Lecture 7- Mendelian Genetics 2 Flashcards
Number of human chromosomes
46 chromosomes
23 pairs
Diploid cell
Diploid number of chromosomes 2n=46 (2 sets of chromosomes)
Haploid cell
Haploid number of chromosomes n=23 (1 set of chromosomes
Mitosis overview
Process by which cells are replicated for growth/ repair
Produces 2 diploid daughter cells
Meiosis overview
Process by which gametes are produced
Produces 4 haploid daughter cells
Meiosis I- overview
Reductional division- homologous pairs are separated, chromosome number halves
Meiosis I- stages
Interplase I
Prophase I
Metaphase I
Anaphase I
Telophase & cytokinesis
Meiosis I- interphase I
Chromosomes duplicate
Meiosis I- prophase I
Homologous chromosomes pair and exchange segments
Meiosis I- metaphase I
Tetrads line up
Meiosis I- anaphase I
Pairs of homologous chromosomes split up
Meiosis I- telophase and cytokinesis
Two haploid cells form, chromosomes are still double
Meiosis II- overview
Equational division- sister chromatids are separated producing 4 haploid gametes
Meiosis II- stages
Prophase II
Metaphase II
Anaphase II
Telophase II
Crossing over
Produces recombinant chromosomes
Average 1-3 crossing over events per pair
Occurs in Prophase I
Pieces of maternal and paternal chromatids joined
produces new combinations of maternal and paternal alleles
Random fertilisation
Adds to there genetic variation that arises from meiosis
Law of segregation
When an organism makes gametes, each gamete receives just one gene copy, which is selected randomly
Law of Independent Assortment
Alleles of two (or more) different genes get sorted into gametes independently of one another
Non mendelian patterns of inheritance- degree of dominance
Alleles can show differing degrees of dominance and recessiveness
Non mendelian patterns of inheritance- incomplete dominance
The phenotype of the heterozygote is intermediate between the phenotype of the dominant and recessive traits
Incomplete dominance
Both alleles of a gene at a locus are partially expressed
Results in an intermediate or different phenotype
Codominance
Both alleles for a trait are expresses in heterozygous offspring
Two dominant genes expressed at the same time
Pleiotriopy
Most genes have multiple phenotypic effects
Epistasis
Phenotypic expression of a gene at one locus affects another gene at a different locus
Polygenic inheritance
One character influences by many genes
generally quantitative traits
Non mendelian patterns of inheritance- mitochondrial inheritance
mtDNA is solely inherited through maternal line
Non mendelian patterns of inheritance- linkage
Two genes that are close together physically
Unlikely to have crossing over between them
Inherited together
Non mendelian patterns of inheritance- linkage disequilibrium
Two alleles that are not inherited separately
