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What do you already know about Gregor Mendel? What do you know about genetics? What questions do you have about genetics?. 1822 in Czech Republic Priest Studied math and science Taught in a monastery In charge of monastery gardens. Gregor Mendel. Peas. Why were they studied?

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Gregor mendel

1822 in Czech Republic

Priest

Studied math and science

Taught in a monastery

In charge of monastery gardens

Gregor Mendel


Peas

Why were they studied?

Fertilization/Pollination

Mostly self-pollinating

Mendel’s experiments

True-breeding plants

Forcibly cross-pollinated

Created hybrids

Looked at several traits


Round and wrinkled
Round and Wrinkled

  • True-breeding parents, P generation

  • Offspring, F1 generation

    • Only round peas

  • Similar results with other traits

  • Conclusion

    • Traits passed from parents

    • Genes

    • Alleles



Crossing f1 generations

Self-pollination of F1

Produced F2

¼ exhibited recessive traits

Conclusion

Alleles separate in sex cells (gametes)

One allele from each parent

Crossing F1 Generations


Inheritance of genes

Mathematical model

Assumptions

Tall vs. short

Dominant (T)

Recessive (t)

Genotype

Phenotype

Homozygous

Heterozygous

TT

Tt = tT

tt

Inheritance of Genes


Punnett squares
Punnett Squares

  • Mendel’s first cross (round x wrinkled)

  • True-breeding = homozygous

  • 1 allele from each parent

  • 2 alleles in a genotype


  • Mendel crossed true-breeding yellow and green peas. All the offspring were yellow.

    • Write the genotype for these parents and the offspring. Use a Punnett square to help with the offspring.

    • Now cross the F1 with itself and write the genotypes of possible offspring along with the phenotypes. Use a Punnett square.


What about two traits at once
What about two traits at once? offspring were yellow.

  • Will one allele affect the other?

    • Short always yellow?

    • Get new combinations?

  • Mendel

    • Homozygous plants

    • Round, yellow x wrinkled, green plants

    • Assume: independence



F2 offspring were yellow.

  • Genotype

  • Alleles?


Independent assortment
Independent Assortment offspring were yellow.

  • Genes for different traits separate independently during gamete formation

  • Not all tall plants have yellow seeds

  • Some genes are linked to each other

    • Not in those studied by Mendel


Other patterns of inheritance
Other Patterns of Inheritance offspring were yellow.

  • Peas are simple

  • Incomplete dominance

    • Neither dominant nor recessive

    • Mixture phenotype

    • Plants

      • Red (RR)

      • White (rr)

      • Pink (Rr)

Red flower x Pink flower


  • Codominance offspring were yellow.

    • Both alleles expressed

    • Blood types

    • Chicken feathers

  • Multiple alleles

    • More than 2 forms

    • Blood types

    • Rabbit coat color

  • Polygenic traits

    • Controlled by more than 1 gene

    • Skin and eye color


  • In Chaparral llamas, brown coat color and blue eyes are dominant to white coat color and brown eyes.

  • A heterozygous (for both traits) female llama breeds with a homozygous recessive male llama. Draw a Punnett square and describe the fraction of each phenotype possible in the offspring.


Cells and chromosomes
Cells and Chromosomes dominant to white coat color and brown eyes.

  • Somatic cells

    • Most cells in the body

    • Reproduce through mitosis

    • 46 chromosomes, 23 pairs

    • Diploid (2n)

  • Gamete cells

    • Reproductive cells; sperm and egg

    • Unite with another cell in fertilization

    • 23 chromosomes, no pairs

    • Haploid (n)


  • Diploid vs. haploid dominant to white coat color and brown eyes.

    • Why does there need to be a difference?

    • If 2N = 8, then N =

    • If N = 12, then 2N =

  • How does this relate to genes?

    • DNA

    • Chromosomes

    • Homologous chromosomes


Meiosis
Meiosis dominant to white coat color and brown eyes.

  • 2N  N

  • 2 parts: meiosis I and meiosis II

  • Meiosis I

    • DNA replicates during interphase

    • Diploid

    • Prophase I

      • Similar to mitosis

      • Homologous chromosomes pair  tetrad

      • Crossing over can occur


  • Metaphase I dominant to white coat color and brown eyes.

    • Homologous chromosomes line up

  • Anaphase I

    • Separate homologous chromosomes

  • Telophase I

    • Nuclear membrane re-forms

  • Cytokinesis

  • Results

    • 2 daughter cells

    • Haploid or diploid?

    • May not be genetically identical


Meiosis ii
Meiosis II dominant to white coat color and brown eyes.

  • No replication in interphase

  • Prophase II

    • Chromosomes visible

  • Metaphase II

    • Chromosomes line up

  • Anaphase II

    • Chromatids separate

  • Telophase II

  • Cytokinesis


  • Results dominant to white coat color and brown eyes.

    • 4 cells from original 1

    • Each haploid

    • ½ genetic information of parent

  • Males – all 4 cells used

  • Females

    • 1 out of 4 used

    • Meiosis II doesn’t occur until fertilization

  • Fertilization

    • Egg and sperm unite

    • Diploid zygote

    • Goes through mitosis rapidly, repeatedly


Mitosis vs meiosis
Mitosis vs. Meiosis dominant to white coat color and brown eyes.

  • Both – require DNA replication first

  • Mitosis

    • Daughter cells diploid

    • Produces 2 cells

  • Meiosis

    • Daughter cells haploid

    • Produces 4 cells


Genes and the environment
Genes and the Environment dominant to white coat color and brown eyes.

  • Effect gene expression

  • Western white butterfly

    • Wing color varies

    • Spring – darker

    • Need specific body temp. to fly

    • Absorb more sunlight to be warmer


Karyotype
Karyotype dominant to white coat color and brown eyes.

  • Genome

  • Karyotype

    • Definition

  • 23 pairs, 46 chromosomes


Sex vs autosome
Sex vs. Autosome dominant to white coat color and brown eyes.

  • Sex

    • 2 chromosomes

    • Female

    • Y

      • XY = male

      • Smaller

      • Male specific genes

  • Autosomal

    • 44 chromosomes


How are traits inherited
How are traits inherited? dominant to white coat color and brown eyes.

  • Mendelian patterns

  • Dominant vs. recessive

  • Codominant

  • Multiple alleles

  • Sex-linked

    • Sex chromosomes

    • Y  only in males

    • X  both sexes

    • Recessive traits

    • Example


Pedigree
Pedigree dominant to white coat color and brown eyes.

  • Family tree

  • Circles vs. squares

  • Determine

    • Dominance

    • Sex-linked


  • Define dominant to white coat color and brown eyes.

    • Karyotype

    • Genome

    • Pedigree

  • What is an example of a sex-linked trait and why are sex-linked traits different than other traits?

  • What is the difference between sex and autosomal chromosomes?


Genetic disorders
Genetic Disorders dominant to white coat color and brown eyes.

  • Sickle cell

    • Recessive

    • Irregularly shaped RBC

    • Stick together

    • Don’t carry O2 as well

    • Painful

    • No cure

    • Advantages

      • Carriers

      • Malaria resistance


  • Cystic fibrosis dominant to white coat color and brown eyes.

    • Recessive

    • Necessary protein destroyed

    • Digestive and respiratory problems

    • Advantage

      • Europeans

      • Block typhoid bacterium

  • Huntington’s disease

    • Dominant allele

    • Different protein

    • Mental deterioration


Chromosome disorders
Chromosome Disorders dominant to white coat color and brown eyes.

  • Nondisjunction

  • Down syndrome

    • Trisomy 21

  • Turner’s syndrome

    • X

  • Klinefelter’s syndrome

    • XXY


Gene linkage
Gene Linkage dominant to white coat color and brown eyes.

  • Mendel

    • Independent assortment of genes

  • Thomas Hunt Morgan

    • Fruit fly research

    • Traits inherited together

    • Genes stay together if on same chromosome


Gene mapping
Gene Mapping dominant to white coat color and brown eyes.

  • Alfred Sturtevant

    • Fruit flies

    • Location of genes on chromosome


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