Inheritance 1.0

Karyotype

A picture of homologous chromosome pairs (one each from biological mom and dad) that can show mutations and gender.

Heredity

The process of passing down traits found on DNA from parent(s) to offspring

XX

Female Sex chromosomes

XY

Male Sex Chromosomes

46

The number of chromosomes in a human's somatic cells

23

The number of chromosome pairs in a human's somatic cells

Gametes

Sex cells (egg and sperm)

Meiosis

Cell division that makes 4 haploid sex cells (egg or sperm)

Haploid

One set of chromosomes

Diploid

Two sets of chromosomes

Mitosis

Process of cell division that makes 2 identical body cells. This can be used for growth and repair.

Genotype

The Allele combination (the letters) of a trait

Phenotype

The outward expression of a trait (ie how it looks)

allele

A number of alternative forms of the same gene. (represented by letters).

crossing-over

when two homologous chromosomes exchange pieces of their DNA in prohase I; creates genetic variation and makes new combinations of alleles on the chromosome.

Dominant

An allele that is "stronger" and can cover up another allele. Only 1 copy is necessary to show the trait; It is represented by a capital letter.

Recessive

An allele that is "weaker" and can "hide" behind a stronger allele. Two copies are necessary to show the trait; represented by a lowercase letter.

Homozygous Dominant

Two copies of the same dominant allele. It is represented by two Uppercase letters.

Homozygous Recessive

Two copies of the same recessive allele. It is represented by two Lowercase letters.

Heterozygous

An organism has two different alleles of a gene. It is represented by an upper case and a lower case letter Aa; AKA hybrid

Fertilization

The process that occurs when a sperm combines with an egg. Two haploid cells join together to form one diploid cell.

Zygote

A fertilized egg.

Variation

An advantage of sexual reproduction. This causes genetic differences in the offspring.

Sexual Reproduction

When two haploid sex cells or gametes (egg and sperm) come together to form a zygote.

Asexual Reproduction

A form of reproduction that needs only one individual that makes two identical daughter cells.

Carrier

Someone who has the recessive allele for a trait, but the trait does not show in their phenotype.

Punnet Square

A diagram used to predict the outcome of a particular cross or breeding experiment. Used by biologists to determine the probability of an offspring having a particular genotype.

homozygous

An organism that has two identical alleles for a trait

Genotypic ratio

The number of times a genotype would appear in the offspring after a test cross. For example, when 2 heterozygous organisms are crossed, the ratio of the possible genotypes would be 1:2:1.

phenotypic ratio

The number of times a phenotype would appear in the offspring after a test cross. For example, when 2 heterozygous organisms are crossed, the ratio of the possible phenotypes would be 3:1

gene

a segment of DNA that codes for a trait

P1 generation

the original, parent generation

F1 generation

the first generation of offspring

F2 generation

the 2nd generation of offspring

Principle of Dominance

The idea that some alleles are dominant and others are recessive; the recessive allele appears to "skip generations" when paired with a dominant allele

monohybrid cross

a cross of two parents that are both heterozygous for ONE trait

Independent assortment

alleles for different traits are distributed to sex cells independently of each other; for example, the genes for brown eyes and brown hair do NOT stay together.

sex-linked traits

genetic traits that are found on the sex chromosomes (X or Y) and thus are sex-based