Inheritence
- Created by: boy_repellent
- Created on: 10-04-14 18:19
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- Inheritance in animals and plants
- Cell division and growth
- cell division is necessary for the growth or repair of damaged cells/tissues
- Mitosis results in two identical cells being produced from the original cell
- the chromosomes contain genes (alleles) which must be passed on to each new cell
- a copy of each chromosome is made before the cell divides and one of each chromosome goes to each new cell
- in early development of animal and plant embryos the cells are unspecialised (stem cells)
- most animal cells differentiate and cell division is mainly for repair and replacement
- plant cells can differentiate throughout the life of the plant as it grows
- cells of offspring produced by asexual reproduction are produced by mitosis from the parent cell. they contain the same alleles as the parent
- cell division is sexual reproduction
- cells in reproductive organs divide by meiosis to form gametes (sperm and ova)
- each gamete has one chromosome from each original pair, all cells are different from each other and the parent cell
- results in variation as the gametes from each parent cell fuse. so half of the genetic info is from the father and half from the mother
- at fertilisation, a single body cell with new pairs of chromosomes is formed
- a new individual then develops by this cell repeatedly dividing by mitosis
- Stem cells
- unspecialised
- are found in the human embryo and in adult bone marrow
- change into all the different types of blood cell (nerve cell, muscle cell etc)
- layers of cells in the embryo differentiate into all the cells the body needs
- stem cells can be used to cure some disorders
- DNA
- Mendel was the first person to suggest the idea of separately inherited 'factors'
- Mendel's 'factors' are now called genes
- chromosomes are made of DNA which is a very long molecule with a double helix structure
- Genes are short sections of DNA
- Every individual, except identical twins, has different DNA
- Genes are short sections of DNA
- Mendel was the first person to suggest the idea of separately inherited 'factors'
- Inheritance
- humans have 23 pairs of chromosomes, one pair are the sex chromosomes
- females have two X chromosomes (**) and males have an X and a Y chromosome (XY)
- Genes controlling the same characteristics are called alleles
- if an allele 'masks' the effect of another it is 'dominant'. the allele where the effect is 'masked' is 'recessive
- some genetic disorders are caused by a dominant allele and some by recessive allele
- the person only has to inherit one dominant allele to have the genetic disorder (polydactyly etc)
- the person has to inherit two recessive alleles to have the disorder (cystic fibrosis etc)
- some genetic disorders are caused by a dominant allele and some by recessive allele
- if an allele 'masks' the effect of another it is 'dominant'. the allele where the effect is 'masked' is 'recessive
- humans have 23 pairs of chromosomes, one pair are the sex chromosomes
- science and ethics of stem cells
- Embryonic stem cells can be used in medical research and treatments
- Embryos can be screened for genetic disorders (embryo screening)
- there are economic, social and ethical issues concerning the use of embryos and in embryo screening
- Cell division and growth
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