genetics presentation ’10

04/14/232/3/03 10:39 AM 1

Genetics

04/14/23 2

Genetics & Inheritance

What you get isn’t always what you get

Intro to Inheritance http://learn.genetics.utah.edu/content/begi

n/tour/inheritance.swf

04/14/232/3/03 10:39 AM 3

04/14/232/3/03 10:39 AM 4

Gregor Mendel (7/22/1822 - 1/6/1884)

“Father of Modern Genetics” Born in 1822 in Heinzendorf Moravia

in what is now the Czech Republic Born in Heinzendorf, Austria on July

22, 1822. He died in Brno, Austria January 6, 1884

Augustinian monk employed as high school natural science teacher for 20 years

04/14/232/3/03 10:39 AM 5

Gregor Mendel (7/22/1822 - 1884)

Experimented with garden peas Pisum sativum

Tested some 28,000 pea plants in 7 years Used artificial feritization Worked in limited space in monastery

garden First to consider single traits of

hybridization experiments results Devised precise mathematical pattern Did not understand biological process, eg.

chromosomes & DNA 1900 three botanists “discovered” his

papers while researching their own findings

Mendel, O.S.A., experimental garden (35x7 meters) in the grounds of the

Augustinian Monastery in Old Brno.Its appearance before 1922.

04/14/232/3/03 10:39 AM 6

Mendel’s Pea Plants Pisum sativum

Diploid Seven pairs of traits

• Axial / terminal flowers (Aa)

• Purple / white Flower coats (Pp)

• Tall / short (Tt)• Round / wrinkled (Ss)• Green / yellow seeds

(Gg)• Inflated / constricted

(Ii)• Green / yellow unripe

pods (Gg)

Mendel’s Pea Plants

Pisum sativum Mendel fertilized the

pea flowers and removed other underdeveloped reproduction parts before self-fertilization could take place.

04/14/232/3/03 10:39 AM 7

William Bateson, English Gave name genetics

based on Greek term "to generate"

Promoted Mendell's view of paired genes using term allelomorph, shortened to allele.

04/14/232/3/03 10:39 AM 8

04/14/232/3/03 10:39 AM 9

Basic Ideas Mendel used term unit

characters based on physical elements and occurring in pairs of allele. We now call these genes.

The paired genes (allele pairs) separate form one another and are distributed to different sex cells through meiosis

Mendel's 3 Laws1. The Law of

Dominance In a cross of parents

that are pure for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are hybrid for a trait will have only the dominant trait in the phenotype.

04/14/232/3/03 10:39 AM 10


Segregation During the formation

of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other.

Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring.

04/14/232/3/03 10:39 AM 11


Independent Assortment Alleles for different

traits are distributed to sex cells (& offspring) independently of one another.

04/14/232/3/03 10:39 AM 12

04/14/232/3/03 10:39 AM 13

Terms Allele: an alternate form of a

gene. Variants that occur at the same locus.

Homozygous: having the same alleles for same trait

Heterozygous: having different alleles for same trait

Phenotype — physical looks of genes

Genotype — the actual genes Dominance — phenotypic

recognition Recessive —carriers

04/14/232/3/03 10:39 AM 14

Labeling:

The standard way of labeling the variation information of a trait in a particular organism is using two letters.

Capital letters represent information which is dominant.

Lowercase letters represent the recessive. The letter being used describes a variation (usually the recessive) of the trait.

GG stands for a plant where both pieces of color information are dominant - yellow. The plant is yellow.

Gg stands for a plant where one piece of color information is dominant - yellow, and the other is recessive - green. The plant is yellow.

Gg stands for a plant where one piece of color information is recessive - green, and the other is dominant - yellow. The plant is yellow.

gg stands for a plant where both pieces of color information are recessive - green. The plant is green.

04/14/232/3/03 10:39 AM 15

Pea Plant Traits

Trait:

Dominant

Expression:

Recessive

Expression:

1 Form of ripe seed Smooth Wrinkled

2 Color of seed albumen Yellow Green

3 Color of seed coat Grey White

4 Form of ripe pods Inflated Constricted

5 Color of unripe pods Green Yellow

6 Position of flowers Axial Terminal

7 Length of stem Tall Dwarf

04/14/232/3/03 10:39 AM 16

Examples of genetic traits studied by Mendel

04/14/232/3/03 10:39 AM 17

Examples of Phenotypes & Genotypes

Phenotypes for garden peas

Genotypes for garden peas

04/14/232/3/03 10:39 AM 18

Terms Codominance

Heterozygote expressing each allele equally

Semidominance Similar to codominance, but

not equal expression of both alleles

Filial Latin for progeny F1 -- F2 --

04/14/232/3/03 10:39 AM 19

Law of Probability The chance of two

or more independent events occurring together is the product of the chances for their separate occurrences.

04/14/232/3/03 10:39 AM 20

Terms

04/14/232/3/03 10:39 AM 21

Monohybrid Cross

04/14/232/3/03 10:39 AM 22

Punnett Square

Diagram of a Monohybrid Cross

04/14/232/3/03 10:39 AM 23

Monohybrid Cross—Punnett Square

04/14/232/3/03 10:39 AM 24

Monohybrid Cross, P1

Genotype Phenotype

Gg Green

Homozygous GreenX

Homozygous Yellow

04/14/232/3/03 10:39 AM 25

Monohybrid Cross, ƒ1

Genotype Phenotype

GG Green

Gg Green

gg Yellow

Heterozygous GreenX

Heterozygous Green

04/14/232/3/03 10:39 AM 26

Monohybrid Ratios

Genotypic Ratio 1:2:1

Phenotypic Ratio 3:1

# Genotype Phenotype #

1 GG Green 3

2 Gg Green

1 gg Yellow 1

04/14/232/3/03 10:39 AM 27

Dihybrid Cross

04/14/232/3/03 10:39 AM 28

Dihybrid Cross

04/14/232/3/03 10:39 AM 29

Dihybrid Cross

04/14/232/3/03 10:39 AM 30

Dihybrid Punnett Square

04/14/232/3/03 10:39 AM 31


04/14/232/3/03 10:39 AM 32


04/14/232/3/03 10:39 AM 33


04/14/232/3/03 10:39 AM 34


04/14/232/3/03 10:39 AM 35

Dihybrid Punnett Square Genotypes

GGRR GGRr GgRR GgRr GGrr ggRR Ggrr ggRr ggrr

Genotypic Ratio 1:1:2:2:4:2:2:1:1

04/14/232/3/03 10:39 AM 36


04/14/232/3/03 10:39 AM 37


04/14/232/3/03 10:39 AM 38


Phenotypes Green Round Green Wrinkled Yellow Round Yellow Wrinkled

Phenotypic Ratio 9:3:3:1

04/14/232/3/03 10:39 AM 39

Partial Dominance When one allele isn't

fully dominant over its partner

04/14/232/3/03 10:39 AM 40

Partial Dominance Example

Genotype Phenotype

RR Red

Rr Pink

rr White

Pink flowers

X

Pink flowers

04/14/232/3/03 10:39 AM 41

Epistiasis - two genes affecting property do not have equal vote

Example: melanin and melanin deposition (black, white, and brown coat of guinea pig). Black is dominant brown is recessive when melanin producing gene is present. Coat is white when no melanin is deposited.

04/14/232/3/03 10:39 AM 42

Collaboration - two genes interact to produce a novel phenotype Example: comb

types in chickens

04/14/232/3/03 10:39 AM 43

Multiple Gene Inheritance (polygenic)

Nilsson-Ehle's trigenic cross of wheat (10-8)

Frequency distribution (10-9)

04/14/232/3/03 10:39 AM 44

Sex-related Characteristics Holandric - genes

unique to Y chromosome, hair pinna on ears

Eye color in fruit flies Hemophilia Color blindness

04/14/232/3/03 10:39 AM 45

Sex-linked Inheritance Drosophila

04/14/232/3/03 10:39 AM 46

Sex-linked Inheritance Hemophilia

04/14/232/3/03 10:39 AM 47

Pedigree

04/14/232/3/03 10:39 AM 48

Slugs Mating

04/14/232/3/03 10:39 AM 49

Webpage Links The Genetic Code - S.D. Black, U. of Texas Health Center at Tyler Table relating

nucleic acid triplet to the corresponding amino acid.

Molecular Biology - The Biology Project, Biology, University of Arizona Activities, Problems sets, and Tutorials: Molecular Genetics; Nucleic Acids; Recombinant DNA Technology; Eukaryotic Gene Expression

Prokaryotic Genetics and Gene Expression from the MIT Hypertextbook - M.I.T. Tools for studying prokaryotic genetics, biochemical genetics, Lac operation, etc.

The making of the nucleosome - D. Pruss Simplified images and a tour.

http://www.agen.ufl.edu/~chyn/age2062/lect/lect_10/lect_10.htm

http://www.borg.com/~lubehawk/mendel.htm

http://www.sonic.net/~nbs/projects/anthro201/disc/

genetics presentation ’10

Education