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Mendelian Genetics 1

Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Page 2: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Evolutionary Timeline

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Page 3: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Gregor Mendel(1822-1884)

• Studied peas

• Laws for inheritance of

Traits

Page 4: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Described offspring from 28,000 pea crosses

Page 5: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Mendel’s Pea Plant

Experiments

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Page 6: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Selective Breeding

• Humans control the mating or

breeding of plants and animals

desired traits

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Page 7: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Selective Breeding = Artificial Selection

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Page 8: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

List Pros and Cons of selective

breeding

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Page 9: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Why peas, Pisum sativum?

lots of offspring = lots of data

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Page 10: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Pea flowers have male and female parts

•Pollen contains sperm

–Produced by the stamen

•Flowers contain eggs

–Produced in an ovary

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Page 11: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Self-pollinate pure bred plants

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Page 12: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Cross-pollinate hybrids

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Page 13: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Mendel Described Particulate Inheritance =

Traits are inherited as “particles” from

parents

Page 14: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Now we call Mendel’s “particles” genes

Genes = pieces of DNA on chromosomes14

Page 15: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Cells of sexually reproducing

organisms• Body cells have 2 copies of gene

• Why?

• One copy from each parent

• Gametes = Eggs and Sperm

• How many copies of each gene do gametes have

• Gametes = only 1 copy of each trait

• Why?

• Meiosis gametes with ½ number of chromosomes

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Page 16: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Draw and label a chromosome with

lots of genes

then answer questions 1-3

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Page 17: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Chromosome

Page 18: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Genetics Vocabulary

Traits – characteristics determined by genes

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Hereditary molecule

=DNA

Genes =

pieces of DNA traits

Found on chromosomes

Page 19: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Dominant Genes / alleles

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Only need one copy trait (ex: brown eyes

Page 20: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Recessive Genes / Alleles• need 2 copies trait

• ex: blue eyes (ee)

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Page 21: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Genotypes

Describes the genes inherited

Homozygous = (BB or bb)

Heterozygous = (Bb)

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Page 22: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Phenotype

Describes a physical

characteristic

Ex: brown or blue

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Page 23: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Mendel studied 7 different traits

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Page 24: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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How Mendel BeganMendel produced pure strains by

self-pollinating several generations

Page 25: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Genotype & Phenotype in Flowers

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All genes occur in pairs =2 copies (one from each parent)

Flower color Genotypes

Rr

Which genotype is dominant

R

Page 26: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Genotype & Phenotype in Flowers

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Flower color Phenotypes

R=Redr=white

Which phenotype is dominant

Red

Page 27: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Questions• List the possible genotypes

• RR Rr rr

• List the possible phenotypes for each genotype

• Red red white

• Which genotypes are homozygous

• RR rr

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Page 28: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Pure bred plants = homozygous

• What is the genotype for a plant that is

homozygous dominant?

• RR

• What is the genotype for a plant that is

homozygous recessive?

• rr

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Page 29: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Mendel’s (P1 ) Pure bred Cross

• Trait = Seed Shape

• Alleles = R – Round and r – Wrinkled

• Cross:

• Homozygous round x Homozygous wrinkled

• RR x rr29

Page 30: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Predict what the offspring will look

like and what their genotype will be

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Page 31: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Punnett Square• Used to determine

the probability of

inheriting a trait

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Page 32: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Mendel’s (P1 ) Pure bred Cross• Trait = Seed Shape

• Alleles = R – Round and r – Wrinkled

• Cross: • Homozygous round x Homozygous wrinkled

• RR x rr

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R

R

rr

Rr

RrRr

Rr

Offspring

Genotypes:

100% Rr

Phenotypes:

100% Round

Page 33: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Mendel’s F1 heterozygous cross

• Cut stamens to prevent self-pollination

• Cross pollinate offspring of the P1 cross

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Page 34: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

F1 Monohybrid Cross• Trait: Seed Shape

• Genes: R – Round r – Wrinkled

• Cross: Heterozygous x Heterozygous

• Rr x Rr

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R

r

rR

RR

rrRr

Rr

Offspring

Genotypes: RR, Rr, rr

Genotype Ratio: 1:2:1

25% : 50% : 25%

Phenotypes: Round & wrinkled

Phenotype Ratio: 3:1

75% : 25%

Page 35: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Mendel’s Experimental Results

Page 36: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Mendel’s hybrid cross results

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•Expected is 3 round :1 wrinkled

•Mendel observed ratio 2.96:1

•The discrepancy is due to statistical error

•The larger the sample size the closer you

get to expected ratio

Page 37: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Remember

• More times you repeat an experiment more

accurate results

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Page 38: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Following the Generations

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Cross 2 Pure Plants

TT x tt

Results in all

HybridsTt

Cross 2 Hybridsget

3:1 (tall:Short)1TT, 2Tt, 1tt

Page 39: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Genes and Environment Determine

Characteristics

Remember:

the environment controls gene expression

Page 40: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Open notes quiz

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Page 41: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Mendel’s Laws

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Page 42: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

1) Law of Dominance

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• Pure bred cross experiments law of dominance

Page 43: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

2) Law of Segregation

a) Meiosis gametes with one copy of

each gene

b) Genes are "recombined" at fertilization,

Offspring = 2copies of each

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Page 44: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Applying the Law of Segregation

Meiosis

Meiosis

Page 45: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

3) Law of Independent Assortment

• Different traits are sorted out independently

• every gamete is different

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Page 46: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Page 47: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Exceptions to Mendel’s laws

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Page 48: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Some traits = controlled by multiple genes

Ex: eye color

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Page 49: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Page 50: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Incomplete dominance

• Neither trait is dominant

• Ex: Red flowers + white flowers

• Pink

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Page 51: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Codominance

• Both traits get expressed

• Ex: AB blood types

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Page 52: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Do the codominance problems in

notes

• Father (homozygous B) X Mother (heterozygous A)

• BB X Ao

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B B

A

o

BA BA

Bo Bo

Offspring

50% AB

50% B

Page 53: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Do 2 practice problems in notes

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Page 54: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Sex Linked traits

• Answer video questions in notes

• Meal worm body cells = 20

• Meal worm egg cells = 10

• Meal worm sperm cells = 10

• Difference =

• males have one small chromosome

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Page 55: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

• Sex linked traits = traits (genes) found on sex

chromosomes

• Sex chromosomes are X and Y

• Females have XX

• Males have XY

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Page 56: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Example: White eye color in fruit

flies

• Males only get 1 copy of the gene

• Females get 2

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White

Eye gene

XX chromosome - female Xy chromosome - male

Page 57: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Sex-linked recessive traits

• More common in boys

• Because they only need to inherit one

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Page 58: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

REMEMBER

• GENES are on CHROMOSOMES

• X and Y are different types of sex

chromosomes

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Page 59: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Page 60: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Sex-linked Trait Problem

Sex Chromosomes

XX chromosome - female XY chromosome - male

Color

blindness

Example: color blindness in humans is sex-linked

Page 61: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Sex-linked Trait Problem• Example: color blindness

• R = normal color vision

• r = color blind

• normal male x color blind female

XRY x XrXr

XR

Xr Xr

Y

Page 62: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Sex-linked Trait Solution:

XR Xr

Xr Y

XR Xr

Xr Y

Normal vision father all daughters = normal vision

Color blind mother all sons colorblind

XR

Xr Xr

Y

Page 63: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Pedigree Charts• Diagrams to follow traits through generations.

• For recessive traits carriers have one copy of the trait but are not affected

Page 64: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

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Female Carriers

Answer animation questions in notes

Page 65: Mendelian Genetics · 2018-05-07 · Mendelian Genetics 1. Evolutionary Timeline 2. 3 Gregor Mendel (1822-1884)

Practice questions in notes

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