Chapter 7 Genes and Inheritance Family resemblance how
Chapter 7: Genes and Inheritance Family resemblance: how traits are inherited
Selective Breeding: by observing heredity Breeding animals for ages Even though there was no knowledge about the transmission of traits from parents to offsprings. Race Horse Breeding
PLANT BREEDING • Green revolution – High yielding wheat and rice varieties • Norman Borlaug : Nobel peace prize
Gregor Mendel (Mid 1800 s) Father of Genetics • a monk • an agronomist • a mathematician Petal Stamen Carpel • Didn’t know about – DNA, genes – Chromosomes – meiosis
Existing theories during Mendel’s time. . …. Pre-made Humans? ? ? Blending theory? ? ?
Why did Mendel use pea plants? – short life cycles – easy to maintain – Easy to breed – Several traits which were easily distinguishable
Mendel’s success (was because of hard work and luck) 1. Choice of ideal organism 2. Established true breeding populations 3. Choice of traits which occurred only in ____ versions 4. Traits controlled by ___ gene
Freckles Widow’s peak Free earlobe No freckles Straight hairline Attached earlobe RECESSIVE TRAITS DOMINANT TRAITS Human traits determined by a single gene
Alleles of a gene – alternate forms Homologous chromosomes have the same genes but can have different ______ Trait: Stem length Alleles: Tall allele (T) Short allele (t)
How many copies of each gene do you have? A. One copy B. Two copies C. Twenty three copies D. Differs from person to person
Dominant and Recessive traits 2 dominant alleles for gene ‘A’ AA: homozygous dominant 1 dominant & 1 recessive allele for gene ‘B’ Bb: heterozygous dominant 2 recessive alleles for gene ‘D’ dd: homozygous recessive
Check out your neighbor’s earlobes. Are they attached or free? Free (Dominant) Attached(Recessive)
The letter F represents the earlobe allele. If your neighbors earlobes are attached, and this trait is recessive, what alleles did they inherit? A. B. C. D. Ff FF ff ff. F
Some genetics vocabulary • Phenotype: the outward appearance of an individual – Free or Attached • Genotype: the individual’s genetic composition – FF (homozygous dominant) – ff (homozygous recessive) – Ff (heterozygous dominant)
Writing genotypes for Cystic Fibrosis
Dominant and Recessive traits The blue arrows point to a pair of alleles that are ____ A. Homozygous dominant B. Heterozygous dominant C. Homozygous recessive D. Recessive
Brain Storm…. • If some traits are single gene and recessive (like fish odor syndrome), shouldn’t there be fewer people in a population that have the recessive gene? • Dominant traits are not necessarily normal or more common
q q Mendel’s monohybrid experiment with pea plants looking at a single trait (like flower color), lead to Law of segregation A dominant trait masks the effect of a recessive trait.
Law of _____: you’ve got two copies of each gene but ____ helps put only ____ copy in each sperm or egg.
Three Ideas Mendel Used for Explaining This Pattern of Inheritance 1. Each parent puts into every sperm or egg it makes a single set of instructions for building the trait. 2. Offspring receive two copies of the instructions for any trait (called alleles). 3. The actual trait observed in an individual depends on the two copies of the gene that they inherit from their parents. Homozygous and heterozygous
How do we determine what traits offsprings inherit? Answer: By doing _______ To do punnett square you need to know 1. Genotypes 2. Type of gametes made 3. Then do the punnett square
Genotype Dimples No dimples Dd dd
genetic contribution of one parent dimples D d genetic contribution of one parent no dimples d d D d d d offspring genotype D d d d possibilities
What is the chance that a man homozygous for dimples and woman with no dimples will have a kid with dimples (No dimples is a recessive trait) A. B. C. D. 25% 50% 75% 100%
Mendels dihybrid experiments looking at two traits in a plant (like flower color and seed shape) resulted in Law of independent assortment 7. 16 Most traits are passed on as independent features: Mendel’s law of independent assortment.
What are the type of gametes made from an organism with genotype Ll. Ww? FOIL method LW Lw l. W lw Law of Independent Assortment: each pair of alleles ( Ll or Ww) segregates independently during gamete formation
You have a pea plant that is heterozygous for pea shape and homozygous dominant for pea color, Rr. YY. Which of the following are possible allele combinations that you could see in the sex cells from your plant? A. You could get gametes with Rr. YY B. You could get gametes with Rr or YY C. You could get gametes with RY or r. Y D. You could get gametes with R or r or Y
If you are heterozygous for earlobe attachment, what percentage of your gametes will have the “F” gene? A. B. C. D. 25% 50% 75% 100%
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