Gregor Mendel – Father of Genetics

3 minute intro to Mendel/Genetics

https://www.youtube.com/watch?v=NWqgZUnJdAY

Mendelian genetics

Trait• color, height,

•ex: purple True-bred / Homozygous

• HH or hh Hybrid

• Heterozygous / Hh• Cross of two pure breeding

P generation = parents F1 generation = first filial

generation

Alleles = Different form of genes •one from each

parent If the two alleles

are different •the dominant

allele is expressed

• the recessive allele is “hidden”

Genetic vocabulary……. Punnett square:

• Cross for working out problems

Homozygous: BB / bb• alleles are the same

Heterozygous: Bb• two alleles are different

Phenotype: • an organism’s traits • (what you SEE)

Genotype: • an organism’s genetic

makeup: TT, Tt, tt Testcross:

• cross with a homozygous recessive = tt

• With dominant phenotype • (but unknown genotype)

A a

A

a

Monohybrid Cross – (one trait)

LAB: “Variation in Human Beings”

Lab # 22

LE 14-14a

Ww ww ww Ww

Ww wwWwwwwwWw

WW wwor

Ww

No widow’s peak

Thirdgeneration

(two sisters)

Widow’s peak

Second generation(parents plus aunts

and uncles)

First generation(grandparents)

Dominant trait (widow’s peak)

LE 14-14b

First generation(grandparents) Ff Ff

FF or Ff ff ff Ff Ff

ff

ff

Ff

Second generation(parents plus aunts

and uncles)

Thirdgeneration

(two sisters)

Attached earlobe Free earlobe

ff FForFf

Recessive trait (attached earlobe)

Genetics II

Genes working together

Incomplete dominance: blending of the phenotypes of the 2 parents. • Ex: snapdragons

Codominance: two alleles affect the phenotype in separate ways • Ex: human blood types A & B

Multiple alleles: more than 2 possible alleles for a gene. • Ex: human blood types

LE 14-10

RedCRCR

Gametes

P Generation

CR CW

WhiteCWCW

PinkCRCW

CRGametes CW

F1 Generation

F2 Generation Eggs

CR CW

CR

CRCR CRCW

CRCW CWCW

CW

Sperm

12

12

12

12

12

12

Blood Typing

A & B are Co-Dominant O is recessive

•AA or AO = type A ( IA IA or IA i )

•BB or BO = type B ( IB IB or IB i )

•AB = type AB ( IA IB )

•OO = type O ( ii )

Blood Types - USA

•O+ = 37.4%

•O- = 6.6%

•A+ = 35.7%

•A- = 6.3%

•B+ = 8.5%

•B- = 1.5%

•AB + = 3.4%

•AB- = .6%

Gene Interaction

Pleiotropy: genes with multiple phenotypic effect.

• Ex: sickle-cell anemia

Epistasis: a gene can interfere with another gene showing up; even if it is dominant

• Ex: mice coat color

Polygenic Inheritance: an additive effect of two or more genes on a single phenotypic character Ex: human skin pigmentation and height

Pleiotropy

LE 14-11

Sperm

BC bC Bc bc

BbCcBBCcBbCCBBCC

BbCC bbCC BbCc bbCc

BbccBBccBbCcBBCc

BbCc bbCc Bbcc bbcc

BC

bC

Bc

bc

BbCc BbCc

14

14

14

14

14

14

14

14

916

316

416

Epistasis

•Polygenic inheritance

•Quantitative variation usually is additive effect of two or more genes on a phenotype

•Skin color in humans is an example

Human disordersThe family pedigree Recessive disorders:

••Cystic fibrosis

••Tay-Sachs

••Sickle-cell Dominant disorders:

•Huntington’s Can be determined by a

Karyotype

TESTING

•Amniocentesis •CVS = Chorionic villi (villus)

sampling

Female Down’s SyndromeFemale Down’s Syndrome

322n = 47

copyright cmassengale

Klinefelter’sKlinefelter’s Syndrome Syndrome

332n = 47

copyright cmassengale

Turner’s SyndromeTurner’s Syndrome

342n = 45copyright cmassengale

LE 14-8

P Generation

F1 Generation

YYRR

Gametes YR yr

yyrr

YyRr

Hypothesis ofdependentassortment

Hypothesis of independent assortment

SpermEggs

YR

Yr

yrYR

YR

yr

Eggs

YYRR YyRr

YyRr yyrr yR

yrPhenotypic ratio 3:1

F2 Generation(predictedoffspring)

YYRR YYRr YyRR YyRr

YYRr YYrr YyRr Yyrr

YyRR YyRr yyRR yyRr

YyRr Yyrr yyRr yyrr

Phenotypic ratio 9:3:3:1

YR Yr yR yr

Sperm

12

14

14

14

14

1 43

4

12

12

12

14

916

316

316

316

14

14

14

http://learn.genetics.utah.edu/content/begin/traits/karyotype/