2: Genetics
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Transcript of 2: Genetics
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Geneticsand Heredity
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Genetics and Evolution
Evolution = change in gene frequencies within populations over time.
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Cell Diagram
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DNA (deoxyriboneucleic acid)
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Protein Synthesis
• DNA is a molecule that provides the cell instructions on how to create proteins.
• Protein Synthesis refers to the construction of proteins from the DNA sequence
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Proteins
• Proteins are large organic compounds composed of amino acids.
• Most enzymes are proteins. Many hormones are also proteins.
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The DNA Code
• Four Bases: Adenine Thymine Guanine Cytosine
• A T C G A T T A T C G C G
• T A G C T A A T A G C G C
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Protein Synthesis (simplified)
• The DNA molecule “unzips” itself.
• One side of the DNA molecule is “read” and a complementary strand is made by messenger RNA (mRNA).
• Transfer RNA (tRNA) transports amino acids to the ribosome in order to make protein based on the messenger RNA sequence.
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DNA and Genes
• A gene is a unit of DNA that codes for one protein.
• A gene is located at particular region or locus of a particular chromosome.
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DNA, Genes and Chromosomes
Long strands of DNA (containing many genes) are wound up into structures called chromosomes.
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Chromosomes
• Humans have 23 pairs of chromosomes (46 total).
• 22 pairs of autosomes.
• 1 pair of sex chromosomes.
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Sex Chromosomes
XX = Female (two copies of the same chromosome)
XY= Male (two different chromosomes)
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Chromosomes
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Meiosis and Mitosis
• Mitosis = cellular division resulting in new cells with the same number of chromosomes as their “parents.”
• Meiosis = cellular division resulting in cells with HALF the number of chromosomes as our body cells (sperm & ova).
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Mutation
• Random changes in genetic material occur all the time. We refer to these as mutations.
• Mutations are responsible for the genetic variation we see within a population of organisms.
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Alleles
• Allele: a variation of a particular gene.
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Genes and Inheritance
In most circumstances, we inherit two copies of each gene (allele): one from each parent.
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Genotype vs. Phenotype
• Genotype = the genes you’ve inherited from your parents
• Phenotype = a particular observable trait (blood type, hair color…etc.).
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Genes and Inheritance
• Alleles (gene variants) can be said to be dominant or recessive in relationship to each other.
• Dominant alleles can “hide” or “cover up” the expression of recessive alleles.
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Heterozygous vs. Homozygous
• Heterozygous: having two different alleles. (A and a)
• Homozygous: having two of the same alleles (A and A)
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Eye Color: an Exercise
• The Eye-Color gene has two alleles:
• B (brown) is dominant
• b (blue) is recessive
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Genotype vs. Phenotype
Genotype:
BB
Phenotype
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Genotype vs. Phenotype
Genotype:
Bb
Phenotype
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Genotype vs. Phenotype
Genotype:
bb
Phenotype
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Eye Color Exercise
Mother Father
Bb X bb
Child
B b
Bb
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Punnett Square
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Incomplete Domination
• The Petal color gene has two alleles: R (red) and W (white)
Genotype Phenotype
RR Red
WW White
RW Pink
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Blood Groups
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Blood Type
• Three alleles: A, B & O
• A is dominant to O
• B is dominant to O
• A and B are co-dominant
Possible Genotypes: AO, AA, BO, BB, OO, AB
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Monogenic vs. Polygenic
• Monogenic = one gene
• Polygenic = multiple genes
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Gene to Trait
Genotype
+
Environmental Influences
=
Phenotype