Chapter 5.5 1,2,3,4, and 5.6 1,2 and 3

1) Distinguish between autosomes and sex chromosomes.

Autosomes are chromosomes that determine traits of the organism. Sex Chromosomes determine the sex of the organisms.

2) Explain how sex determined in humans.

In humans, sex is determined by a specific set of chromosomes. Females have two X chromosomes (XX), whereas males have an X and a Y chromosome (XY). A mature female will produce eggs, each with one X chromosome, a mature male will produce sperm with either an X chromosome or a Y chromosome.

2) Complete incomplete dominance with cododominance, using examples as support.

Incomplete dominance (sometimes called partial dominance) is a heterozygous genotype that creates an intermediate phenotype. In this case, only one allele (usually the wild type) at the single locus is expressed in a doseage dependent manner, which results in an intermediate phenotype. A cross of two intermediate phenotypes (= monohybrid heterozygotes) will result in the reappearance of both parent phenotypes and the intermediate phenotype. The classic example of this is the color of flowers. In codominance, neither phenotype is recessive. Instead, the heterozygous individual expresses both phenotypes. A common example is the ABO blood group system. The gene for blood types has three alleles: A, B, and i. i causes O type and is recessive to both A and B. The A and B alleles are codominant with each other. When a person has both an A and a B allele, the person has type AB blood.

4) Describe the concept of independent assortment.

Independent assortment is the concept that the segregation of one set of allels during gamete formation is not affected by the presence or segregation of other sets of alleles. The condition that causes this principle not to function as expected is when two traits are on the same chromosome.

3) Describe the condition of multiple alleles. What human characteristics are controlled by multiple alleles?

Multiple alleles occurs when one of more than two alleles can occupy a given locus. Blood type in humans because AB and O are all at the same locus eventhough each individual will just have one.

5) Describe polygenic inheritance and distinguish between it and multiple alleles.

Multiple gene interaction occures when two or more genes are needed to produce a single trait. Multiple alleles is when several alleles may be at a given locus. The phenotype depends on which allele is at the locus.

1) Compare simple dominance with incomplete dominance. List several examples of incomplete dominance.

Simple dominance is when the dominant gene in a heterozygous organism expresses the dominant phenotype. Incomplete dominance is when a heterozygous organism exhibits a blending of the two genes both recessive and dominant. Plant flower color white and red make pink flowers. A human example is brachydactyly. Heterozygous individuals have some short fingers and toes homozygous individual for the abnormal gene are severely crippled with lack of finger and toes.

3) Why are X-linked traits passed from father to daughter but not father to son? Can a mother give an X-linked trait to her son and to her daughter.

Usually sexlinked traits are on the X chromosome, since it is so much bigger than the y chromosome. most of the sex-linked genetic problems would be found due to mutations in the X chromosome. since the father can only donate the X chromosome to the daughter and not the son, therefore, usually the sex linked traits are passed from father to daughter. Yes, a mother can also pass on the x chromosome to her son and her daughter. If the sex-linked trait is found on x chromosome, the son will definitely get it since the father donates the y chromosome to the son. The daughter will get the sex-linked trait depending on the type of the gene- whether it's dominant or recessive. If it is dominant, just one x is enough for the daughter to express that trait; if recessive, the daughter needs both x's to express that trait.