This presentation summarizes key concepts in plant genetics: - It defines genetics and discusses Mendel's experiments with pea plants that established the laws of inheritance. - The presentation covers Mendel's work with mono and dihybrid crosses and how this led to an understanding of dominant and recessive traits. - Additional concepts are discussed like cytoplasmic and polygenic inheritance, gene interaction with the environment, and how our understanding of genetics has expanded beyond Mendel's original work.

1. Bota 103 Group 6
Plant Genetics
Presented by: Emma Ford
Watta Kamara
Betty Lablah
Sayenawuo Seekpee
Marcus Jensen
Tegeste Kollie
Louisa Smith
December 6, 2018

2. Lesson Outline
• Overview of plant genetics
• Mono and Dihybrid crosses
• Beyond Mendel’s Work
• Laws of Inheritance
• Gene interaction with the environment

3. Lesson Objectives
By the end of this presentation, the students should be able to:
• Define genetics
• Distinguish between a mono and dihybrid cross
• Discuss Mendel's laws of inheritance
• Discuss the cytoplasmic and polygenic inheritance

4. Overview of Genetics
• Genetics from the word “genetikos”
meaning genesis or origin
• It deals with the study of genes,
genetic variation and heredity
• Gregor Mendel is known as the father
of genetics
Gregor Mendel

5. Gregor Johann Mendel
• Between 1856 and 1863, Mendel
cultivated and tested some
28,000 pea plants
• He found that the plants’
offspring retained traits of the
parents
• Called the “Father of Genetics”

6. Mendel's Experiment on Inheritance
• Chromosomes are the particular carriers of genetic information
• These information are encode by genes
• These Genes consists of nucleotides on a strand of DNA’s double
helix
• Genes consists information about an organisms feature ..
• Ex: plant height , seed color, leaf shape

8. • Each character may appear in two or more forms called a trait
• The variant form of each trait, known as allele, is a code for each
trait
• Monohybrid cross involves individuals that have different alleles for
a specific gene
• This type of hybrid cross is based on the law of segregation
Mendel's Experiment on Inheritance Cont’d

9. Monohybrid Cross
• The monohybrid cross is between two parents, using a pair of
contrasting characters.
• These characters that are being studied are governed by two
multiple variations called locus.
• A locus is a fixed position on a chromosome, like the position of a
gene

10. • When two plants of the same trait are bred with each other, and all
their offspring have the same trait, is called Pure breeding.
• In the cross, each parent is chosen to be homozygous for a given
trait.
Monohybrid Cross Cont’d

11. Usage of Monohybrid Cross
• It is used to determine the relationship between two alleles
• The offspring make up the first fillal generation (F1 Gen)
• Members of F1 are heterozygous.
• Phenotypes of the F1 expresses dominant traits
• Crossing the F1, produces the F2 generation with the phenotypic ratio of
3:1

12. Procedures of Mendel's Experiment

13. Results From Mendel's Experiment
• Mendel recorded the Data and conclusions from his experiment in a
paper titled ‘experiment on plants hybridization in 1865

14. Results Cont’d
• He called the visible traits dominant and
the masked traits recessive
• The dominant and recessive traits are
controlled by two alleles of a specific gene
• A plant that has two copies of the same
allele is homozygous
• A plant that has two different alleles is
heterozygous
Visible traits dominant
Masked traits recessive

15. • The combination of alleles of a plant is its genotype
̶ Example pp or PP
• The physical appearance of plant is its phenotype
• The results of Mendel's cross can be represented by a
Punnett square
Results Cont’d

17. The law of Segregation

18. Segregation of Alleles occurs during Anaphase 1 of
Meiosis

19. Testcross
• Testcross is a genetic cross between a homozygous recessive
individual and a corresponding suspected heterozygous.
• To determine the phenotype of the latter
• This cross determines if an individual is homozygous
dominant or heterozygous.

20. Testcross:

21. Dihybrid Cross
• A cross between two different genes that differ in two
observed traits
• Mendel crossed a plant that produced smooth, yellow
seeds ( two dominant phenotypes) with a plant that
produce wrinkled, green seeds (two recessive traits)

22. Dihybrid Cross:

23. The Law of Independent Assortment

24. Law of Independent Assortment Cont’d
• Independent assortment of alleles occur because the segregation
of alleles in one tetrad does not affect the segregation of alleles in
another
• Another feature of independent assortment is recombination
• Recombination occurs during meiosis and it’s a process that breaks
and recombines pieces of DNA to produce new combination of
genes

25. Beyond Mendel's work
• Mendel didn’t report on trihybrid crosses which involves
plants that differ in three characters
• A trihybrid cross can be analyzed by using his Method

26. Trihybrid Cross:

27. Incomplete Dominance
• If Mendel had used snapdragon instead of Peas during his
experiments, he would have had a hard time formulating his laws of
inheritance
• Crossing of pure breeding strain of white flower with red flower will
produce an F1 generation of pink Flowers
• The Flowers are pink because neither allele exhibits complete
dominance over the other and this is referred to as incomplete
dominance.

28. Incomplete Dominance:

29. Polygenic Inheritance and Pleiotropy
• Polygenic Inheritance occurs when some characters are controlled by
genes with more than one allele
• It also occurs when characters are controlled by more than one gene
• Examples: in wheat when a plants with dark kernel is crossed with one
that has a white kernel, the resulting F1 generation will have medium red
kernel
• Pleiotropy occurs when a gene has more than one effect on an organism’s
phenotype

31. Location of Genes Affects Inheritance
Pattern
• Linked genes are genes on a chromosomes that segregates as a unit
during meiosis, causing the traits specified by those genes to be
inherited together
• When linked gene are involved in a genetic cross the law of
independent assortment does not apply
• Crossing over answers the question of the linked behavior of genes
on the same chromosome

32. Location of Genes Affects Inheritance Pattern
Cont’d
• Chiasma is an X-shaped structure formed when two chromatids of two
homologous chromosomes lie across each other
• The chromatids in the Chiasma may break and exchange fragments and
also alleles located on those fragments
• When two genes are very close together on a chromosome it is likely that
they will be included in the same fragments
• Location is important for genes on sex chromosomes

33. Crossing Over:

35. Cytoplasmic inheritance
• Inheritance pattern are further complicated by genes not on
chromosomes in the nucleus
• Chloroplasts and mitochondria have small cellular DNA molecules
• Characters coded for by genes in the DNA of these organelles are
passed from parents to offspring through cytoplasmic inheritance
• It is the transmission of genes that occurs outside the nucleus.

37. Genes Interact With Each Other In The
Environment
• Genes do act in isolation to affect an organism’s phenotype
• Epistasis occurs when one gene alters the effects of another
• In sweet peas two genes interact to determine flower color
• Each gene codes for an enzyme in the biochemical pathway of
pigment synthesis

38. Genes Interaction

39. • The actual interpretation of plant genes often depends on
environmental factors. Ex: hydrangea

40. • In other plants, temperature affects
flower color ex: buttercup
• Buttercup leaves look different when
they grow in air than when they grow
in water
Genes Interact With Each Other In The
Environment Cont’d

41. Mendel’s Genes For Heights In Pea Plants
• DNA and RNA behaves as the molecule that carry genetic
information
• In 1953, Watson and Cricks analysis revealed the structure of DNA
• The gene for height in Mendel's pea plants is known as the Le gene
• Tall pea plants contains 10 - 18 times as much growth-promoting
hormone Gibberellin 1(GAI) as dwarf pea plants

42. • Dwarf plants contain three to five time as much as Gibberellin 20
(GA20) as tall plants
• GA20 do not promote growth
Mendel’s Genes For Heights In Pea Plants

43. Summary:
• Genetic is the study of genes, genetic variation and heredity in living
things
• Genes carry information about an organism’s features
• Monohybrid cross involves individual with a pair of contrasting traits
while dihybrid cross involves two pairs of contrasting traits
• Genes also interact with the environment to affect an organism’s
phenotype

44. Reference:
• Nabor, Murray W., INTRODUCTION TO BOTANY, Copyright 2004
Pearson Education, Inc., publishing as Benjamin Cummings, 1301
Sansome St., San Francisco, CA 94111
• www.googleimage.com

45. THANK YOU FOR LISTENING
• Questions!
• Comments!!
• Contributions!!!