Plant genetics
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Transcript of 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