BIOL1003 Lecture Notes - Lecture 4: Gregor Mendel, Blending Inheritance, Genetic Recombination
BIOL1003: Module 2 - Genetics
Lecture 4 – Consequences of Meiosis; Inheritance
Consequences of meiosis
1. Production of haploid gametes
2. New combinations of paternal and maternal genes due to crossing over
3. Produces genetic recombination via chiasma formation
Variation generates my meiosis
• The chromosomes can be randomly combined
• 4 different types of gametes from 2 pairs of chromosomes
• The number of combinations of chromosomes that can be incorporated into an gamete = 2n
o Ie. Humans 2 = 2²³ = 8 388 608 gametes
o Although it takes 2 so: 2²³ x 2²³= 70 368 744 177 664
Blending inheritance
• The belief that offspring carry a blend of the characteristics of both parents - inheritance is a
process of averaging the phenotypes of both parents
• Does not quite fit into Darwin’s theory
• OMIM - at ncbi
Particulate inheritance - Gregor Mendel
• Never published anything - rediscovered century later
• Only held 2 talks
• Did controlled crosses - reoed the goads to esure they did’t self-pollinate
• All of the F1 were uniform
• Mendel’s observations
o The phenotype is determined by heritable factors called alleles (gene)
o Alternate forms of genes are responsible for variation in inherited
• Heterozygote - chromosomes carry different alleles
• Homozygote - chromosomes carry same alleles
• Crossed F1 heterozygotes: got a 3:1 ratio of white to purple flowers - phenotype ratio -
Mendel's ratio
o Genotype ratio 1,2,1 (homozygous dominate, heterozygous, homozygous recessive)
o Punnet squares
• Albinism - didn't have the enzyme DOPO 'to transfer tyrosine to melanin
o Only people with 2 non-functional copies of this gene will have it
o It is recessive
o Phenylketonuria - high ketone content in blood, retardation in mental and physical
development in early stages of life. If you have a single good copy, you will be fine
o Phenothalassemia - haemoglobin can't carry oxygen around the body properly,
metabolism slows. Point mutations, recombination can occur
• Dominate disorders
o Achondroplasia dwarfism - heart development, arthritis
• No homozygous dominate - 2 copies of this will cause the death of the child
o Huntington's Disease - neurodevelopment disease
• Starts at 45 - so did’t atter years ago eause people died efore they shoed
the disease
• Strange things with Medelian inheritance
o Incomplete dominance - both dominate shows a combination of traits
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Consequences of meiosis: production of haploid gametes, new combinations of paternal and maternal genes due to crossing over, produces genetic recombination via chiasma formation. Variation generates my meiosis: the chromosomes can be randomly combined, 4 different types of gametes from 2 pairs of chromosomes, the number of combinations of chromosomes that can be incorporated into an gamete = 2n. Humans 2 = 2 = 8 388 608 gametes: although it takes 2 so: 2 x 2 = 70 368 744 177 664. Blending inheritance: the belief that offspring carry a blend of the characteristics of both parents - inheritance is a process of averaging the phenotypes of both parents, does not quite fit into darwin"s theory, omim - at ncbi. Mendel"s ratio: genotype ratio 1,2,1 (homozygous dominate, heterozygous, homozygous recessive, punnet squares, albinism - didn"t have the enzyme dopo "to transfer tyrosine to melanin, only people with 2 non-functional copies of this gene will have it.
