Plant genetics

Plant GeneticsPlant GeneticsJJA Obico, Department of BiologyJJA Obico, Department of Biology

University of the Philippines Manila

Study of heredity and hereditary variationS udy o d y a d d a y a a o

Genes- hereditary units- Segments of DNA

Chromosomes - DNA + proteins

GeneticsGeneticsGeneticsGenetics

A. Interphasep as1. Gap 1 or G1 phase2. Synthesis phase or S phase3. G2 phaseB. M-phase (Mitosis or Meiosis)

Cell CycleCell CycleCell CycleCell Cycle

1. G1h th ll d ◦ where the cell spends

most of its functional life

◦ Performs metabolic acitivities

2. S-phase◦ DNA molecules are

copied or replicatedcopied or replicated◦ from single

stranded DNA in G1phase to double stranded DNAstranded DNA

3. G2◦ preparing for the

actual division events

InterphaseInterphase

(much protein synthesis- tubulin)

InterphaseInterphase

MeiosisMeiosisMeiosisMeiosis

Asexual or Sexual Reproduction?p

1. Crossing over2. Independent assortment of chromosomes3. Random fertilization

SOURCES OF VARIATIONSOURCES OF VARIATIONSOURCES OF VARIATIONSOURCES OF VARIATION

Crossing overCrossing overCrossing overCrossing over

Independent assortment of chromosomesIndependent assortment of chromosomesIndependent assortment of chromosomesIndependent assortment of chromosomes

2n

223 The no. of possible combination of maternal and paternal chromosomes in the gametes

Random fertilization of an ovum Random fertilization of an ovum by a spermby a spermby a spermby a sperm

True-breeding plantsu b d g p a sTwo varities◦ Purple flower◦ White flowerHybridizationM h b id Monohybrid cross

Whatever the factor that caused the a a o a aus dpurple color was more powerful than the factor for white color

Mendel said that the yellow factor "d i t d" th f t"dominated" the green factor.

1. Alternative version of genes account for a s o o g s a ou ovariations in inherited character

Mendel’s findingsMendel’s findingsMendel s findingsMendel s findings

2. For each character, an organism inherits o a a a , a o ga s s2 alleles: one from each parent

Homozygous– identical allelesHeterozygous– different alleles

3. Dominant allele – fully expressed3 o a a u y p ss dRecessive allele – masked

Dominant- uppercaseRecessive – lowercase

P- purple; p- white

4. Two alleles for each character segregate o a s o a a a s g gaduring gamete production – LAW of SEGREGATION

AN ovum or sperm get only ONE of alleles f ll th of all the genes

PUNNETT squareU squa- A tool for predicting the results of a

genetic cross

P Pp Pp Ppp Pp Pp

What will be the physical What will be the physical appearance?appearance?appearance?appearance?

Self pollinate Pp individualsS po a p d dua s

P pP PP PpP Pp pp

Pp, PPPp, PP-- same phenotype but different genotypesame phenotype but different genotype

Seed shape and seed colorpRound and wrinkled; yellow and green RRYY x rryyG t RY RY d Gametes: RY;RY and ry;ryF1: RrYy self pollinateRrYy x RrYyRrYy x RrYyGametes (dependent assortment): RY;ryand RY; ryyF2?Are they transmitted as package?Will Y d R d d t t th ?

DihybridDihybrid crosscross

Will Y and R; and r and y stay together?

DihybridDihybrid crosscross

Probabilityobab yThe number of ways an event can occurtotal number of possible outcomespranges from 0 to 1

MendelianMendelian inheritance reflects inheritance reflects rules of probabilityrules of probabilityrules of probabilityrules of probability

Product Ruleodu u◦ For independent eventsSum Rule◦ Events that can occur in two or more different ways

What is the probability of getting a heterozygote What is the probability of getting a heterozygote (Pp) in this cross?

A B Pp x Pp

1. P= ½ ; p= ½ ¼2 p= ½; P = ½ ¼ 2. p= ½; P = ½ ¼

1. Incomplete dominance

Non Non mendelianmendelian inheritanceinheritanceNon Non mendelianmendelian inheritanceinheritance

2. Multiple alleles- more than 2 allelesu p a s o a a s

3. Polygenic inheritance

4. pleiotropy- single gene controls more p o opy s g g o o s othan one character

eg. one gene affects corolla, anther, calyx, leaf and capsule of tobacco

5. Linked genes- genes are on the same 5 d g s g s a o sachromosome

6. Cytoplasmic inheritance6 Cy op as a- Maternal inheritance- Extra nuclear genesg

7. Epistasis – Cucurbita pepop s as s Cu u b a p po