STA6178_2005(2) - Basic Genetics (1) Mendelian genetics How...

Info iconThis preview shows pages 1–11. Sign up to view the full content.

View Full Document Right Arrow Icon
Basic Genetics (1) Mendelian genetics How does a gene transmit from a parent to its progeny (individual)? (2) Population genetics How is a gene segregating in a population (a group of individuals)? (3) Quantitative genetics How is gene segregation related with the phenotype of a character? (4) Molecular genetics What is the molecular basis of gene segregation and transmission? (5) Developmental genetics (6) Epigenetics (genetic imprinting)
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Genomic Imprinting The callipygous animals 1 and 3 compared to normal animals 2 and 4 (Cockett et al. Science 273: 236-238, 1996)
Background image of page 2
Mendelian Genetics × Probability Population Genetics × Statistics Quantitative genetics × Molecular Genetics Statistical Genetics × Mathematics with biology (our view) Cutting-edge research into the interface among genetics, evo lution and deve lopment (Evo-Deve) Wu, R. L. Functional mapping of complex traits. Nature Reviews Genetics (submitted).
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Mendel’s Laws Mendel’s first law There is a gene with two alleles on a chromosome location (locus) These alleles segregate during the formation of the reproductive cells, thus passing into different gametes Diploid Gene A A | a | Centromere A | a | Probability ½ ½ Gamete Gamete
Background image of page 4
Mendel’s second law There are two or more pairs of genes on different chromosomes They segregate independently (partially correct) Diploid A|a|, B|b| A|, B| A|, b| a|, B| a|, b| Probability ¼ ¼ ¼ ¼ Four two-gene gametes
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
What about three genes?
Background image of page 6
Linkage (exception to Mendel’s second law) There are two or more pairs of genes located on the same chromosome They can be linked or associated (the degree of association is described by the recombination fraction) High linkage Low linkage A A B B
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
How the linkage occurs? – consider two genes A and B A a B b A B A B a a b b A B a b a A B b A B a b a A B b 1 2 3 4 Stage 1: A pair of chromosomes, one from the father and the other from the mother Stage 2: Each chromosome is divided into two sister chromatids Stage 3: Non-sister chromatids crossover Stage 4: Meiosis generates four gametes AB, aB, Ab and ab – Nonrecombinants (AB and ab) and Recombinants (aB and Ab)
Background image of page 8
How to measure the linkage? – based on a design Parents AABB × aabb Gamete AB ab F1 AaBb × aabb Gamete AB Ab aB ab ab Backcross AaBb Aabb aaBb aabb Observations n1 n2 n3 n4 Gamete type Non-recom/ Recom/ Recom/ Non-recom/ Parental Non-parental Non-parental Parental Define the proportion of the recombinant gametes over the total gametes as the recombination fraction (r) between two genes A and B r = (n2+n3)/(n1+n2+n3+n4)
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Several concepts Genotype and Phenotype Locus (loci), chromosomal location of a gene Allele (A, a), a copy of gene Dominant allele, one allele whose expression inhibits the expression of its alternative allele Recessive allele (relative to dominant allele) Dominant gene (AA and Aa are not distinguishable, denoted by A_) Codominant gene (AA, Aa and aa are mutually distinguishable) Genotype (AA, Aa or aa) Homozygote (AA or aa) Heterozygote (Aa) Phenotype: trait value
Background image of page 10
Image of page 11
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 55

STA6178_2005(2) - Basic Genetics (1) Mendelian genetics How...

This preview shows document pages 1 - 11. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online