A & P II, TCC NE, Dr. Bracks, Lab Section 28

Monohybrid inheritance

A cross between two parents who possess different forms (alleles) of a gene is called monohybrid inheritance. Example: M: AA / F: aa Outcome all the same of phenotype and genotype. Cystic fibrosis.

Dominant gene

A dominant allele produces a dominant phenotype in individuals who have one copy of the allele, which can come from just one parent. Example: Brown eyes

Heterozygous genotype

A genotype with two different alleles. Example: Bb

Recessive gene

A recessive gene is a gene that can be masked by a dominant gene. In order to have a trait that is expressed by a recessive gene, such as blue eyes, you must get the gene for blue eyes from both of your parents. Example: Green eyes

Gene recombination

Aka genetic reshuffling. Is the production of offspring with combinations of traits that differ from those found in either parent.

Autosomes

An autosome is a chromosome that is not an allosome (a sex chromosome) They are the first 22 homologuos pairs of human chromosome that do not influence the sex of and individual. Example: Chromosomes 1 - 22.

Genotype

An organism genetic makeup can only be observed through biological tests not observation. The genes that are inherited by the parent. Example: BB, Bb, bb

Multiple allele inheritance

Any one of a series of three or more alternative or allelic forms of a gene, only two of which can exist in any normal, diploid individual. Example: ABO blood type.

Diploid

Cells containing two complete sets of chromosomes, one from each parent. Example: All body cells, except reproductive cells.

Independent assortment

Describes how different genes independently separate from one another when reproductive cells develop. Occurs in anaphase I. Leads to different combinations of chromosomes in gametes.

Allele

Different forms of genes. An example of an allele is the gene that determines hair color.

Haploid

Having a single set of unpaired chromosomes. Example: sperm cell.

Homozygous genotype

Homozygous is a word that refers to a particular gene that has identical alleles on both homologous chromosomes. It is referred to by two capital letters (XX) for a dominant trait, and two lowercase letters (xx) for a recessive trait. Example: RR or rr

Crossover of homologous

Occurs between prophase 1 and metaphase 1 and is the process where homologous chromosomes pair up with each other and exchange different segments of their genetic material to form recombinant chromosomes.

Crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

Random fertilization

Sperm + egg = ? Any 2 parents will produce a zygote with over 70 trillion possible diploid combinations.

Sex chromosomes

The 23 rd pair of chromosomes that determine the sex of the individual. Examples: Female (XX), Male (XY)

Synapsis

The fusion of chromosome pairs at the start of meiosis (prophase I).

Sex-linked inheritance

The inheritance of a trait (phenotype) that is determined by a gene located on one of the sex chromosomes. Recessive traits are more prevalent in males. Examples: Baldness Color blindness

Phenotype

The phenotype is the physical expression, or characteristics, of that trait. The characteristics a person displays. Example: Brown eyes, curly hair, widows peak.

Chromosome segregation

The process by which two sister chromatids separate from each other and migrate to opposite poles of the nucleus. This segregation process occurs during both mitosis and meiosis.

Strict (or simple) dominant recessive inheritance

This pattern occurs when the dominant phenotype is not expressed even though an individual carries a dominant allele. Example: Dominant trait: normal skin Recessive trait: albinism

Co-dominance inheritance

Two alleles are dominant. Both phenotypes are expressed in the heterozygote. Example: ABO blood groups.

Incomplete dominance inheritance

Two or more alleles influence the phenotype. Neither allele is dominant over the other. Example: RR/WW = all RW Sickle cell anemia.