C-Notes: Patterns of Inheritance (Variations on Mendel’s Law) Stnd: 3a C-Notes: Patterns of Inheritance (Variations on Mendel’s Law) 01/29/14 Objective: SWBAT: identify the many factors that affects the phenotypes by the interactions of alleles in a gene.

How is Sex Determination (gender) in humans determined? Last pair of chromosomes (# 23; x and y) The Male determines sex of the offspring How is Sex Determination (gender) in humans determined?

INHERITANCE PATTERNS XX XY SEX DETERMINATION **Male determines sex** 50% chance male 50% chance female X Y XX XY X X

What are Sex Chromosomes? The chromosomes carries the genes that determine whether an individual is female or male. Mendel’s peas did not have sex chromosomes. Mendel worked with peas that had female and male parts on the same plant. What are Sex Chromosomes?

How are Male and Female chromosomes expressed? During Meiosis, the “sex chromosome” pair separate. Female chromosome is symbolized with an X and the Male chromosome with a Y. A female produces egg cells with two X chromosomes in her body cells. Ex: genotype is XX. A male produces sperm cells with an X and a Y chromosome in his body cells. Ex: His genotype is XY What is the probability for having a girl or boy child? (using a Punnett square) How are Male and Female chromosomes expressed?

What is Incomplete Dominance? Neither allele is completely dominant nor completely recessive. The heterozygous phenotypes is intermediate between the two homozygous phenotypes. The phenotypes shows a blend of the 2 traits just like “mixing paints”. Ex: Parent flowers Red and White makes pink offspring EX: Straight and curly hair makes Wavy hair What is Incomplete Dominance?

List the genotypes. 4RW List the phenotypes. 4 Pink W W R W R W R pink Example: Cross a homozygous red carnation flower (RR) with a homozygous white flower (WW). List the genotypes. 4RW List the phenotypes. 4 Pink W W R W R W R pink pink R W R W pink pink

List the genotypes. 2RW, 2WW List the phenotypes. 2 Pink, 2White R W R Example: Cross one heterozygous pink (RW) 4 o’clock flower with a White flower (WW). List the genotypes. 2RW, 2WW List the phenotypes. 2 Pink, 2White R W R W W W W pink white R W W W pink white

Incomplete dominance

Example 2-Incomplete Dominance

An organism that has both alleles equally expressed in a heterozygote (displays both phenotypes at the same time). Ex: ABO Blood type Ex: For example, a cross between a black cat (BB) and a tan cat (TT) results in a tabby cat (black and tan mixed together). What is Codominance?

Codominance red white roan Defined: When both alleles are dominant and equally expressed The colors do NOT blend together, but are equally seen Ex: Cattle Coat Red cow x White cow = Roan Cow Ex: Human Blood types Type A x Type B = Type AB red white roan

Blood types are another example of codominance. The ABO blood types result from codominant alleles This blood group consists of 3 different alleles Dominant A allele Dominant B allele Recessive O allele A and B are equally dominant Many genes have more than two alleles.

B B A A B A B A B A B List the genotypes. 4AB List the phenotypes. Ex: Cross Jason who is homozygous for type A blood with Maria who is homozygous for type B blood. List the genotypes. 4AB List the phenotypes. 4 type AB blood B B A A B A B A B A B

B o A o A B A o B o o o List the genotypes. 1AB, 1Ao, 1Bo, 1oo Ex: Cross Mike who is heterozygous for type A blood with Lisa who is heterozygous for type B blood. List the genotypes. 1AB, 1Ao, 1Bo, 1oo List the phenotypes. 1 type AB blood 1 type A blood 1 type B blood 1 type o blood Probability of Heterozygous individual? 75% B o A o A B A o B o o o

In humans, hair, eye and skin color are polygenic traits. Some traits which have many possible phenotypes that are determined by more than one gene The interactions of theses genes allows for the large numbers of phenotypes. Ex: Feather color in parakeets is determined by two genes. One gene controls yellow color and the other controls blue color. In humans, hair, eye and skin color are polygenic traits. The range in skin colors of humans is determined by no less than four genes! What is Polygenic Traits?

Many genes may interact to produce one trait. Polygenic traits are produced by two or more genes. Order of dominance: brown > green > blue.

What factors interacts (affects) with genotypes? Environmental Genes provide a tendency toward a phenotype that the environment can alter. Phenotype is a combination of genotype and environment EX: The sex in sea turtles is determined by both genes and the temperature of the environment During the development of the embryo, higher temperature favors the production of males. 2. Nutrition EX: In humans, height is an example of a phenotype determined by genes and by the environment. But if a person does not get the proper nutrients, he or she may not reach his or her potential height. What factors interacts (affects) with genotypes?