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Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata...
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Transcript of Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata...
![Page 1: Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata form Recombination 1st cell division 2nd cell divisionGametes.](https://reader035.fdocuments.net/reader035/viewer/2022081821/5515d73e550346cf6f8b48fa/html5/thumbnails/1.jpg)
Lecture 39
Prof Duncan Shaw
![Page 2: Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata form Recombination 1st cell division 2nd cell divisionGametes.](https://reader035.fdocuments.net/reader035/viewer/2022081821/5515d73e550346cf6f8b48fa/html5/thumbnails/2.jpg)
Meiosis and Recombination
Chromosomes pair up DNA replicationChiasmata form
Recombination
1st cell division
2nd cell divisionGametes
Result: meiosis generates new combinations of alleles
![Page 3: Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata form Recombination 1st cell division 2nd cell divisionGametes.](https://reader035.fdocuments.net/reader035/viewer/2022081821/5515d73e550346cf6f8b48fa/html5/thumbnails/3.jpg)
Terms & Definitions• Genes can have several different forms due to
small changes in DNA sequence. These forms are called alleles. Property of having different forms is called polymorphism
• Organism with 2 copies of the same allele of a gene in diploid cells is homozygous for the gene
• Organism with different alleles of a gene in diploid cells is heterozygous for the gene
• Males are hemizygous for genes on X and Y chromosomes
![Page 4: Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata form Recombination 1st cell division 2nd cell divisionGametes.](https://reader035.fdocuments.net/reader035/viewer/2022081821/5515d73e550346cf6f8b48fa/html5/thumbnails/4.jpg)
Phenotype & Genotype• The phenotype of an organism is its observable
properties• The genotype is the set of alleles it has for all of
its genes (35,000 in humans)• The relationship between genotype and phenotype
is what genetics is all about• The effect that alleles have on the phenotype
depends on whether they are dominant or recessive
![Page 5: Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata form Recombination 1st cell division 2nd cell divisionGametes.](https://reader035.fdocuments.net/reader035/viewer/2022081821/5515d73e550346cf6f8b48fa/html5/thumbnails/5.jpg)
Modes of inheritance
• Dominant alleles affect the phenotype when present in 1 copy (heterozygous), e.g. Huntington’s disease
• Recessive alleles affect the phenotype only when present in 2 copies (homozygous), e.g. cystic fibrosis
• Can tell whether dominant or recessive by studying Mode of Inheritance in families
![Page 6: Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata form Recombination 1st cell division 2nd cell divisionGametes.](https://reader035.fdocuments.net/reader035/viewer/2022081821/5515d73e550346cf6f8b48fa/html5/thumbnails/6.jpg)
Autosomal dominant inheritance
![Page 7: Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata form Recombination 1st cell division 2nd cell divisionGametes.](https://reader035.fdocuments.net/reader035/viewer/2022081821/5515d73e550346cf6f8b48fa/html5/thumbnails/7.jpg)
![Page 8: Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata form Recombination 1st cell division 2nd cell divisionGametes.](https://reader035.fdocuments.net/reader035/viewer/2022081821/5515d73e550346cf6f8b48fa/html5/thumbnails/8.jpg)
Autosomal recessive inheritance
![Page 9: Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata form Recombination 1st cell division 2nd cell divisionGametes.](https://reader035.fdocuments.net/reader035/viewer/2022081821/5515d73e550346cf6f8b48fa/html5/thumbnails/9.jpg)
![Page 10: Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata form Recombination 1st cell division 2nd cell divisionGametes.](https://reader035.fdocuments.net/reader035/viewer/2022081821/5515d73e550346cf6f8b48fa/html5/thumbnails/10.jpg)
X-linked recessive inheritance
![Page 11: Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata form Recombination 1st cell division 2nd cell divisionGametes.](https://reader035.fdocuments.net/reader035/viewer/2022081821/5515d73e550346cf6f8b48fa/html5/thumbnails/11.jpg)
![Page 12: Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata form Recombination 1st cell division 2nd cell divisionGametes.](https://reader035.fdocuments.net/reader035/viewer/2022081821/5515d73e550346cf6f8b48fa/html5/thumbnails/12.jpg)
![Page 13: Lecture 39 Prof Duncan Shaw. Meiosis and Recombination Chromosomes pair upDNA replication Chiasmata form Recombination 1st cell division 2nd cell divisionGametes.](https://reader035.fdocuments.net/reader035/viewer/2022081821/5515d73e550346cf6f8b48fa/html5/thumbnails/13.jpg)