Science 10 Unit 4 - Traits Vocabulary

Haploid

Cells that have only one set of chromosomes - in humans this only occurs in gametes

Homologous Chromosomes

Chromosome pairs that have the same type of gene, 1 from each parent (different code, same gene)

Diploid

Cells that have 2 sets of chromosomes, 2n

Sister Chromatids

Identical copies of a chromosome that are connected by a centromere, formed during the DNA replication process.

Meiosis

Division process that takes us from a diploid to haploid cell - one with 2 sets of chromosomes to ones with a single set of chromosomes and involves two rounds of cell division, resulting in four genetically diverse haploid cells.

Gamete

A reproductive cell of an animal or plant - in humans: female = ova/egg, male = sperm

Crossing Over

Homologous chromosomes trade parts - the sports where crossovers occur are more or less random. Forms new “remixed” chromosomes with unique combinations of alleles

Cytokinesis

The division of cytoplasm into the 2 daughter cells at the end of mitosis or meiosis

Gene

A section of DNA which controls a trait

Allele

A variant form of a gene that can result in different traits. Alleles can be dominant or recessive and determine the genetic variation among individuals.

Homozygous

Having two identical alleles for a specific gene.

Heterozygous

Having 2 different alleles for a specific gene.

Dominant

The inheritance of traits that are passed down where both the parent and the child are affected by the trait.

Recessive

The weaker unexpressed trait of alleles that are only when homozygous - otherwise it doesn’t affect the phenotype

Genotype

The alleles that an organism has for a particular characteristic - represented with capital and lowercase letters.

Phenotype

The visible characteristics of an organism which occur as a result as a result of its genes.

F₁ and F₂ Generation

F1 - first generation bred from a pair of parents. F2 second generation obtained by crossing the F1 generation.

Punnett Square

A table in which all of the possible outcomes for a genetic cross between 2 individuals with known genotypes are given.

Codominance

A genetic scenario where both alleles in a heterozygote are fully expressed, resulting in offspring with a phenotype that is neither dominant nor recessive. Examples include blood type AB in humans.

Incomplete Dominance

A genetic situation in which one allele does not completely dominate another allele, resulting in a blended phenotype in the offspring. An example is the flower color in snapdragons, where crossing red and white flowers produces pink flowers.

Polygenic Inheritance

Traits are determined by multiple genes - ex. height is determined by many genes, each with a small effect.

Sex-Linked Inheritance

Characteristics or traits influenced by genes carried on the sex chromosomes. In humans: Traits of disorders influenced by genes on the X chromosome

Single Gene Mutations

The alteration of a DNA nucleotide as a result of: 1. substitution of nucleotides, 2. insertion, 3. deletiom

Chromosome Mutations

Alterations that affect whole chromosomes and genes rather than just individual nucleotides.

Autosomal Recessive

Pattern of inheritance - autosomal = not in the sex chromosomes, recessive = needs 2 copies (1 from each parent) of the mutation to cause disorder

Autosomal Dominant

Pattern of inheritance - autosomal = not in sex chromosome, in a numbered chromosome, dominant = needs only 1 parent with the gene - 50% chance of inheriting

Pedigree Chart

A chart that diagrams the inheritance of a trait or health condition through generations of a family - shows relationships among family and, when available, indicates which individuals have traits of interest.