Unit 9: Inheritance and Mutations

Gametes

Sex cells - sperm cells and egg cells

Fertilization

The process when a sperm and egg unite to form a zygote (first single cell)

Homologous Chromosomes

A pair of the same chromosome, one from each biological parent. The position of genes on these chromosomes are the same, but alleles can be different.

Gene

A segment of DNA that codes for a protein that expresses a characteristic.

Genotype

Letters (upper and lowercase) representing a gene. Ex. Rr

Phenotype

The characteristic the gene produces - Words Ex. Brown fur

Dominant

Represented by an uppercase letter; an allele that masks a recessive trait. Ex. A

Recessive

Represented by a lowercase letter; the trait that is masked by a dominant trait. Ex. a

Allele

A form or version of a gene Ex. Blue eyes vs. green eyes

Heterozygous

A genotype with two different alleles Ex. Aa

Homozygous

A genotype with two of the same alleles Ex. aa or AA

Codominant

A type of inheritance where 'Both' alleles are expressed fully (or both are dominant) when heterozygous. Typically animals or plants with stripes or spots. Ex. Flower with red and white spots

Incomplete dominance

A type of inheritance where the dominant allele is only partially expressed. Think 'Blended.' Ex. A flower that is pink due to the dominant allele being red and recessive allele being white.

Autosomal chromosome

Chromosomes #1-22 found in body (somatic) cells. They contain no sex-specific characteristics.

Sex Chromosomes

The pair of chromosomes #23 that determines the biological sex of the offspring. XX = female XY = male

Mutation

A permanent change in gene that may change the protein produced.

Carrier

A person who has one copy of a recessive gene for a trait or disorder but does not show symptoms. Carriers can pass the gene on to their children.

Law of Dominance

A law in genetics that says if an organism has both a dominant and a recessive allele, the dominant one will show up in the organism's traits.

Law of Segregation

This law states that when cells make gametes (sperm or egg), the two copies of each gene (one from each parent) separate so each gamete only gets one copy.

mRNA

A molecule that copies the instructions from DNA and carries them to the ribosome, where proteins are made.

Protein

Large molecules made of amino acids that do most of the work in cells. Proteins help build body structures and control how cells work.

Punnett Square

A chart that shows all the possible combinations of alleles from two parents and predicts the chances of an offspring having certain traits.

Pedigree

A diagram that shows how a trait is passed through generations in a family. It uses symbols to represent individuals and their traits.

X-Linked Trait

Traits that are controlled by genes found on the X chromosome. These traits often show up more in biological males because they only have one X chromosome.