 chromosomes – half from the father and half from the mother.. Summed up‚ it is where the male gamete and a female gamete join. The fusion of gametes enables the genetic information to mix. Proteins
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