Chap. 11/14 Genetics or Why do you look Like that!?!
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Transcript of Chap. 11/14 Genetics or Why do you look Like that!?!
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Chap. 11/14 Genetics
orWhy do you look Like
that!?!
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Trait Inventory ActivityPart 1
• Complete H.O. on traits of peers
• Write “yes” or “no” based on what you see!
• How are we all alike? (trait)• How do some of us differ?
(characteristic)• Part II later!!
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I. Meiosis - Reduction Division
•Produces gametes… •Gametes are 1n/haploid…
• In males – 4 sperm cells produced
• In females – 1 egg cell and 3 polar bodies (“duds”) produced.
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Recall…•Mitosis …•Somatic cells/body cells…
•2n/diploid…
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Terms-•Homologous pairs – original chromosome pair and their copies.
•Tetrad – chromosome pair &
corresponding homologous pair
•A tetrad contains 4 chromatids
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II. Gregor Mendel – •“Father of genetics”
•Pea plants… •Characteristics and traits
•Some characteristics were visible,some were not
•Ex. Plant height – tall or short…
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3 Principles of Genetics•They are based on alleles – contrasting genes that determine a trait.
•Ex. BLUE vs BROWN EYES
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*A. Principle of Segregation – •Alleles segregate/separate
•Occurs during meiosis…
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*B. Prin. of Independent Assortment –
•Alleles are randomly arranged
•Ex. Trait “a” is not dependant
on trait “b”
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*C. Prin. Of Genes and Dominance –
•One allele “hides“ another.
•Dominant… •Recessive…
• Fig. 11-3
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III. Crash course in crossing
•P1 – original parents with
pure traits – called true
•F1 – first generation with a mix of parent traits – hybrids
•F2 – second generation with a mix of their parents traits
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A. Punnett squares -•Predicts…•Tells the – –Genotype …–Phenotype …
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•Capitals represent dominant characteristics
•AA, BB•Lower case represent recessive characteristics
•aa bb
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•Purebred means two identical alleles
•GG, mm, •Can be dominant or recessive
•This is homozygous •“same trait/allele”
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•Hybrid means two different alleles
•Nn,Oo•Will always be dominant --- why???)
•This is heterozygous •“different trait/allele”
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B. Types: •Monohybrid cross - “One trait; one letter”
•Dihybrid cross - “Two traits; two letters”
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V. Gene expression is…
•Based on the environment, and the effect of other
genes. –Toxins, disease, drugs…
•“Nature vs nurture”–Over/under nutrition–Soil acidity & flower color
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A.Dominant Alleles • Conditions that are expressed provided one
dominant allele is present
• Ex. PP or Pp – Tall plants• HH or Hh – Huntington’s
disease
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B. Recessive Alleles• Trait is expressed provided two recessive alleles are present.
• Ex. tt – short plants• In humans …• tt – Tay-sachs• aa - albinism
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C. Incomplete Dominance - • There is no dominance.
• The heterozygous genotype shows a mix of both phenotypes.
• Ex. White and red roses make pink roses.
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D. Codominance – •A type of incomplete dominance.
•Both alleles share dominance & are expressed in the
organism.•Ex. Roan cattle have both red and white fur.\
• In humans – sickle-cell anemia
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Codominance in humans …• Expressed in varying degrees
• Sickle-cell anemia–Person is either unaffected, a carrier, or affected
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E. Multiple Alleles – •Genes that have more than 2 possible alleles -
C, cch, ch, c •Each allele being expressed, not contrasting like in
peas!•Ex. Rabbit fur – p. 273
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Multiple Alleles in humans…• Blood types• A• B • AB (universal receiver)• O (universal donor)• Could be + or -
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F. Polygenic traits – •“Many genes” – traits due to the interaction of more than 3 genes.
•These traits tend to “blend” from one extreme to the other.
•Ex. Skin/fur color, eye color….
Very dark to very light
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Polygenic traits in humans• Height• Healthy weight• All vary from one to the other extreme
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G. Determing Sex•Only one X is required for survival.
•XX – female•XY - male
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H. Sex-linked Conditions – •Traits that are linked or found on the X or Y chromosomes
•Ex. Colorblindness,
hemophilia, muscular dystrophy
•Y – says “just make me a boy!”
P.350
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VI. Determining Genetics•A. Karyotype - picture of an individual’s
chromosomes–Homologous chromosomes
are paired & analyzed
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B. Pedigree•Family record that shows how a trait is inherited over
several generations.
• Identifies the carriers, those that are normal, & the affected individuals.
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VII. MUTATIONS & HUMAN GENETICS
A. CHROMOSOMAL MUTATIONS affect the entire chromosome–May be deletion, duplication, inversion, or translocation
B. NUCLEOTIDE MUTATION–Affects the nucleotide of DNA which makes the chromosome
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C. NONDISJUNCTION•Homologous chromosomes do not
separate during meiosis.
•Some effects may or may not be lethal.
•Autosomal chromosome:
•Ex. Down syndrome - due to trisomy 21 - having 3 of #21 chromosomes
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•Can affect sex chromosomes–Turner’s Syndrome – XO – affects females
–Klienfelter’s Syndrome – XXY- affects males
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•Chromosomes carry the alleles that produce the trait that makes you look the way you do!!!