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Review Mendel’s “rules of the game” 3) Segregation- during formation of the gametes, the paired alleles separate or segregate randomly. 1) Genes occur.

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Presentation on theme: "Review Mendel’s “rules of the game” 3) Segregation- during formation of the gametes, the paired alleles separate or segregate randomly. 1) Genes occur."— Presentation transcript:

1 Review Mendel’s “rules of the game” 3) Segregation- during formation of the gametes, the paired alleles separate or segregate randomly. 1) Genes occur in pairs - Genetic characteristics are controlled by genes that exist in pairs called alleles. 2) Dominance/Recessiveness- When two unlike alleles responsible for a single character are present in a single individual, one is dominant (expressed) to the other which is said to be recessive (silent).

2 Yellow seeded plants in the F 2 are predicted to have either GG or Gg genotypes. Is there a way to distinguish the genotype? Question Test Cross The organism of dominant phenotype but unknown genotype is crossed to a homozygous recessive individual.

3 + o o X Gg gg g G g g Possible sperm cells Possible egg cells gg Gg gg GG ? Test Cross If the offspring show 1:1 ratio of dominant:recessive phenotypes, the parent in question must have been heterozygous (Gg).

4 + o o X Gg gg GG ? g G G g Possible sperm cells Possible egg cells Gg Test Cross If the offspring show only the dominant phenotype, the parent in question must have been a homozygous dominant (GG) individual.

5 Discovering genes via Mutant analysis Generating mutants – Chemical mutagenesis (EMS) – base transition, point mutation – Radiation – deletions – Transposons/ T-DNA tags – insertion/deletions (indels)

6 ID the phenotype ID the gene (DNA sequence) ID the physiological, developmental, molecular differences Forward Genetics - from phenotype to gene

7 And observing segregation ratios Planned crosses and Punnett squares, Pedigree analysis –Mutant or polymorphism analysis Autosomal dominant/recessive Sex-linked genes

8 If A represents a gene that displays autosomal dominant/recessive inheritance. The genotype of I-1 must be: a.AA b.Aa c.Aa d.Insufficient data to tell The genotype of I-1 must be: a.AA b.Aa c.Aa d.Insufficient data to tell

9 If the DNA seen on gel 1 is from a pea plant heterozygous for “R” and “r” at the SBE1 locus, the DNA in lane 2 is most likely from a pea plant a.Homozygous for the “R” allele b.Homozygous for the “r” allele c.Unable to make functional starch branching enzyme 1 d.That is making twice the normal amount of starch branching enzyme 1 If the DNA seen on gel 1 is from a pea plant heterozygous for “R” and “r” at the SBE1 locus, the DNA in gel 2 is most likely from a pea plant a.Homozygous for the “R” allele b.Homozygous for the “r” allele c.Unable to make functional starch branching enzyme 1 d.That is making twice the normal amount of starch branching enzyme 1 RrRr 1 2 3

10 Reverse Genetics - from gene to phenotype ID a gene Mutate, knockout, over-express the gene Analyze the morphological, physiology, developmental effects (the phenotype).

11 Independent Assortment Chapter 3

12 Dihybrid cross - crosses between individuals that differ in two traits.

13 X yellow, round P 1 cross F1F1 green, wrinkled yellow, round X green, round P 1 cross yellow, wrinkled Mendel’s dihybrid crosses

14 Self-pollination of the F 1 X yellow, round 9/16 yellow, round 1/16 green, wrinkled 3/16 green, round 3/16 yellow, wrinkled F1F1 F2F2

15 X yellow (Gg), round (Ww) GW Gw gW gw + o o GW Gw gW gw GGWW GgWw GgWW GgWw GgWW GgWw GGWw ggWw ggWW ggww Ggww GGww Ggww GenerationGeneration F2F2

16 Mendel’s Second Principle of Inheritance Independent Assortment - during gamete formation, segregating pairs of unit factors assort independently of each other. Mendel’s dihybrid ratio9:3:3:1

17 But, what if X yellow (Gg), round (Ww)

18 X + o o GW GGWW GgWw GGWW ggww GgWw GGWW GgWw GenerationGeneration F2F2 GW gw GW

19 Phenotypic Ratio 9 Yellow, round 1 green, wrinkle 3 green, round 3 Yellow, wrinkle Expected F 2 12 Yellow, round 4 green, wrinkle 0 green, round 0 Yellow, wrinkle Resulting F 2 X yellow (Gg), round (Ww)

20 Chromosomal Basis of Inheritance

21 Meiosis (the prelude to sexual reproduction) For sexual reproduction to occur, chromosomes must be duplicated and divided between the gametes.

22 Meiosis I

23 Meiosis II

24 Independent Assortment - during gamete formation, segregating pairs of chromosomes (not genes) assort independently of each other.

25 Mitosis takes place in a.Haploid cells only b.Diploid cells only c.Haploid or diploid cells d.Bacterial cells e.None of the above Mitosis takes place in a.Haploid cells only b.Diploid cells only c.Haploid or diploid cells d.Bacterial cells e.None of the above

26 Meiosis takes place in a.Haploid cells only b.Diploid cells only c.Haploid or diploid cells d.Somatic cells e.None of the above Meiosis takes place in a.Haploid cells only b.Diploid cells only c.Haploid or diploid cells d.Somatic cells e.None of the above

27 Polygenic Traits (Quantitative trait loci, QTLs) Observation: Wheat kernel color is a continuum from whitedark red

28 Experiment 1 + o o X P1P1 F 1 - all light red

29 Experiment 2 + o o X F1F1 F2F

30 Frequency Diagram

31 Wheat Kernel Color 3 loci (polygenic), 6 different alleles F 2 seed color Dark white red # of dominant alleles

32 Continuous variation is determined by two or more genes. These are polygenic or quantitative traits.

33 Cytoplasmic Segregation (Non-Mendelian Genetics) Chloroplast DNA (cpDNA) Mitochondrial DNA (mt DNA)

34 Cytoplasmic Segregation

35 Test Cross ? Reciprocal crosses –Who’s the pollen donor?

36

37

38 A human disease associated with dysfunction of mitochondria, which results from a mutation in a single autosomal gene locus in nuclear DNA, is most likely to: a.Be inherited from the mother, because mitochondria are not inherited from the father b.Show heteroplasmy in the progeny of affected individuals, depending on chance events during meiosis c.Show a non-Mendelian inheritance pattern, because the number of mitochondria varies from cell to cell d.Show a Mendelian inheritance pattern e.None of the above A human disease associated with dysfunction of mitochondria, which results from a mutation in a single autosomal gene locus in nuclear DNA, is most likely to: a.Be inherited from the mother, because mitochondria are not inherited from the father b.Show heteroplasmy (a mix of WT and mutant mitochondria) in the progeny of affected individuals, depending on chance events during meiosis c.Show a non-Mendelian inheritance pattern, because the number of mitochondria varies from cell to cell d.Show a Mendelian inheritance pattern e.None of the above


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