Multiple alleles for the ABO blood groups

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Multiple alleles for the ABO blood groups
A and B are codominant, O is recessive to A and B
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PLEIOTROPY One gene (or genotype) results in
multiple phenotypes. Many different outward
effects on the organism.
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Pleiotropic effects of the sickle-cell allele
in a homozygote
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POLYGENIC INHERITANCE -Multiple genes resulting
in one phenotype. Ex. Skin color, eye color.
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At least 2 genes invloved in pigment formation.
(Location of color also important)
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A simplified model for polygenic inheritance of
skin color
Environmental effects also affect the range of
phenotype (multifactorial trait)
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The effect of environment of phenotype
Soil acidity effects the color of hydrangeas.
Temperature sensitive mutations for pigment
formation
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HEREDITY
What is it that allows life to continue from
generation to generation? What is it that is
passed on? What is the common thread that
connects all life?
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Late 1850s - Principles of inheritance Concept
of genes, discrete units of inheritance that
determine specific traits. Genes segregate and
re-assort. Microscopy showed chromosomes
segregating during cell division.
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WHAT IS THE GENETIC MATERIAL?
PROTEIN OR DNA?
Chromosomes are composed of both DNA and Protein.
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Nucleic Acids
The subunits of nucleic acids are nucleotides.
The two types of nucleic acids are RNA and DNA.
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Figure 16.2a The Hershey-Chase experiment phages
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Figure 16.2b The Hershey-Chase experiment
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THE RACE IS ON TO DETERMINE THE MOLECULAR
STRUCTURE OF DNA! Linus Pauling Wilkins and
Franklin Watson and Crick
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Chemical composition of DNA
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Base pairing in DNA
Chargaffs Rules G C, A T
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Figure 16.4 Rosalind Franklin and her X-ray
diffraction photo of DNA
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Figure 16.0 Watson and Crick
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Figure 16.5 The double helix
Strands anti-parallel
5 end
3 end
3 end
5 end
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J.D. Watson, F.H.Crick, Molecular Structure of
Nucleic Acids A Structure for Deoxyribonucleic
Acids. Nature 171 (1953) 738 It has not
escaped our notice that the specific pairing we
have postulated immediately suggests a possible
copying mechanism for the genetic material.
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Semi-Conservative Replication
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Origins of replication in eukaryotes
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Incorporation of a nucleotide into a DNA strand
Anti-parallel DNA strands
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3
3
5
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DNA REPLICATION
Helicase separates strands and unwinds DNA DNA
polymerase reads template and incorporates
proper nucleotide. DNA Ligase seals newly made
fragments.
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DNA polymerase incredible fast and
accurate! 50-500 nt/second! Error rate 1/10,000
DNA Polymerase Proofreading Excision/Repair
enzymes
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Nucleotide excision repair of DNA damage
(Caused by U.V. irradiation)
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Mutations which affect DNA replication and DNA
repair have been associated with some cancers and
in premature aging diseases.
Xeroderma Pigmentosum
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HOW IS THE INFORMATION STORED IN THE DNA
UTILIZED? DNA RNA PROTEIN WHAT IS
THE GENETIC CODE?
Transcription
Translation
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The triplet code
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• By the mid-1960s the entire code was deciphered.
• 61 of 64 triplets code for amino acids.
• The codon AUG not only codes for the amino acid
  methionine but also indicates the start of
  translation.
• Three codons do not indicate amino acids but
  signal the termination of translation.

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The Process of Transcription
Production of an RNA copy (transcript) of a
gene. 3 main types of RNAs (both proks. and
euks.) - mRNA (messenger RNA) - rRNA
(ribosomal RNA) - tRNA (transfer RNA)
How are these RNAs made? What are their functions
in the cell?
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• Transcriptioncan beseparatedinto
  threestagesinitiation, elongation,
  andtermination.

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• As RNA polymerase moves along the DNA, it
  untwists the double helix, 10 to 20 bases at
  time.
• The enzyme addsnucleotides to the3 end of
  thegrowing strand.
• Behind the pointof RNA synthesis,the double
  helixre-forms and theRNA moleculepeels away.

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1. Messenger RNA Structure and Function
The Genetic Code is a triplet code. 3 nucleotides
1 amino acid 4x4x4 64 3 nucleotide codons,
more than enough to code for the 20 different
amino acids found in proteins.