Products of meiosis

1. gametes with the haploid # of chromosomes (23)

2. a sperm and ovum, they form a zygote with 46 chromosomes

Principle of independent assortment

a. As sperm and ovum are formed during meiosis, two members of a pair of homolgous chromosomes seperate(the pricniple of segregation) and the maternal and paternal chromosomes get mixed up and redistributed independently in each gamete, with having a different set of 23 chromosomes

b. Genetic variation-indeendent assortment of chromosomes ensures that each offspring from a single set of parents is genetically equal

c. Applies to individual genes of groups of genes

d. Crossing over-during one phase of meiosis(meiosis 1) pairs of matching chromosomes line up along the equator and echange genes with ine another

Gene linkage- sometimes an entire group of genes stays together and crosses over a single unit

Dominant Gene

 effects are seen; capable of masking the effects of a recessive gene for the same trait

Recessive gene

effects are masked by the effects of a dominant gene for the same trait

Genotype

combination of genes within the cells of an individual

Genotype

combination of genes within the cells of an individual

Phenotype

manner in which genotype is expressed; how an individual looks because of genotype

2 genotypes

homozygous

heterozygous

homozygous-genotype with two idnetical types of a gene

heterozygous-genotype with two different forms of a gene

carrier

person who posesses the gene for a recessive trait but does not exhibit the trait

polygenic traits

when more than one gene is involved in producing a particular trait; a 'combined trait' because it results froma combination of genes 

codominant traits

when two different dominant genes occur together each will have an equal effect

abnormal disease

genes that persist in a population often provide some biological advantage, as in the case of the sickle gene that protects against malaria

sex linkes traits

1. x-chromosomes

2. y-chromosomes

3.sex linked traits

1. "female chromosome"; larger than y chromosome; includes genes to determine female sexual characteristics, as well as nonsexual charactersitics

2. "male chromosome"; smaller than x chromosome; contains few genes other than male characterisitcs

3. traits carried on sex chromosomes; also known as x-linked traits

mutation

change in the genetic code

Types of mutations

1. deletion-missing information in the genetic code

2. insertion-extra information in the genetic code

3. insertions and deletions result in a failure to make the usual protein encoded by a particular gene

True/false

Mutations can occur without outside influence

True

Mutagens

agents that can cause most genetic mutations

Mechanisms of

genetic disorders

1. Nuclear in heritance

2. mitichondrial inheritance

Nuclear inheritance

a. single gene diseases

b. genetic predispositions

c. chromosomal genetic diseases

a. caused by individual mutant gene in nuclear DNA that passes form ine generation to the next. Ex of single genes dieases-Cystic fibrosis, PKU , Tay-sachs diease(TSD), osteogenisis imperfecta, Neurofibromatosis, Duchene muscular dystrophy(DMD), Hypercholesterolemia, sickle cell anemia, Albinism, huningtons disease (HD), and some other forms of hemophelia

b.disease ocurring because of combined affects of inheritance and environmental factors

c. congenital conditions such as trisomy and monosomy that often produce abnormalities; trysomic and monosomic individuals may die before they can reproduce. ex Down syndrome, Klinefelter syndrome, and turner syndrome

Mitochondrial inheritance

a. mitichondrial DNA (mtDNA)

b.inheritance of mtDNA

c. mtDNA

a. each mitochondrion has its own DNA molecule

b. occurs through ones mother because sperm does not contribute mitochondria to the ovum during fertilization

c. contains only genetic code for several important enzymes

Genetic basis of cancer

1. oncogenes

2. tumor supressor genes

3. genetic abnormalities

1. abnormal genes that cause forms of cancer

2. regulate cell division so it proceeds normally; when nonfunctional because of a mutation, it allows cells to divide abnormally

3. may inhibit the cells cancer-preventing mechansims