What is Genetics Genetics Study of heredity Heredity
- Slides: 15
What is Genetics? • Genetics: Study of heredity • Heredity: passing of traits from parent to child • Patterns of relatedness can help predict offspring characteristics – – – Autosomal recessive Autosomal dominance Sex-Linked Incomplete dominance Codominance
• “Father of Genetics” • Famous for pea plant studies • Mendel studied seven pea plant traits – Color, shape, texture, height, etc… • Results shaped our understanding of genetics
Each trait had a 3: 1 ratio. No way that can be a coincidence!
• 1 gene may prevent the expression of another • Organisms inherit 2 copies of each gene – One from each parent
• Genes are located on chromosomes • Genes inherited from mom and dad • Genes come in several forms called alleles – Allele: Alternative forms of a gene – Ex: Flower color • White allele or Purple allele • Letters used to abbreviate alleles – Dominant Allele = Capital letter – Recessive Allele = Lowercase letter
• Phenotype: Actual appearance of a gene • Genotype: Genetic makeup of an organism • Genotype determines phenotype
Genetics Vocabulary Review Choices: 1) YY 2) Tall 3) Yy 4) SS 5) y. Y 6) gg 7) Smooth 8) Green 9) TT 10) Dwarf Which choice(s) are examples of: Genotypes? 1, 3, 4, 5, 6, 9 Phenotypes? 2, 7, 8, 10 Homozygous genotypes? 1, 4, 6, 9 Heterozygous genotypes? 3, 5 Homozygous recessive genotypes? 6 Homozygous dominant genotypes? 1, 4, 9
Punnett Squares • Defined: Tools used to determine genetic probability • Probability = likelihood that a certain event will happen • 2 Steps: – 1) Place parent genotypes on the outside of the box – 2) Fill in the boxes
Cross a homozygous dominant yellow (YY) plant with a homozygous recessive green (yy) plant Key Y = yellow y = green 100% Probability of growing a yellow plant? _______ 0% Probability of growing a homozygous recessive plant? ______ 0% Probability of growing a homozygous dominant plant? ______
Cross a heterozygous dominant yellow (Yy) plant with a heterozygous dominant yellow (Yy) plant Key Y = Yellow y = green 50% Probability of growing a heterozygous plant? ____ 25% Probability of growing a green plant? ____ 25% Probability of growing pure yellow? _____
Bravo! You can predict pea color! So What?
Maria is a heterozygous healthy (Hh) female and Jeff suffers from recessive cystic fibrosis (hh). Key H = healthy h = cystic fibrosis Probability of having a healthy 50% child? _____ Probability of having a homozygous 0% dominant child? ____
Kobe Kuiz 1) How are dominant alleles expressed? Recessive? 2) Which of the following are genotypes? Phenotypes? TT Green y. Y Pp Purple gg Smooth 3) Which of the following are heterozygous genotypes? TT Green y. Y Pp Purple gg Smooth 4) Genes may often be found in two forms (dominant and recessive). What are these alternate forms of a gene called? 5) Genes are segments of DNA found on ________. 6) If item A is found in a 2: 1 ratio compared to item B, what percentage is item A? 7) If item A is found in a 4: 1 ratio compared to item B, what percentage is item A? 8) George & Martha are planning a family. Each has a family history of autosomal recessive disorder and they agree to have their blood tested. George is found to be heterozygous healthy and Martha is found to be homozygous dominant healthy. What are the chances they have a healthy child? Homozygous dominant child? Heterozygous child? Homozygous recessive child?
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