A&P II Chapter 29

Gene

are segments of DNA that contain the "recipe," or blueprints, for synthesis of proteins

Allele

genes that occur at same locus (location) on homologous chromosomes

Genotype

genetic makeup (genetic code) of a person for a trait

Phenotype

physical expression of genotype (what you see)

Dominant

one allele masks (suppresses) expression of its recessive partner

Recessive

expressed only if both alleles are recessive. When a particular allele does not manifest itself in the presence of other alleles that generate traits that are dominant too.

Homozygous

alleles are same for single trait

Heterozygous

alleles are different for single trait

"carrier" for a trait

meaning you do not express the trait but can pass it on to offspring. Heterozygous people are carriers.

Segregation

two alleles of one particular trait will be separated and distributed to two different daughter cells (gametes). Random process.

Where does Segregation occurs

metaphase Meiosis I

Independent assortment

alleles of two different traits on two different chromosomes are distributed independently of each other.

Where does Independent assortment occur

metaphase Meiosis I

Crossing over

the exchange of genetic material between paired maternal and paternal chromosomes increases the genetic variability of the offspring.

Where does crossing over occur

Prophase of meiosis I

Random fertilization

Single egg is fertilized by a single sperm in a random manner

Where does random fertilization occur

Anywhere the sperm and egg meet its random

Dominant-recessive

reflects the interaction of dominant and recessive alleles. Punnet sqquare can help figure it out

Examples of Recessive inheritance

Albinism, cystic fibrosis, Tay-Sachs disease, normal digits, absence of Huntington’s disease, and normal endochondral ossification

Examples of dominant inheritance

Syndactyly (webbed digits), Achondroplasia (heterozygous: dwarfism; homozygous: lethal), Huntington’s disease, Normal skin pigmentation, absence of Tay-Sachs disease and Absence of cystic fibrosis

Incomplete dominance

Heterozygous individuals have intermediate phenotype that is between homozygous dominant and homozygous recessive

Example of incomplete dominance

Sickling gene (homozygous recessive disorder)

Multiple-allele inheritance

Genes that exhibit more than two allele forms

Example of Multiple-allele inheritance

ABO blood groups have three alleles: I A, I B, and i 

Sex-linked inheritance

inherited traits determined by genes on sex chromosomes. Genes only found on the X chromosomes are called X-linked. X has more genes than Y

Examples of sex-linked inheritance

Hemophilia and red-green color blindness (X-linked recessive conditions)

Polygene inheritance

Traits that are result of actions of several gene pairs at different locations (basically, multiple traits control it)

Polygene inheritance examples

Skin color, height, intelligence, and metabolic rate.

Punnett square

Diagram/model used to predict possible gene combinations resulting from mating of parents of known genotypes for a single trait

Mitochondrial DNA (mtDNA)

It is DNA found in the mitochondria

Mitochondrial DNA inheritance

It is inherited from mother in embryo

Mitochondrial DNA mutations

Mutations lead to problems associated with oxidative phosphorylation (cellular respiration, some muscle and neurological problems, and possibly Alzheimer's and Parkinson's diseases).