1 / 18

DIHYBRID CROSS

DIHYBRID CROSS. Mendel also investigated the inheritance of two pairs of contrasting characters in the pea plant. This is referred to as the dihybrid cross. Pure breeding X pure breeding round seeds wrinkled seeds yellow cotyledons green cotyledons F1 progeny all round

tiger
Download Presentation

DIHYBRID CROSS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. DIHYBRID CROSS

  2. Mendel also investigated the inheritance of two pairs of contrasting characters in the pea plant. • This is referred to as the dihybrid cross.

  3. Pure breeding X pure breeding round seeds wrinkled seeds yellow cotyledons green cotyledons F1 progeny all round yellow peas

  4. The F1 progeny were selfed:- • F2 progeny Round round wrinkled wrinkled Yellow green yellow green 315 108 101 32

  5. The ratio between the numbers of different seeds reduces to: 9.8 : 3.38 : 3.15 : 1.0 Or about 9 : 3 : 3 : 1

  6. Mendel also noticed that two new combinations not represented in the parents appeared in the progeny • Round or wrinkled seeds can turn up with either green or yellow cotyledons. • The two pairs of factors were inherited independently.

  7. Either one of the contrasting characters could be passed on to the offspring • Therefore the heterozygote plant (F1 – round and yellow) must produce four types of gamete in equal numbers

  8. F1 phenotype RrYy Produces 4 different gametes RY Ry rY ry

  9. Use this information to draw the initial cross and the F1 cross on your worksheet. • How many different phenotypes are there and what will they be?

  10. Answers • CROSS 1 • Parents Round yellow X wrinkled green genotype RRYY rryy gametes RY ry

  11. F1 phenotype – all round and yellow • F1 genotype – all RrYy (heterozygous for both characters)

  12. F1 generation crossed • F1 phenotype – round yellow X round yellow • Genotype - RrYy X RrYy • Gametes RY Ry rY ry

  13. F2 generation Phenotypes – Round and yellow – 9 Round and green – 3 Wrinkled and yellow - 3 Wrinkled and green - 1

  14. The Dihybrid Test Cross • As with monohybrids the appearance of the heterozygous dominant offspring will be identical to that of the homozygous dominant organism. • How could they be distinguished?

  15. If the organism in question is heterozygous dominant and is crossed with a homozygous recessive individual then the resulting progeny would show all possible combinations of characters in the ratio • 1 : 1 : 1 : 1

  16. This is described as a test cross in which the genotype of the F1 offspring can be determined. • Perform a genetic cross to show the possible genotypes resulting from a test cross for a homozygous dominant individual (RRYY) and a heterozygote (RrYy)

More Related