Basic Genetic Concepts & Terms & Punnett Squares

1. Chapter 2.2 - Heredity and Genetics Basic Genetic Concepts & Terms & Punnett Squares

2. Genetics: what is it? • What is genetics? • “Genetics is the study of heredity, the process in which a parent passes certain genes onto their children.” • What does that mean? • Children inherit their biological parents’ genes that express specific traits, such as some physical characteristics, natural talents, and genetic disorders.

3. Word Match Activity Match the genetic terms to their corresponding parts of the illustration. Handout Word Match WS • base pair • cell • chromosome • DNA(Deoxyribonucleic Acid) • *double helix*? • genes • nucleus

4. Word Match Activity chromosome nucleus cell base pair (doublehelix) DNA genes • base pair • cell • chromosome • DNA(Deoxyribonucleic Acid) • double helix* • genes • nucleus Illustration Source: Talking Glossary of Genetic Terms http://www.genome.gov/glossary.cfm?key=chromosome

5. Genetic Concepts H describes how some traits are passed from parents to their children. The traits are expressed by g , which are small sections of DNA that are coded for specific traits. Genes are found on ch ___. Humans have two sets of _(hint: a number) chromosomes—one set from each parent.

6. Genetic Concepts Heredity describes how some traits are passed from parents to their children. The traits are expressed by genes, which are small sections of DNA that are coded for specific traits. Genes are found on chromosomes. Humans have two sets of 23 chromosomes—one set from each parent.

7. Genetic Terms • Allele: An allele is an alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome. • Genes: It is a name given a part of DNA and RNA • Dominant : The stronger of the two alleles. Expressed • Recessive: The weaker of the two alleles. Hidden • Homozygous: Both alleles are the same. • Heterozygous: Two different alleles. • Genotype: This is the "internally coded, inheritable information" carried by all living organisms. “Blueprint” • Phenotype: This is the "outward, physical manifestation" of the organism. • Mendellian Inheritance: A scientific theory of how hereditary characteristics are passed from parent organisms to their offspring. • Hybrid: A cross breeding of two purebreds. Red & White flowers.

8. Mendelian Inheritance The inherited traits are determined by genes that are passed from parents to children. A child inherits two sets of genes—one from each parent. A trait may not be observable, but its gene can be passed to the next generation.

9. Mendelian Inheritance Each person has 2 copies of every gene—one copy from mom and a second copy from dad. These copies may come in different variations, known as alleles, that express different traits. For example, 2 alleles in the gene for freckles are inherited from mom and dad: • allele from mom = has freckles (F) - Dominant • allele from dad = no freckles (f) - Recessive • child has the inherited gene pair of alleles, Ff(F allele from mom and f allele from dad).

10. Punnett Squares

11. What is a PUNNETT SQUARE? A tool to predict the probability of certain traits in offspring that shows the different ways alleles can combine A way to show phenotype & genotype A chart that shows all the possible combinations of alleles that can result when genes are crossed

12. What is a PUNNETT SQUARE? Letters stand for dominant and recessive alleles An uppercase letter stands for a dominant allele Lowercase letters stand for recessive alleles

13. Using a PUNNETT SQUARE To set up a Punnett square, draw a large square, and then divide it into 4 equal sections (also squares). It should look something like this:

14. Using a PUNNETT SQUARE Now you need two parents to mate, ones with a known genotype For example, a red flower (genotype Rr) and a white flower (genotype rr). Rr x rr

15. Using a PUNNETT SQUARE Place one of the parents on top, and one on the left. You should get a something similar to this:

16. Using a PUNNETT SQUARE Finally, take each letter in each column and combine it with each letter from each row in the corresponding square. You should now have a picture close to this:

17. Using a PUNNETT SQUARE The two-letter combinations are the possible genotypes of offspring They are: Rr, Rr, rr, and rr genotypes From this it is possible to determine the probability (chance) that a flower will have a red phenotype (2/4 or 50%) or a white phenotype (2/4 or 50%)

18. Mendel’s Laws of Inheritance • Law of Dominance: In heterozygous genotypes, dominant alleles hide recessive alleles when both are inherited by an organism. (Hh means the dominant trait will show up in the phenotype)

19. Mendel’s Laws of Inheritance 1. The Law of Segregation (separation): Each organism has 2 alleles for a gene. Only one allele from each gene pair will be passed on to the offspring.

20. Homozygous/Heterozygous Hmzg / Htzg • Cross a homozygous dominant tall plant with a homozygous recessive short plant. • Dominant trait = tall • Recessive trait = short • T = tall • What letters would you use to represent this cross? • t = short

21. TT • What is the genotype of a homozygous recessive short plant? • What is the genotype of a homozygous dominant tall plant? • tt • TT x tt • Genotype % TT % Tt % tt 0 t t 100 Tt Tt T T 0 • Phenotype % tall % short 100 Tt Tt 0

22. What letters would you use to represent this cross? 2. Cross a heterozygous brown haired rabbit with a homozygous recessive white haired rabbit. • Dominant trait = brown hair • Recessive trait = white hair • B = brown • b = white

23. Bb • What is the genotype of a homozygous recessive white haired rabbit? • What is the genotype of a heterozygous brown haired rabbit? • bb • Bb x bb • Genotype % BB % Bb % bb 0 b b 50 Bb Bb B b 50 • Phenotype % brown % white 50 bb bb 50

24. 3.. Cross a homozygous dominant long haired guinea pig with a heterozygous long haired guinea pig. • What letters would you use to represent this cross? • Dominant trait = long hair • Recessive trait = short hair • L = long • l = short

25. LL • What is the genotype of a heterozygous long haired guinea pig? • What is the genotype of a homozygous dominant long haired guinea pig? • Ll • LL x Ll • Genotype % LL % Ll % ll 50 L l 50 LL Ll L L 0 • Phenotype % long % short 100 LL Ll 0

26. What letters would you use to represent this cross? 4. Cross a heterozygous wrinkly elephant with another heterozygous wrinkly elephant. • Dominant trait = wrinkly skin • Recessive trait = smooth skin • W = wrinkly • w = smooth

27. Ww • What is the genotype of a heterozygous wrinkly-skinned elephant? • What is the genotype of a heterozygous wrinkly-skinned elephant? • Ww • Ww x Ww • Genotype % WW % Ww % ww 25 W w 50 WW Ww W w 25 • Phenotype % wrinkly % smooth 75 Ww ww 25

28. A plant that is homozygous dominant for round seeds is crossed with a heterozygous plant. What is the probability that the offspring will have wrinkled seeds? • R = round • r = wrinkled RR x Rr • Genotype % RR % Rr % rr 50 R r 50 RR Rr R R 0 • Phenotype % round % wrinkled 100 RR Rr 0