Final Concepts for Chapter 11 Mendelian Genetics - PowerPoint PPT Presentation

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Final Concepts for Chapter 11 Mendelian Genetics

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Final Concepts for Chapter 11 Mendelian Genetics Codominance Complete dominance Dihybrid cross Genotype Genotypic ratio Heterozygous Homozygous Incomplete dominance – PowerPoint PPT presentation

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Title: Final Concepts for Chapter 11 Mendelian Genetics


1
Final Concepts for Chapter 11Mendelian Genetics
  • Codominance
  • Complete dominance
  • Dihybrid cross
  • Genotype
  • Genotypic ratio
  • Heterozygous
  • Homozygous
  • Incomplete dominance
  • Monohybrid cross
  • Phenotype
  • Phenotypic ratio
  • Probability
  • Punnett square
  • Testcross
  • Expected/predicted results
  • Actual/observed results
  • Karyotype
  • Amniocentesis
  • Linked genes
  • Sex-linked disorders
  • Autosomal disorders
  • Allele
  • Dominant
  • Recessive
  • P-generation
  • F1 generation
  • F2 generation
  • Law of independent assortment
  • Law of segregation
  • Chromosomes
  • Pure breed
  • Trait

2
Independent Assortment vs. Linked Genes
  • Mendel did not know about chromosomes when he
    proposed the Law of Independent Assortment.
  • The pea traits he studied happened to be located
    on different chromosomes so they did assort
    independently.

3
Independent Assortment vs. Linked Genes
  • Question How many traits do you have?
  • Question How many chromosomes (per cell) do you
    have?
  • Question Is it possible to have only one trait
    per chromosome?
  • No, lots of genes are carried or linked together
    on the same chromosome.

4
Independent Assortment vs. Linked Genes
  • Do the punnett square for the following cross
    assume independent assortment.
  • Cross two heterozygous tall, heterozygous red
    flowered plants
  • Ttall Rred flower
  • t short r white flower

5
Independent Assortment vs. Linked Genes
What is the phenotypic ratio?
  • TtRr x TtRr

TR
Tr
tR
tr
TTRR TTRr TtRR TtRr
TTRr TTrr TtRr Ttrr
TtRR TtRr ttRR ttRr
TtRr Ttrr ttRr ttrr
TR
Tr
tR
tr
6
Independent Assortment vs. Linked Genes
  • 9331 ratio
  • 9 tall and red
  • 3 tall and white
  • 3 short and red
  • 1 short and white
  • PROBABILITY
  • From this cross, 48 offspring were produced.
  • How many offspring would you expect to be tall
    and red?
  • How many would expect to be tall and white?
  • How many would you expect to be short and white?

7
Independent Assortment vs. Linked Genes
  • Now, do the following cross BUT the genes for
    tallness and red flowers are linked.

Cross two heterozygous tall, heterozygous red
flowered plants Ttall Rred flower t short r
white flower
8
Independent Assortment vs. Linked Genes
  • Hint
  • T t
  • R r

TtRr X TtRr
Is it possible to produce a Tr gamete?
9
Independent Assortment vs. Linked Genes
TtRr X TtRr
What is the phenotypic ratio?
tr
TR
TTRR TtRr
TtRr ttrr
31 3 Tall and Red 1 Short and white
TR
tr
10
Independent Assortment vs. Linked Genes
  • So out of the 48 offspring, if the genes are
    linked, how many would be
  • 1. tall and red?
  • 2. tall and white?
  • 3. short and red?
  • 4. short and white?
  • Answer
  • tall and red 36 tall/white 0
  • short and white 12 short/red 0

EXPECTED RESULTS!
11
Independent Assortment vs. Linked Genes
  • Is it possible for our Actual Results to show any
    flowers that are tall/white or short/red?
  • Yes how?
  • Crossing over

12
Crossing over occurs in meiosis
  • Pieces of the chromosomes actual switch places.

13
Complete vs Incomplete Dominance
14
Codominance the alleles are equally dominant
  • Roan Cow Human Blood Type

15
Sex-linked Traits
  • Traits carried on the X chromosome

Fill in the genotypes on the pedigree.
16
Autosomal disorders
  • Disorders carried on non-sex chromosomes (first
    22 pairs)
  • Some are autosomal dominant
  • Huntingtons disease
  • Most are autosomal recessive
  • Sickle-cell anemia
  • Cystic fibrosis

17
  • Question How do you know if the pure bred dog
    you just paid big bucks for is actually pure?

GG?
Gg?
18
Test Cross
  • Cross using a homozygous recessive individual
    with a dominant individual to determine if the
    dominant individual is heterozygous or homozygous
    dominant (pure)
  • Why use a homozygous recessive individual?

19
Test Cross
  • Do the punnett squares for each case
  • GG x gg Gg x gg

20
Test Cross
  • All offspring produced should show the dominant
    characteristics if the dominant parent is pure
    (GG) for the trait.
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