BABS1201 Lecture Notes - Lecture 15: Haemophilia, Monosomy, Blending Inheritance
28 May 2018
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Mendel's Law of heredity
Genetics: the study of heredity
• How biological information is passed on
• Biological information - arrangement of bases in DNA
• How is information stored in the nucleus
Genetic information
• Genome: the complete genetic composition of an organism or a cell or an organelle
• Genotype: genetic state
• Phenotype: physical trait of organism
What do genomes look like?
• Eukaryotes
o Linear chromosomes
o Multiple chromosomes per genome
• Prokaryotes
o Circular chromosomes
o Sometimes contain plasmids small circular DNA molecules
▪ Plasmids
• Small circular DNA molecules
• Self replicating
• Often carry genes
Concepts in genetics
• Locus - A place on a chromosomes where a gene is located
• Allele - A form or variant of a gene (of a locus)
• Genotype - allele(s) in an individual
• Phenotype - the physical traits of an organism
• Homozygote - genotype with two same alleles at a locus (YY)
• Heterozygote - genotype with two different alleles at a locus (Yy)
• Dominant allele - allele the determines phenotype in heterozygote e.g. Y
• Recessive allele - allele that does not affect phenotype in a heterozygote e.g. y
E.g. bacteria
• Variation in metabolic gene
o Leu+ - can synthesise leucine
o Leu- - cannot synthesise leucine, needs leucine in medium to grow
• Neutral variation, e.g.
o Single nucleotide polymorphism (SNP) in a region of DNA between genes
• Variation produced through mutation
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Asexual and sexual reproduction
• Asexual
o Offspring are genetic copies of parents
o Prokaryotes - binary fission
• Sexual
o Genetic combinations of parents
▪ Most plants and animals
▪ Yeast (sometimes)
Human chromosomes
• 22 pairs of autosomes (not sex chromosomes) + 1 pair of sex chromosomes XX or XY
Sexual reproduction
• 22 autosomes + X from mother
• 22 autosomes + X or Y from father
•
Meiosis
• Produce cell containing half the number of chromosomes
• Making of gametes
• Mixture of parental chromosomes (crossing over etc)
•
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•
• Independent assortment (of chromosomes)
o Creates variation
o Random alignment of parental gametes
o 4 different combinations of gametes
▪ MM, FF, MF, FM
•
• Crossing over
o Leads to recombination of genetic information
▪ Bits of chromosome arms are attached to the wrong chromosome
▪ Arms tangled
o 4 different types of gametes
▪ Varying location of crossing over (higher or lower down the arm)
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Document Summary
Genetics: the study of heredity: how biological information is passed on, biological information - arrangement of bases in dna, how is information stored in the nucleus. Genetic information: genome: the complete genetic composition of an organism or a cell or an organelle, genotype: genetic state, phenotype: physical trait of organism. What do genomes look like: eukaryotes, linear chromosomes, multiple chromosomes per genome, prokaryotes, circular chromosomes, sometimes contain plasmids small circular dna molecules, plasmids. Asexual and sexual reproduction: asexual, offspring are genetic copies of parents, prokaryotes - binary fission. Sexual: genetic combinations of parents, most plants and animals, yeast (sometimes) Human chromosomes: 22 pairs of autosomes (not sex chromosomes) + 1 pair of sex chromosomes xx or xy. Sexual reproduction: 22 autosomes + x from mother, 22 autosomes + x or y from father. Meiosis: produce cell containing half the number of chromosomes, making of gametes, mixture of parental chromosomes (crossing over etc)
