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B13 Revision - Reproduction - Coggle Diagram
B13 Revision - Reproduction
Types
Asexual
No fusion of gametes and only 1 parent. no mixing of genetic information, leading to genetically identical offspring.
Needs only 1 parent, time and energy efficient. Faster than sexual reproduction. Many identical offspring are produced.
Sexual
Only mitosis involved. Fusion of male and female gametes by meiosis. leads to formation of non-identical. Sperm and egg in animals. Pollen and egg in plants. Mixing of genetic information that leads to variation.
Produces variation, helps survival through natural selection of environment changes.
Cell division
Meiosis
Cells in reproductive organs divide to from gametes.
Genetic material is copied and then cell divides twice to form 4 gametes, with single set of chromosomes.
Fertilisation
Gametes join to restore normal number of chromosomes. New cell divides by mitosis. Number of cells increase and embryo develops, cells differentiate.
DNA & Genome
Genome
Organism is entire genetic material of that organism.
Great importance for medicine in future.
DNA
Polymer made up of two strands forming a double helix.
Small section of DNA on chromosome. Each gene codes for a particular sequence of amino acids, to make a specific protein.
Inheritance
Some characteristics are controlled by a single gene. Each gene may have different alleles.
Alleles / genotype operate at a molecular level to develop characteristics that can be expressed as phenotype.
If two alleles are same, individual is homozygous, but if different they are heterozygous.
Dominant allele is always expressed in phenotype. Recessive allele is only expressed if two copies are present.
Most characteristics are the result of multiple genes interacting, rather than a single gene.
Genetics
Human females sex chromosome are homozygous- XX. Male sex chromosome are heterozygous - XY.
Inherited disorders
Polydactyly
Dominant allele
Inherited from either / both parents
Cystic fibrosis
Recessive allele
Inherited from both parents
Screening
Cells from embryos / fetuses can be screened for alleles that cause genetic disorders.
Embryo and fetal cells are used to identify genetic disorders.
Raises economic, social and ethical issues.