 Gene – segment of DNA. Carries genetic information that codes for a trait.  Chromosome - compact packages of DNA. Inside nucleus.  Sperm – male sex cell (gamete)  Egg – female sex cell (gamete)

 Karyotype – arrangement of chromosomes. A picture.  Autosome - any chromosome that is not a sex chromosome

 Genotype = the genes of an organism; for one specific trait we use two letters to represent the genotype. ◦ A capital letter represents the dominant form of a gene (allele) ◦ A lowercase letter is the abbreviation for the recessive form of the gene (allele). Example: V = dominant v = recessive

 Dominant: a gene that is expressed, regardless of whether its counterpart allele on the other chromosome is dominant or recessive. ◦ Ex: VV or Vv = Long wings  Recessive : gene that produces its characteristic phenotype only when its allele is identical; vv= short wings

 Phenotype = the physical appearance of a trait in an organism ◦ BB, Bb = brown eyes ◦ bb = blue eyes

 Allele: different versions of the same gene occupying a given position on a chromosome Chromosome from Mom Chromosome from Dad

 Organisms that have 2 identical alleles for a particular trait are called homozygous (TT or tt).  Organisms that have 2 different alleles for a particular trait are called heterozygous (Tt).

 The use of a microscope to analyze cells during mitosis shows condensed chromosomes  Scientists cut pictures of these chromosomes out in and arrange them into a karyotype (right). =The number and visual appearance of the chromosomes in the cell nuclei of an organism or species

 2 haploid gametes (egg and sperm) join together during fertilization.  The result is a fertilized egg called a zygote which is diploid.  Humans have 46 chromosomes

 Two of the 46 chromosomes are sex chromosomes because they determine whether the zygote will develop into a male or female  Females have XX chromosomes  Males have XY chromosomes

 The 44 chromosomes that are not sex chromosomes are called autosomes.

 Because of the way sex chromosomes segregate, there is a 50:50 chance of both males and females being born  All human egg cells carry a single X chromosome, but only half of sperm cells carry an X while the other half carries a Y Which parent determines the sex of the baby?

 To identify an inherited trait controlled by a single gene, first we need to determine if that the trait is inherited and not a result of environmental influences. Then, we have to study how it’s passed from one generation to the next

 A pedigree chart shows the relationships within a family and how particular traits are passed from one generation to the next

 Nope. Unfortunately, many traits are polygenic, meaning they are controlled by many genes. ◦ Example: eye or ear shape  Additionally many traits are influenced by the environment ◦ Example: genetics determines a person’s maximum possible height, nutrition also plays a role in whether or not that height is ever reached

 While it’s important to consider environmental effects on expression of genes…  Environmental effects on genes expression ARE NOT INHERITED!!! ◦ Analogy: Just because someone’s arm gets cut off doesn’t mean their child will be born missing an arm!

Recessive aaAa aa Aa

 Dominant alleles will be expressed even if the recessive allele is present  Codominance: both alleles of a gene pair in a heterozygote are fully expressed, with neither one being dominant or recessive to the other R = Red flower W = White flower RW = Red & White spotted flowers

 Incomplete Dominance: both alleles of a gene are expressed in the phenotype- resulting in combined phenotype red flowers crossed with white flowers = pink flowers

 The trick is to recognize when you are dealing with a question involving incomplete dominance.  There are two steps to this: 1) Notice that the offspring is showing a 3rd phenotype. The parents each have one, and the offspring are different from the parents. 2) Notice that the trait in the offspring is a blend (mixing) of the parental traits.

 When meiosis goes wrong and homologous chromosomes fail to separate its called nondisjunction. This means “not coming apart.”  When this happens abnormal numbers of chromosomes end up in gametes and a disorder of chromosome numbers may result. ◦ Examples: Down Syndrome, Turner’s Syndrome, Klinefelter’s Syndrome

 If 2 copies of an autosomal chromosome fail to separate in meiosis an individual may be born with 3 copies of a chromosome. This is known as “trisomy”  Down Syndrome is the most common form of this, called Trisomy 21.

Child with Downs Syndrome The extra chromosome causes problems with the way the body and brain develop.

 In females, nondisjunction can lead to Turner’s Syndrome ◦ She inherits only 1 X (45, X) ◦ Sterile and sex organs don’t develop at puberty  In males, nondisjunction can lead to Klinefelter’s Syndrome (47, XXY) ◦ Extra X interferes with meiosis and usually prevents individuals from reproducing ◦ Estimated 1 in every males ◦ XXXY and XXXXY have been found!

 The Human Genome Project may help in finding cures for genetic disorders through gene therapy.  Gene therapy is the process of changing a gene that causes a genetic disorder. An absent or faulty gene is replaced by a normal, working gene.

 The most common form of gene therapy involves using DNA that encodes a functional, therapeutic gene in order to replace a mutated gene.  Today, most gene therapy studies are aimed at cancer and hereditary diseases linked to a genetic defect

 If scientists can find ways to cure genetic diseases is it okay if they also start engineering taller people, or their hair color, skin color, sex, blood group or appearance??????  What are the kinds of ramifications (effects) gene therapy in this way could have on human populations in the world?

 There have been NO incidences in which an individual lacks an X chromosome all together  This suggests that the X chromosome contains genes that are vital for the survival and development of an embryo

1. Single Allele Dominant 2. Single Allele Recessive 3. Sex Linked (X-Linked) 4. Multiple Alleles 5. Polygenic Traits

 Regular traits that are either determined by a dominant or recessive allele on an autosome 1. Autosomal Dominant examples: a. Huntington’s Disease b. Achondroplasia (dwarfisim) c. Polydactyly (extra fingers and toes) 2. Autosomal Recessive examples: a. Albinism b. Cystic Fibrosis c. Sickle Cell Anemia

Huntington’s Disease (HD)  Results in loss of muscle control and mental deterioration  No signs are shown until 30’s  Brain degeneration  Treatment: No cure, but drug treatments are available to help manage symptoms.

Achondroplasia  Dwarfism  Person grows no taller than 4’4

Polydactyly  The presence of more than the normal number of fingers or toes.  Can usually be corrected by surgery.

Albinism  Lack of pigment in skin, hair, and eyes  Mutation in one of several genes which provide the instructions for producing one of several proteins in charge of making melanin.

Cystic Fibrosis (CF)  Caused by recessive allele on chromosome 7  Small genetic change (removes one Amino Acid)  changes protein  Results in: Excess mucus in the lungs, liver and digestive tract, gets infection easily, and early death unless treated.

Sickle Cell Disease  Red blood cells are bent and twisted  Get stuck in capillaries  damage tissues  Results in weakness, damage to brain and heart

How do we determine the sex of an individual?  through sex chromosomes  Sex Chromosomes: X and Y Female: XX Male: XY  Who is responsible for gender determination in the child? The father because he gives an X or Y to the gametes. The mother only gives an X to the gamete  Which sex chromosome is bigger?  the X chromosome (y is much smaller)

 X-linked genes are genes found on the X chromosome, symbolized by X r, X R, Y 0.  Y-linked genes are found on the Y chromosome, symbolized by X 0, Y R, Y r  Thomas Morgan experimented with the eye color of fruit flies (Drosophilia) to determine X- linkage

1. Color Blindness 2. Muscular Dystrophy 3. Hemophilia 4. Icthyosis simplex (scaly skin)

 Turns out, there’s a special pattern of inheritance for genes located on the X or Y chromosome.  Because these chromosomes determine sex, genes located on them are termed sex-linked

 About 1 in 10 males is color blind, while 1 in 100 females are color blind in the U.S.  Colorblindness is X-linked. This means that the genes for color vision are located on the X chromosome.  Since females have 2 Xs they have a better shot at color vision, while males only have 1 X which means all X-linked alleles are expressed even if they are recessive.

 A person with normal color vision sees a number seven in the circle above.  Those who are color blind usually do not see any number at all.

 RED-GREEN COLORBLINDNESS:  People with red-green color blindness see either a three or nothing at all.  Those with normal color vision see an 8.

 Sex-linked  Results in progressive weakening and loss of skeletal muscle  1 in 3,000 U.S. males is born with it

 Males only get one copy of the X chromosome, so what happens to the extra one in females?  One X is randomly turned “off”. This is called X-Chromosome Inactivation. It forms a dense region in the nucleus called a Barr Body

 One X chromosome may have the allele for orange spots while the other X may have the allele for black spots  In cells in different parts of the body one X may be turned on while the other X is turned on elsewhere  The cat’s fur will have a mixture of orange and black spots  Fact: If a cat has 3 colors, it’s female. Males can only have 2 colors (unless they have genetic disorder)!

Hemophilia- Lacking in the ability to clot blood ◦ There is a gene on the “X” chromosome that controls blood clotting ◦ People who have hemophilia are missing the protein to clot blood ◦ They can bleed to death by a minor cut.

- Results in weakening/loss of muscles - Caused by defective version of gene that codes for muscle

 Sex-Influenced traits are those that are on autosomes, but occur because of the sex hormones in male and female bodies.  Examples: Facial hair Baldness

Multiple Alleles – any gene that has 3 or more alleles (not just 1 dominant and 1 recessive) Example: Blood type has 3 alleles: Example: Blood type has 3 alleles: I A = Type A blood (dominant) I B = Type B blood (dominant) I B = Type B blood (dominant) i = Type O blood (recessive) i = Type O blood (recessive)

GenotypesPhenotypes I A I A or I A iType A I B I B or I B iType B IAIBIAIB Type AB iiType O

 If you have I A I B as your genes, you have both Type A and Type B blood, also known as Type AB  If you have I A i, i is recessive to I A, so you have type A blood  Q. When would you have Type O blood?  A. When you have ii as your genotype.

 Usually show a wide range of phenotypes  Ex: Skin color, eye color, foot size, height  Wide range of skin colors because there are more than 4 genes that control this trait.  These may also be influenced by the environment, for example height. If not given the proper nutrition as a child, they might not be as tall as their genes dictate.