Lecture 1 Notes - The Genetics of Child Development GENETIC...

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PLANTSANIMALS FLOWERSDOGS TREESFISH BUSHESBIRDS TulipChihuahua RoseCollie DaffodilPoodle JuniperSalmon MapleClownfish ElmShark HollyCanary BlueberryRobin SageMacaw The Genetics of Child Development 18:06 GENETIC FOUNDATION The Genetic Code Chromosomes – “Colored bodies” Genes – Multiple genes per chromosome; most genes lead to production of some protein. Genes composed of: DNA (deoxyribonucleic acid) – Genes differ in length of the segments of DNA o Double helix structure (Twisted ladder) o Ladder rungs consist of pairs of nucleotides (nitrogen-based molecules) attached to the sugar units of the sides: Adenine (A) paired with Thymine (T) Cytosine (C) with Guanine (G) Karyotype : depicts homologous pairs (except for the XY pair in males)—in humans, 22 of the pairs are known as autosomes, and 1 pair are sex chromosomes. Gametes – Sex cells (egg, sperm) Mitosis – Process by which DNA duplicates itself Meiosis – Process by which gametes, or sex cells are formed o Crossing Over – Pairs of chromosomes exchange corresponding segments to create new genetic combinations o Genetic variability is important from a evolutionary standpoint (red hair example) Alleles – The different forms/versions of each gene (ex. Brown-eye, blue-eye, green-eye, etc.) o Occur at the same locus on the autosomes, one each from mother and father Genotype – One’s genetic inheritance (ex. BB or Bb or bb for eye color) o Homozygous – Having some two alleles for a trait (ex. BB or bb) o Heterozygous – Having two different alleles for a trait (ex. Bb) Phenotype – One’s expression of a trait (ex. Brown eyes vs. blue eyes) Monozygotic Twins – Share a genotype (mono- = one zygote); dizygotic (fraternal) twins do not GENETIC INHERITANCE
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Autosomes Dominant Traits – Supersede expression of recessive traits Recessive Traits – Exhibited only when inherit two alleles (only one allele makes one a carrier) Co-Dominance – With some traits, a combination of the alleles is phenotypically expressed, as with AB blood. Dominant Recessive Brown eyes Gray, green, blue Curly hair Straight hair Brown hair Blond or light hair Rhesus-positive blood RH-negative blood Dominant Recessive Type A blood Type O Type B blood Type O Polygenic inheritance – More than one gene influences expression of a trait, such as intelligence and height Dominant & Recessive Disorders: o Dominant: Huntingtons: Occurs 35-40 years of age, causes brain deterioration, loss of motor control, memory personality, etc. Familial Alzheimer’s: Marfan’s Syndrome: Extremely long limbs Ex. Abraham Lincoln o Recessive: Albinism: Congenital deafness: PKU, or phenylketonuria (chromosome 12): 1 in 10,000 births
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Lack the ability for the liver to produce the enzyme phenylalanine hydroxylase, that converts a amino acid phenylalanine into tyrosine Toxic excess of phenlalanine builds up in nervous system, leading to symptoms by 3-5 months; death by age 4 if dietary restrictions
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