Mendelian Genetics

Artificial Selection Inherited variations in traits

Mendelian Genetics

Heredity – The passing of traits from parents to offspring through generations. –Genetics – The study of genes. “Genesis” to be born Genes – Individual bits of information made of DNA and located on chromosomes

Mendelian Genetics Gregor Mendel – Father of Genetics Austrian monk/mathemetician Experimented with pea plants Mid 1800’s – work was not accepted Work rediscovered in 1900’s

Pea plants Advantages: 1.Grow quick in a small plot. 2.Easy to cross (mate) 3.Dioecious – both sexes on same plant. 4.Many viable offspring from a variety of crosses

Pea plants Advantages: 1.Grow quick in a small plot. 2.Easy to cross (mate) 3.Dioecious – both sexes on same plant. 4.Many viable offspring from a variety of crosses

Pea plants Advantages: 1.Grow quick in a small plot. 2.Easy to cross (mate) 3.Dioecious – both sexes on same plant. 4.Many viable offspring from a variety of crosses male -female

Pea plants Advantages: 1.Grow quick in a small plot. 2.Easy to cross (mate) 3.Dioecious – both sexes on same plant. 4.Many viable offspring from a variety of crosses

Pea plants Advantages: 1.Grow quick in a small plot. 2.Easy to cross (mate) 3.Dioecious – both sexes on same plant. 4.Many viable offspring from a variety of crosses

Pea plants Advantages: 1.Grow quick in a small plot. 2.Easy to cross (mate) 3.Dioecious – both sexes on same plant. 4.Many viable offspring from a variety of crosses

Pea plants Advantages: 1.Grow quick in a small plot. 2.Easy to cross (mate) 3.Dioecious – both sexes on same plant. 4.Many viable offspring from a variety of crosses

Differences in Mendel’s study 1.Repeated results 2.Large numbers (in a small space) 3.Limited traits 4.Used readily identified traits and pure varieties

Probability Dealing with chance The determination of what is most likely to happen Only works for large numbers Each event is independent over another

Probability Dealing with chance The determination of what is most likely to happen Only works for large numbers Each event is independent over another

Probability Dealing with chance The determination of what is most likely to happen Only works for large numbers Each event is independent over another Deviation – the difference between the results you expect and the results you actually get.

Mendel’s studies Pure varieties – Always produce same results and same traits Bred for 10 generations to ensure viability

X = 6 feet tall

X = 1 foot tall

Pure variety cross Pure TallxPure dwarf

Pure variety cross Pure TallxPure dwarf All Tall

Pure variety cross Pure TallxPure dwarf All Tallx Tall

Pure variety cross Pure TallxPure dwarf All Tallx Tall Tall : Dwarf

Pure variety cross Pure TallxPure dwarf All Tallx Tall Tall : Dwarf 3 : 1 75% : 25%

Genetic terms Hybrid – Contains both dominant and recessive genes or traits Dominant – Always appears in a hybrid. Capital letter denotes the dominant trait T = Tall Recessive – Never appears in a hybrid. Lower case denotes the recessive trait. t = dwarf

Genetic terms Phenotype– How the genes appear. Ex. Tall, dwarf, Green, yellow Genotype – Shows the gene combinations present. Ex. TT, Tt, tt Tt = tT (capital 1 st )

Genetic terms Genotype – Shows the gene combinations present. Ex. TT, Tt, tt Tt = tT (capital 1 st ) Allele – Refers to one of the two forms of a gene. Ex. “T” or “t” locus – the location of an allele on a chromosome

Genetic terms Genotype – Shows the gene combinations present. Ex. TT, Tt, tt Tt = tT (capital 1 st ) Allele – Refers to one of the two forms of a gene. Ex. “T” or “t” locus – the location of an allele on a chromosome

Genetic terms Genotype – Shows the gene combinations present. Ex. TT, Tt, tt Tt = tT (capital 1 st ) Allele – Refers to one of the two forms of a gene. Ex. “T” or “t” locus – the location of an allele on a chromosome

Genetic Crosses Law of Complete Dominance – When a dominant and recessive trait appear in a hybrid. The dominant trait always appears. Capital = Dominant, lower case = recessive Homozygous – Organisms which have the same 2 genes (alleles – letters) for a trait. TT or tt (purebred) Heterozygous – Organisms which have 2 different genes (alleles- letters) for a trait. Tt (hybrid)

Genetic Crosses Calculating phenotypes and genotypes P 1 = parent generation F 1 = first offspring (filial) F 2 = 2 nd offspring from F 1 cross. Punnett Square – Diagram used to calculate probabilities, genotype, and phenotype from genetic crosses. Right side – father’s alleles – letters Left side – mother’s alleles – letters Each square = offspring (4) = 25%

25% Gametes Offspring Phenotype = Tall Genotype Phenotype = TallPhenotype = Short Phenotype = Tall 25%

Haploid - 23 Diploid-46

Law of segregation: Law of segregation – the 2 alleles for each trait separate when gametes form Haploid - 23 Diploid-46

25%

Gametes Offspring Phenotype = Tall Genotype Phenotype = TallPhenotype = Short Phenotype = Tall 25%

Sample Genetic Problems Solve on Punnett Square Sample # 1 and 2 Tall (T) is dominant over short (t) (recessive) pea plants. Mate a homozygous tall with a homozygous recessive and calculate the genotypes and phenotypes per cents and ratios for the F1 and F2 generations. Round ( R ) seeds are dominant over wrinkled ( r ) seeds. Mate a heterozygous round seed plant with a homozygous wrinkled. Calculate the genotypes, phenotypes, and % and ratios for the F1 generation. Sample # 4 Green (G) is the dominant color for pods in pea plants. Yellow (g) is recessive. Calculate the F1 generation genotypes, phenotypes, % and ratios from a cross between two heterozygous Green podded plants.

# 3 Round ( R ) seeds are dominant over wrinkled ( r ) seeds. Mate a heterozygous round seed plant with a homozygous wrinkled. Calculate the genotypes, phenotypes, and % and ratios for the F1 generation.

Sample # 4 Green (G) is the dominant color for pods in pea plants. Yellow (g) is recessive. Calculate the F1 generation genotypes, phenotypes, % and ratios from a cross between two heterozygous Green podded plants.

4 Chromosomes 2 Chromosomes 1 Diploid Cell 4 Haploid Cells

Crossing over and Independent assortment

Haploid - 23 Diploid-46

25% Gametes Offspring Phenotype = Tall Genotype Phenotype = TallPhenotype = Short Phenotype = Tall 25%

Test cross To determine an unknown genotype. A known genotype (homozygous recessive) is mated with an unknown (pure or hybrid?) to determine from the results

Test cross Tall = TT or Tt dwarf = tt A tall plant of unknown genotype is crossed with a dwarf. 2 possible choices

Dihybrid Cross 2 differents characters with two different traits on different chromosomes

Dihybrid Cross 2 differents characters with two different traits on different chromosomes Law of Independent Assortment – States that alleles of each gene segregate into gametes independently of alleles of other genes, as shown in a dihybrid cross

Human Genetics and Exceptions to Mendel’s Studies

Exceptions to Mendel’s studies Mendel – Traits showed complete dominance (autosomal) with traits on separate homologous chromosomes

Exceptions to Mendel’s studies 1)Incomplete or Co- dominance – Neither gene is hidden in a hybrid Causes a blending of traits or both traits appear

Exceptions to Mendel’s studies 1)Incomplete or Co- dominance – Neither gene is hidden in a hybrid Causes a blending of traits or both traits appear Ex. 4 o’clock flower, carnations, shorthorn cattle

Incomplete Dominance Two different traits. Neither is dominant, so there is a blending of the traits.

X

Codominance Two different traits, both are dominant and both appear

Sample Problem #1 Shorthorn cattle – Red fur = R White fur = R ’ RR x R’R’ = RR’ = Roan (pink) Cross two Roan cattle

2) Multiple Alleles More than two alleles possible to choose for a trait, but only two alleles present

Multiple alleles Rabbit fur - 4 possible alleles C = normal c = albino C ch = chinchilla c h = himalayan

Multiple alleles Rabbit fur - CC = Cc = cc = CC ch = c h c = C ch c h =

Multiple Alleles – Blood type Human blood Antigens - Foreign clotting factor 3 alleles – I A, I B, i (no antigen) Phenotypes: Type A = I A I A or I A I Type B = I B I B or I Bi Type AB = I A I B Type O = i i

OO AA BB AO BO AB or

Sample # 2 Blood type – A woman who is hybrid for type B blood marries a man with type O blood. What type of blood could their children NOT have?

Chromosomes and Sex determination

44 Autosomes 2 Sex Chromosomes

Male Genotype

44 Autosomes 2 Sex Chromosomes

Female Genotype

Probability of Boy vs. Girl? 50:50

3) Sex-linked Traits Sets of alleles found only on the X chromosome. Females have two alleles X+X, males have only one X+Y

3) Sex-linked traits Some traits are found on the alleles of only X chromosomes and not on the Y. (Females = XX and Males = XY) First discovered in fruit flies

Fruit Flies Drosophila melanogaster

3) Sex-linked traits 1910 – Thomas Morgan Drosophila (fruit flies) white eyed flies – recessive mutation (r) 3/1000 Red eyes = dominant (R) Homozygous cross – all red Hybrid cross = 3:1 ? Results = 3,470:782 with all white eyes being male Traits on X but not Y chromosome

3) Sex-linked traits 1910 – Thomas Morgan Drosophila (fruit flies) white eyed flies – recessive mutation (r) 3/1000 Red eyes = dominant (R) Homozygous cross – all red Hybrid cross = 3:1 ? Results = 3,470:782 with all white eyes being male Traits on X but not Y chromosome

Drosophila Fruit Fly Cultures - Chromosome 1, White Drosophila Fruit Fly Cultures - Wild Type (+)- Genetics

X R = Red eyes X r = white eyes Cross 2 Hybrid red-eyed flies. Calculate the genotypes and phenotypes for male and female offspring Sample # 3

Sample # 4 Red-Green or Green-Red Colorblindness, Hemophilia X N = Normal trait X n = colorblind A colorblind female marries a normal eyed male. Which offspring will be colorblind?

Everyone should see a 12.

Normal visioned people should see 45. Colorblind people won't see any numbers.

Normal visioned people should see 29. Colorblind people should see 70.

Normal visioned people won't readily see any number, but colorblind people will easily see a number 5.

Normal visioned people will see 26. If you are red-blind, you should only clearly see the 6. If you are green-blind, you should only see the 2. A totally colorblind person won't see any number in this plate.

This is illustrated by calico cats. Coat color in cats is an X-linked gene, with alleles for black and orange-brown, so X B X B and X B Y cats will have a black coat, while X O X O and X O Y will have an orange-brown coat. Another possible combination for female cats would be X B X O. Both of the color alleles would be expressed, so the cat would end up being partially brown and partially black. or only X B X B and X B Y X O X O and X O YXBXOXBXO

Hemophilia Family Tree

4) Sex influenced traits Gene present plus the proper hormone required Examples: Male pattern baldness, hairy pinna (ears), horns in sheep.

5) Polygenic traits More than two alleles on more than two chromosomes, with more than two alleles appearing at once.

Polygenic traits in humans Non – Blue Eye color Skin color Hair color Height

Dark Brown eyes Light skin Short Light Green eyes Dark skin Tall

Non – Blue Eye color Hair color

Skin color

Genes and the Environment The environment influences the phenotype for some genotypic traits. The norm of reaction is the phenotypic range of a genotype influenced by the environment For example, hydrangea flowers of the same genotype range from blue- violet to pink, depending on soil acidity Genes are what an organism may become not will become Ex. Genes for chlorophyll – no sunlight = no chlorophyll Human behavior – identical twins - differences

Acidic soil Basic or alkali soil

Norms of reaction are generally broadest for polygenic characters Such characters are called multifactorial because genetic and environmental factors collectively influence phenotype Genes and the Environment

Genetic disorders Pedigree : Chart used to trace family histories of genetic traits

Hemophilia Family Tree

Sickle Cell Anemia

Polydactyly

PKU Phenylketonuria

PKU - 1 in 15,000 Americans. A non-food source of phenylalanine is the artificial sweetener Aspartame. This compound, sold under the trade names "Equal" and "NutraSweet", is metabolized by the body into several chemical byproducts including phenylalanine.

Porphyry ?